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Predictors of under-weight among children younger than 24 months in Nimule Border Town, Eastern Equatoria State, South Sudan: a community-based cross sectional study

Underweight is a public health problem globally, and more severe in South Sudan with wide sub-regional differences. In Nimule border town, which represents other border towns in South Sudan, data on underweigh...

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Prediction of influenza outbreaks in Fuzhou, China: comparative analysis of forecasting models

Influenza is a highly contagious respiratory disease that presents a significant challenge to public health globally. Therefore, effective influenza prediction and prevention are crucial for the timely allocat...

Exploring food poverty experiences in the German Twitter-Sphere

This study investigates the subjective perceptions of food poverty in Germany by analysing Twitter discourse using the German-language hashtag #IchBinArmutsbetroffen (#IamPovertyAffected) and examines the exte...

Incomplete tuberculosis reporting and registration to the surveillance system in southwestern China of Yunnan Province: an inventory survey

The real-world tuberculosis (TB) surveillance data was generally incomplete due to underreporting and underdiagnosis. The inventory study aimed to assess and quantify the incompletion of surveillance systems i...

Epidemiological characteristics of neuroendocrine neoplasms in Beijing: a population-based retrospective study

The incidence of neuroendocrine neoplasms (NENs) is rising rapidly worldwide. However, there are few reports on these heterogeneous diseases in China. Our study aimed to explore the epidemiological characteris...

Epidemiologic profile of inflammatory bowel disease in Eastern Mediterranean Region (EMRO) countries: a systematic review and meta-analysis

Inflammatory bowel disease (IBD) consists of two main types: Crohn’s disease (CD) and ulcerative colitis (UC). The epidemiology of IBD patients has not been comprehensively studied in EMRO countries; therefore...

The association between gender equality and climate adaptation across the globe

Climate change has a disproportionate impact on women in comparison to men, and women have a key role to play in climate adaptation. However, evidence is lacking on how gender inequalities may be associated wi...

Public perspectives on COVID-19 public health and social measures in Japan and the United Kingdom: a qualitative study

The COVID-19 pandemic, caused by SARS-CoV-2, was one of the greatest modern public health crises that the world has faced. Countries undertook sweeping public health and social measures (PHSM); including envir...

Exercise, grit, and life satisfaction among Korean adolescents: a latent growth modeling analysis

Life satisfaction among Korean students is declining substantially, and multifaceted improvement efforts are required.

Multi-level analysis of intimate partner violence and its determinants among reproductive age group women in Ethiopia: evidence from Ethiopian Demographic Health Survey, 2016

Intimate partner violence (IPV) is recognized as a main public health challenge, with serious consequences for women’s physical, mental, sexual, and reproductive health. Despite its public health importance, m...

Determinants of premenstrual dysphoric disorder and associated factors among regular undergraduate students at Hawassa University Southern, Ethiopia, 2023: institution-based cross-sectional study

Premenstrual dysphoric disorder (PMDD) is a condition causing severe emotional, physical, and behavioral symptoms before menstruation. It greatly hinders daily activities, affecting academic and interpersonal ...

Exploring the working life of people with multiple sclerosis during the COVID-19 pandemic in Sweden

The COVID-19 pandemic led to vast changes in working life and conditions in which we work. These changes may affect people with multiple sclerosis (PwMS) differently. We aimed to describe the working situation...

The effect of replacing sedentary behavior with different intensities of physical activity on depression and anxiety in Chinese university students: an isotemporal substitution model

Previous research has suggested that engaging in regular physical activity (PA) can help to reduce symptoms of depression and anxiety in university students. However, there is a lack of evidence regarding the ...

Bone fracture is associated with incident myocardial infarction in long-term follow-up

The association between bone fracture and cardiovascular diseases is examined in this study. While basic research has established a connection between fractures and heart attacks through the linkage between bo...

Socio-demographic predictors of not having private dental insurance coverage: machine-learning algorithms may help identify the disadvantaged

For accessing dental care in Canada, approximately 62% of the population has employment-based insurance, 6% have some publicly funded coverage, and 32% have to pay out-of pocket. Those with no insurance or pub...

Machine learning algorithms using national registry data to predict loss to follow-up during tuberculosis treatment

Identifying patients at increased risk of loss to follow-up (LTFU) is key to developing strategies to optimize the clinical management of tuberculosis (TB). The use of national registry data in prediction mode...

#Bartender: portrayals of popular alcohol influencer’s videos on TikTok ©

Despite widespread use of the short-video social media platform TikTok © , limited research investigates how alcohol is portrayed on the platform. Previous research suggests that a driver of alcohol content on TikT...

Energy, nutrient and overall healthiness of processed packaged foods in Fiji, a comparison between 2018 and 2020

In Fiji, packaged foods are becoming increasingly available. However, it is unknown if nutrition composition of these foods has changed. This study aims to assess changes in energy, nutrient content and health...

A cohort study of self-perception of ageing and all-cause mortality among older adults in China: a multiple mediators analysis

Positive self-perception of aging (SPA) is a well-known predictor of longevity, while how and to what extent SPA is linked with all-cause mortality among older adults is still unclear. This study aims to eluci...

Family cohesion and quality of life significantly affecting personality changes in adult epilepsy patients: a case-control study

The goal of epilepsy treatment is not only to control convulsive seizures but also to improve the quality of life of patients. This study aimed to investigate personality changes and the risk factors for their...

Assessment of handwashing impact on detection of SARS-CoV-2, Staphylococcus aureus , Escherichia coli on hands in rural and urban settings of Côte d’Ivoire during COVID-19 pandemic

Handwashing is the first line of hygiene measures and one of the oldest methods of preventing the spread of infectious diseases. Despite its efficacy in the health system, handwashing is often inadequately pra...

Feasibility and acceptability of a cohort study baseline data collection of device-measured physical behaviors and cardiometabolic health in Saudi Arabia: expanding the Prospective Physical Activity, Sitting and Sleep consortium (ProPASS) in the Middle East

Physical behaviors such physical activity, sedentary behavior, and sleep are associated with mortality, but there is a lack of epidemiological data and knowledge using device-measured physical behaviors.

Risk factors and their association network for young adults’ suicidality: a cross-sectional study

Understanding the intricate influences of risk factors contributing to suicide among young individuals remains a challenge. The current study employed interpretable machine learning and network analysis to unr...

Cold waves and fine particulate matter in high-altitude Chinese cities: assessing their interactive impact on outpatient visits for respiratory disease

Extreme weather events like heatwaves and fine particulate matter (PM 2.5 ) have a synergistic effect on mortality, but research on the synergistic effect of cold waves and PM 2.5 on outpatient visits for respirator...

Process evaluation of implementation of the early stages of a whole systems approach to obesity in a small Island

The small Atlantic island of St Helena is a United Kingdom Overseas Territory (UKOT) with a high prevalence of childhood obesity (over a quarter of 4–5 and 10–11 year olds) and, anecdotally, adulthood obesity ...

Risk of not being in employment, education or training (NEET) in late adolescence is signalled by school readiness measures at 4–5 years

Not being in employment, education, or training (NEET) is associated with poor health (physical and mental) and social exclusion. We investigated whether England’s statutory school readiness measure conducted ...

The state of health in the European Union (EU-27) in 2019: a systematic analysis for the Global Burden of Disease study 2019

The European Union (EU) faces many health-related challenges. Burden of diseases information and the resulting trends over time are essential for health planning. This paper reports estimates of disease burden...

The association between non-alcoholic fatty liver disease and urinary incontinence among adult females in the United States

Non-alcoholic fatty liver disease (NAFLD) and urinary incontinence (UI) are both highly prevalent and age-related diseases. Nevertheless, the link between NAFLD and UI is unclear. Hence, the study was designed...

Factors influencing risk perception during Public Health Emergencies of International Concern (PHEIC): a scoping review

The unknownness and dread potential of a risk event shapes its perceived risk. A public health emergency of international concern (PHEIC) declaration by the World Health Organisation (WHO) is a signal for such...

Examining determinants of stunting in Urban and Rural Indonesian: a multilevel analysis using the population-based Indonesian family life survey (IFLS)

In Indonesia, chronic malnutrition leading to stunted growth in children represents a significant issue within the public health domain. The prevalence of stunting varies between urban and rural areas, reflect...

Associated lifestyle factors of elevated plasma aldosterone concentration in community population, gender-stratified analysis of a cross-sectional survey

Aldosterone plays important parts in development of cardio-metabolic diseases as end product of renin-angiotensin-aldosterone system. However, factors elevating circulating aldosterone are not clear, and lifes...

Human resource shortage in India’s health sector: a scoping review of the current landscape

For healthcare delivery to be optimally effective, health systems must possess adequate levels and we must ensure a fair distribution of human resources aimed at healthcare facilities. We conducted a scoping r...

Effects of electronic screen exposure time on hypertensive disorders in pregnancy: a retrospective cohort study

We previously conducted a case-control study and found that exposure to electronic screen before nocturnal sleep was associated with hypertensive disorders in pregnancy (HDP). Hence, we carried out this cohort...

The relationship between oxidative balance scores and chronic diarrhea and constipation: a population-based study

Oxidative stress is closely related to gut health. Exposures to oxidative stress in one’s diet and lifestyle can be evaluated by the oxidative balance score (OBS). However, the relationship between OBS and int...

The effect of physical fitness on psychological health: evidence from Chinese university students

Despite frequent discussions on the link between physical and mental health, the specific impact of physical fitness on mental well-being is yet to be fully established.

New sagittal abdominal diameter and transverse abdominal diameter based equations to estimate visceral fat area in type 2 diabetes patients

Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) are considered gold standards for measuring visceral fat area (VFA). However, their relatively high prices and potential radiation exposure limit th...

Lag effect of ambient temperature on respiratory emergency department visits in Beijing: a time series and pooled analysis

Although the association between ambient temperature and mortality of respiratory diseases was numerously documented, the association between various ambient temperature levels and respiratory emergency depart...

The effect of soy isoflavones supplementation on metabolic status in patients with non-alcoholic fatty liver disease: a randomized placebo controlled clinical trial

Non-alcoholic fatty liver disease (NAFLD) accounts as a crucial health concern with a huge burden on health and economic systems. The aim of this study is to evaluate the effect of soy isoflavones supplementat...

Smokeless tobacco consumption among women of reproductive age: a systematic review and meta-analysis

Smokeless tobacco (SLT) poses many negative health impacts. Despite its longstanding presence in societies across the world, the health implications of SLT have only been rigorously studied in recent decades. ...

Prevalence of HIV-related stigma manifestations and their contributing factors among people living with HIV in Sweden – a nationwide study

With access to  antiretroviral therapy (ART) HIV infection is a chronic manageable condition and non-sexually transmissible. Yet, many people living with HIV still testify about experiencing HIV-related stigma...

Disease burden of mental disorders among children and adolescents considering both co-morbidities and suicide in Northeastern China

Few studies have assessed the burden of mental disorders among children and adolescents considering the impact of co-morbidities and suicide on disability adjusted life years (DALYs).

Factors associated with antiretroviral treatment adherence among people living with HIV in Guangdong Province, China: a cross sectional analysis

Understanding factors associated with antiretroviral treatment (ART) adherence is crucial for ART success among people living with HIV (PLHIV) in the “test and treat” era. Multiple psychosocial factors tend to...

Postpartum depression symptoms: prevalence, risk factors, and childbirth experiences in Palestine

Worldwide mothers are suffering from postpartum depression (PPD) which impairs mothers’ well-being, children, and families, and leads to adverse outcomes for mothers and their growing newborns. Low and middle-...

COVID-19 vaccine intentions and attitudes in Black American emerging adults with asthma

Emerging adults (aged 18–29) are less likely to receive the COVID-19 vaccine than any other adult age group. Black Americans are less likely than non-Hispanic white Americans to be fully vaccinated against COV...

Physical activity and functional social support in community-dwelling older adults: a scoping review

Globally, the population of older people is increasing and is estimated to reach nearly 2.1 billion by 2050. Physical activity (PA) is one of the key components for successful ageing. However, PA decreases wit...

Structural relations of illness perception, fatigue, locus of control, self-efficacy, and coping strategies in patients with multiple sclerosis: a cross-sectional study

Patients with multiple sclerosis (MS) experience extensive problems due to fatigue and illness perception. Reducing these problems may improve these patients’ quality of life (QoL). Accordingly, the current st...

Community medical service construction: identifying factors that influence medical choice for patients with non-communicable chronic diseases in the Southwest China

Community medical institutions play a vital role in China’s healthcare system. While the number of these institutions has increased in recent years, their construction contents remain insufficient. The potenti...

Impact of COVID-19 on women living with HIV who are survivors of intimate partner violence

Women living with HIV (WLWH) experience higher rates of intimate partner violence (IPV) compared to women without HIV, but there has been minimal research to date on the impact of the COVID-19 pandemic on the ...

Prediction of adolescent weight status by machine learning: a population-based study

Adolescent weight problems have become a growing public health concern, making early prediction of non-normal weight status crucial for effective prevention. However, few temporal prediction tools for adolesce...

Air pollution, life’s essential 8, and risk of severe non-alcoholic fatty liver disease among individuals with type 2 diabetes

The impacts of long-term exposure to air pollution on the risk of subsequent non-alcoholic fatty liver disease (NAFLD) among participants with type 2 diabetes (T2D) is ambiguous. The modifying role of Life’s E...

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Effectiveness of public health measures in reducing the incidence of covid-19, SARS-CoV-2 transmission, and covid-19 mortality: systematic review and meta-analysis

Linked editorial.

Public health measures for covid-19

• Related content
• Peer review
• Stella Talic , lecturer in clinical epidemiology and public health 1 2 ,
• Shivangi Shah , honours student 1 ,
• Holly Wild , lecturer and honours student 1 3 ,
• Danijela Gasevic , senior lecturer in epidemiology and chronic disease prevention 1 4 ,
• Ashika Maharaj , lecturer quality and safety and cancer epidemiology 1 ,
• Zanfina Ademi , associate professor of medical outcomes and health economics 1 2 ,
• Xue Li , assistant professor 4 6 ,
• Wei Xu , research student 4 ,
• Ines Mesa-Eguiagaray , statistical geneticist 4 ,
• Jasmin Rostron , research student 4 ,
• Evropi Theodoratou , professor of cancer epidemiology and global health 4 5 ,
• Xiaomeng Zhang , research student 4 ,
• Ashmika Motee , research student 4 ,
• Danny Liew , professor of medical outcomes and health economics 1 2 ,
• Dragan Ilic , professor of medical education and public health 1
• 1 School of Public Health and Preventive Medicine, Monash University, Melbourne, 3004 VIC, Australia
• 2 Monash Outcomes Research and health Economics (MORE) Unit, Monash University, VIC, Australia
• 3 Torrens University, VIC, Australia
• 4 Centre for Global Health, The Usher Institute, University of Edinburgh, Edinburgh, UK
• 5 Cancer Research UK Edinburgh Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, UK
• 6 School of Public Health and The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
• Correspondence to: S Talic stella.talic{at}monash.edu
• Accepted 21 October 2021

Objective To review the evidence on the effectiveness of public health measures in reducing the incidence of covid-19, SARS-CoV-2 transmission, and covid-19 mortality.

Design Systematic review and meta-analysis.

Data sources Medline, Embase, CINAHL, Biosis, Joanna Briggs, Global Health, and World Health Organization COVID-19 database (preprints).

Eligibility criteria for study selection Observational and interventional studies that assessed the effectiveness of public health measures in reducing the incidence of covid-19, SARS-CoV-2 transmission, and covid-19 mortality.

Main outcome measures The main outcome measure was incidence of covid-19. Secondary outcomes included SARS-CoV-2 transmission and covid-19 mortality.

Data synthesis DerSimonian Laird random effects meta-analysis was performed to investigate the effect of mask wearing, handwashing, and physical distancing measures on incidence of covid-19. Pooled effect estimates with corresponding 95% confidence intervals were computed, and heterogeneity among studies was assessed using Cochran’s Q test and the I 2 metrics, with two tailed P values.

Results 72 studies met the inclusion criteria, of which 35 evaluated individual public health measures and 37 assessed multiple public health measures as a “package of interventions.” Eight of 35 studies were included in the meta-analysis, which indicated a reduction in incidence of covid-19 associated with handwashing (relative risk 0.47, 95% confidence interval 0.19 to 1.12, I 2 =12%), mask wearing (0.47, 0.29 to 0.75, I 2 =84%), and physical distancing (0.75, 0.59 to 0.95, I 2 =87%). Owing to heterogeneity of the studies, meta-analysis was not possible for the outcomes of quarantine and isolation, universal lockdowns, and closures of borders, schools, and workplaces. The effects of these interventions were synthesised descriptively.

Conclusions This systematic review and meta-analysis suggests that several personal protective and social measures, including handwashing, mask wearing, and physical distancing are associated with reductions in the incidence covid-19. Public health efforts to implement public health measures should consider community health and sociocultural needs, and future research is needed to better understand the effectiveness of public health measures in the context of covid-19 vaccination.

Systematic review registration PROSPERO CRD42020178692.

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Introduction

The impact of SARS-CoV-2 on global public health and economies has been profound. 1 As of 14 October 2021, there were 239 007 759 million cases of confirmed covid-19 and 4 871 841 million deaths with covid-19 worldwide. 2

A variety of containment and mitigation strategies have been adopted to adequately respond to covid-19, with the intention of deferring major surges of patients in hospitals and protecting the most vulnerable people from infection, including elderly people and those with comorbidities. 3 Strategies to achieve these goals are diverse, commonly based on national risk assessments that include estimation of numbers of patients requiring hospital admission and availability of hospital beds and ventilation support.

Globally, vaccination programmes have proved to be safe and effective and save lives. 4 5 Yet most vaccines do not confer 100% protection, and it is not known how vaccines will prevent future transmission of SARS-CoV-2, 6 given emerging variants. 7 8 9 The proportion of the population that must be vaccinated against covid-19 to reach herd immunity depends greatly on current and future variants. 10 This vaccination threshold varies according to the country and population’s response, types of vaccines, groups prioritised for vaccination, and viral mutations, among other factors. 6 Until herd immunity to covid-19 is reached, regardless of the already proven high vaccination rates, 11 public health preventive strategies are likely to remain as first choice measures in disease prevention, 12 particularly in places with a low uptake of covid-19 vaccination. Measures such as lockdown (local and national variant), physical distancing, mandatory use of face masks, and hand hygiene have been implemented as primary preventive strategies to curb the covid-19 pandemic. 13

Public health (or non-pharmaceutical) interventions have been shown to be beneficial in fighting respiratory infections transmitted through contact, droplets, and aerosols. 14 15 Given that SARS-CoV-2 is highly transmissible, it is a challenge to determine which measures might be more effective and sustainable for further prevention.

Substantial benefits in reducing mortality were observed in countries with universal lockdowns in place, such as Australia, New Zealand, Singapore, and China. Universal lockdowns are not, however, sustainable, and more tailored interventions need to be considered; the ones that maintain social lives and keep economies functional while protecting high risk individuals. 16 17 Substantial variation exists in how different countries and governments have applied public health measures, 18 and it has proved a challenge for assessing the effectiveness of individual public health measures, particularly in policy decision making. 19

Previous systematic reviews on the effectiveness of public health measures to treat covid-19 lacked the inclusion of analytical studies, 20 a comprehensive approach to data synthesis (focusing only on one measure), 21 a rigorous assessment of effectiveness of public health measures, 22 an assessment of the certainty of the evidence, 23 and robust methods for comparative analysis. 24 To tackle these gaps, we performed a systematic review of the evidence on the effectiveness of both individual and multiple public health measures in reducing the incidence of covid-19, SARS-CoV-2 transmission, and covid-19 mortality. When feasible we also did a critical appraisal of the evidence and meta-analysis.

This systematic review and meta-analysis were conducted in accordance with PRISMA 25 (supplementary material 1, table 1) and with PROSPERO (supplementary material 1, table 2).

Eligibility criteria

Articles that met the population, intervention, comparison, outcome, and study design criteria were eligible for inclusion in this systematic review (supplementary material 1, table 3). Specifically, preventive public health measures that were tested independently were included in the main analysis. Multiple measures, which generally contain a “package of interventions”, were included as supplementary material owing to the inability to report on the individual effectiveness of measures and comparisons on which package led to enhanced outcomes. The public health measures were identified from published World Health Organization sources that reported on the effectiveness of such measures on a range of communicable diseases, mostly respiratory infections, such as influenza.

Given that the scientific community is concerned about the ability of the numerous mathematical models, which are based on assumptions, to predict the course of virus transmission or effectiveness of interventions, 26 this review focused only on empirical studies. We excluded case reports and case studies, modelling and simulation studies, studies that provided a graphical summary of measures without clear statistical assessments or outputs, ecological studies that provided a descriptive summary of the measures without assessing linearity or having comparators, non‐empirical studies (eg, commentaries, editorials, government reports), other reviews, articles involving only individuals exposed to other pathogens that can cause respiratory infections, such as severe acute respiratory syndrome or Middle East respiratory syndrome, and articles in a language other than English.

Information sources

We carried out electronic searches of Medline, Embase, CINAHL (Cumulative Index to Nursing and Allied Health Literature, Ebsco), Global Health, Biosis, Joanna Briggs, and the WHO COVID-19 database (for preprints). A clinical epidemiologist (ST) developed the initial search strategy, which was validated by two senior medical librarians (LR and MD) (supplementary material 1, table 4). The updated search strategy was last performed on 7 June 2021. All citations identified from the database searches were uploaded to Covidence, an online software designed for managing systematic reviews, 27 for study selection.

Study selection

Authors ST, DG, SS, AM, ET, JR, XL, WX, IME, and XZ independently screened the titles and abstracts and excluded studies that did not match the inclusion criteria. Discrepancies were resolved in discussion with the main author (ST). The same authors retrieved full text articles and determined whether to include or exclude studies on the basis of predetermined selection criteria. Using a pilot tested data extraction form, authors ST, SS, AM, JR, XL, WX, AM, IME, and XZ independently extracted data on study design, intervention, effect measures, outcomes, results, and limitations. ST, SS, AM, and HW verified the extracted data. Table 5 in supplementary material 1 provides the specific criteria used to assess study designs. Given the heterogeneity and diversity in how studies defined public health measures, we took a common approach to summarise evidence of these interventions (supplementary material 1, table 6).

Risk of bias within individual studies

SS, JR, XL, WX, IME, and XZ independently assessed risk of bias for each study, which was cross checked by ST and HW. For non-interventional observational studies, a ROBINS-I (risk of bias in non-randomised studies of interventions) risk of bias tool was used. 28 For interventional studies, a revised tool for assessing risk of bias in randomised trials (RoB 2) tool was used. 29 Reviewers rated each domain for overall risk of bias as low, moderate, high, or serious/critical.

Data synthesis

The DerSimonian and Laird method was used for random effects meta-analysis, in which the standard error of the study specific estimates was adjusted to incorporate a measure of the extent of variation, or heterogeneity, among the effects observed for public health measures across different studies. It was assumed that the differences between studies are a result of different, yet related, intervention effects being estimated. If fewer than five studies were included in meta-analysis, we applied a recommended modified Hartung-Knapp-Sidik-Jonkman method. 30

Statistical analysis

Because of the differences in the effect metrics reported by the included studies, we could only perform quantitative data synthesis for three interventions: handwashing, face mask wearing, and physical distancing. Odds ratios or relative risks with corresponding 95% confidence intervals were reported for the associations between the public health measures and incidence of covid-19. When necessary, we transformed effect metrics derived from different studies to allow pooled analysis. We used the Dersimonian Laird random effects model to estimate pooled effect estimates along with corresponding 95% confidence intervals for each measure. Heterogeneity among individual studies was assessed using the Cochran Q test and the I 2 test. 31 All statistical analyses were conducted in R (version 4.0.3) and all P values were two tailed, with P=0.05 considered to be significant. For the remaining studies, when meta-analysis was not feasible, we reported the results in a narrative synthesis.

Public and patient involvement

No patients or members of the public were directly involved in this study as no primary data were collected. A member of the public was, however, asked to read the manuscript after submission.

A total of 36 729 studies were initially screened, of which 36 079 were considered irrelevent. After exclusions, 650 studies were eligible for full text review and 72 met the inclusion criteria. Of these studies, 35 assessed individual interventions and were included in the final synthesis of results ( fig 1 ) and 37 assessed multiple interventions as a package and are included in supplementary material 3, tables 2 and 3. The included studies comprised 34 observational studies and one interventional study, eight of which were included in the meta-analysis.

Flow of articles through the review. WHO=World Health Organization

Risk of bias

According to the ROBINS-I tool, 28 the risk of bias was rated as low in three studies, 32 33 34 moderate in 24 studies, 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 and high to serious in seven studies. 59 60 61 62 63 64 65 One important source of serious or critical risk of bias in most of the included studies was major confounding, which was difficult to control for because of the novel nature of the pandemic (ie, natural settings in which multiple interventions might have been enforced at once, different levels of enforcement across regions, and uncaptured individual level interventions such as increased personal hygiene). Variations in testing capacity and coverage, changes to diagnostic criteria, and access to accurate and reliable outcome data on covid-19 incidence and covid-19 mortality, was a source of measurement bias for numerous studies ( fig 2 ). These limitations were particularly prominent early in the pandemic, and in low income environments. 47 52 62 63 65 The randomised controlled trial 66 was rated as moderate risk of bias according to the ROB-2 tool. Missing data, losses to follow-up, lack of blinding, and low adherence to intervention all contributed to the reported moderate risk. Tables 1 and 2 in supplementary material 2 summarise the risk of bias assessment for each study assessing individual measures.

Summary of risk of bias across studies assessing individual measures using risk of bias in non-randomised studies of interventions (ROBINS-I) tool

Study characteristics

Studies assessing individual measures.

Thirty five studies provided estimates on the effectiveness of an individual public health measures. The studies were conducted in Asia (n=11), the United States (n=9), Europe (n=7), the Middle East (n=3), Africa (n=3), South America (n=1), and Australia (n=1). Thirty four of the studies were observational and one was a randomised controlled trial. The study designs of the observational studies comprised natural experiments (n=11), quasi-experiments (n=3), a prospective cohort (n=1), retrospective cohorts (n=8), case-control (n=2), and cross sectional (n=9). Twenty six studies assessed social measures, 32 34 35 37 38 39 40 41 42 44 46 47 48 52 53 55 56 57 58 59 60 61 63 64 65 67 12 studies assessed personal protective measures, 36 43 45 49 50 57 58 60 63 66 68 three studies assessed travel related measures, 54 58 62 and one study assessed environmental measures 57 (some interventions overlapped across studies). The most commonly measured outcome was incidence of covid-19 (n=18), followed by SARS-CoV-2 transmission, measured as reproductive number, growth number, or epidemic doubling time (n=13), and covid-19 mortality (n=8). Table 1 in supplementary material 3 provides detailed information on each study.

Effects of interventions

Personal protective measures.

Handwashing and covid-19 incidence —Three studies with a total of 292 people infected with SARS-CoV-2 and 10 345 participants were included in the analysis of the effect of handwashing on incidence of covid-19. 36 60 63 Overall pooled analysis suggested an estimated 53% non-statistically significant reduction in covid-19 incidence (relative risk 0.47, 95% confidence interval 0.19 to 1.12, I 2 =12%) ( fig 3 ). A sensitivity analysis without adjustment showed a significant reduction in covid-19 incidence (0.49, 0.33 to 0.72, I 2 =12%) ( fig 4 ). Risk of bias across the three studies ranged from moderate 36 60 to serious or critical 63 ( fig 2 ).

Meta-analysis of evidence on association between handwashing and incidence of covid-19 using modified Hartung-Knapp-Sidik-Jonkman adjusted random effect model

Meta-analysis of evidence on association between handwashing and incidence of covid-19 using unadjusted random effect model

Mask wearing and covid-19 incidence —Six studies with a total of 2627 people with covid-19 and 389 228 participants were included in the analysis examining the effect of mask wearing on incidence of covid-19 ( table 1 ). 36 43 57 60 63 66 Overall pooled analysis showed a 53% reduction in covid-19 incidence (0.47, 0.29 to 0.75), although heterogeneity between studies was substantial (I 2 =84%) ( fig 5 ). Risk of bias across the six studies ranged from moderate 36 57 60 66 to serious or critical 43 63 ( fig 2 ).

Study characteristics and main results from studies that assessed individual personal protective and environmental measures

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Meta-analysis of evidence on association between mask wearing and incidence of covid-19 using unadjusted random effect model

Mask wearing and transmission of SARS-CoV-2, covid-19 incidence, and covid-19 mortality —The results of additional studies that assessed mask wearing (not included in the meta-analysis because of substantial differences in the assessed outcomes) indicate a reduction in covid-19 incidence, SARS-CoV-2 transmission, and covid-19 mortality. Specifically, a natural experiment across 200 countries showed 45.7% fewer covid-19 related mortality in countries where mask wearing was mandatory ( table 1 ). 49 Another natural experiment study in the US reported a 29% reduction in SARS-CoV-2 transmission (measured as the time varying reproductive number Rt) (risk ratio 0.71, 95% confidence interval 0.58 to 0.75) in states where mask wearing was mandatory. 58

A comparative study in the Hong Kong Special Administrative Region reported a statistically significant lower cumulative incidence of covid-19 associated with mask wearing than in selected countries where mask wearing was not mandatory ( table 1 ). 68 Similarly, another natural experiment involving 15 US states reported a 2% statistically significant daily decrease in covid-19 transmission (measured as case growth rate) at ≥21 days after mask wearing became mandatory, 50 whereas a cross sectional study reported that a 10% increase in self-reported mask wearing was associated with greater odds for control of SARS-CoV-2 transmission (adjusted odds ratio 3.53, 95% confidence interval 2.03 to 6.43). 45 The five studies were rated at moderate risk of bias ( fig 2 ).

Environmental measures

Disinfection in household and covid-19 incidence.

Only one study, from China, reported the association between disinfection of surfaces and risk of secondary transmission of SARS-CoV-2 within households ( table 1 ). 57 The study assessed disinfection retrospectively by asking participants about their “daily use of chlorine or ethanol-based disinfectant in households,” and observed that use of disinfectant was 77% effective at reducing SARS-CoV-2 transmission (odds ratio 0.23, 95% confidence interval 0.07 to 0.84). The study did not collect data on the concentration of the disinfectant used by participants and was rated at moderate risk of bias ( fig 2 ).

Social measures

Physical distancing and covid-19 incidence.

Five studies with a total of 2727 people with SARS-CoV-2 and 108 933 participants were included in the analysis that examined the effect of physical distancing on the incidence of covid-19. 37 53 57 60 63 Overall pooled analysis indicated a 25% reduction in incidence of covid-19 (relative risk 0.75, 95% confidence interval 0.59 to 0.95, I 2 =87%) ( fig 6 ). Heterogeneity among studies was substantial, and risk of bias ranged from moderate 37 53 57 60 to serious or critical 63 ( fig 2 ).

Meta-analysis of evidence on association between physical distancing and incidence of covid-19 using unadjusted random effect model

Physical distancing and transmission of SARS-CoV-2 and covid-19 mortality

Studies that assessed physical distancing but were not included in the meta-analysis because of substantial differences in outcomes assessed, generally reported a positive effect of physical distancing ( table 2 ). A natural experiment from the US reported a 12% decrease in SARS-CoV-2 transmission (relative risk 0.88, 95% confidence interval 0.86 to 0.89), 40 and a quasi-experimental study from Iran reported a reduction in covid-19 related mortality (β −0.07, 95% confidence interval −0.05 to −0.10; P<0.001). 47 Another comparative study in Kenya also reported a reduction in transmission of SARS-CoV-2 after physical distancing was implemented, reporting 62% reduction in overall physical contacts (reproductive number pre-intervention was 2.64 and post-intervention was 0.60 (interquartile range 0.50 to 0.68)). 61 These three studies were rated at moderate risk of bias 40 61 to serious or critical risk of bias 47 ( fig 2 ).

Study characteristics and main results from studies assessing individual social measures

Stay at home or isolation and transmission of SARS-CoV-2

All the studies that assessed stay at home or isolation measures reported reductions in transmission of SARS-CoV-2 ( table 2 ). A retrospective cohort study from the US reported a significant reduction in the odds of having a positive reproductive number (R0) result (odds ratio 0.07, 95% confidence interval 0.01 to 0.37), 41 and a natural experiment reported a 51% reduction in time varying reproductive number (Rt) (risk ratio 0.49, 95% confidence interval 0.43 to 0.54). 58

A study from the UK reported a 74% reduction in the average daily number of contacts observed for each participant and estimated a decrease in reproductive number: the reproductive number pre-intervention was 3.6 and post-intervention was 0.60 (95% confidence interval 0.37 to 0.89). 65 Similarly, an Iranian study projected the reproductive number using serial interval distribution and the number of incidence cases and found a significant decrease: the reproductive number pre-intervention was 2.70 and post-intervention was 1.13 (95% confidence interval 1.03 to 1.25). 55 Three of the studies were rated at moderate to serious or critical risk of bias, 55 58 65 and one study was rated at low risk of bias 41 ( fig 2 ).

Quarantine and incidence and transmission of SARS-CoV-2

Quarantine was assessed in two studies ( table 2 ). 34 59 A prospective cohort study from Saudi Arabia reported a 4.9% decrease in the incidence of covid-19 at eight weeks after the implementation of quarantine. 34 This study was rated at low risk of bias ( fig 2 ). A retrospective cohort study from India reported a 14 times higher risk of SARS-CoV-2 transmission associated with no quarantine compared with strict quarantine (odds ratio 14.44, 95% confidence interval 2.42 to 86.17). 59 This study was rated at moderate risk of bias ( fig 2 ).

School closures and covid-19 incidence and covid-19 mortality

Two studies assessed the effectiveness of school closures on transmission of SARS-CoV-2, incidence of covid-19, or covid-19 mortality ( table 2 ). 44 48 A US population based longitudinal study reported on the effectiveness of state-wide closure of primary and secondary schools and observed a 62% decrease (95% confidence interval −49% to −71%) in incidence of covid-19 and a 58% decrease (−46% to−68%) in covid-19 mortality. 48 Conversely, a natural experiment from Japan reported no effect of school closures on incidence of covid-19 (α coefficient 0.08, 95% confidence interval −0.36 to 0.65). 44 Both studies were rated at moderate risk of bias ( fig 2 ).

School closures and transmission of SARS-CoV-2

Two natural experiments from the US reported a reduction in transmission (ie, reproductive number); with one study reporting a reduction of 13% (relative risk 0.87, 95% confidence interval 0.86 to 0.89) 40 and another reporting a 10% (0.90, 0.86 to 0.93) reduction ( table 2 ). 58 A Swedish study reported an association between school closures and a small increase in confirmed SARS-CoV-2 infections in parents (odds ratio 1.17, 95% confidence interval 1.03 to 1.32), but observed that teachers in lower secondary schools were twice as likely to become infected than teachers in upper secondary schools (2.01, 1.52 to 2.67). 32 All three studies were rated at moderate risk of bias ( fig 2 ).

Business closures and transmission of SARS-CoV-2

Two natural experiment studies assessed business closures across 50 US states and reported reductions in transmission of SARS-CoV-2 ( table 2 ). 40 58 One of the studies observed a significant reduction in transmission of 12% (relative risk 0.88, 95% confidence interval 0.86 to 0.89) 40 and the other reported a significant 16% (risk ratio 0.84, 0.79 to 0.90) reduction. 58 Both studies were rated at moderate risk of bias ( fig 2 ).

Lockdown and incidence of covid-19

A natural experiment involving 202 countries suggested that countries that implemented universal lockdown had fewer new cases of covid-19 than countries that did not (β coefficient −235.8 (standard error −11.04), P<0.01) ( table 2 ). 52 An Indian quasi-experimental study reported a 10.8% reduction in incidence of covid-19 post-lockdown, 56 whereas a South African retrospective cohort study observed a 14.1% reduction in risk after implementation of universal lockdown ( table 2 ). 46 These studies were rated at high risk of bias 52 and moderate risk of bias 46 56 ( fig 2 ).

Lockdown and covid-19 mortality

The three studies that assessed universal lockdown and covid-19 mortality generally reported a decrease in mortality ( table 2 ). 35 38 42 A natural experiment study involving 45 US states reported a decrease in covid-19 related mortality of 2.0% (95% confidence interval −3.0% to 0.9%) daily after lockdown had been made mandatory. 35 A Brazilian quasi-experimental study reported a 27.4% average difference in covid-19 related mortality rates in the first 25 days of lockdown. 42 In addition, a natural experiment study reported about 30% and 60% reductions in covid-19 related mortality post-lockdown in Italy and Spain over four weeks post-intervention, respectively. 38 All three studies were rated at moderate risk of bias ( fig 2 ).

Lockdown and transmission of SARS-CoV-2

Four studies assessed universal lockdown and transmission of SARS-CoV-2 during the first few months of the pandemic ( table 2 ). The decrease in reproductive number (R0) ranged from 1.27 in Italy (pre-intervention 2.03, post-intervention 0.76) 39 to 2.09 in India (pre-intervention 3.36, post-intervention 1.27), 64 and 3.97 in China (pre-intervention 4.95, post-intervention 0.98). 33 A natural experiment from the US reported that lockdown was associated with an 11% reduction in transmission of SARS-CoV-2 (relative risk 0.89, 95% confidence interval 0.88 to 0.91). 40 All the studies were rated at low risk of bias 33 39 to moderate risk 40 64 ( fig 2 ).

Travel related measures

Restricted travel and border closures.

Border closure was assessed in one natural experiment study involving nine African countries ( table 3 ). 62 Overall, the countries recorded an increase in the incidence of covid-19 after border closure. These studies concluded that the implementation of border closures within African countries had minimal effect on the incidence of covid-19. The study had important limitations and was rated at serious or critical risk of bias. In the US, a natural experiment study reported that restrictions on travel between states contributed about 11% to a reduction in SARS-CoV-2 transmission ( table 3 ). 36 The study was rated at moderate risk of bias ( fig 2 ).

Study characteristics and main results from studies that assessed individual travel measures

Entry and exit screening (virus or symptom screening)

One retrospective cohort study assessed screening of symptoms, which involved testing 65 000 people for fever ( table 3 ). 54 The study found that screening for fever lacked sensitivity (ranging from 18% to 24%) in detecting people with SARS-CoV-2 infection. This translated to 86% of the population with SARS-CoV-2 remaining undetected when screening for fever. The study was rated at moderate risk of bias ( fig 2 ).

Multiple public health measures

Overall, 37 studies provided estimates on the effectiveness of multiple public health measures, assessed as a collective group. Studies were mostly conducted in Asia (n=15), the US (n=11), Europe (n=6), Africa (n=4), and South America (n=1). All the studies were observational. The most commonly measured outcome was transmission of disease (ie, measured as reproductive number, growth number, or epidemic doubling time) (n=23), followed by covid-19 incidence (n=19) and covid-19 mortality (n=8). This review attempted to assess the overall effectiveness of the public health intervention packages by reporting the percentage difference in outcome before and after implementation of measures or between regions or countries studied. Eleven of the 37 included studies noted a difference of between 26% and 50% in transmission of SARS-CoV-2 and incidence of covid-19, 70 71 72 73 74 75 76 77 78 79 80 nine noted a difference of between 51% and 75% in SARS-CoV-2 transmission, covid-19 incidence, and covid-19 mortality, 81 82 83 84 85 86 87 88 89 and 14 noted a difference of more than 75% in transmission of SARS-CoV-2, covid-19 incidence and covid-19 mortality. 79 80 89 90 91 92 93 94 95 96 97 98 99 100 For the remaining studies, the overall effectiveness was not assessed owing to a lack of comparators (see supplementary material 3, table 3). Two studies that assessed universal lockdown and physical distancing reported a decrease of between 0% and 25% in SARS-CoV-2 transmission and covid-19 incidence. 79 101 Studies that included school and workplace closures, 91 95 96 isolation or stay at home measures, 80 94 or a combination of both 79 89 93 97 98 99 reported decreases of more than 75% in SARS-CoV-2 transmission. Supplementary material 3, table 2 provides detailed information on each study.

Worldwide, government and public health organisations are mitigating the spread of SARS-CoV-2 by implementing various public health measures. This systematic review identified a statistically significant reduction in the incidence of covid-19 through the implementation of mask wearing and physical distancing. Handwashing interventions also indicated a substantial reduction in covid-19 incidence, albeit not statistically significant in the adjusted model. As the random effects model tends to underestimate confidence intervals when a meta-analysis includes a small number of individual studies (<5), the adjusted model for handwashing showed a statistically non-significant association in reducing the incidence of covid-19 compared with the unadjusted model.

Overall effectiveness of these interventions was affected by clinical heterogeneity and methodological limitations, such as confounding and measurement bias. It was not possible to evaluate the impact of type of face maks (eg, surgical, fabric, N95 respirators) and compliance and frequency of wearing masks owing to a lack of data. Similarly, it was not feasible to assess the differences in effect that different recommendations for physical distancing (ie, 1.5 m, 2m, or 3 m) have as preventive strategies.

The effectiveness of measures such as universal lockdowns and closures of businesses and schools for the containment of covid-19 have largely been effective, but depended on early implementation when incidence rates of covid-19 were still low. 42 52 58 Only Japan reported no decrease in covid-19 incidence after school closures, 44 and other studies found that different public health measures were sometimes implemented simultaneously or soon after one another, thus the results should be interpreted with caution. 32 46 56

Isolation or stay at home was an effective measure in reducing the transmission of SARS-CoV-2, but the included studies used results for mobility to assess stay at home or isolation and therefore could have been limited by potential flaws in publicly available phone data, 41 58 102 and variations in the enforcement of public health measures in different states or regions were not assessed. 55 58 102 Quarantine was found to be as effective in reducing the incidence of covid-19 and transmission of SARS-CoV-2, yet variation in testing and case detection in low income environments was substantial. 59 96 98 Another study reported that quarantine was effective in reducing the transmission of SARS-CoV-2 in a cohort with a low prevalence of the virus, yet it is unknown if the same effect would be observed with higher prevalence. 34

It was not possible to draw conclusions about the effectiveness of restricted travel and full border closures because the number of empirical studies was insufficient. Single studies identified that border closure in Africa had a minimal effect in reducing SARS-CoV-2 transmission, but the study was assessed as being at high risk of bias. 62 Screening for fever was also identified to be ineffective, with only 24% of positive cases being captured by screening. 54

Comparison with other studies

Previous literature reviews have identified mask wearing as an effective measure for the containment of SARS-CoV-2 103 ; the caveat being that more high level evidence is required to provide unequivocal support for the effectiveness of the universal use of face masks. 104 105 Additional empirical evidence from a recent randomised controlled trial (originally published as a preprint) indicates that mask wearing achieved a 9.3% reduction in seroprevalence of symptomatic SARS-CoV-2 infection and an 11.9% reduction in the prevalence of covid-19-like symptoms. 106 Another systematic review showed stronger effectiveness with the use of N95, or similar, respirators than disposable surgical masks, 107 and a study evaluating the protection offered by 18 different types of fabric masks found substantial heterogeneity in protection, with the most effective mask being multilayered and tight fitting. 108 However, transmission of SARS-CoV-2 largely arises in hospital settings in which full personal protective measures are in place, which suggests that when viral load is at its highest, even the best performing face masks might not provide adequate protection. 51 Additionally, most studies that assessed mask wearing were prone to important confounding bias, which might have altered the conclusions drawn from this review (ie, effect estimates might have been underestimated or overestimated or can be related to other measures that were in place at the time the studies were conducted). Thus, the extent of such limitations on the conclusions drawn remain unknown.

A 2020 rapid review concluded that quarantine is largely effective in reducing the incidence of covid-19 and covid-19 mortality. However, uncertainty over the magnitude of such an effect still remains, 109 with enhanced management of quality quarantine facilities for improved effective control of the epidemics urgently needed. 110 In addition, findings on the application of school and workplace closures are still inconclusive. Policy makers should be aware of the ambiguous evidence when considering school closures, as other potentially less disruptive physical distancing interventions might be more appropriate. 21 Numerous findings from studies on the efficacy of school closures showed that the risk of transmission within the educational environment often strongly depends on the incidence of covid-19 in the community, and that school closures are most successfully associated with control of SARS-CoV-2 transmission when other mitigation strategies are in place in the community. 111 112 113 114 115 116 117 School closures have been reported to be disruptive to students globally and are likely to impair children’s social, psychological, and educational development 118 119 and to result in loss of income and productivity in adults who cannot work because of childcare responsibilities. 120

Speculation remains as how best to implement physical distancing measures. 121 Studies that assess physical distancing measures might interchangeably study physical distancing with lockdown 35 52 56 64 and other measures and thus direct associations are difficult to assess.

Empirical evidence from restricted travel and full border closures is also limited, as it is almost impossible to study these strategies as single measures. Current evidence from a recent narrative literature review suggested that control of movement, along with mandated quarantine, travel restrictions, and restricting nationals from entering areas of high infection, are effective measures, but only with good compliance. 122 A narrative literature review of travel bans, partial lockdowns, and quarantine also suggested effectiveness of these measures, 123 and another rapid review further supported travel restrictions and cross border restrictions to stop the spread of SARS-CoV-2. 124 It was impossible to make such observations in the current review because of limited evidence. A German review, however, suggested that entry, exit, and symptom screening measures to prevent transmission of SARS-CoV-2 are not effective at detecting a meaningful proportion of cases, 125 and another review using real world data from multiple countries found that border closures had minimal impact on the control of covid-19. 126

Although universal lockdowns have shown a protective effect in lowering the incidence of covid-19, SARS-CoV-2 transmission, and covid-19 mortality, these measures are also disruptive to the psychosocial and mental health of children and adolescents, 127 global economies, 128 and societies. 129 Partial lockdowns could be an alternative, as the associated effectiveness can be high, 125 especially when implemented early in an outbreak, 85 and such measures would be less disruptive to the general population.

It is important to also consider numerous sociopolitical and socioeconomic factors that have been shown to increase SARS-CoV-2 infection 130 131 and covid-19 mortality. 132 Immigration status, 82 economic status, 81 101 and poverty and rurality 98 can influence individual and community compliance with public health measures. Poverty can impact the ability of communities to physically distance, 133 especially in crowded living environments, 134 135 as well as reduce access to personal protective measures. 134 135 A recent study highlights that “a one size fits all” approach to public health measures might not be effective at reducing the spread of SARS-CoV-2 in vulnerable communities 136 and could exacerbate social and economic inequalities. 135 137 As such, a more nuanced and community specific approach might be required. Even though screening is highly recommended by WHO 138 because a proportion of patients with covid-19 can be asymptomatic, 138 screening for symptoms might miss a larger proportion of the population with covid-19. Hence, temperature screening technologies might need to be reconsidered and evaluated for cost effectiveness, given such measures are largely depended on symptomatic fever cases.

Strengths and limitations of this review

The main strength of this systematic review was the use of a comprehensive search strategy to identify and select studies for review and thereby minimise selection bias. A clinical epidemiologist developed the search strategy, which was validated by two senior medical librarians. This review followed a comprehensive appraisal process that is recommended by the Cochrane Collaboration 31 to assess the effectiveness of public health measures, with specifically validated tools used to independently and individually assess the risk of bias in each study by study design.

This review has some limitations. Firstly, high quality evidence on SARS CoV-2 and the effectiveness of public health measures is still limited, with most studies having different underlying target variables. Secondly, information provided in this review is based on current evidence, so will be modified as additional data become available, especially from more prospective and randomised studies. Also, we excluded studies that did not provide certainty over the effect measure, which might have introduced selection bias and limited the interpretation of effectiveness. Thirdly, numerous studies measured interventions only once and others multiple times over short time frames (days v month, or no timeframe). Additionally, the meta-analytical portion of this study was limited by significant heterogeneity observed across studies, which could neither be explored nor explained by subgroup analyses or meta-regression. Finally, we quantitatively assessed only publications that reported individual measures; studies that assessed multiple measures simultaneously were narratively analysed with a broader level of effectiveness (see supplementary material 3, table 3). Also, we excluded studies in languages other than English.

Methodological limitations of studies included in the review

Several studies failed to define and assess for potential confounders, which made it difficult for our review to draw a one directional or causal conclusion. This problem was mainly because we were unable to study only one intervention, given that many countries implemented several public health measures simultaneously; thus it is a challenge to disentangle the impact of individual interventions (ie, physical distancing when other interventions could be contributing to the effect). Additionally, studies measured different primary outcomes and in varied ways, which limited the ability to statistically analyse other measures and compare effectiveness.

Further pragmatic randomised controlled trials and natural experiment studies are needed to better inform the evidence and guide the future implementation of public health measures. Given that most measures depend on a population’s adherence and compliance, it is important to understand and consider how these might be affected by factors. A lack of data in the assessed studies meant it was not possible to understand or determine the level of compliance and adherence to any of the measures.

Conclusions and policy implications

Current evidence from quantitative analyses indicates a benefit associated with handwashing, mask wearing, and physical distancing in reducing the incidence of covid-19. The narrative results of this review indicate an effectiveness of both individual or packages of public health measures on the transmission of SARS-CoV-2 and incidence of covid-19. Some of the public health measures seem to be more stringent than others and have a greater impact on economies and the health of populations. When implementing public health measures, it is important to consider specific health and sociocultural needs of the communities and to weigh the potential negative effects of the public health measures against the positive effects for general populations. Further research is needed to assess the effectiveness of public health measures after adequate vaccination coverage has been achieved. It is likely that further control of the covid-19 pandemic depends not only on high vaccination coverage and its effectiveness but also on ongoing adherence to effective and sustainable public health measures.

What is already known on this topic

Public health measures have been identified as a preventive strategy for influenza pandemics

The effectiveness of such interventions in reducing the transmission of SARS-CoV-2 is unknown

What this study adds

The findings of this review suggest that personal and social measures, including handwashing, mask wearing, and physical distancing are effective at reducing the incidence of covid-19

More stringent measures, such as lockdowns and closures of borders, schools, and workplaces need to be carefully assessed by weighing the potential negative effects of these measures on general populations

Further research is needed to assess the effectiveness of public health measures after adequate vaccination coverage

Ethics statements

Ethical approval.

Not required.

Data availability statement

No additional data available.

Acknowledgments

We thank medical subject librarians Lorena Romero (LR) and Marshall Dozier (MD) for their expert advice and assistance with the study search strategy.

Contributors: ST, DG, DI, DL, and ZA conceived and designed the study. ST, DG, SS, AM, HW, WX, JR, ET, AM, XL, XZ, and IME collected and screened the data. ST, DG, and DI acquired, analysed, or interpreted the data. ST, HW, and SS drafted the manuscript. All authors critically revised the manuscript for important intellectual content.. XL and ST did the statistical analysis. NA obtained funding. LR and MD provided administrative, technical, or material support. ST and DI supervised the study. ST and DI had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. ST is the guarantor. The corresponding author attests that all listed authors meet authorship criteria and that no others meeting the criteria have been omitted.

Funding: No funding was available for this research. ET is supported by a Cancer Research UK Career Development Fellowship (grant No C31250/A22804). XZ is supported by The Darwin Trust of Edinburgh.

Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/disclosure-of-interest/ and declare: ET is supported by a Cancer Research UK Career Development Fellowship and XZ is supported by The Darwin Trust of Edinburgh; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; and no other relationships or activities that could appear to have influenced the submitted work.

The lead author (ST) affirms that the manuscript is an honest, accurate, and transparent account of the study reported; no important aspects of the study have been omitted. Dissemination to participants and related patient and public communities: It is anticipated to disseminate the results of this research to wider community via press release and social media platforms.

Provenance and peer review: Not commissioned; externally peer reviewed.

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/ .

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What are the trending topics in Public Health and related disciplines?

You can identify some of the most discussed and influential topics with the help of Altmetric attention scores, which take into account several outlets including social media, news articles, and policy documents.

Drawing from a selection of Public Health and Medicine journals, we have compiled a list of the articles that have been mentioned the most over the past few months.

Discover the articles that are trending right now, and catch up on current topics in Public Health and related disciplines. We will update our collection every few weeks; come back to this page to be on top of the latest conversations in Public Health and Medicine. Previously featured articles are listed here .

You can also sign up for e-alerts to make sure you never miss the latest research from our journals.

*Last updated October 2021*

Age and Ageing

Alcohol and alcoholism, american journal of epidemiology, annals of work exposures and health, epidemiologic reviews, european journal of public health, family practice, health education research, health policy and planning, health promotion international, international health, international journal of epidemiology, international journal for quality in health care, journal of public health, journal of travel medicine, journal of tropical pediatrics, nicotine & tobacco research, transactions of the royal society of tropical medicine & hygiene, behaviour change interventions to increase physical activity in hospitalised patients: a systematic review, meta-analysis and meta-regression.

There is moderate-certainty evidence that behaviour change interventions are associated with increased physical activity levels among older hospitalised patients.

Attention-Deficit/Hyperactivity Disorder and Alcohol and Other Substance Use Disorders in Young Adulthood: Findings from a Canadian Nationally Representative Survey

This study from Canada found that one in three young adults with ADHD had a lifetime alcohol use disorder, and that young adults with ADHD were also three times more likely to develop a substance use disorder. Targeted outreach and interventions for this extremely vulnerable population are warranted.

Expiring Eviction Moratoriums and COVID-19 Incidence and Mortality

According to this study, resuming evictions in summer 2020 was associated with increased COVID-19 incidence and mortality in US states, with an estimated 433,700 excess cases and 10,700 excess deaths. Explore more research on COVID-19 in a curated collection from the AJE: https://academic.oup.com/aje/pages/covid-19

The Development of a Covid-19 Control Measures Risk Matrix for Occupational Hygiene Protective Measures

The British Occupational Hygiene Society (BOHS) developed a control banding matrix for employers and others to help assess the risks of COVID-19 infection, and calls for further work to validate the reliability of the tool. Browse the Annals' collection on occupational hygiene for virus protection: https://academic.oup.com/annweh/pages/covid-19 

Immunization to Protect the US Armed Forces: Heritage, Current Practice, and Prospects

In 1777, George Washington ordered a mandatory inoculation program for his troops, in what would become the first mass immunization mandate in the US. This archival article discussess and contextualizes immunization practices for US Armed Forces.

Does face mask use elicit risk-compensation? Quasi-experimental evidence from Denmark during the SARS-CoV-2 pandemic

Responding to concerns that that face mask use could elicit a false sense of security and lead to riskier behaviours, this study from Denmark found that mask use overall correlated positively with protective behaviours.

Evidence reversals in primary care research: a study of randomized controlled trials

While medical practice is often undermined by subsequent investigation, randomized trials relevant to primary care generally hold up over time.

Social media influencers can be used to deliver positive information about the flu vaccine: findings from a multi-year study

This study shows the potential for using social media influencers to inspire positive engagements on pro-vaccine health messaging. For more content on accurate information's importance for public health, browse the latest article collection from HER: https://academic.oup.com/her/pages/covid-19

COVID-19 Preparedness and Response Plans from 106 countries: a review from a health systems resilience perspective

Current emergency response planning does not have adequate coverage to maintain health systems functionality for essential health service delivery alongside emergency-specific interventions and healthcare. The findings from this study can help align health emergency planning with broader population health needs.

Rise and demise: a case study of public health nutrition in Queensland, Australia, over three decades

This case study shows that that ongoing efforts are needed to improve sustainability of nutrition policy and programmes to address all diet-related diseases.

Institutional and behaviour-change interventions to support COVID-19 public health measures: a review by the Lancet Commission Task Force on public health measures to suppress the pandemic

This review article outlines evidence for a range of institutional measures and behaviour-change measures, and highlights research and knowledge gaps.

Quantifying impacts of the COVID-19 pandemic through life-expectancy losses: a population-level study of 29 countries 

The COVID-19 pandemic triggered significant mortality increases in 2020 of a magnitude not witnessed since World War II in Western Europe or the breakup of the Soviet Union in Eastern Europe.

Gender in the Consolidated Criteria for Reporting Qualitative Research (COREQ) Checklist

The authors propose an update to the Equator’s Consolidated criteria for reporting qualitative research (COREQ) checklist, with the aim of enhancing inclusivity.

Rate of reinfections after SARS-CoV-2 primary infection in the population of an Italian province: a cohort study

This study confirms previous findings on a low risk of SARS-CoV-2 reinfection. If confirmed, these findings suggest that more targeted restriction policies can be applied to the subjects that recovered after a first infection. Read highly cited papers on COVID-19 from the Journal of Public Health: https://academic.oup.com/jpubhealth/pages/covid-19

The reproductive number of the Delta variant of SARS-CoV-2 is far higher compared to the ancestral SARS-CoV-2 virus

Given the Delta variant's high reproductive number associated with higher transmissibility, in a context of globally still low vaccine coverage rates and lower vaccine effectiveness, public health and social measures will need to be substantially strengthened. A high reproductive number also means that much higher vaccine coverage rates need to be achieved compared to the originally assumed.

Neurological Complications of SARS-CoV-2 Infection in Children: A Systematic Review and Meta-Analysis

Neurological complications are rare in children suffering from COVID-19. Still, these children are at risk of developing seizures and encephalopathy, more in those suffering from severe illness.

Reactions to Sales Restrictions on Flavored Vape Products or All Vape Products Among Young Adults in the United States

The researchers examined support for and perceived impact of e-cigarette sales restrictions. Findings suggest that bans on flavored vape products could have a positive impact on lower-risk users, but that other young adult user subgroups may not experience benefit.

Covid-19 and Health at Work 

An editorial from the earlier stages of the pandemic highlights the importance of properly fitted respirators for worker safety and outlines occupational hygiene measures.

Lessons from the field: delivering trachoma mass drug administration safely in a COVID-19 context

Guidelines for safe mass drug administration for neglected tropical diseases were developed in a COVID-19 context; training and implementation were assessed through an observation checklist.

For more research on the impact of COVID-19 on NTDs, explore the March 2021 special issue: https://academic.oup.com/trstmh/issue/115/3

Previously featured

Age and frailty are independently associated with increased COVID-19 mortality and increased care needs in survivors: results of an international multi-centre study

Trajectories of Alcohol Use and Related Harms for Managed Alcohol Program Participants over 12 Months Compared with Local Controls: A Quasi-Experimental Study

Estimating the Effect of Social Distancing Interventions on COVID-19 in the United States

Selecting Controls for Minimizing SARS-CoV-2 Aerosol Transmission in Workplaces and Conserving Respiratory Protective Equipment Supplies

What Do We Know About the Association Between Firearm Legislation and Firearm-Related Injuries?

Denialism: what is it and how should scientists respond?

Acute cooling of the feet and the onset of common cold symptoms

The effect of falsely balanced reporting of the autism–vaccine controversy on vaccine safety perceptions and behavioral intentions

Climate change: an urgent priority for health policy and systems research

Power, control, communities and health inequalities I: theories, concepts and analytical frameworks

Research ethics in context: understanding the vulnerabilities, agency and resourcefulness of research participants living along the Thai–Myanmar border

Tobacco smoking and mortality among Aboriginal and Torres Strait Islander adults in Australia

Quality and safety in the time of Coronavirus: design better, learn faster

Years of life lost associated with COVID-19 deaths in the United States

In-flight transmission of SARS-CoV-2: a review of the attack rates and available data on the efficacy of face masks

Stability of the Initial Diagnosis of Autism Spectrum Disorder by DSM-5 in Children: A Short-Term Follow-Up Study

Impact of Tobacco Smoking on the Risk of COVID-19: A Large Scale Retrospective Cohort Study

Mental health of staff working in intensive care during COVID-19

The benefits and costs of social distancing in high- and low-income countries

A classification tree to assist with routine scoring of the Clinical Frailty Scale

Recent Advances in the Potential of Positive Allosteric Modulators of the GABAB Receptor to Treat Alcohol Use Disorder

The recent oubreak of smallpox in Meschede, West Germany

Your Hair or Your Service: An Issue of Faith for Sikh Healthcare Professionals During the COVID-19 Pandemic

Emerging Infections: Pandemic Influenza

Identifying the views of adolescents in five European countries on the drivers of obesity using group model building 

Novel multi-virus rapid respiratory microbiological point-of-care testing in primary care: a mixed-methods feasibility evaluation

Public health crisis in the refugee community: little change in social determinants of health preserve health disparities

In search of ‘community’: a critical review of community mental health services for women in African settings

COVID-19, a tale of two pandemics: novel coronavirus and fake news messaging 

Disrupting vaccine logistics

Use of directed acyclic graphs (DAGs) to identify confounders in applied health research: review and recommendations

Measurement and monitoring patient safety in prehospital care: a systematic review

Black Lives Matter protests and COVID-19 cases: relationship in two databases

The positive impact of lockdown in Wuhan on containing the COVID-19 outbreak in China

Severe Malnutrition and Anemia Are Associated with Severe COVID in Infants

A Single-Arm, Open-Label, Pilot, and Feasibility Study of a High Nicotine Strength E-Cigarette Intervention for Smoking Cessation or Reduction for People With Schizophrenia Spectrum Disorders Who Smoke Cigarettes

Healthcare workers and protection against inhalable SARS-CoV-2 aerosols

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Development of Conceptual Models to Guide Public Health Research, Practice, and Policy: Synthesizing Traditional and Contemporary Paradigms

Sonya s. brady.

Division of Epidemiology & Community Health, University of Minnesota School of Public Health, Minneapolis, MN, 55454, USA

Linda Brubaker

Department of Obstetrics, Gynecology and Reproductive Sciences, University of California San Diego, La Jolla, California, 92037, USA

Cynthia S. Fok

Department of Urology, University of Minnesota Medical School, Minneapolis, MN, 55454, USA

Sheila Gahagan

Division of Academic General Pediatrics, University of California San Diego, San Diego, CA, 92093, USA

Cora E. Lewis

Department of Epidemiology, School of Public Health, University of Alabama at Birmingham, Birmingham, AL, 35294, USA

Jessica Lewis

Yale School of Public Health, New Haven, CT, 06520, USA

Jerry L. Lowder

Division of Female Pelvic Medicine and Reconstructive Surgery, Washington University in St. Louis School of Medicine, St. Louis, MO, 63110, USA

Jesse Nodora

Department of Family Medicine and Public Health and Moores UC San Diego Cancer Center, University of California San Diego, La Jolla, CA, 92161, USA

Ann Stapleton

Department of Medicine, University of Washington, Seattle, WA, 98195, USA

Mary H. Palmer

School of Nursing, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA

This applied paper is intended to serve as a “how to” guide for public health researchers, practitioners, and policy makers who are interested in building conceptual models to convey their ideas to diverse audiences. Conceptual models can provide a visual representation of specific research questions. They also can show key components of programs, practices, and policies designed to promote health. Conceptual models may provide improved guidance for prevention and intervention efforts if they are based on frameworks that integrate social ecological and biological influences on health and incorporate health equity and social justice principles. To enhance understanding and utilization of this guide, we provide examples of conceptual models developed by the P revention of L ower U rinary Tract S ymptoms (PLUS) Research Consortium. PLUS is a transdisciplinary U.S. scientific network established by the National Institutes of Health in 2015 to promote bladder health and prevent lower urinary tract symptoms, an emerging public health and prevention priority. The PLUS Research Consortium is developing conceptual models to guide its prevention research agenda. Research findings may in turn influence future public health practices and policies. This guide can assist others in framing diverse public health and prevention science issues in innovative, potentially transformative ways.

Public health and prevention science students, researchers, practitioners, and policy makers all stand to benefit by becoming skilled in the development of conceptual models. Over 25 years ago, Jo Anne Earp and Susan Ennett (1991) described how a conceptual model could be used to depict the mechanisms by which a selected set of risk and protective factors may be associated with a health behavior or outcome of interest, as well as the conditions under which such associations are typically observed. This work demonstrated how conceptual models can be used to provide a visual representation of specific research questions and display the key components of prevention and intervention programs, practices, and policies designed to promote health. Since Earp and Ennett’s contribution, many publications that can be used to generate conceptual models have been introduced to the public health sphere. These writings describe frameworks that integrate social ecological and biological influences on health and highlight the potential for health equity and social justice principles to guide public health research, practice, and policy. By integrating diverse perspectives, those who design conceptual models can consider a wide range of factors that may influence health. A better understanding of what influences health can lead to the development of more effective health promotion programs, practices, and policies, as well as more efficient use of limited public health resources. Conceptual model development is an increasingly valued skill. For example, the National Institutes of Health have called for the inclusion of conceptual models when teams of researchers and practitioners respond to specific requests for proposals to conduct research on health promotion, including mental health (RFA-MH-18-705), bladder health (RFA-DK-19-015), and shared decision-making between patients and providers (PA-16-424; NIH, n.d. ).

This paper is intended to serve as a contemporary guide for building conceptual models. It is consistent with the mission of Health Promotion Practice to publish practical tools that advance the science and art of health promotion and disease prevention, particularly with respect to achieving health equity, addressing social determinants of health, and advancing evidence-based health promotion practice. To enhance understanding, examples of conceptual model development are provided from the P revention of L ower U rinary Tract S ymptoms (PLUS) Research Consortium, a transdisciplinary scientific network established by the National Institute of Diabetes and Digestive and Kidney Diseases in 2015 to study bladder health and prevention of lower urinary tract symptoms (LUTS) in girls and women ( Harlow et al., 2018 ). LUTS encompass a variety of bothersome bladder symptoms, including urgency urinary incontinence (i.e., strong urge “to go” with urine loss before reaching a toilet), stress urinary incontinence (i.e., urine loss with physical activity or increases in abdominal pressure such as a cough or sneeze), bothersome frequent and/or urgent urination, nocturnal enuresis (i.e., bed-wetting), difficulty urinating, dribbling after urination, and bladder or urethral pain before, during, or after urination ( Abrams et al., 2010 ; Haylen et al., 2010). LUTS are common. For example, more than 200 million people worldwide and over 15% of women aged 40 years or older experience urinary incontinence, one of the most prevalent LUTS ( Minassian, Bazi, & Stewart, 2017 ; Norton & Brubaker, 2006 ).

While many multidisciplinary research networks focus on clinical treatment of LUTS, the PLUS Consortium stands alone in its focus on bladder health promotion and prevention of LUTS. Consistent with the World Health Organization’s (WHO) definition of health (WHO, 2006), the PLUS Consortium conceptualizes bladder health as “a complete state of physical, mental, and social well-being related to bladder function, and not merely the absence of LUTS,” with function that “permits daily activities, adapts to short term physical or environmental stressors, and allows optimal well-being (e.g., travel; exercise; social, occupational, or other activities)” ( Lukacz et al., 2018 ).

Conceptual models are different from other tools and concepts.

Table 1 highlights the distinction between conceptual models and closely related visual tools and concepts. The contrast between conceptual frameworks and conceptual models is of particular relevance to the present guide. A research-oriented conceptual framework encapsulates what is possible to study and is intentionally comprehensive; in contrast, a research-oriented conceptual model encapsulates what a team has prioritized and chosen to study and is intentionally focused in scope ( Earp & Ennett, 1991 ; Brady et al., 2018 ). Similarly, conceptual frameworks and models may depict the “universe” and selected focus, respectively, of public health practices and policies. The contrast between a theory and conceptual model is also of particular relevance to the present guide. While both theories and conceptual models describe associations among constructs in order to explain or predict outcomes, a theory is intentionally broad with respect to application. It can guide the development of one or more conceptual models to address a specific public health behavior or outcome. While a review of prominent theories is beyond the scope of this paper, several public health textbooks provide an overview of theories that may be used to guide etiologic research and health promotion programs, practices, and policies (e.g., DiClemente, Salazar, & Crosby, 2019 ; Edberg, 2015 ; Glanz, Rimer, & Viswanath, 2015 ; Simons-Morton, McLeroy, & Wedndel, 2012 ).

Distinctions between conceptual models and other visual tools and concepts used in public health and related disciplines.

Traditional and contemporary conceptualizations of public health can identify a broad range of factors that may function as determinants of health.

Traditional conceptual frameworks include social ecological and biopsychosocial models. Social ecological models , a foundation of public health approaches for more than 40 years ( McLeroy, Bibeau, Steckler, & Glanz, 1988 ; Sallis & Owen, 2015 ; Richard, Gauvin, & Raine, 2011 ), situate individuals within an ecosystem of risk and protective factors that extend outward from the intrapersonal level (e.g., biology, psychology) through the interpersonal (e.g., family, peers, partner), institutional (e.g., school, workplace, health clinic), community (e.g., cultural norms), and societal (e.g., policies, laws, economics) levels. These nested spheres of influence interact to produce individual and population health. Similarly, the biopsychosocial model posits that health is defined by a complex reciprocal interaction of biological, psychological, and social factors ( Engel, 1981 ). Given the focus of this paper, we note that both social ecological and biopsychosocial models are more consistent with the definition of a conceptual framework than a conceptual model (see Table 1 ).

Contemporary conceptualizations of public health enhance traditional frameworks by more explicitly integrating biology and social ecology, adopting life course perspectives, and incorporating health equity, social justice, and community engagement principles to guide research, practice, and policy. The Society-Behavior-Biology Nexus depicts nested spheres of influences both within and outside of an individual, who moves through life stages from infancy to old age ( Glass & McAtee, 2006 ). Systems of biological organization include multi-organ systems, cellular and molecular influences, and the genomic substrate. Levels of ecology include the micro (e.g., family, social networks), mezzo (e.g., schools, worksites, communities, healthcare systems), macro (e.g., states, nations), and global (e.g., geopolitics, environment). Biology and social ecology are integrated through the multi-level concept of embodiment (e.g., gene-environment interactions; impact of varying social-ecological resources on biology within and across populations) ( Glass & McAtee, 2006 ; Krieger, 2005 ). Social determinants are framed as societal constraints against and opportunities for health – risk regulators – which include material conditions; discriminatory practices, policies, and attitudes; neighborhood and community conditions; behavioral norms, rules, and expectations; conditions of work; and laws, policies, and regulations. Risk regulators can impact behavior or become embodied with respect to biological function ( Glass & McAtee, 2006 ; Krieger, 2005 ).

The WHO Conceptual Framework for Action on Social Determinants of Health describes how the structure of societies (i.e., governance, policies, values) determines population health ( Solar & Irwin, 2010 ). Social stratification by race, ethnicity, sex, gender, social class, and other factors leads to social hierarchies, which in turn shape social determinants of health. Distal structural determinants of health inequities (e.g., public policy, macroeconomics) are distinguished from more proximal social determinants of health (e.g., living and working conditions). The WHO framework asserts that societies produce health and disease, obligating policy makers to promote health equity and redress structural factors that produce under-resourced communities. Without such attention, health inequities evolve, often widening over time and across generations. The WHO framework can inform conceptual model development by encouraging the consideration of determinants at distal, structural levels (e.g., national policies).

Research teams have utilized contemporary conceptualizations of public health to promote health equity and social justice ( Warnecke et al., 2008 ; Balazs & Ray, 2014 ). For example, the National Institutes of Health (NIH) sponsored Centers for Population Health and Health Disparities developed a framework to show how distal factors (population-level policies and social conditions, institutional contexts) influence intermediate social context (e.g., collective efficacy, social capital), social relationships (e.g., networks, support, and influence), and physical context (e.g., building quality, neighborhood stability), which in turn influence factors that are more proximal to health (individual demographics and risk behaviors, biologic responses and pathways) ( Warnecke et al., 2008 ). The Energy and Resources Group at the University of California, Berkeley developed a framework to display mechanisms through which natural, built, and sociopolitical factors, along with state, county, and community actors, can create drinking water disparities ( Balazs & Ray, 2014 ). These frameworks highlight the key role of distal structural factors in both generating health inequities and remedying them.

Community partners can aid in developing conceptual models.

Increasingly, teams are incorporating community-engaged approaches in the development of research, practice, and policy (e.g., community members actively contributing to problem definition, agenda setting, implementation, and dissemination) ( Warnecke et al., 2008 ; O’Mara-Eves et al., 2013 ). Different resources exist to guide community engagement and enhance the likelihood of sustained, relevant action. For example, Lezine and Reed (2007) outlined different steps to build and apply political will in the development and implementation of public health policy; their approach integrates scientific evidence and community participation. Cacari-Stone and colleagues (2014) developed a conceptual model to show how community-based participatory research (CBPR), one approach to community engagement, can lead to policy change.

Three Steps of Conceptual Model Development.

The development of conceptual models can be divided into three basic steps: (1) identify resources for idea generation; (2) consider risk and protective factors; and (3) select factors for inclusion in the conceptual model. First, team members identify existing conceptual frameworks and models, theories, and key stakeholders (e.g., practitioners, policy makers, community members) that will serve as resources for idea generation. This step defines the “universe” of factors that can be studied in relation to specific health behaviors or outcomes of interest. Second, team members systematically consider risk and protective factors suggested by resources. This step highlights the importance of carefully selecting resources for idea generation; the risk and protective factors considered by a team will be constrained by its selected frameworks and models, theories, and stakeholders. Existing evidence linking risk and protective factors to the health behaviors or outcomes under study, as well as potential effect modifiers and confounders, can be identified through literature reviews. When data are insufficient, a team may wish to conduct key stakeholder interviews, focus groups, and other forms of hypothesis-generating data collection. The third step in the development of conceptual models is to narrow down considered risk and protective factors to those that will be included in the conceptual model. This can be achieved through a combination of theoretically-based, key stakeholder-based, and evidence-based rationales. Theories point to clusters of risk and protective factors that could be studied in relation to health behaviors or outcomes of interest, or targeted through prevention or intervention efforts. Key stakeholders can assess the relevance of different theories to a given public health context and suggest additional risk and protective factors that seem critical to the context. Findings from the extant literature can provide evidence in support of different links in the conceptual model.

If the intent of building a conceptual model is to develop an evidence-based program, practice, or policy, a team can conduct a literature review to answer the following “narrowing down” questions: (a) Is the risk or protective factor strongly linked to the health behavior or outcome of interest? (b) Have previous prevention or intervention programs, practices, or policies shown that the risk or protective factor is feasible to modify? (c) Was health improved as a result of modifying the risk or protective factor? Risk and protective factors can be retained in the conceptual model if they are strongly supported by evidence and judged highly relevant to context.

When the intent of building a conceptual model is to conduct research to better understand a health behavior or outcome, a team may choose to consult existing theories, key stakeholders, and the evidence-base for guidance in selecting risk and protective factors. To maximize potential public health impact, a team can answer the following “narrowing down” question: What potential risk and protective factors are judged to be highly likely to influence health behaviors or outcomes of interest? Ideally, the answers to public health research questions will expand the evidence base in a way that can directly inform programs, practices, and policies. Expansion of the evidence-base can be accomplished in a variety of potentially transformative ways, including the synthesis of ideas from more than one discipline and the application of paradigms from one discipline to another.

Regardless of the approach and rationale used to select risk and protective factors, the utility of the conceptual model may be enhanced by answering the final three sets of questions: (a) Have key “mechanistic factors” been considered and included in the model? What biological, psychological, and social processes might explain links between identified risk and protective factors and health behaviors or outcomes of interest? (b) Have key “upstream factors” been considered and included in the model? For example, are there societal and institutional policies and practices that serve as facilitators or barriers to health? (c) Have key “effect modifiers” been considered and included in the model? For example, are there factors that might make prevention or intervention programs, practices, or policies more or less effective among specific communities and populations?

Examples from the PLUS Research Consortium.

The PLUS Consortium is comprised of a transdisciplinary network of professionals, including community advocates, health care professionals, and scientists specializing in pediatrics, adolescent medicine, gerontology and geriatrics, nursing, midwifery, behavioral medicine, preventive medicine, psychiatry, neuroendocrinology, reproductive medicine, female pelvic medicine and reconstructive surgery, urology, infectious diseases, clinical and social epidemiology, prevention science, medical sociology, psychology, women’s studies, sexual and gender minority health, community-engaged research, community health promotion, scale development, research methods, and biostatistics. The PLUS Consortium has developed several conceptual models to guide research questions that will test whether specific risk and protective factors contribute to LUTS and bladder health.

Because the evidence-base for LUTS prevention is sparse, the traditional and contemporary conceptualizations of public health reviewed above, as well as expertise of PLUS investigators, were used as key resources to identify potential risk and protective factors for study (Step 1). Traditional and contemporary conceptualizations of public health encouraged consortium members to step outside of their disciplinary “comfort zones” to integrate social ecological and biological influences on health across the life course and consider the potential for health equity and social justice principles to guide the consortium’s prevention research agenda. While all of the conceptualizations reviewed above were considered, Glass and McAtee’s Society-Behavior-Biology Nexus was particularly influential because it visually represented different levels of social ecology and biology across the life course, as well as the process of embodiment. PLUS members served as an initial key stakeholder group that generated a conceptual framework and over 400 risk and protective factors prioritized for study in relation to bladder health and LUTS (Step 2) ( Brady et al., 2018 ). The conceptual models presented in this paper represent the work of subsets of consortium members who designed models to guide specific research questions (Step 3). Models were designed with the assistance of public health and prevention science team members who were familiar with social ecological frameworks and the development of conceptual models. Initial development of models occurred in real time during in-person and virtual (WebEx) meetings. This was often followed by revision of models via emailed chains of conversation. One person with experience in conceptual model development was responsible for integrating and communicating comments and mutual decisions, as well as revising the models.

Each conceptual model featured in this paper represents hypothesized associations between constructs; some links in each model are supported by existing evidence, while others are based on theoretical or biological plausibility. Figure 1 highlights institutional-level factors in relation to bladder health and LUTS, while Figure 2 highlights family- and community-level factors and Figure 3 highlights societal and commercial factors.

Work-related structural and social influences on musculoskeletal function and bladder health: Hypothesized mechanisms.

Explanation of Pathways: Four different work-related factors (shaded boxes) affect different aspects of musculoskeletal function, which in turn affect bladder health and LUTS. Workplace physical and psychological demands directly affect musculoskeletal function. Workplace ergonomics and travel/commute patterns indirectly affect musculoskeletal function through prolonged sitting or standing and posture (mediation pathways).

Trajectories of risk and resilience among individuals and communities exposed to ACEs and traumatic stressors: Hypothesized mechanisms.

Explanation of Pathways: Executive functioning difficulties and central nervous system dysregulation are shown in a single, partitioned box because these constructs are hypothesized to covary in their manifestation. Direct effects between two adjacent constructs are shown by solid lines (1a, 2a, 3a, 4, 5); effect modification by resources for resilience (shaded box) is shown by dashed lines (1b, 2b, 3b). ADHD: Attention-Deficit/Hyperactivity Disorder.

Societal and commercial influences on bladder health and LUTS: Hypothesized mechanisms involving fast food and soda.

Explanation of Pathways: This conceptual model highlights hypothesized mechanisms (mediators) that can explain associations between societal and commercial factors (shaded boxes) and bladder health and LUTS. This model can guide a set of statistical analyses that require the identification of predictor, mediating, and outcome variables. The model does not reflect the full complexity of associations that likely exist among constructs (e.g., bi-directional associations, feedback loops; see Systems Model entry in Table 1 ).

Figure 1 depicts a basic conceptual model showing how specific work-related structural and social factors may influence musculoskeletal function, which in turn may impact bladder health and LUTS development. Four key aspects of musculoskeletal dysfunction are overuse injury, strain, pain, and weakness (see center-right of Figure 1 ), which may be directly and indirectly influenced by work-related factors. The top, bottom, and left-most boxes depict work-related factors that are external to the individual and arguably imposed by society and institutions. Workplace physical and psychological demands are shown to directly impact musculoskeletal function. Workplace physical demands (e.g., repetitive heavy lifting) may result in musculoskeletal dysfunction, which in turn may lead to LUTS ( Park & Palmer, 2015 ). In addition, workplace psychological demands (e.g., job performance pressures, conflict with coworkers, inequitable expectations and evaluations of work) may be accompanied by stress, anxiety, and other forms of negative affect ( Larsman, Kadefors, & Sandsjö, 2013 ), which may lead to chronically increased pelvic floor muscle dysfunction and LUTS ( van der Velde, Laan, & Everaerd, 2001 ). Workplace ergonomics (e.g., improper chair or desk height) and travel/commute patterns (e.g., daily, long commutes and long airplane flights) may indirectly impact musculoskeletal dysfunction through prolonged sitting or standing and poor posture ( Barone Gibbs et al., 2018 ).

Additional research is needed to support hypothesized associations in Figure 1 , which are based in large part on the authors’ clinical and community-based observations. If different links are supported, corresponding workplace policies and practices can be promoted to ensure that physical demands are offset by varying the type and intensity of activity and providing breaks; psychological demands are fair, reasonable, and offset by supports; and workplace ergonomics are conducive to the health of all employees, regardless of status within the organization. In addition, local and state governments can support policies and practices that ensure adequate access to acceptable bathroom facilities along transportation routes and when possible, within public transportation conveyances.

Figure 2 shows an example of a more complex conceptual model. A trajectory of risk among individuals or communities exposed to adverse childhood experiences (ACEs) (e.g., abuse, neglect, household disruptions) (Felitti et al., 1998) and other traumatic stressors can be seen by following the solid lines from left to right. ACEs and traumatic stressors indirectly affect local dysregulation through two potential pathways: (I) development of executive functioning difficulties and central nervous system dysregulation (shown by 1a links) ( Nusslock & Miller, 2016 ; Smith et al., 2016 ), which in turn lead to local dysregulation (shown by link 4) ( Kanter et al., 2016 ); and (II) development of depression, anxiety, and ADHD symptoms (shown by 2a links), which in turn lead to executive functioning difficulties and central nervous system dysregulation (shown by link 3a) ( Nusslock & Miller, 2016 ), which then leads to local dysregulation (shown by link 4) ( Kanter et al., 2016 ; Yousefichaijan, Sharafkhah, Rafiei, & Salehi, 2016 ). Constructs that explain associations between stressful life circumstances and LUTS may collectively be thought of as a “chain of mediation,” in that they lie along a hypothesized causal, sequential pathway. Figure 2 also shows how a trajectory of risk/chain of mediation may be weakened or broken at different points along the pathway. The dashed lines of Figure 2 show modification of effects (“effect modification”) by resources for resilience (i.e., coping, social support). Effects of stressful life circumstances on LUTS are weakened in the presence of resources for resilience (shown by the dashed lines 1b, 2b, and 3b).

Although several of the links in Figure 2 are supported by evidence, additional research is needed. Figure 2 illustrates the importance of structural factors that stratify the citizens of a society into communities that are more or less likely to experience adverse childhood experiences and traumatic stressors, and have more or less opportunities to garner resources for resilience ( Glass & McAtee, 2006 ; Solar & Irwin, 2010 ; Warnecke et al., 2008 ). Policies attempting to ensure equitable allocation of resources, including but not limited to health care, are essential to preventing and weakening trajectories of risk that disproportionately impact under-resourced communities and families.

Figure 3 , our final example, highlights broader, societal and commercial influences on bladder health and LUTS, along with environmental, behavioral, and biological mechanisms specific to fast food and soda consumption. Consistent with the WHO Conceptual Framework for Action on Social Determinants of Health ( Solar & Irwin, 2010 ), Figure 3 begins with societal structures. Governance and policies shape the built environments of communities, in part through zoning of fast food restaurants, convenience stores, grocery stores, and farmers markets; these, in turn, impact the availability of fast food and soda in communities ( Sallis & Glanz, 2009 ). Additional policies can impact the affordability of fast food and soda relative to healthy products (e.g., taxation of sugar-sweetened beverages; subsidies for fresh produce) ( Franck, Grandi, & Eisenberg, 2013 ), as well as the advertising and marketing of fast food and beverages, especially towards children ( Harris et al., 2015 ). Low-income communities of color in the United States have historically received fewer resources as a result of inequitable policies; they have also been targeted by the fast food and soda industries ( Sallis & Glanz, 2009 ; Harris et al., 2015 ).

Availability, relative affordability, advertising, and marketing of fast food and soda within a community increase the likelihood that residents will consume “super-sized” food portions and soda, which contributes to obesity ( Sallis & Glanz, 2009 ; Harris et al., 2015 ). Obesity may directly impact LUTS by intra-abdominal pressure on the bladder ( Bavendam et al., 2016 ); it may also impact LUTS through diabetes-related mechanisms, including neurogenic bladder and urinary tract infections ( Bavendam et al., 2016 ; Podnar & Vodusek, 2015 ). Diet soda, which many individuals embrace as a means to reduce caloric intake and combat obesity, contains components that may increase urine volume (caffeine) and harm the health of the bladder lining (artificial sweeteners, carbonation/acidity) (Robinson, Hanna-Mitchell, Rantell, Thiagamoorthy, & Cardozo, 2015). A healthy bladder may be maintained or restored by healthy food and beverage choices; Figure 3 highlights constraints on healthy choices that are determined by upstream, societal factors.

Because the PLUS Research Consortium is just beginning its prevention research agenda, its current models are intended to guide etiologic research, as opposed to selection, implementation, and evaluation of health promotion and prevention strategies. Broader planning frameworks exist for this purpose, including PRECEDE-PROCEED and intervention mapping ( Bartholomew, Markham, Mullen, & Fernández, 2015 ; Bartholomew, Parcel, & Kok, 1998 ; Green & Kreuter, 2005 ), the Substance Abuse and Mental Health Services Administration’s (SAMHSA) Strategic Prevention Framework (2017) , and the Center for Disease Control and Prevention’s (CDC) Framework for Program Evaluation in Public Health (1999) . These frameworks not only guide practitioners in assessing risk and protective factors at different levels of social ecology that may influence health, but also provide a structure for applying theories and conceptual models to the planning and evaluation of health promotion programs, practices, and policies. The PLUS Research Consortium will utilize existing planning frameworks when its work progresses to the point of designing, implementing, and evaluating bladder health promotion and LUTS prevention strategies through research.

Lessons Learned and Recommendations for Other Conceptual Model Development Teams.

After developing the conceptual models and supporting materials presented in this paper, authors reflected on lessons they had learned and what they would recommend to other teams.

Recommendation 1: Develop a shared language.

Students, researchers, practitioners, and policy makers interested in developing conceptual models may benefit from reviewing the terms in Table 1 , determining what is consistent with and distinct from their own discipline and training, and identifying additional tools and concepts that could aid in conceptual model development. Few of this paper’s authors were initially familiar with all of the visual tools and related concepts defined in Table 1 . Terms were added not only by authors, but also by other PLUS Consortium members (e.g., epidemiologists recommended the inclusion of “directed acyclic graph” and “systems model”). Teams who are developing conceptual models may develop a shared language through the process of reviewing, adding, and defining terms.

Recommendation 2: Establish a conceptual framework before developing a conceptual model.

Authors appreciated the distinction between conceptual frameworks and models, particularly with respect to how a framework could be a starting point to broaden one’s conceptualization of health beyond one’s own disciplinary training. Consortium members valued the integration of social ecological, behavioral, and biological perspectives of what influences health, as well as the opportunity to incorporate multiple levels of influence into a single conceptual model and corresponding set of research questions. Consortium members appreciated how the creation and refinement of conceptual models could then assist in clarifying specific research questions; identifying potential pathways through which different risk and protective factors may influence a health outcome; examining and challenging one’s own disciplinary assumptions; and articulating what is known or speculative with respect to the factors that influence health.

Recommendation 3: Seek to develop a diverse team and solicit input from others.

Authors appreciated how steps of conceptual model development included the consideration of how community partners and other key stakeholders can become involved in the process of development. By design, the PLUS Research Consortium includes community advocates, community-engaged researchers, and health care professionals and scientists representing a broad array of disciplines. Authors did not reach beyond the PLUS Consortium to develop the conceptual models featured in this paper, in part because the present paper was intended to describe the process of conceptual model development, rather than to present definitive models. Other conceptual model development teams may benefit from soliciting the input of individuals who are not well represented on their team, including community members, researchers, practitioners, and policy makers.

Recommendation 4: Anticipate and embrace the iterative, “trial and error” nature of conceptual model development.

Early in the process of developing conceptual models, authors developed a shared understanding that it was not necessary for all proposed links in a conceptual model to be informed by existing evidence. Theory, clinical observations, and the lived experience of community members are valid sources of information, as well. Authors also came to appreciate that it was not necessary to develop the “perfect” model during a first attempt to understand a health behavior or outcome, or to select the key components of an evidence-based program, practice, or policy. Indeed, attempting to achieve perfection may stifle creativity and innovation. The conceptual models presented in this paper were developed iteratively, both within the team of authors and consortium members who assisted in their development (see Acknowledgements ). Conceptual models should be evaluated through research, which may support or fail to support proposed links in a model. Conceptual models are meant to be refined, not only during their initial stage of development, but also in response to new information that is gleaned through subsequent research.

Summary and Conclusion.

Researchers, practitioners, and policy makers can use conceptual models to convey ideas to diverse audiences. We posit that conceptual models may have the greatest impact on public health if they integrate social ecological and biological influences on health and highlight the potential for health equity and social justice principles to guide public health research, practice, and policy. To illustrate this point, we have provided examples of conceptual model development from the P revention of L ower U rinary Tract S ymptoms (PLUS) Research Consortium, a transdisciplinary scientific network established in the United States in 2015 to promote bladder health and prevent lower urinary tract symptoms, an emerging public health and prevention priority. The PLUS Consortium is developing conceptual models to guide its bladder health promotion and LUTS prevention research agenda. In concert with other researchers and community partners, the PLUS Consortium will be poised to inform future public health practices and policies. We hope our shared work will assist others in framing diverse public health matters in innovative, potentially transformative ways.

Acknowledgements

The authors acknowledge special contributions to featured conceptual models by the following PLUS Research Consortium members: Amanda Berry, Neill Epperson, Colleen Fitzgerald, Missy Lavender, Ariana Smith, and Beverly Williams. The authors also acknowledge the foundational work of Jo Anne Earp, Professor Emerita, and Susan T. Ennett, Professor, Department of Health Behavior, Gillings School of Public Health, University of North Carolina, Chapel Hill. Dr. Earp and Dr. Ennett’s pioneering “how to” guide for building conceptual models, published in 1991, inspired the present guide. In addition, the authors acknowledge Kenneth L. McLeroy, Professor Emeritus and retired Regents and Distinguished Professor, School of Public Health, Texas A&M University, for helpful discussion about manuscript content.

Participating PLUS research centers at the time of this writing are as follows:

Loyola University Chicago - 2160 S. 1 st Avenue, Maywood, Il 60153-3328

Linda Brubaker, MD, MS, Multi-PI; Elizabeth Mueller, MD, MSME, Multi-PI; Colleen M. Fitzgerald, MD, MS, Investigator; Cecilia T. Hardacker, RN, MSN, Investigator; Jeni Hebert-Beirne, PhD, MPH, Investigator; Missy Lavender, MBA, Investigator; David A. Shoham, PhD, Investigator

University of Alabama at Birmingham - 1720 2nd Ave South, Birmingham, AL 35294

Kathryn Burgio, PhD, PI; Cora E. Lewis, MD, MSPH, Investigator; Alayne Markland, DO, MSc, Investigator; Gerald McGwin, PhD, Investigator; Beverly Williams, PhD, Investigator

University of California San Diego - 9500 Gilman Drive, La Jolla, CA 92093-0021

Emily S. Lukacz, MD, PI; Sheila Gahagan, MD, MPH, Investigator; D. Yvette LaCoursiere, MD, MPH, Investigator; Jesse N. Nodora, DrPH, Investigator

University of Michigan - 500 S. State Street, Ann Arbor, MI 48109

Janis M. Miller, PhD, MSN, PI; Lawrence Chin-I An, MD, Investigator; Lisa Kane Low, PhD, MS, CNM, Investigator

University of Pennsylvania – Urology, 3rd FL West, Perelman Bldg, 34th & Spruce St, Philadelphia, PA 19104

Diane Kaschak Newman, DNP, ANP-BC, FAAN PI; Amanda Berry, PhD, CRNP, Investigator; C. Neill Epperson, MD, Investigator; Kathryn H. Schmitz, PhD, MPH, FACSM, FTOS, Investigator; Ariana L. Smith, MD, Investigator; Ann Stapleton, MD, FIDSA, FACP, Investigator; Jean Wyman, PhD, RN, FAAN, Investigator

Washington University in St. Louis - One Brookings Drive, St. Louis, MO 63130

Siobhan Sutcliffe, PhD, PI; Colleen McNicholas, DO, MSc, Investigator; Aimee James, PhD, MPH, Investigator; Jerry Lowder, MD, MSc, Investigator;

Yale University - PO Box 208058 New Haven, CT 06520-8058

Leslie Rickey, MD, PI; Deepa Camenga, MD, MHS, Investigator; Shayna D. Cunningham, PhD, Investigator; Toby Chai, MD, Investigator; Jessica B. Lewis, PhD, MFT, Investigator

Steering Committee Chair: Mary H. Palmer, PhD, RN: University of North Carolina

NIH Program Office: National Institute of Diabetes and Digestive and Kidney Diseases, Division of Kidney, Urologic, and Hematologic Diseases, Bethesda, MD

NIH Project Scientist: Tamara Bavendam MD, MS; Project Officer: Ziya Kirkali, MD; Scientific Advisors: Chris Mullins, PhD and Jenna Norton, MPH; Scientific and Data Coordinating Center (SDCC): University of Minnesota - 3 Morrill Hall, 100 Church St. S.E., Minneapolis MN 55455

Bernard Harlow, PhD, Multi-PI; Kyle Rudser, PhD, Multi-PI; Sonya S. Brady, PhD, Investigator; John Connett, PhD, Investigator; Haitao Chu, MD, PhD, Investigator; Cynthia Fok, MD, MPH, Investigator; Todd Rockwood, PhD, Investigator; Melissa Constantine, PhD, MPAff, Investigator

This work of the Prevention of Lower Urinary Tract Symptoms (PLUS) Research Consortium was supported by the National Institutes of Health (NIH) through cooperative agreements (grant numbers U01DK106786, U01DK106853, U01DK106858, U01DK106898, U01DK106893, U01DK106827, U01DK106908, U01DK106892). Additional support was provided by the National Institute on Aging, NIH Office of Research on Women’s Health, and NIH Office of Behavioral and Social Sciences Research. The content of this article is solely the responsibility of the authors and does not necessarily represent the official views of NIH.

Contributor Information

Sonya S. Brady, Division of Epidemiology & Community Health, University of Minnesota School of Public Health, Minneapolis, MN, 55454, USA.

Linda Brubaker, Department of Obstetrics, Gynecology and Reproductive Sciences, University of California San Diego, La Jolla, California, 92037, USA.

Cynthia S. Fok, Department of Urology, University of Minnesota Medical School, Minneapolis, MN, 55454, USA.

Sheila Gahagan, Division of Academic General Pediatrics, University of California San Diego, San Diego, CA, 92093, USA.

Cora E. Lewis, Department of Epidemiology, School of Public Health, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.

Jessica Lewis, Yale School of Public Health, New Haven, CT, 06520, USA.

Jerry L. Lowder, Division of Female Pelvic Medicine and Reconstructive Surgery, Washington University in St. Louis School of Medicine, St. Louis, MO, 63110, USA.

Jesse Nodora, Department of Family Medicine and Public Health and Moores UC San Diego Cancer Center, University of California San Diego, La Jolla, CA, 92161, USA.

Ann Stapleton, Department of Medicine, University of Washington, Seattle, WA, 98195, USA.

Mary H. Palmer, School of Nursing, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.

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Public health and research: an overview

Journal of Health Research

ISSN : 2586-940X

Article publication date: 15 October 2020

Issue publication date: 15 June 2021

This paper was to describe the overview of public health research.

Design/methodology/approach

It is a commentary piece of work from own long experience in working with the World Health Organization.

This study has innovative ideas in approaching priority areas in public health research.

Originality/value

This study opens up new thought in public health research.

• Public health

Public health research

Plianbangchang, S. (2021), "Public health and research: an overview", Journal of Health Research , Vol. 35 No. 4, pp. 374-378. https://doi.org/10.1108/JHR-03-2020-0074

Emerald Publishing Limited

Copyright © 2020, Samlee Plianbangchang

Published in Journal of Health Research . Published by Emerald Publishing Limited. This article is published under the Creative Commons Attribution (CC BY 4.0) licence. Anyone may reproduce, distribute, translate and create derivative works of this article (for both commercial and non-commercial purposes), subject to full attribution to the original publication and authors. The full terms of this licence may be seen at http://creativecommons.org/licences/by/4.0/legalcode

An overview of public health

Public health is the science and art of preventing disease, prolonging life and promoting human health through organized community efforts as well as the informed choice of society, public, private and voluntary organizations and communities at large. Analyzing the health of a population and the threats to that health forms the basis for public health.

Additionally, “health”, as defined in the WHO Constitution in 1948 [ 1 ], considers physical, mental and social well-being and is not merely the absence of disease or infirmity. Furthermore, public health is interdisciplinary, thus, a “public health team” may include several related disciplines in health and other social fields. Access to public health initiatives for comprehensive and integrated health care and services is always a difficult challenge in any population setting.

The objective of this commentary is to provide an overview of public health research and highlight innovative thinking in the field.

Public health systems

Public health systems are commonly defined as “all public, private, and voluntary entities that contribute to the delivery of essential public health services to people within a jurisdiction” [ 2 ]. This concept is to ensure, among other things, that all contributions to the improved health and well-being of the community or state are appropriately recognized and counted in the assessment of the provision of public health services to the community. The public health system includes public health agencies at state and local levels; all healthcare providers; public safety agencies; human services and charity organizations; education and youth development agencies; recreation and art-related organizations; economic and philanthropic agencies and environmental organizations.

The 10 essential public health services/functions

Monitoring community health situations to identify and solve health problems and prevent any health risks in the community;

Investigating and diagnosing specific health threats and health hazards in the community with the view to their early prevention;

Through modern technology in communication, informing, educating and empowering people in the community about health issues and challenges and their interventions;

Identifying/investigating and solving any problems of public health importance;

Through the full participation of people, developing policies and plans that support individual and combined health efforts in the community;

Ensuring effective enforcement of laws and regulations that protect environmental health and assure the safety of the population;

Linking people to needed personal health services and ensuring the provision of quality health care when otherwise unavailable;

Assuring the availability of effective public health workforce and competent healthcare personnel in both public and private facilities;

Objectively evaluating efficiency, effectiveness, accessibility and quality of personal as well as population-based health care facilities and services and

Undertaking study/research for new insights and innovative solutions to effectively counter prevailing and emerging health problems.

Public health rsearch aims to elucidate the influence of factors that determine the health of a population, i.e. genetic, environmental, social-cultural, economic, political, etc. The objective of public health research is to use the knowledge gained to propose policies and interventions, based on scientific evidence, and to help improve the health and well-being of the population and ultimately reduce/eradicate health inequalities.

Public health research is characterized by its multidisciplinary approach. It draws on several disciplines in its development and management, especially epidemiology/human ecology; biostatistics; physical and social sciences as applied to health; biology; genetics and toxicology. It usually entails the analysis of data on population samples on varying scales, depending on the scope and purpose of the research [ 4 ].

In practical terms, public health researchers study the statuses of population health and well-being, disability and loss of independence. They analyze the determining risk factors of these statuses or conditions, whether biological, behavioral, psycho-social or environmental. In addition, the researchers develop and assess the interventions aiming to effectively promote population health, prevent disease and compensate for disabilities and loss of independence. They also develop and assess innovation to improve efficiency and effectiveness of the organization of healthcare facilities and personnel, in public health, medical and other social service areas.

Research in health may be in the fields of health research, medical research, public health research, health services research, health systems research, environmental health research and others. These are interlinked and need to be pursued in a parallel manner in public health development.

Funding agencies

Mission and role of funding agencies

(2)Quality of research proposal

Relevance to current health-related issues and problems; responding to priority public health needs and the challenges of community and country are crucial. Applications should also be in the interest of the international/global health community.

Formulation with rational and logical thinking; Research proposals should be well-conceived and developed according to sound research methodology/protocol on epidemiological principles.

Expected result of the proposal; The result must be of high quality and should imply strong feasibility in its subsequent application/implementation in both technical, managerial and financial terms.

Public health system development research

DEIDS (development and evaluation of integrated health delivery system) (Thailand Lampang Health Development Project), 1973-1978 [ 6 ].

(2)District Health Services Development Project based on the principle of the primary health care approach, Mongar Health Development Project in Bhutan, 1984–1990 [ 7 ].

(3)Comprehensive and Integrated Health Research Development Project on hill- tribe population, 2014–present (still ongoing)

This is a long-term large research and development project with many sub-projects focusing on various specific issues of the target population. It is a multi-agency and interdisciplinary endeavor developed and implemented through the coordination of the Maefah Luang University Center of Excellence on health of the hill-tribe population. It includes the development of integrated and comprehensive social and health care services with an emphasis on equity, social justice and self-reliance in the community. There are multiple sources of funding, however mainly from the National Research Council of Thailand.

Some suggested areas for contemporary public health research

Universal health coverage for all

Financial sustainability in the long term

Equal accessibility by all people, regardless of their social and economic status

The right approach to development, proactive or passive strategy

Affordability in financial and managerial terms of the country concerned.

(2)Social impact of drug abuse /addiction

The social and economic impact of (chaotic situations created by) drug abuse and addiction

The general health of a population that is gradually undermined by drug abuse and drug addiction, leading, among other things to worsened national social and economic growth.

(3)Health and social care of elderly population

Intervention to reduce the degree of morbidity/disability and dependence

Efforts to increase social and economic productivity/independence

Program for self-help and self-reliance in an aged population

Preference between aging and aged programs, the difference between the two.

(4)Emerging infectious disease (EID)

The epidemiological, environmental and ecological approach in an integrated manner

The importance of social and behavioral change

Emerging mutation, assortment and genetic change in infectious agents

Impact of global climate change on EID, etc.

Even though it is mainly conceptual, the article may be able to help open new visions in public health research for better and sustainable health in the entire population in various localities.

1 World Health Organization [WHO] . WHO basic document . 47th ed. Geneva : WHO ; 2009 [cited 2019 Nov 28]. Available from: https://apps.who.int/iris/handle/10665/44192 .

2 World Health Organization [WHO] . What is health policy and systems research (HPSR)? [cited 2019 Nov 28]. Available from: https://www.who.int/alliance-hpsr/about/hpsr/en/ .

3 Centers for Disease Control and Prevention [CDC] , Office for state, tribal, local and territorial support . The 10 Essential Public Health Services: An Overview [cited 2019 Nov 28]. Available from: https://www.cdc.gov/publichealthgateway/publichealthservices/pdf/essential-phs.pdf .

4 Centers for Disease Control and Prevention [CDC] . Public health 101 series [cited 2019 Nov 28]. Available from: https://www.cdc.gov/publichealth101/ .

5 Centers for Disease Control and Prevention [CDC] . 24/7 Saving Lives, Protecting People [cited 2019 Nov 28]. Available from: https://www.cdcfoundation.org/cdc-247-saving-lives-protecting-people# .

6 Memoir on Occasion of the Death Anniversary of Dr. Somboon Vacharothai . Bangkok ; 2014 : 39 - 43 . (On Thailand DEIDS Project) .

7 World Health Organization [WHO] , Regional office for south-east asia [SEARO]. Sasakawa health prize: stories from south-east asia . New Delhi : WHO/SEARO ; 2012 : 125 - 146 [cited 2019 Nov 28]. Available from: https://apps.who.int/iris/bitstream/handle/10665/205878/B4905.pdf?sequence=1&isAllowed=y .

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• 15 May 2024

Neglecting sex and gender in research is a public-health risk

• Sue Haupt 0 ,
• Cheryl Carcel 1 &
• Robyn Norton 2

Sue Haupt is an honorary senior research fellow at Peter MacCallum Cancer Centre in Melbourne, Australia, and a research associate at The George Institute for Global Health, Women’s Health Program, Centre for Sex and Gender Equity in Health and Medicine, University of New South Wales (UNSW) Sydney, Australia.

You can also search for this author in PubMed   Google Scholar

Cheryl Carcel is the head of the brain health programme at The George Institute for Global Health UNSW Sydney, Australia.

Robyn Norton is a founding director of The George Institute for Global Health, a professor of public health at UNSW Sydney and chair of global health at Imperial College London, UK.

Illustration: Sophi Gullbrants

You have full access to this article via your institution.

In 2022, clinical trials indicated that a drug called lecanemab could slow cognitive decline in people with Alzheimer’s disease; soon after the results were published, the global Alzheimer’s community heralded lecanemab as a momentous discovery. However, closer inspection of the data by independent investigators revealed that the drug might significantly help men, but not women 1 .

The finding is a reminder that, even though tremendous advances are being made in the clinical application of cutting-edge technologies, such as gene editing and artificial intelligence (AI), there is a remarkable lack of understanding about how many aspects of human health are affected by variables as seemingly basic as sex and gender.

Sex and gender in science

Over the past decade or so, funders and publishers have made extensive efforts to encourage researchers to address the effects of sex and, in human studies, gender where appropriate. Thanks in part to these efforts, more insights are beginning to emerge. For Alzheimer’s and many other diseases that are common causes of death, including cardiovascular diseases, cancer, chronic respiratory conditions and diabetes, a person’s sex and gender can influence their risk of developing the disease, how quickly and accurately they are diagnosed, what treatment they receive and how they fare.

But even for the most-studied conditions, many questions remain. Few investigators have begun to probe the interrelationships between sex and gender , for example. And in cases in which researchers are managing to unpick the multifaceted effects of sex, this knowledge is not being sufficiently incorporated into the design of clinical trials or adequately changing the practice of medicine.

The consideration of sex and, where appropriate, gender in biological research must become routine — especially as molecular genetics, biomedical engineering and AI open up possibilities for treatments that are better tailored to the needs of individuals. Likewise, the culture of medicine must be transformed so that approaches to treatment evolve in response to the data. This will require further engagement from funders and publishers, but action from many other players, too. Pharmaceutical companies and intergovernmental organizations, among others, must acknowledge three things: how sex and gender can have huge effects on health outcomes; how these effects are often disregarded in basic research and clinical trials; and that change can come only through increasing awareness among all stakeholders of the importance of shifting the dial.

Health outcomes affected

In most human clinical records so far, sex is reported by physicians or participants in studies ticking one of two boxes: ‘female’ or ‘male’. In those clinical studies in which data are collected on chromosomes, hormone levels, reproductive anatomy or other sex characteristics, these features will frequently reflect a person’s sex assigned at birth. But this is not always the case. Added to this, sex and gender have often been used interchangeably, but they are not the same and they do not always align. Current definitions of gender include the social, psychological, cultural and behavioural aspects of being a man or woman (whether cisgender or transgender), non-binary or identifying with one or more other evolving terms 2 .

In several countries, new recommendations about how researchers should obtain data on people’s sex and gender should mean that, in the future, investigators will be able to more-accurately probe the roles of both in human health. But in general, there has been incomplete capture of information for sex and gender so far, including for individuals whose sex characteristics and/or gender identities don’t fall into a binary categorization scheme.

Women are more likely to die after a severe heart attack than are men. Credit: Simon Dawson/Reuters

In this article, consistent with much of the published population-wide data, we refer to a woman as someone who identifies with that gender and was assigned female sex at birth (a cis woman), and a man as someone who identifies with that gender and was assigned male sex at birth (a cis man). But we recognize that participants in the studies we describe might not have been asked about both their gender and their sex.

For all sorts of non-communicable diseases, there are differences between men and women in the average age at which they are diagnosed, the average age at which they die and even in their rates of death.

We need more-nuanced approaches to exploring sex and gender in research

Such variations, from the earlier onset of cardiovascular diseases in men to the more frequent occurrence of Alzheimer’s disease in women, might stem from differences in biology, which can affect people’s likelihood of developing a disease and how they respond to treatment. Or these discrepancies might stem from variation in people’s exposure to the environmental factors that trigger the disease, how they manage their condition, how they are treated by carers and so on, all of which can be influenced by a person’s gender. Often, a combination of factors will be at work.

Take heart attacks. Studies conducted over the past decade have revealed extensive sex differences in the expression of certain genes in heart tissue, which in turn affect the type and function of the cells that make up the heart.

Such variation could help to explain why men are likely to have a heart attack for the first time around six years earlier than women — in the United States, at 65.6 years old in men compared with 72 years old in women 3 — and why (in Australia, at least) heart attacks are at least twice as common in men relative to women of comparable ages (see go.nature.com/3qbvrxq ). Likewise, although mechanisms are yet to be fully understood, it is plausible that differences in people’s biology help to explain why women are more likely to experience pain between their shoulder blades, nausea or vomiting and shortness of breath during a heart attack; why men are more likely to experience chest pain and increased sweating; and why women are nearly twice as likely as are men to die after a severe heart attack.

Yet, when it comes to the risk of dying, social and environmental factors — shaped by gender — also seem to be important.

Tobacco consumption increases a person’s risk of having a heart attack, and smoking is much more common among men globally. Worldwide, around 37% of men smoke compared with around 8% of women . Also, in part because health-care professionals and others are more familiar with the heart attack symptoms commonly seen in men, when women have a heart attack, they are more likely to delay seeking help, and carers are often slower to intervene 4 . In fact, in a study of more than 500,000 people who experienced a heart attack and were admitted to hospital in the United Kingdom between 2004 and 2013, women were 37% more likely to receive an incorrect initial diagnosis after a severe heart attack than were men 5 . Even when women tell their physicians that they have chest pain, they are two to three times less likely to be referred to a cardiologist than are men 6 .

A similarly complicated picture has been emerging in relation to strokes 7 — another cardiovascular disease — and, in the past few years, in relation to cancer.

Smoking is more common among men than women globally. Credit: Behrouz Mehri/AFP/Getty

Most cancers that occur in non-reproductive organs develop earlier in men than they do in women. In the United States, oesophageal cancer is 4.5 times more likely to occur and cause death in men than in women, for example, and lung cancers, the most common drivers of cancer-associated deaths worldwide, kill around 40% more men than women 8 .

Just as with heart disease and stroke, some of this variation seems to stem from behavioural differences. Tobacco consumption increases a person’s risk of developing several cancers 7 . For thyroid cancers, however, women are more likely to develop the disease than are men — three times more likely in some places — which suggests that other factors might drive the different rates of this particular cancer in women and men 9 . But tumours typically arise because of problems with cells’ genetic-repair systems, together with inadequate damage clearance, and genetic differences between men and women that affect cancers are beginning to emerge.

Male–female comparisons are powerful in biomedical research — don’t abandon them

Much more research is needed to understand how sex affects the rate at which genes mutate, cells’ capacities to repair and clear damaged DNA, and when genetic damage starts causing disease. Yet research led by one of us (S.H.) on lung adenocarcinoma, the most common type of lung cancer, suggests that women can survive for longer than men after they are diagnosed, in part thanks to cancer-defence genes in women driving more-robust immune responses 10 . X chromosomes encode many genes that are linked to immunity, and women with two X chromosomes might express these genes at higher levels than men with XY chromosomes.

Responses to cancer treatments also differ between men and women. Chemotherapies tend to work better in women than in men. This could be because it can take longer for women’s bodies to clear certain drugs, which could partly explain why women are also 34% more likely than men to experience harmful side effects 11 . Moreover, women with lung cancer typically have better outcomes after surgery, which they undergo more often than men 8 . This is probably due, at least in part, to women having less advanced disease when they are diagnosed than men do 12 . But the generally stronger immune responses in women might also help their recovery 8 .

Too often ignored

Despite these compelling indications that sex and gender matter, when it comes to many diseases that are leading causes of death, many researchers and health practitioners still fail to adequately take sex and gender into account. They might also be influenced by conscious or unconscious bias.

In the case of heart disease, the differences in gene expression and cellular make-up and activity found in men and women’s hearts highlight the need for sex-specific cardiac tissue models, sustained by sex-appropriate vasculature 13 . (Women on average have smaller hearts with narrower vessels compared with men.) Currently, researchers tend to construct heart models using either animal or human cells, but without necessarily ensuring that cells are sourced from individuals of only one sex per model. In fact, identifying sex disparities in basic heart biology is crucial to engineering relevant heart models with stem cells, for example, which investigators are now developing to aid the study of heart disease 13 .

For both heart disease and stroke, because of decades of under-representation of women in clinical trials, many of today’s standard treatments are based on studies of what happens in men who weigh around 70 kilograms. In clinical trials conducted for stroke and heart conditions between 2010 and 2017, women worldwide were under-enrolled relative to the prevalence of these diseases in the general population — by around 20% 14 . There is also significant underfunding of research for many conditions that are more prevalent in women compared with those that are more common in men (see ‘Disparities in health and disease’).

Source: A. A. Mirin J. Womens Health 30 , 956–963 (2021).

Basic research on cancer is similarly riddled with problems. Take the sex of the cell lines that are stored in commercial cell banks, which have been studied for decades and are the source of much of today’s textbook knowledge. For lung cancers, male lines outnumber female lines by two to one. For liver cancers, the ratio is seven to one. Until a few years ago, few researchers studying cancer in cultured cells in the lab even considered the sex of the cells they were studying. Also, the standard media in which cells are grown is frequently supplemented with fetal calf serum from a mixture of male and female calves, and so contains both male and female sex hormones. And phenol red, a dye commonly used to monitor the pH of tissue culture media mimics the hormone oestrogen 8 .

To add to the difficulties, research findings that emerge from the use of these cell lines are often tested in mice of only one sex. The results of these studies are then used to guide human trials that include both men and women participants. And in oncological clinical trials, just as with stroke and heart disease, women are still under-enrolled relative to the burden of disease they experience 7 .

Inclusivity in human trials will ensure the best possible outcomes for all participants, including cis and trans women and men, gender-diverse and intersex people (see ‘Inclusivity in practice’). Studies are showing, for example, that circadian rhythms — which can affect heart function and might impact how drugs are metabolized — differ between men and women 15 . So how might they compare in non-binary or transgender people? Likewise, knowledge about the immune responses of people with atypical numbers of sex chromosomes is likely to be crucial when it comes to the use of immune checkpoint inhibitors and other immune therapies for treating cancer. Those with Klinefelter syndrome, for example, who, similar to cis women, are at a higher risk of developing breast cancer than are cis men, have multiple X chromosomes that are rich in genes involved in the immune response.

Inclusivity in practice

How researchers include diverse groups of people in clinical trials with enough participants to be able to uncover between-group differences is a challenge.

Women represent nearly half of the population, but they are still under-represented in many clinical trials for numerous diseases, even in cases in which disease prevalence for women has been measured. For smaller population groups, such as transgender people, there are not enough data to even know what representative inclusion looks like. In fact, even if participation does reflect the prevalence of disease in the broader population in any one trial, teasing out effects might require combining the results of multiple studies in meta-analyses.

Advisory governing boards for pharmaceutical companies, such as the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use, funders and regulatory agencies could help with this by ensuring that terminology is adequately and consistently defined, and that populations are properly profiled.

Heightened awareness

Routinely taking sex and gender into account in research and using that knowledge to change health care could benefit billions of people. So what’s needed to make this happen?

Policy changes — such as the US National Institutes of Health’s 2016 call for the inclusion of male and female sexes in studies involving cells, tissues and animals — are crucial. But for many researchers, such calls seem burdensome, especially because studying more than one sex can increase costs. ( Sample sizes might need to be increased to achieve sufficient statistical power when comparing groups.)

Alongside initiatives from funders and publishers, awareness must be built — among students, researchers, clinicians, medical ethics committees, research governance bodies and community groups — of the ramifications of failing to consider sex and gender, and how to correct the problem.

Accounting for sex and gender makes for better science

Efforts led by the Canadian Institutes of Health Research (CIHR) are encouraging. Even though the permeation of knowledge from research to health care has been glacial, between 2011 and 2019, the proportion of all research grant applications submitted to the CIHR that took sex into consideration increased from around 22% to 83%. Gender as a variable is now also included in many of the human studies funded by the CIHR .

Several initiatives have contributed to this. As an example, as well as asking grant applicants to include a section in their research proposals on whether they are considering sex and gender and how they will do so, or why this is not considered applicable, the CIHR has provided training for scientists and organized workshops involving researchers and specialists in sex and gender. Applicants are more likely to receive funding if they provide a satisfactory rationale for their choices.

Convincing people in leadership roles — in governments, laboratories, medical ethics boards, education and so on — of the importance of including sex and gender in research is especially crucial. More studies demonstrating the financial costs of not doing so could help. Between 1997 and 2000, for instance, eight prescription drugs were retracted from the US market because inadequate clinical testing in women had failed to identify that the drugs put women at greater risk of developing health problems than men. This error cost pharmaceutical companies and taxpayers an estimated US$1.6 billion per drug 16 .

The scale of transformation needed will also require more engagement from global players.

Even as far back as 2007, the 60th World Health Assembly — the decision-making body of the World Health Organization (WHO) — passed a resolution to urge researchers to split their data according to sex and to include gender analyses where appropriate. Steps to improve care for transgender people or those with diverse genders are also starting to be taken; in December last year, the WHO established a Guideline Development Group, to provide recommendations on how to address the health of transgender and gender-diverse people . But more extensive efforts, comparable to all United Nations member states committing to target 5.b of the 2015 Sustainable Development Goals by 2030, will be crucial. (This target is to “enhance the use of enabling technology, in particular information and communications technology, to promote the empowerment of women”.)

Lastly, under the guidance of regulatory bodies such as the European Medicines Agency and the scientific entrepreneur community, the pharmaceutical industry must do more to ensure that preclinical work is robust, and that products are tested on enough people of different sexes and genders. Many leading pharmaceutical companies acknowledge on their websites the importance of including diverse groups in clinical trials , but evidence of actions to address the issue is only just emerging.

Awareness of the problems around sex and gender is growing fast. And although many are concerned that medical applications of AI will perpetuate already existing biases 17 , promising developments are emerging in the use of machine learning to make diagnoses that are appropriate for people’s sex and gender.

For decades, for instance, physicians worldwide have been determining whether a person has had a heart attack by using the Global Registry of Acute Coronary Events (GRACE) score, which was derived from trials mainly involving men. In 2022, the application of machine learning to data that had been split for men and women refined the predictors for women. And these revised predictors did a better job of matching individuals to appropriate interventions 18 .

Greater awareness, the wealth of data now emerging and the possibilities presented by new tools, from AI to gene editing, could mean a new era for research and medicine.

Nature 629 , 527-530 (2024)

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Approximately one in nine U.S. children diagnosed with ADHD, as new national study highlights an 'ever-expanding' public health concern

One million more children in the u.s. are diagnosed with adhd in 2022 than in 2016.

An exploration into the national U.S. dataset on children ever diagnosed with ADHD has revealed an "ongoing and ever-expanding" public health issue.

Findings published in the peer-reviewed Journal of Clinical Child & Adolescent Psychology uncover that approximately one million more children, aged 3-17, had received an ADHD diagnosis in 2022 than in 2016.

The paper reveals around one in nine children have ever received an ADHD diagnosis -- 11.4%, or 7.1 million children. Some 6.5 million children (10.5%) currently live with ADHD.

Among children currently living with ADHD, 58.1% have moderate or severe ADHD. 77.9% have at least one co-occurring disorder, approximately half of children with current ADHD (53.6%) received ADHD medication, and 44.4% had received behavioral treatment for ADHD in the past year. Nearly one third (30.1%) did not receive any ADHD-specific treatment.

The results follow an analysis of the 2022 National Survey of Children's Health (NSCH) dataset. They demonstrate that the estimated prevalence of ADHD (based on a parent report) is higher in the United States than comparable estimates from other countries.

The expert team of authors come from institutions including the Centers for Disease Control and Prevention, the Oak Ridge Institute for Science and Education, and the Health Resources and Services Administration.

In the paper, the team explains the increase of ADHD prevalence can partially be explained by "sociodemographic and child characteristics," whilst they state societal context can also "contribute to the overall trends in the diagnosis of ADHD." These include the context around children's mental health before and during the COVID-19 pandemic.

"Public awareness of ADHD has changed over time. ADHD was historically described as an externalizing disorder with a focus on easily observable hyperactive-impulsive symptoms, and was thought to primarily affect boys," the authors say.

"With increased awareness of symptoms related to attention regulation, ADHD has been increasingly recognized in girls, adolescents, and adults.

"Moreover, ADHD has previously been diagnosed at lower rates among children in some racial and ethnic minority groups. With increased awareness, such gaps in diagnoses have been narrowing or closing.

"Circumstances related to the pandemic may also have increased the likelihood that a child's ADHD symptoms could cause impairment. For example, in families where children needed to engage in virtual classroom learning while parents were also working from home, previously manageable ADHD symptoms may have become more impairing or symptoms that were previously unobserved by parents may have become recognizable."

The aim of this new paper was to provide updated U.S. prevalence estimates of diagnosed ADHD; ADHD severity; co-occurring disorders; and receipt of ADHD medication and behavioral treatment.

The team assessed 45,483 completed interviews, monitoring, as well, differences in demographic and clinical subgroups. Questions asked parents for details such as the severity of the condition.

Findings highlight how socioeconomic and geographic factors play a part in diagnosis/prevalence of ADHD.

For example:

• Asian and Hispanic/Latino children had a lower prevalence of diagnosed ADHD than White children.
• Children living in households with high school as the highest level of education and lower-income households had a higher prevalence than children living in households with more education and with income ≥200% of the federal poverty level, respectively.
• Children with public insurance (with or without private insurance) had a higher prevalence than children with private insurance alone.
• Prevalence was also higher for children living in the Northeast, Midwest, or South compared to those living in the West and for children living in rural or suburban areas compared to children living in urban areas.

The results also demonstrated how such factors impacted upon medicated treatment:

• Hispanic children and children living in non-English-speaking households had a lower prevalence of taking ADHD medication than non-Hispanic children and children living in primarily English-speaking homes, respectively.
• A higher prevalence of children with both public and private insurance were taking ADHD medication than children with private insurance only.
• A higher prevalence of children living in the Midwest and South were taking ADHD medication compared to children in the West.

Other behavioral treatments, such as mental health counseling, also followed similar patterns. Explaining the findings further, the authors state: "Shifts in patterns of treatments may also be affected by changes in the demographic distribution of who receives ADHD diagnoses.

"There is evidence that the sex difference for diagnosis of ADHD may be narrowing; in prior years, the ratio of boys to girls diagnosed with ADHD was more than 2:1."

Concluding, the team state that they hope their findings can be used by clinicians to understand diagnosis and treatment patterns to better inform clinical practice. As well, they hope it could be used by policymakers, government agencies, health care systems, public health practitioners, and other partners to plan for the needs of children with ADHD, such as by ensuring access to care and services for ADHD.

Future research, the team states, could investigate patterns of service delivery during and after the pandemic; as well as modes of ADHD service delivery; uptake and discontinuation of ADHD medication; and receipt of evidence-based behavioral treatment and other recommended services such as school services.

This study is subject to a number of limitations, including it being based on a survey of parent recall and reporting decisions and have not been validated against medical records or clinical judgment.

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• Melissa L. Danielson, Angelika H. Claussen, Rebecca H. Bitsko, Samuel M. Katz, Kimberly Newsome, Stephen J. Blumberg, Michael D. Kogan, Reem Ghandour. ADHD Prevalence Among U.S. Children and Adolescents in 2022: Diagnosis, Severity, Co-Occurring Disorders, and Treatment . Journal of Clinical Child & Adolescent Psychology , 2024; 1 DOI: 10.1080/15374416.2024.2335625

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The blue histogram bars depict the frequency of T scores among participants per Child Behavior Checklist index scale including the internalizing problems scale (A), externalizing problems scale (B), and total problems scale (C). Frequencies and percentages are based on a total of 229 participants.

eFigure 1. Participant Selection Flowchart for the Current Study Sample

eFigure 2. Directed Acyclic Graph (DAG) for Covariate Selection

eTable 1. Maternal Demographics According to Fluoride Sample

eFigure 3. Distributions of Raw Scores for CBCL Syndrome Scales Among Children in the MADRES Study at Age 3; n = 229

eFigure 4. Distributions of Raw Scores for CBCL DSM-Oriented Scales Among Children in the MADRES Study at Age 3; n = 229

eTable 2. CBCL Scores at Age 36-Months in the MADRES Cohort

eTable 3. Poisson Regression Estimating the Risk Ratio for Third Trimester MUFsg in Relation to CBCL Clinical Index Scores

eTable 4. Sensitivity Analysis Including “Borderline Clinical” with “Non-Clinical” Group as the Reference in Logistic Regression of Trimester 3 MUFsg With CBCL Clinical Index Scores

eTable 5. Sensitivity Analysis of Associations of MUFsg in Trimester 1 With CBCL Clinical Index Scores

eTable 6. Sensitivity Analysis of Associations of Trimester 1 MUFsg With Composite T-Scores, and Syndrome or DSM Scale Raw CBCL Scores at Age 3

eTable 7. Associations of MUFsg in Trimester 1 with CBCL Scores Adjusting for Blood Lead

eTable 8. Associations of MUFsg in Trimester 3 With CBCL Scores Adjusting for Trimester 1 Blood Lead

eTable 9. Associations of MUFsg in Trimester 3 with CBCL Clinical Index Scores Adjusting for Trimester 1 Blood Lead

eTable 10. Associations of MUFsg in Trimester 3 with CBCL Scores Among Women Who Fasted for ≥ 8 Hours

eTable 11. Trimester 3 MUFsg in Relation to CBCL Clinical Index Scores Among Women who Fasted for ≥ 8 Hours

eTable 12. Associations of MUFsg in Trimester 3 with CBCL Scores Including Women Who Smoked During Pregnancy

eTable 13. Trimester 3 MUFsg in Relation to CBCL Clinical Index Scores Including Women Who Smoked During Pregnancy

eTable 14. Associations of Average MUFsg Across Trimesters 1 and 3 With CBCL Scores

eTable 15. Average MUFsg Across Trimesters 1 and 3 in Relation to CBCL Clinical Index Scores

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Malin AJ , Eckel SP , Hu H, et al. Maternal Urinary Fluoride and Child Neurobehavior at Age 36 Months. JAMA Netw Open. 2024;7(5):e2411987. doi:10.1001/jamanetworkopen.2024.11987

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Maternal Urinary Fluoride and Child Neurobehavior at Age 36 Months

• 1 Department of Epidemiology, College of Public Health and Health Professions University of Florida, Gainesville
• 2 College of Medicine, University of Florida, Gainesville
• 3 Department of Population and Public Health Sciences, Keck School of Medicine of University of Southern California, Los Angeles
• 4 Department of Dental Public Health and Dental Informatics, School of Dentistry, Indiana University, Indianapolis

Question   Is prenatal fluoride exposure associated with child neurobehavior in a US-based sample?

Findings   In this cohort study of 229 pregnant women and their children, a 0.68 mg/L (ie, 1 IQR) increase in specific gravity–adjusted maternal urinary fluoride during pregnancy was associated with nearly double the odds of T scores for total child neurobehavioral problems being in the borderline clinical or clinical range.

Meaning   These findings suggest that prenatal fluoride exposure may increase risk of neurobehavioral problems among children living in an optimally fluoridated area in the US.

Importance   Recent studies in Canadian and Mexican populations suggest an association of higher prenatal fluoride exposure with poorer neurobehavioral development, but whether this association holds for US-based populations is unknown.

Objective   To examine associations of third trimester maternal urinary fluoride (MUF) with child neurobehavior at age 3 years in the US.

Design, Setting, and Participants   This prospective cohort study utilized urine samples archived from 2017 to 2020 and neurobehavioral data assessed from 2020 to 2023 from the Maternal and Developmental Risks from Environmental and Social Stressors (MADRES) pregnancy cohort, which consisted of predominately Hispanic women residing in Los Angeles, California. Cohort eligibility criteria at recruitment included being 18 years of age or older, less than 30 weeks’ gestation, and a fluent English or Spanish speaker. Exclusion criteria included having a disability preventing participation or provision of informed consent, being HIV positive or incarcerated, and having a multiple gestation pregnancy. There were 263 mother-child pairs who completed the 3-year study visit. In this analysis, women who reported prenatal smoking were excluded. Data analysis was conducted from October 2022 to March 2024.

Exposure   Specific gravity-adjusted MUF (MUF SG ), a biomarker of prenatal fluoride exposure.

Main Outcomes and Measures   Neurobehavior was quantified using the Preschool Child Behavior Checklist (CBCL), which included composite scores for Total Problems, Internalizing Problems, and Externalizing Problems. CBCL composite T scores range from 28 to 100. T scores from 60 to 63 are in the borderline clinical range, whereas scores above 63 are in the clinical range. Linear and logistic regression models adjusted for covariates were conducted.

Results   A total of 229 mother-child pairs (mean [SD] maternal age, 29.45 [5.67] years; 116 female children [50.7%] and 113 male children [49.3%]) who had MUF SG measured were included in the study. Median (IQR) MUF SG was 0.76 (0.51-1.19) mg/L, and 32 participants (14.0%) had a Total Problems T score in the borderline clinical or clinical range. A 1-IQR (0.68 mg/L) increase in MUF SG was associated with nearly double the odds of the Total Problems T score being in the borderline clinical or clinical range (odds ratio, 1.83; 95% CI, 1.17-2.86; P  = .008), as well as with a 2.29-point increase in T score for the Internalizing Problems composite (B = 2.29; 95% CI, 0.47-4.11; P  = .01) and a 2.14-point increase in T score for the Total Problems composite (B = 2.14; 95% CI, 0.29-3.98; P  = .02).

Conclusions and Relevance   In this prospective cohort study of mother-child pairs in Los Angeles, California, prenatal fluoride exposure was associated with increased neurobehavioral problems. These findings suggest that there may be a need to establish recommendations for limiting fluoride exposure during the prenatal period.

Fluoride levels in community drinking water systems in the US have been adjusted to prevent dental caries since 1945. 1 Currently, 73% of the US receives fluoridated water at a targeted concentration of 0.7 mg/L (to convert to millimoles per liter, multiply by 0.05263). This has been considered optimal for preventing dental caries while minimizing risk of adverse systemic health effects. 2 Most of Los Angeles County, California is at least partially fluoridated. 3 , 4 Fluoride can also naturally occur in soil and rock or be released into the environment via industrial processes. 5 , 6

It is widely established that exposure to high fluoride levels can adversely affect neurodevelopment 7 ; however, findings from recent studies conducted in Mexico and Canada 8 - 11 suggest that fluoride exposure at lower US-relevant levels may also be associated with poorer neurodevelopment. Specifically, higher prenatal fluoride exposure in Canada and/or Mexico has been associated with lower IQ among children aged 3 to 4 years in Canada 10 and children aged 6 to 12 years in Mexico, 9 increased symptoms of attention-deficit/hyperactivity disorder (ADHD) among children aged 6 to 12 years, 12 poorer executive function among children aged 3 to 5 years, 13 and poorer performance on measures of global cognition among 12- and 24-month-old boys. 14 A recent systematic review conducted by the National Toxicology Program reported “with moderate confidence that higher fluoride exposure…is consistently associated with lower IQ in children.” 15 The report 15 also highlighted the lack of US studies investigating associations of fluoride exposure with neurodevelopment or cognition and stated that US studies would be valuable. To our knowledge, we conducted the first, US-based study to examine associations of prenatal fluoride exposure with child neurobehavioral outcomes.

This cohort study was approved by the institutional review boards at The University of Southern California and The University of Florida and followed the Strengthening the Reporting of Observational Studies in Epidemiology ( STROBE ) reporting guideline. This study included mother-child pairs from the Maternal and Developmental Risks from Environmental and Social Stressors (MADRES) cohort. 16 MADRES is a prospective pregnancy cohort consisting of 1065 predominately Hispanic women of low socioeconomic status residing in urban Los Angeles, California. 16 Briefly, in 2015, pregnant women were recruited from prenatal care clinicians in Los Angeles serving predominantly medically underserved communities and provided written informed consent. Eligibility criteria include being 18 years of age or older, less than 30 weeks’ gestation at the time of recruitment, and being able to speak English or Spanish fluently. Exclusion criteria included having a multiple gestation pregnancy; being HIV positive; having a physical, mental, or cognitive disability that would prevent participation or provision of informed consent; and current incarceration. 16 The current study included mother-child pairs from the MADRES prospective cohort who had maternal urinary fluoride (MUF) measured during the third trimester of pregnancy and child scores on the Preschool Child Behavior Checklist (CBCL) for ages 1.5 to 5 years at age 36 months (eFigure 1 in Supplement 1 ).

Single spot urine samples were collected from MADRES participants during the third trimester of pregnancy (from 2017-2020). The mean (range) gestational age at third trimester urine collection was 31.6 (26.9-36.0) weeks. MUF was measured at the Oral Health Research Institute at the Indiana University School of Dentistry using the Martinez Mier et al modification 17 , 18 of the hexamethyldisiloxane microdiffusion method of Taves et al 19 (see the eMethods in Supplement 1 for additional details). MUF measurements were adjusted for specific gravity (MUF SG ). Urinary fluoride was utilized because it provides a reliable measure of total fluoride intake. It is also the most widely employed measure of individual fluoride exposure in epidemiological studies, including those assessing neurodevelopment. 10 - 12 , 20 , 21

We examined child neurobehavioral problems. These included internalizing and externalizing symptoms and symptoms consistent with Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition [ DSM-5 ]) diagnostic categories.

Child neurobehavioral outcomes were assessed from 2020 to 2023 via the Preschool CBCL, a valid measure of neurobehavior. 22 - 24 The Preschool CBCL is a parent-reported measure of 99 items that was administered in MADRES when the child was approximately 36 months old. Children were rated on the CBCL by their mothers. The CBCL is available in English and Spanish. CBCL scores comprise 7 syndrome scales (Emotionally Reactive, Anxious-Depressed, Somatic Complaints, Withdrawn, Sleep Problems, Attention Problems, and Aggressive Behavior) characterizing problems that tend to co-occur together. The CBCL also includes 5 DSM-5 –oriented scales that are comprised of items determined to be consistent with DSM-5 diagnostic categories (Depressive Problems, Anxiety Problems, Oppositional Defiant Problems, Autism Spectrum Problems, and ADHD Problems). Scores on CBCL syndrome scales are grouped to produce an Internalizing Problems composite score and Externalizing Problems composite score. Scales that focus primarily on issues within the self comprise the Internalizing Problems composite. Conversely, scales that focus on other-directed problems and expectations for the child comprise the Externalizing Problems composite. Lastly, a Total Problems composite score is calculated by summing scores on all 99 items. 24 Internalizing Problems, Externalizing Problems, and Total Problems composite T scores range from 28 to 100. T scores ranging from 60 to 63 are in the borderline clinical range, whereas those above 63 are in the clinical range. 24 We calculated 2-category clinical index variables of normal vs borderline clinical or clinical for statistical analyses for each composite variable (see the eMethods in Supplement 1 for additional details about the CBCL scales).

Covariates were selected using a directed acyclic graph (eFigure 2 in Supplement 1 ), and included maternal age (continuous), education (less than 12th grade, completed 12th grade, some college or technical school, completed college, and some graduate training), ethnicity by nativity (non-Hispanic, US-born Hispanic, or non–US-born Hispanic), marital status (decline to answer, married, living together, never married and single, divorced or separated, or widowed), prepregnancy body mass index (continuous; calculated as weight in kilograms divided by height in meters squared) and prenatal household income (unknown,<$15 000, $15 000-$29 999, $30 000-$49 999, $50 000-$99 999, and ≥$100 000), as well as child sex. Categories for ethnicity by nativity were defined by study principal investigators, and ethnicity was included because it has been shown to be associated with fluoride exposure and neurodevelopment. We adjusted for ethnicity as a proxy for structural racism rather than as a biological difference. We recoded marital status based on cohabitation status (eMethods in Supplement 1 ).

Descriptive statistics were calculated for MUF SG , sociodemographic variables, and scores on the CBCL. We conducted linear regression adjusted for covariates to examine associations of third trimester MUF SG with CBCL composite T scores as well as raw scores on CBCL syndrome scales and DSM-5 –oriented scales. Assumptions of linear regression were satisfied for models examining associations of MUF SG with CBCL composite T scores; however, for several models examining associations of MUF SG with CBCL syndrome scales and DSM-5 –oriented scales, linear regression assumptions were not satisfied. Therefore, a natural logarithm transformation was applied and a constant of 1 was added (to account for scores of 0) to the raw scores for these scales to satisfy linear regression assumptions (see the eMethods in Supplement 1 for an expanded statistical analysis plan). We also tested whether child sex modified associations of MUF SG with CBCL scores by including a MUF SG  × sex term in regression models to be retained if statistically significant. We conducted logistic regression examining associations of MUF SG with binary clinical index variables. Additionally, in sensitivity analyses, we conducted Poisson regression with robust error variances to determine the relative risk of scoring in the normal compared with borderline clinical or clinical range for clinical index variables. We also conducted binary logistic regression that included 2-category clinical index dependent variables of nonclinical (ie, normal or borderline) vs clinical for each clinical index variable. We conducted several additional sensitivity analyses that are reported in the eMethods in Supplement 1 . We excluded women who reported prenatal smoking (6 participants). Statistical analyses were performed using SPSS statistical software version 28 (IBM) and STATA/MP version 13.0 (Stata Corp). The criterion for statistical significance was an α < .05. Data analysis occurred from October 2022 to March 2024.

There were 229 mother-child pairs (mean [SD] maternal age, 29.45 [5.67] years; 116 female children [50.7%] and 113 male children [49.3%]) included in this study. See Table 1 for sociodemographic characteristics and exposure variables. For a comparison of sociodemographic characteristics between the current study sample and overall MADRES cohort with a live birth, see eTable 1 in Supplement 1 . Most participants (192 participants) reported fasting in the third trimester for at least 8 hours. MUF SG did not differ between women who reported fasting and those who did not. Median (IQR) MUF SG was 0.76 (0.51-1.19) mg/L. Mean (SD) T scores were 47.69 (11.60) for the Total Problems composite, 47.13 (11.62) for the Internalizing Problems composite, and 46.48 (10.68) for the Externalizing Problems composite ( Figure ). Of all participants, 32 (14.0%) had a Total Problems T score in the borderline clinical or clinical range, 35 (15.3%) had an Internalizing Problems T score in the borderline clinical or clinical range, and 23 (10.0%) had an Externalizing Problems T score in the borderline clinical or clinical range. Descriptive statistics for CBCL syndrome and DSM-oriented scale raw scores are presented in eFigure 3, eFigure 4, and eTable2 in Supplement 1 .

Associations of MUF SG with CBCL composite T scores and binary clinical index variables are presented in Table 2 . A 1-IQR (0.68 mg/L) increase in MUF SG was associated with nearly double the odds of having a Total Problems T score in the borderline clinical or clinical range compared with the normal range (odds ratio [OR], 1.83; 95% CI, 1.17-2.86; P  = .008). Additionally, a 1-IQR increase in MUF SG was associated with a 2.29-point increase in Internalizing Problems T scores (B = 2.29; 95% CI, 0.47-4.11; P  = .01) and 2.14-point increase in Total Problems T scores (B = 2.14; 95% CI, 0.29-3.98; P  = .02). Associations of MUF SG with Externalizing Problems T scores or odds of having an Internalizing Problems T score in the borderline clinical or clinical range compared with the normal range were also positive but not statistically significant ( Table 2 ). Risk ratios were generally consistent with these ORs; however, magnitudes were smaller, and the P value for the risk ratio for the Internalizing Problems binary clinical index variable was statistically significant (eTable 3 in Supplement 1 ). Sensitivity analyses that included nonclinical vs clinical index dependent variables were also consistent (eTable 4 in Supplement 1 ).

Associations of MUF SG with raw scores for CBCL syndrome scales and DSM-5 –oriented scales are presented in Table 3 . A 1-IQR increase in MUF SG was associated with a 13.54% increase in raw scores for the Emotionally Reactive CBCL syndrome scale (B = 0.13; 95% CI, 0.02-0.24; P  = .02), and a 19.60% increase in raw scores for the Somatic Complaints CBCL syndrome scale (B = 0.18; 95% CI, 0.07-0.28; P  = .001). Additionally, a 1-IQR increase in MUF SG was associated with an 11.29% increase in scores on the DSM-5 –oriented Anxiety Problems scale of the CBCL (B = 0.11; 95% CI, 0.003-0.21; P  = .045) and an 18.53% increase in scores on the DSM-5 –oriented Autism Spectrum Problems scale of the CBCL (B = 0.17; 95% CI, 0.04-0.30; P  = .009). There were no other associations of MUF SG with other syndrome scales or DSM-5 –oriented scales. There was no interaction between fluoride and sex.

MUF SG during the first trimester was also positively associated with CBCL scores (eTable 5 and eTable 6 in Supplement 1 ) and when first trimester blood lead level was included as a covariate in sensitivity analyses, the magnitudes of associations became larger and previously nonsignificant findings became significant associations in models for both the first and third trimester (eTables 7-9 in Supplement 1 ). Associations of MUF SG with CBCL scores in the third trimester remained generally the same when examined among only the sample of women who fasted for at least 8 hours (192 participants) and when adjusting for maternal smoking during pregnancy (eTables 10-13 in Supplement 1 ). Lastly, magnitudes of associations of mean MUF SG across the first and third trimesters with CBCL scores were larger than associations of MUF SG in only the third trimester with CBCL scores (eTable 14 and eTable 15 in Supplement 1 ).

To our knowledge, this is the first US-based cohort study to examine associations of prenatal fluoride exposure with child neurobehavior. The study sample resided in a predominately fluoridated region and had fluoride exposures that are typical of those living in fluoridated communities in North America. 17 , 25 , 26 For example, Till et al 25 reported a median MUF SG of 0.77 mg/L among women living in fluoridated communities in Canada. We found that women with higher fluoride exposure during pregnancy tended to rate their children higher on overall neurobehavioral problems and internalizing symptoms, including emotional reactivity, anxiety, and somatic complaints by age 3 years. Furthermore, each 0.68 mg/L increase in MUF SG was associated with nearly double the odds of total neurobehavioral problems being in the borderline clinical or clinical range. Women with higher MUF SG during pregnancy also tended to rate their children higher on Autism Spectrum Disorder symptoms. The effect sizes observed in this study are sizable considering the relatively low urinary fluoride levels of participants.

Findings from this study are consistent with a recent Canadian study 13 of over 600 maternal-child pairs in the Calgary cohort of the Alberta Pregnancy Outcomes and Nutrition study. The study found that exposure to drinking water fluoridated at 0.7 mg/L throughout pregnancy was associated with symptoms of executive dysfunction, including poorer inhibitory control, and decreased cognitive flexibility among children aged 3 to 5 years. However, associations were most pronounced among girls. 13 Although we did not observe sex-specific associations in the current study, higher MUF SG was associated with higher symptoms of Autism Spectrum Disorder and anxiety, which are also associated with poorer cognitive flexibility. 27 - 29 Another recent study 12 conducted in the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) cohort found that higher creatinine-adjusted MUF was associated with higher scores on measures of inattention and overall ADHD symptoms from ages 6 to 12 years. While we did not find associations of MUF SG with symptoms of inattention or ADHD, this may reflect the timing of neurobehavioral assessment because symptoms of inattention are more difficult to assess (and ADHD is more difficult to diagnose) in children younger than 4 years. Although no other prospective studies, to our knowledge, have examined associations of prenatal fluoride exposure with CBCL scores, a recent cross-sectional study 30 of 12-year-old children in the Cincinnati Childhood Allergy and Air Pollution Study found that higher specific gravity-adjusted urinary fluoride levels were associated with higher somatic symptoms scores and odds of internalizing T scores being in a clinically at-risk range (defined as a T score ≥60) on the Behavior Assessment System for Children (Second Edition), particularly among boys. Still, an earlier study of 7- to 11-year-old children residing in Boston 31 found no association of dental fluorosis or environmental fluoride exposure (assessed via questionnaire) with parent-reported neurobehavioral problems on the CBCL.

Other studies conducted in Canada and Mexico have found associations of higher prenatal fluoride exposure at US-population–relevant levels with poorer neurocognitive outcomes, including lower IQ. 8 - 10 , 12 , 14 , 21 For example, a study conducted in the ELEMENT cohort found that each 0.5 mg/L increase in creatine-adjusted MUF was associated with a more than 2-point reduction in global cognitive functioning or IQ across 3 time points during middle to late childhood. 21 Similarly, research conducted in the Canadian Maternal-Infant Research on Environmental Chemicals cohort found that each 1 mg/L increase in MUF SG was associated with a 4.49-point lower IQ score in boys. 8 , 10 Taken together, the weight of the scientific literature supports an association of prenatal fluoride exposure with adverse child cognitive and neurobehavioral development in North America. Still, when considering the global body of scientific literature, there are some inconsistencies. 32 - 34

It is well-established that the prenatal and early postnatal periods are windows of susceptibility for neurodevelopmental impacts of environmental toxicant exposures. 35 , 36 Animal studies have delineated potential mechanisms underlying the association of prenatal fluoride exposure with neurobehavioral development. A 2022 study 37 found that at 90 days of age, male rats who were prenatally and perinatally exposed to relatively low fluoride levels exhibited altered neurobiochemical markers of oxidative damage, glutamate metabolism, and acetylcholinesterase activity. Another recent study 38 found that at 90 days of age, female rats exposed to low fluoride levels during gestation and lactation exhibited decreased messenger RNA expression of the α7 nicotinic acetylcholine receptor (α7nAChR) and reduced hippocampal catalase activity (an indicator of oxidative stress). Neurochemical changes observed in both studies 37 , 38 have been replicated in other animal as well as in vitro studies that included high fluoride exposures. 39 - 41 Interestingly, both oxidative stress and alterations of the α7nAChR in particular have been implicated in the pathophysiology of neurodevelopmental disorders, including Autism Spectrum Disorder. 42 , 43 Furthermore, alterations in glutamate pathways have been implicated in the cause and treatment of anxiety disorders. 44 Prenatal fluoride exposure may also adversely affect neurodevelopment and cognition by causing mitochondrial dysfunction which can increase oxidative stress, blocking autophagosome-lysosome fusion which can contribute to cellular damage, and by causing synaptic dysfunction. 45 - 47 Additionally, prenatal fluoride exposure, even at low levels, can suppress maternal thyroid gland activity which can contribute to cognitive and neurobehavioral problems in offspring. 48 , 49

There are notable strengths of the current study, including the use of individual biomarker measures of exposure assessment that provide an estimate of fluoride intake from all sources, and the adjustment for a breadth of covariates associated with fluoride exposure, metabolism, and neurodevelopment. Additionally, our study addressed a limitation of prior studies on fluoride exposure and neurodevelopment by including a sample of predominately fasting pregnant women, which can be difficult to achieve. However, there are also limitations. First, we measured fluoride in spot samples rather than 24-hour urine samples, which can be influenced by daily behaviors (eg, food and beverage consumption or use of fluoridated dental products), and therefore increase random error. Still, the inclusion of mostly fasting urine samples reduces the potential impact of food and beverage consumption on urinary fluoride concentrations. Second, we were limited in our ability to examine patterns of associations of fluoride exposure with neurobehavior according to trimester because only a subsample of participants had urine available for fluoride analyses in the first trimester and most participants did not fast prior to urine collection. Nevertheless, associations of first trimester MUF SG with CBCL scores after adjusting for blood lead were in the same direction as for the third trimester. Third, we did not have data on tap water consumption habits for the study sample; however, home cooking rates were high, and rice tended to be a dietary staple among MADRES participants, which can be a source of tap water fluoride exposure. Fourth, given that the study sample resided in Los Angeles, California, and was predominately Hispanic, we do not know whether findings observed in this study are generalizable to other US populations or are nationally representative. Fifth, this study excluded participants who delivered their babies prior to 30 weeks’ gestation which precluded examination of associations of MUF SG with neurobehavior among children who were born very preterm. Sixth, lead concentrations in whole blood were only measured for most of the study sample during the first trimester, and therefore we were only able to adjust for first trimester blood lead in our third trimester analyses. Still, we do not anticipate confounding of associations of MUF SG with CBCL scores by blood lead given that the inclusion of first trimester blood lead in first and third trimester models increased the magnitude of the associations. Furthermore, blood lead has been shown to be stable between the first and third trimesters of pregnancy, 50 which supports the use of first trimester blood lead as a proxy for third trimester blood lead.

This cohort study found that prenatal fluoride exposure was associated with increased risk for neurobehavioral problems among children residing in the US. These findings suggest that there may be a need to establish recommendations for limiting exposure to fluoride from all sources during the prenatal period, a time when the developing brain is known to be especially vulnerable to injury from environmental insults.

Accepted for Publication: March 18, 2024.

Published: May 20, 2024. doi:10.1001/jamanetworkopen.2024.11987

Open Access: This is an open access article distributed under the terms of the CC-BY License . © 2024 Malin AJ et al. JAMA Network Open .

Corresponding Author: Ashley J. Malin, PhD, Department of Epidemiology, College of Public Health and Health Professions, University of Florida, 2004 Mowry Rd, Gainesville, FL 32603 ( [email protected] ).

Author Contributions: Dr Malin and Ms Yang had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Malin, Hu, Bastain.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Malin, Eckel, Hu, Martinez-Mier, Bastain.

Critical review of the manuscript for important intellectual content: All authors.

Statistical analysis: Malin, Eckel, Hu, Hernandez-Castro, Yang.

Obtained funding: Malin, Farzan, Habre, Breton, Bastain.

Administrative, technical, or material support: Martinez-Mier, Farzan, Habre, Bastain.

Supervision: Hu, Martinez-Mier, Farzan, Habre, Bastain.

Conflict of Interest Disclosures: Dr Hu reported having testified as a nonretained expert witness at the request of the US Department of Justice on his previously published research on the subject of prenatal fluoride exposure and neurodevelopmental outcomes as part of an ongoing trial in US District Court. Dr Farzan reported receiving grants from the National Institutes of Health outside the submitted work. No other disclosures were reported.

Funding/Support: This work was supported in part by funding from the National Institutes of Health and National Institute of Environmental Health Sciences (grant Nos. R00ES031676, ES030400, P50MD015705, P50ES026086, and R01ES021446) and the US Environmental Protection Agency (grant No. 83615801–0).

Role of the Funder/Sponsor: The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Data Sharing Statement: See Supplement 2 .

Additional Contributions: The authors thank the Maternal and Developmental Risks from Environmental and Social Stressors (MADRES) participants, the study staff, and community clinic partners for making this work possible. The authors also thank Durdana Khan, MPH, PhD (Department of Epidemiology, University of Florida), for conducting an additional reanalysis of the data included in this study. No additional compensation was provided to Dr Khan for this task.

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Plastic junk? Researchers find tiny particles in men's testicles

Researchers have detected microplastics in human testicles. Volodymyr Zakharov/Getty Images hide caption

Researchers have detected microplastics in human testicles.

Whether it's our bloodstream, brain, or lungs, microscopic fragments of plastic seem to turn up every time scientists scour a new corner of the human body.

The male reproductive organs are no exception.

New research published this month finds microplastics can build up in the testicles of humans and dogs — raising more questions about the potential health impacts of these particles.

Animal studies have shown exposure to microplastics can impact sperm quality and male fertility, but scientists are still in the early stages of translating this work to human health.

"Microplastics are everywhere," says Dr. John Yu , a toxicologist in the College of Nursing at the University of New Mexico and lead author of the study. "The quantification of those microplastics in humans is the first step to understanding its potential adverse effects."

For the first time, researchers find microplastics deep in the lungs of living people

When he set out to do the study, Yu didn't expect microplastics would have penetrated the male reproductive system so extensively, given the tight blood-tissue barrier around those organs. To his surprise, the research team unearthed a wide range and heavy concentration of microplastics in the testicles of about two dozen men and close to 50 dogs.

The results may also be relevant to a well-documented global decline in sperm count and other problems related to male fertility. This trend has been linked to a host of environmental and lifestyle factors, including certain endocrine-disrupting chemicals found in plastics.

The growing numbers of studies like this one are "compelling and should be a wake up call for policymakers," says Tracey Woodruff , director of the Environmental Research and Translation for Health Center at the University of California, San Francisco.

How much and what kind of plastics were in the testicles?

This is the largest study to measure how much of these microplastics that permeate the water, food and even air end up in the most intimate recesses of male reproductive anatomy.

It follows a smaller analysis, published last year by a team in China, that detected microplastics in about half a dozen human testicles and in semen.

For the current study, researchers at the University of New Mexico collected the testicles from autopsies of people ranging in age from 16 to 88 and from nearly 50 dogs after they were neutered at local veterinary clinics.

Dogs can function as "sentinel" animals for disease and harmful chemical exposure because they're so embedded in the human environment, plus canine spermatogenesis is more similar to the human process of producing sperm than lab rats, says Yu.

Researchers find a massive number of plastic particles in bottled water

Instead of trying to count each microplastic particle, the researchers were able to quantify the total amount of plastic by dissolving all the biological tissue and separating out the solids.

About 75% of what remained was plastic.

Polyethylene , or PE, made up a large portion of that. It's the most widely used plastic in the world, showing up in packaging, bags and any number of products.

Matthew Campen , who has examined these tiny particles up close, describes them as "shard-like, stabby bits" because of the way they've become "old and brittle and fragmented."

"What they do in the body, we don't know," says Campen, a professor at the UNM College of Pharmacy and one of the authors of the study, "Obviously, little tiny particles can disrupt the way cells behave."

Polyvinyl chloride — what's in PVC piping — emerged as another prominent culprit and was the second most common in the dog testicles. Vinyl chloride is classified as a carcinogen and long-term exposure, for example in drinking water, can increase the risk of cancer.

What's more, Yu and his team found a correlation between lower sperm count in the dog testicles and the presence of PVC (the analysis couldn't be done on the human samples because of how they had been stored).

There was also an association between greater levels of PVC and decreased weight of the testicles. The same was seen with Polyethylene terephthalate , or PET, another common source of plastic, which recent research suggests may be harmful.

Woodruff says weight is a somewhat "crude" marker for the effects on testicular health, although it's frequently used by regulatory agencies to evaluate the impacts of chemicals.

Implications?

The research comes with many caveats and cannot prove microplastics directly cause problems with male fertility. Nonetheless, Yu says the results are "concerning" and lay the foundation for more targeted studies on the "relationship between microplastic exposure and its potential impact on sperm."

An emerging body of evidence suggests microplastics can have toxic effects on reproductive health .

In a 2022 review of the evidence for the state of California, Woodruff and her colleagues concluded that microplastics were "suspected" to harm sperm quality and testicular health, but she says that may soon tip over from "suspected" to "likely" because more high-quality studies are being published.

"In the history of looking at chemical or environmental health issues, at the beginning you see these indicators of health harms and then those that have some type of evidence behind them just tend to grow," says Woodruff, "I anticipate we're just going to see more health harms from these microplastics."

In the University of New Mexico study, the concentration of microplastics in human testicles was on average three times higher than in dogs.

Campen says there are still many unknowns, like what specific concentration would pose a threat to health, or how that might vary depending on the kind of microplastic or where they accumulate in the body.

"We're just at the tip of the iceberg," says Campen, who has used this same technique to quantify the levels of microplastics in other tissues and organs.

The amount in the testicles is considerably higher than what was discovered in placenta, and second to what they observed in the brain, says Yu.

Exactly how the microplastics are making their way into the testicles requires further study. Campen suspects they could be "hitchhiking" through the gut via tiny fat particles that get metabolized and then fan out across the body.

It's plausible the build-up of microplastics in the testicles could affect reproductive health in any number of ways. Yu says microplastics could physically disrupt spermatogenesis, mess with the barrier between the testicles, or be a vehicle for harmful chemicals.

They could lead to inflammation and cause oxidative stress, which down the road might affect fertility, says Dr. Sarah Krzastek , a urologist at Virginia Commonwealth University.

"It's probably one more piece of the puzzle of things that are contributing to declines in male fertility over the years as these environmental exposures keep accumulating," she says, "We don't know the clinical ramifications of that yet."

Richard Lea , a reproductive biologist at the University of Nottingham, calls the findings "alarming."

"Having something unnatural like that in the testes is not particularly good news for good reproductive health," says Lea.

In his lab, Lea has found that exposure to phthalates , which are chemicals that can leach from plastics, can reduce the ability of sperm to swim and increase the fragmentation of DNA in the sperm head. This is one likely contributor to the decline in sperm quality in household dogs over the last several decades, a trend that mirrors what's seen in humans.

Of course, the testicles are just one part of the male reproductive system.

Lea says there's now research showing these chemical contaminants can affect the hormonal control of reproduction, at different levels in the body, including in the brain.

How to study a substance that is ubiquitous

Dr. Shanna Swan , a reproductive epidemiologist who has documented the global decline in sperm count, says she's concerned about the accumulation of microplastics. But it's not yet clear finding them in the testicles rather than other parts of the body is more worrisome from the standpoint of reproductive health.

For example in her work, she's looked at how prenatal exposure to endocrine-disrupting chemicals like phthalates can affect male reproductive function and "lead to lifetime of reproductive damage."

Swan says a limitation running through many of the recent studies on microplastics is that the samples may be inadvertently exposed to microplastics in the environment and that leads to skewed impressions of what was actually present in the person.

She notes there were similar quality control issues nearly a quarter century ago when scientists first started measuring phthalates in human tissues.

"I think there have to be a lot of caveats saying this is really the beginning," says Swan, a professor at the Icahn School of Medicine at Mount Sinai, "It's suggestive, it's important, and it's preliminary."

The University of New Mexico researchers developed a quality control process to protect the samples from being accidentally exposed to microplastics as much as possible. Campen says there's so much plastic in the human body, the amount that might contaminate the samples is "trivial."

More broadly, though, he acknowledges the field faces some huge challenges moving forward — especially as they try to draw a stronger link between these tiny particles and a decline in reproductive health or disease.

"A lot of the problem is they're so ubiquitous. There are no proper controls anymore. Right? Everybody's exposed," he says.

• men's reproductive health
• plastic pollution
• microplastics
• reproductive health
• endocrine disrupters

Environmental Pollution in the Moscow Region According to Long-term Roshydromet Monitoring Data

• Published: 02 November 2020
• Volume 45 , pages 523–532, ( 2020 )

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• G. M. Chernogaeva 1 , 2 ,
• L. R. Zhuravleva 1 ,
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• N. A. Fursov 3 ,
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Long-term Roshydromet monitoring data (2009–2018) on the pollution of the atmosphere, soil, and surface water are considered for the Moscow region (Moscow city within its new boundaries and the Moscow oblast). The air quality in the megacity (Moscow) and in background conditions (Prioksko-Terrasny Reserve) is compared.

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Chernogaeva, G.M., Zhuravleva, L.R., Malevanov, Y.A. et al. Environmental Pollution in the Moscow Region According to Long-term Roshydromet Monitoring Data . Russ. Meteorol. Hydrol. 45 , 523–532 (2020). https://doi.org/10.3103/S1068373920080014

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New grant aims for lasting increases in physical activity by leveraging existing social ties

May 24, 2024  | Erin Bluvas,  [email protected]

Courtney Monroe , an assistant professor in the Arnold School’s Department of Health Promotion, Education, and Behavior has been awarded $3M from the National Institute of Diabetes and Digestive and Kidney Diseases. She will use the five-year R01 grant to attempt to achieve long-term increases in physical activity among U.S. adults by harnessing technology and social support.

Researchers and clinicians – as well as most Americans – are familiar with the health benefits derived from physical activity. So how do we increase physical activity among the 50 percent of U.S. adults who are insufficiently active?  

Fifty percent of adults in the United States do not get enough physical activity.

“Many interventions have been successful in achieving short-term increases in physical activity among adults, but we’re examining a longer-term, scalable solution to maintaining these improvements,” Monroe says. “Although considerable evidence from prior studies points to the role social support plays in facilitating physical activity initiation and maintenance, effective methods of tapping into existing social relationships – an increasingly recognized potent contributor to health outcomes – to promote sustained support for physical activity are less well known.”   

With this study, she will design and implement a digital intervention that aims to effectively harness existing social ties to achieve long-term behavior changes related to physical activity. A faculty member with the South Carolina SmartState Technology Center to Promote Healthy Lifestyles (TecHealth), Monroe will use her expertise in technology, exercise, and behavioral science to encourage and measure physical activity.

Three hundred insufficiently physically active adults from diverse backgrounds across the U.S. will self-select into teams of three to eight individuals with preexisting social ties. Approximately 60 teams will be randomized to receive either a three-month theory-based, technology-delivered (e.g., mobile apps, Fitbit activity trackers) physical activity intervention or this same intervention plus digitally delivered social support training.

Many interventions have been successful in achieving short-term increases in physical activity among adults, but we’re examining a longer-term, scalable solution to maintaining these improvements.

Teams randomized to receive digitally delivered social support training will participate in interactive online modules highlighting the best methods for providing and requesting social support for becoming more physically active. These teams will also have access to additional digital tools that allow for interaction with the research team/staff and peers in ways designed to reinforce the knowledge and skills learned during the social support training.

“Our goal is to provide rigorous evidence on a novel and promising approach for leveraging existing social relationships to enhance physical activity among insufficiently active adults,” Monroe says. “By using technology that can easily deliver the intervention on a much larger scale, this approach has the potential to improve metabolic and cardiovascular health at the population level.”

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The Technology Center to Promote Healthy Lifestyles (TecHealth) is a South Carolina SmartState Center focused on research to develop and evaluate health promotion programs which encourage healthy lifestyles and reduce risk of disease by incorporating technology. 

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