new research on naps

An official website of the United States government

Here’s how you know

Official websites use .gov A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS A lock ( A locked padlock ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

• Heart-Healthy Living
• High Blood Pressure
• Sickle Cell Disease
• Sleep Apnea
• Information & Resources on COVID-19
• The Heart Truth®
• Learn More Breathe Better®
• Blood Diseases and Disorders Education Program
• Publications and Resources
• Blood Disorders and Blood Safety
• Sleep Science and Sleep Disorders
• Lung Diseases
• Health Disparities and Inequities
• Heart and Vascular Diseases
• Precision Medicine Activities
• Obesity, Nutrition, and Physical Activity
• Population and Epidemiology Studies
• Women’s Health
• Research Topics
• Clinical Trials
• All Science A-Z
• Grants and Training Home
• Policies and Guidelines
• Funding Opportunities and Contacts
• Training and Career Development
• Email Alerts
• NHLBI in the Press
• Research Features
• Ask a Scientist
• Past Events
• Upcoming Events
• Mission and Strategic Vision
• Divisions, Offices and Centers
• Advisory Committees
• Budget and Legislative Information
• Jobs and Working at the NHLBI
• Contact and FAQs
• NIH Sleep Research Plan
• < Back To Home

Researchers study how daytime naps may influence health

As the science of sleep evolves, researchers continue to study how napping may influence a person’s health. Shorter, power naps can boost alertness. Longer naps, especially those lasting an hour or more, have been linked with obesity and increased cardiovascular disease risks. Oftentimes, these findings volley back and forth.

To better understand connections between daytime naps and health, researchers assessed data taken from more than 3,200 adults living in Spain, a country where midday naps, or siestas, are common. They found that about one-third of adults took regular siestas – oftentimes four days a week. Among regular nappers, those who snoozed for 30 minutes or less were 21% less likely to have elevated blood pressure compared to non-nappers. Those who napped for more than 30 minutes were more likely to have a higher body weight. They were also 41% more likely to have high blood pressure, high blood sugar, and a larger waist circumference.

Upon further analysis of the data, the researchers found that certain activities, including going to bed later, smoking, and having larger lunches later in the day, helped explain links between longer naps and increased cardiovascular disease risks. They conclude that more research is needed to distinguish how and when daytime naps could support or improve a person’s cardiovascular health . The research published in Obesity and was partially funded by NHLBI and the National Institute of Diabetes and Digestive and Kidney Diseases.

Media Coverage

• Is having a nap good or bad for you?
• Do you take lengthy naps? Study reveals why it may not be a good idea
• You snooze, you lose: why long naps can be bad for your health
• Taking naps for more than 30 minutes may raise your risk of obesity, metabolic syndrome
• Study finds link between long naps and obesity, high blood pressure
• Could long daytime snooze put you at higher risk of high blood pressure and obesity?
• Risk for obesity and hypertension could be raised depending on how long you nap - study
• Midday naps & health: How long you nap may be key
• Want to take a siesta? It's better to make it a short one
• Longer midday naps linked to increased risk of metabolic syndrome
• Study: Napping for more than 30 minutes linked to obesity, high blood pressure
• Is there a wrong way to take a midday nap?
• Longer naps tied to higher risk for obesity, high blood pressure: Brigham research
• Nappers who take longer siestas more likely to develop high blood pressure, obesity
• Longer siestas linked to higher risk of obesity, metabolic syndrome, and high blood pressure

Featured Topics

Featured series.

A series of random questions answered by Harvard experts.

Explore the Gazette

Read the latest.

Putting human past on the MAPS

Does AI help humans make better decisions?

Tracking entwined histories of malaria, humans

Bernard Bodo/iStock

The science of siestas

Timothy Gower

MGH News and Public Affairs

New research reveals the genetic basis for daytime napping

How often a person takes daytime naps, if at all, is partly regulated by their genes, according to new research led by investigators at Harvard-affiliated Massachusetts General Hospital (MGH) and published in  Nature Communications .

In this study, the largest of its kind ever conducted, the MGH team collaborated with colleagues at the University of Murcia in Spain and several other institutions to identify dozens of gene regions that govern the tendency to take naps during the day. They also uncovered preliminary evidence linking napping habits to cardiometabolic health.

“Napping is somewhat controversial,” says Hassan Saeed Dashti of the MGH Center for Genomic Medicine, co-lead author of the report with Iyas Daghlas, a medical student at Harvard Medical School (HMS). Dashti notes that some countries where daytime naps have long been part of the culture (such as Spain) now discourage the habit. Meanwhile, some companies in the United States now promote napping as a way to boost productivity. “It was important to try to disentangle the biological pathways that contribute to why we nap,” says Dashti.

Previously, co-senior author Richa Saxena, principal investigator at the Saxena Lab at MGH, and her colleagues used massive databases of genetic and lifestyle information to study other aspects of sleep. Notably, the team has identified genes associated with sleep duration, insomnia, and the tendency to be an early riser or “night owl.” To gain a better understanding of the genetics of napping, Saxena’s team and co-senior author Marta Garaulet of the department of physiology at the University of Murcia, performed a genome-wide association study (GWAS), which involves rapid scanning of complete sets of DNA, or genomes, of a large number of people. The goal of a GWAS is to identify genetic variations that are associated with a specific disease or, in this case, habit.

For this study, the MGH researchers and their colleagues used data from the UK Biobank, which includes genetic information from 452,633 people. All participants were asked whether they nap during the day “never/rarely,” “sometimes” or “usually.” The GWAS identified 123 regions in the human genome that are associated with daytime napping. A subset of participants wore activity monitors called accelerometers, which provide data about daytime sedentary behavior, which can be an indicator of napping. This objective data indicated that the self-reports about napping were accurate. “That gave an extra layer of confidence that what we found is real and not an artifact,” says Dashti.

Several other features of the study bolster its results. For example, the researchers independently replicated their findings in an analysis of the genomes of 541,333 people collected by 23andMe, the consumer genetic-testing company. Also, a significant number of the genes near or at regions identified by the GWAS are already known to play a role in sleep. One example is  KSR2 , a gene that the MGH team and collaborators had previously found plays a role in sleep regulation.

Digging deeper into the data, the team identified at least three potential mechanisms that promote napping:

• Sleep propensity: Some people need more shut-eye than others.
• Disrupted sleep: A daytime nap can help make up for poor quality slumber the night before.
• Early morning awakening: People who rise early may “catch up” on sleep with a nap.

“This tells us that daytime napping is biologically driven and not just an environmental or behavioral choice,” says Dashti. [gz_explore id=”312769,267782,267346″ alignment=”right” /]

Some of these subtypes were linked to cardiometabolic health concerns, such as large waist circumference and elevated blood pressure, though more research on those associations is needed.

“Future work may help to develop personalized recommendations for siesta,” says Garaulet.

Furthermore, several gene variants linked to napping were already associated with signaling by a neuropeptide called orexin, which plays a role in wakefulness. “This pathway is known to be involved in rare sleep disorders like narcolepsy, but our findings show that smaller perturbations in the pathway can explain why some people nap more than others,” says Daghlas.

Saxena is the Phyllis and Jerome Lyle Rappaport MGH Research Scholar at the Center for Genomic Medicine and an associate professor of anesthesia at HMS.

The work was supported by the National Institute of Diabetes and Digestive and Kidney Diseases, the National Heart, Lung, and Blood Institute, MGH Research Scholar Fund, Spanish Government of Investigation, Development and Innovation, the Autonomous Community of the Region of Murcia through the Seneca Foundation, Academy of Finland, Instrumentarium Science Foundation, Yrjö Jahnsson Foundation, and Medical Research Council.

Share this article

You might like.

Harvard digital atlas plots patterns from history ancient and modern

One judge’s track record — with and without algorithm — surprises researchers

New study of ancient genomes tracks disease over 5,500 years, factors in spread, including trade, warfare, colonialism, and slavery

When should Harvard speak out?

Institutional Voice Working Group provides a roadmap in new report

Had a bad experience meditating? You're not alone.

Altered states of consciousness through yoga, mindfulness more common than thought and mostly beneficial, study finds — though clinicians ill-equipped to help those who struggle

College sees strong yield for students accepted to Class of 2028  

Financial aid was a critical factor, dean says

Alzheimer’s and Daytime Napping Linked in New Research

Summary: Study reveals a bi-directional link between daytime napping and cognitive decline associated with Alzheimer’s disease. Researchers say longer, more frequent napping was associated with worse cognition after one year, and worse cognition was linked to longer and more frequent daytime naps.

Source: Rush University Medical Center

Could there be a link between cognitive decline and excessive daytime napping? New research from the Rush Alzheimer’s Disease Center suggests a potential connection, according to an article published in  Alzheimer’s and Dementia .

The connection appears to occur in both directions, researchers say; longer and more frequent napping was correlated with worse cognition after one year, and worse cognition was correlated with longer and more frequent naps after one year.

Aron Buchman, MD, a neurologist at Rush University Medical Center and co-author of the article, said the study lends evidence to the changing views of Alzheimer’s disease as a purely cognitive disorder.

“We now know that the pathology related to cognitive decline can cause other changes in function,” he said. “It’s really a multi-system disorder, also including difficulty sleeping, changes in movement, changes in body composition, depression symptoms, behavioral changes, etc.”

Researchers followed more than 1,400 patients for up to 14 years as part of the Rush Memory and Aging Project and the Religious Order Study. Participants wore a wrist-worn sensor that recorded activity continuously for up to 10 days, and came in once a year for examinations and cognitive testing. Any prolonged period of no activity during the daytime from 9 a.m. to 7 p.m. was considered a nap.

When the study started, more than 75% of participants showed no signs of any cognitive impairment, 19.5% had mild cognitive impairment and slightly more than 4% had Alzheimer’s disease dementia.

Daily napping increased by about 11 minutes per year among those who didn’t develop cognitive impairment during follow-up. Naps doubled after a diagnosis of mild cognitive impairment, and nearly tripled after a diagnosis of Alzheimer’s disease dementia.

Researchers also compared participants who had normal cognition at the start of the study but developed Alzheimer’s disease dementia to their counterparts whose thinking remained stable during the study. They found that older people who napped more than an hour a day had a 40% higher risk of developing Alzheimer’s.

Buchman stressed that the study does not imply that napping causes Alzheimer’s dementia, or vice versa.

“This is an observational study, so we can’t say that ‘a causes b’,” he said. “But we can say that they unfold at the same time, and it’s possible that the same pathologies may contribute to both.”

Alzheimer’s disease is caused by the accumulation of two proteins, amyloid beta and tau, within the brain. While the decline in cognitive function is the most well-known symptom of Alzheimer’s disease, this protein accumulation can occur in various locations of the brain, brainstem and spinal cord, causing a variety of symptoms.

The study indicates that increases in the frequency and duration of daytime napping may be one of those symptoms.

“Once you’ve identified the pathology and location, you can work on potential treatments,” Buchman said. “There are proteins or genes that might prevent the accumulation of tau and beta, or there’s potentially ways to mitigate or slow their accumulation.”

The study was supported by the National Institutes of Health and the BrightFocus Foundation Alzheimer’s Research Program. Buchman said that one of the study’s primary strengths was its participant cohorts from the Memory and Aging Project and the Religious Order Study. Both studies are decades-long efforts that recruit participants to undergo annual testing, sample collection and organ donation after their death.

“The people in our studies are very special people,” he said. “Without people making this kind of contribution we wouldn’t be able to do the research that we do. They are so excited to be able to participate, they animate the staff with their participation. We’re very lucky to have them.”

About this Alzheimer’s disease research news

Author: Press Office Source: Rush University Medical Center Contact: Press Office – Rush University Medical Center Image: The image is in the public domain

Original Research: Closed access. “ Daytime napping and Alzheimer’s dementia: A potential bidirectional relationship ” by Peng Li et al. Alzheimer’s & Dementia

Daytime napping and Alzheimer’s dementia: A potential bidirectional relationship

Introduction

Daytime napping is frequently seen in older adults. The longitudinal relationship between daytime napping and cognitive aging is unknown.

Using data from 1401 participants of the Rush Memory and Aging Project, we examined the longitudinal change of daytime napping inferred objectively by actigraphy, and the association with incident Alzheimer’s dementia during up to 14-year follow-up.

Older adults tended to nap longer and more frequently with aging, while the progression of Alzheimer’s dementia accelerates this change by more than doubling the annual increases in nap duration/frequency. Longer and more frequent daytime naps were associated with higher risk of Alzheimer’s dementia. Interestingly, more excessive (longer or more frequent) daytime napping was correlated with worse cognition a year later, and conversely, worse cognition was correlated with more excessive naps a year later.

Excessive daytime napping and Alzheimer’s dementia may possess a bidirectional relationship or share common pathophysiological mechanisms.

I would like to reach out to find out does taking a nap during lunch time at certain age also impact the brain in a bad way? And how long of a nap can one take that would be good for the body and not bad for the brain? Thanks

I call bs on this one just because you take a daily nap doesn’t mean you have cognitive decline. Maybe you’re just tired from work or because you didn’t get enough sleep the night before. I’ve read where it’s heart healthy to take a daily short nap. I call bs on this one

I have an issue with this study. How do they know that daytime napping causes cognitive decline? Maybe cognitive decline causes increased daytime napping.

Correlation does not definitively imply causation.

My wife has dementia for about 9 years, since the first year I am giving her in the morning 1-Multivitamin, 1-Turmeric, 1-Neurella C, 1-Fish oil, 1-Alpha GPC, 1-Piracetan, 1-Brain Awake, 1-Quanol TRA CoQ10. At Night 1-Citicoline CDP Choline, 1-Turmeric, 1-Fish Oil, 1-Ginkgo Biloba Extract, 1- Aspirin 81mg. She walk all day long for many hours, in side the house. We are constantly traveling, by RV, by Cruises, by plan, every month we are in a dif State or Country, every we she go to dance 1 or 2 time, we eat Salmon, Salad, Quaker, we don’t Smoke never, we don’t drink alcohol, we used 3 times a week JACUZZI, we never get sick. ThNk GOD.

Daytime napping is linked to every neurological disease duh! That’s like saying it’s linked to narcolepsy! Tell me something I don’t know!

I don’t think they said that anywhere. They actually SPECIFICALLY said they were not claiming causation.

I’m sorry, what did the article state again? I started dozing halfway through it.

With this daytime sleep or napping you would anticipe the french and frencophone countries elders would develop Alzheimer as in any of these countries from 12pm to 2pm it is a nap and break time for both all students and professionals.Do they have high record of Alzheimer? Not that I know of .We have high incidences here in the state than any others country who engages in napping break.

Accumulation of tau is not the problem. Tau is one molecule that is important to connect spin waves between microtubules,where memory is written

I think all the comments were interesting to say the least.

After all the deception of COVID and the supposed studies, safety, and now global deaths specially of our vaccinated children getting this “mysterious HEPATITIS” & dying from liver disease. Does anyone trust science anymore? This study can’t be accurate due to environmental and genetic variables that impact findings. But they decide to single out sleep. Sleep is a necessity napping is for babies and elderly. I’m gonna call BS ON THESE SKEWED FINDINGS.

What is wrong with these people commenting? Can they not read?

An actual nap or siesta is fine and can be quite positive.

Sleeping for hours during the day is not fine or normal.

There is a huge amount of ignorance and/or denial in these comments.If you or someone you know has this problem, please see a doctor for diagnosis as to why. Yes, it could be due to sleep apnea or be a symptom of a cognitive problem.

Does this include the siesta that is common and popular in large areas of the world?

Grandparents took care of each other to 93-94, then grandfather six months into dementia died, grandmother died three months later-stating/wanting not to live anymore… …staying in the here now, we’re caring as long as we can too…

Huh? I think i fell asleep 3-4 times while reading your comment. I thought the articlw was well written and informaaaaaaaaattttt….. zzzzzzzz…..

Old people take naps, old people get Alzheimer’s…. There’s gotta be a link!

Why are you so angry? Maybe you need a nap

The evidence of the aforementioned speaks for itself. I believe napping regenerates the body. Also no specifics were given as the how much or not is too much. There’s an exception to these findings which are baseless.

Interesting article(they may be on to something or may not). This article is just a summary. Click on the link “original research” provided if you want in-depth info about their research(details of age of participants, etc.).

Meanwhile in Latin countries where everyone naps for most of their lives….. Alzheimer’s numbers are no more increased than cultures that do not practice this .

What’s the magic pill?

Two thoughts: 1. Could the need for longer more frequent naps be due to sleep apnea which is what in fact causing the mental decline? 2. Winston Churchill was famous for almost religiously taking a nap and even boasted that because of his naps he was able to work two full work days in 24 hours instead of just one – and he was brilliant even late in his life I know it’s anecdotal but so many people nap that I have a hard time buying this paper’s results without more checks on convoluting factors.

I believe this to be flawed science since it was done in the UK which has a large incidence of BSE and vCJD, both which mimick the signs of Alzheimers.

I mother and my mother-in-law both had dementia before they passed away. I believe your conclusion is wrong. I believe that as the cognition deteriorates your body needs more rest, and then the body is able to continue through the day. But I also know that a little rest or nap never hurt anyone. My grandmother died without dementia and she napped in the afternoons all the time. She awoke bright as ever from her naps, and stayed awake during her gambling at casinos until 2am at times.

I love my afternoon naps. They brighten me up for the rest of my day of feeding my pets and the birds, cleaning up after storms, cleaning my house, working in my little shop, or happily sitting on my nice porch after cooking dinner. I am 72 and don’t believe i am in mental decline. I sleep a couple of glorious hours every afternoon and getting awakened by my cat wanting some cuddling time makes me feel refreshed, happy, and loved.

My mother is 91 with dementia. .health wise a bad back. Ever since my dad died 2 yrs ago all she does is sleep during the day As a widow myself I cannot sleep at night ,but I don’t nap during the day either I think my mother just wants to go in her sleep like my dad. But everyday she’s more confused what do you think?

If my grandpa takes frequent naps during the day should I be worried? He’s between 60-70 years old

This is dangerously close to clickbait. Which is sad for a lot of reasons, there are really people who have Alzheimer’s and Dementia and you, just by your title, suggest not to take naps so you won’t get either.

Dementia typically brings poor sleep or rest, which makes the patient more sleepy and take more naps during the day. At the same time, sleeping poorly is proven to limit the removal of amyloid plaques, and may even cause dementia-like symptoms. I don’t think that long naps could cause dementia in any way. My theory is that poor sleep and needing to take daytime naps may be a very early symptom of dementia, and that’s why napping arrived earlier than the diagnostic in some patients.

this is probably one of the worst examples of garbage pseudo science i have seen! i guess those people did not study any asian, esp japanese! or even people in latin countries. the study title should really be “americans should not nap!” furthermore, “excessive”? what is defined as “excessive”? 12 hours? “longer and more frequent”? than what? 5 min of power nap? my father was a quantum physicist who religiously napped 1.5 hours every single day of his entire life. even when he died from hemorrhage stroke at the age of 87, his mind was better than most of the people i had come cross in this country. lol

I’m sorry with all the respect but the article is missing some information like, the age range, location and other details of the individuals studied.

We know during rem sleep spinal fluid flows on to the brain to kinda wash it and remove toxins. I wonder if the extra napping is a symptom of the brain trying to prolong this function because it’s not doing its job properly

I can say in my experience with my aunts and mothers all had really bad except my grandmother and she was the only one that was stay at home and only one that took a nap religiously her sisters would tease her about it and they all had it but her. So it’s not a very good determining trait.

I guess I’m well on my way then.. I’m 64 years old, retired and I definitely takes naps during the day. Not really intentional naps, but I do fall asleep while watching TV or even a short nap after eating. My parents lived into their 80s and did the same thing without Alzhiemers, but my grandfather had it. I heard Alzhiemers skips a generation, so… is that true? Because if it is then.. it’s our generation’s turn for my 1st cousins and myself.

I agree with Christina I have a father who died from dementia but his mother my grand mother live till she was 97 with our any signs of dementia I believe it’s nutritional it must be linked to nutrients and lower activity because my father declined as his work load decreased it’s nutrition and blow flow speed if that makes any sense.

My grandmother lived to be almost 100 yr old and she took afternoon naps. Until a week before her death, she was sharp as a tack cognitively. I can’t believe that this study hot funding, but then, worse ideas for studies get funding. Maybe a better study would be the effects of overnight workers vs daytime That way it can be certain whether it is nature or nuture.

Is a period of inactivity actually sleeping or not? This isn’t clear in the article.

A FRIEND OF MINE NAPS OFTEN AT 1200 NOON EVERY DAY AND ALTHOUGH HE IS BUSY EVERYDAY DOING SOMETHING I REMEMBER HE HAD A CONCUSSION IN HIGH SCHOOL ON THE FOOTBALL TEAM AND IN HIS EARLIER YEARS HE HAD A LEARNING DISABILITY AND A PROBLEM WITH READING UNTIL HE WAS MOVED TO A PUBLIC SCHOOL FROM A CATHOLIC SCHOOL WHERE HE RECEIVED THE NEEDED, CARING AND PROPER ATTENTION WHICH SAVED HIM , HE STILL COMMENTS & CREDITS TO THIS DAY ❗ I HEARD THAT DIET PLAYS A BIG PART IN DEMENTIA AND I BELIEVE FEAR & ANXIETY PLAY A BIG ROLE IN ACQUIRING DEMENTIA , ALZHEIMERS ❗ MAYBE EATING SALMON TWICE A WEEK IS A GOOD IDEA ?❗

Eat your greens. i don’t eat greens everyday as I opt for corn or cauliflower or some other kind of vegetable. But oh when I have greens like spinach, lettuce, collard greens steamed lightly in a steamer, with a touch of olive oil and juice of a fresh lemon, I notice that my thinking is more clear and eased. EAT YOUR GREENS! Lol….

I did not see any information on labs that could induce napping or tiredness like low iron, low B12, intrinsic factor status, diet, heart rate, cholesterol LDL levels, glucose, or current medications. Increased napping alone doesn’t do it for me at all.

Correlation doesn’t necessarily equal causation. During the summer months there are more shark attacks and more ice cream consumption. Older people tend to nap more and older people tend to get neurological degenerative diseases.

Spain is not in the study ??

Woe. How you heard about siestas aka day napping? Most people from Spain and Latin America have siestas and they are healthy.

This is the most contrived study I’ve ever read.

Correlation does not equal causality.

This “study” is bordering on BS

I’m 62 I nap to block out the other hall’s incessant*****ing. So it cod be argued that long term marriage leads to cognitive decline.

? Potentially valid thought!

This is interesting to me, since I lived with my Father in Law for a number of years (started living with us at 79 yrs old), and he rarely took naps of more than about 20-30 minutes in his recliner, but we watched his dementia get greater and deeper – could not make his own meals, a neurologist stopped him from driving, and he lived with us because he could no longer safely live alone.

Meanwhile, my Step-Dad has taken 2+ hour naps every afternoon for 2+ decades, yet, at 97 yrs old, he has no real signs of dementia – lives in his own home in a suburb (on 3 acres) w/o public transit, still can drive, and still can cook his own meals. He doesn’t even have any grey hair!

I don’t know that I can buy into this study…..

Sleep is very essential for the body’s recovery otherwise we would not sleep. There’s a reason why we sleep because if it wasn’t essential we would not have to be left in a state that leaves us vulnerable to predators, rival tribes, you can’t hunt for food when you sleep. Sleep is a vital recovery mechanism, if it was not vital than nature would have scrapped it.

Please explain Spain’s low rate and the siesta.

A siesta is a nap. Haven’t you ever seen the picture of a Latino leaning up against a tree with his sombrero pulled down to shade his face and wrapped in a serape’ taking a nap?

My mom is 80+ years old.And she told me I get very forget full when I worry a lot She thinks the cause of azh.is too much worrying ,

Comments are closed.

How Music Synchronizes Heart Rates and Collective Emotions

Oxytocin’s Link to Obesity and Postnatal Depression

AI Unveils Evolutionary Patterns Predicted by Darwin and Wallace

Prosthetic Limb Offers Natural Gait via Neural Control

• Alzheimer's disease & dementia
• Arthritis & Rheumatism
• Attention deficit disorders
• Autism spectrum disorders
• Biomedical technology
• Diseases, Conditions, Syndromes
• Endocrinology & Metabolism
• Gastroenterology
• Gerontology & Geriatrics
• Health informatics
• Inflammatory disorders
• Medical economics
• Medical research
• Medications
• Neuroscience
• Obstetrics & gynaecology
• Oncology & Cancer
• Ophthalmology
• Overweight & Obesity
• Parkinson's & Movement disorders
• Psychology & Psychiatry
• Radiology & Imaging
• Sleep disorders
• Sports medicine & Kinesiology
• Vaccination
• Breast cancer
• Cardiovascular disease
• Chronic obstructive pulmonary disease
• Colon cancer
• Coronary artery disease
• Heart attack
• Heart disease
• High blood pressure
• Kidney disease
• Lung cancer
• Multiple sclerosis
• Myocardial infarction
• Ovarian cancer
• Post traumatic stress disorder
• Rheumatoid arthritis
• Schizophrenia
• Skin cancer
• Type 2 diabetes
• Full List »

share this!

July 29, 2023

This article has been reviewed according to Science X's editorial process and policies . Editors have highlighted the following attributes while ensuring the content's credibility:

fact-checked

reputable news agency

Love to nap? Here's more evidence it's good for your brain

by Hanna Webster

A study published last month in the journal Sleep Health found that regular napping is linked to larger brain volume and could indicate anti-aging properties of napping.

While past research looked at people's brains and sleep habits and made correlations, this study—with global collaboration including Harvard Medical School—took it one step further in analyzing participants' genes to locate specific traits associated with napping. The Allegheny Health Network Center for Sleep Medicine thinks it's a step in the right direction for learning more about sleep and cognition.

It is estimated that one in three U.S. adults does not get adequate sleep (an average 7 to 8 hours a night), and that around 18% of Americans have a sleep disorder. Teens need more sleep than adults, to accommodate a developing brain . Chronic poor sleep can decrease immune function and increase risk of high blood pressure, diabetes and other health conditions.

However, power naps—characterized as an intentional 15- to 30-minute nap, typically in the afternoon—can temporarily relieve the burden of a sleep deficit, and some studies have shown they have benefits for cognition.

The new study's researchers asked people aged 40 to 69 about their power-napping habits: Did they nap regularly, sometimes or rarely? They then combed through participants' genomes to find similarities. The study sample came from more than 300,000 people who had registered with the UK Biobank, a vast consortium of participant genetic and medical data. The National Institutes of Health's All of Us Research Program, of which Pitt is a partner, is a similar cohort-based program but said it does not yet have the data to conduct a similar study, an NIH spokesperson said.

In those who napped regularly, they found specific genes consistent across the cohort that were associated with napping behavior, suggesting that some sleep habits are ingrained.

"Although our question is not necessarily unique, our approach is," said Hassan Dashti, assistant investigator in anesthesia, critical care and pain medicine at Massachusetts General Hospital Research Institute, a professor of anesthesia at Harvard Medical School and an author on the study.

Variables such as disease, depression, sleep disorders and poor sleep quality might impact a person's propensity to nap, making it hard to parse out the true reason for napping in a scientific study. But looking at genes, which a person has over their lifetime, can help rule out some of those confounders. "Relying on genetics is a powerful tool because now we can control for those variables," said Dashti.

In addition to the napping genes shared among those who snoozed regularly, the researchers also found that those who reported napping had larger total brain volumes compared to those who only napped sometimes or not at all.

Brain volume has been a measure of overall brain health and propensity for aging in previous studies, as the aging brain tends to shrink. In this study, researchers estimated that the brain size of those who napped was protective against the equivalent to 2.6 to 6.5 years of aging.

"Napping does have a protective effect on overall brain health," said Dashti.

The study also looked at markers of cognition, such as reaction time, visual memory and the size of a participant's hippocampus—a region deep in the brain largely responsible for memory. Researchers did not find correlations between regular napping and these functional measures of cognition, which they said surprised them, as previous research has found benefits to napping on these measures.

Daniel Shade, medical director of the AHN Sleep Disorders Center and a board-certified sleep medicine specialist, said like any study, this one had some strengths and some flaws.

"Brain volume is nice as an anatomical finding, but it's not a functional finding," he said, meaning the results don't signal that a larger brain is linked to functional changes like better reaction time or memory. "I was surprised not to see [that]." Shade was not involved in the research. He said the study was a great foundation to build upon scientific knowledge of links between sleep, napping and dementia, which more than 7 million Americans suffer from. "This is starting to show directions of where we need to go with research," he said.

Being both a researcher and a clinician in a sleep clinic, Shade thought the genetics component was a novel addition to the study, and that it reflected in part what he sees in the clinic. "Some people have a daily nap and that's just them, and others can't nap," he said. "If you don't need to nap, you shouldn't."

Dashti echoed this: "Even with these findings, I would never recommend people to start napping if they don't need it. However, if you feel the need to, napping is OK."

It's important to recognize, said both researchers, that power naps can't erase chronic bad sleep.

"If you consistently sleep six hours, you're going to accrue a sleep deficit," said Shade. "Short naps will increase attention for a period of a few hours, but what [they] won't do is compensate for a preexisting sleep debt."

When we stay awake for long hours and lag on proper sleep, a chemical in our bodies called adenosine builds up, causing us to feel sleepy (caffeine is an adenosine blocker). This behavior, said Shade, also promotes a sort of proinflammatory response, as proteins called cytokines ramp up production. Napping can reduce this sleep pressure, temporarily alleviating the urge to sleep, which accrues throughout the day.

And while the genetic analysis gave more evidence that this protective napping behavior is ingrained in some people, it could also be true that people who nap regularly are able to do so based on other proffered benefits.

"They have the gene, but they also have the opportunity," said Shade.

"Daytime napping is a privilege and a luxury," said Dashti. "These people have a comfy bed, and they have time in the day to nap." And this could signal that those populations are enjoying other health benefits, too.

Using the UK Biobank, study participants were only white Europeans, so there's an opportunity to replicate the study in a more diverse cohort. Shade also suggested the possibility of a longitudinal study, looking at people's napping habits over a period of many years and tracking who gets dementia and who doesn't.

He was also interested to see the napping and memory aspect of the study explored further. "It would be great to see a functional correlation, but that's probably their next step," said Shade.

Researchers reiterated that feeling extremely sleepy throughout the day, sleeping long hours at night (typically 10 hours or more) or taking longer naps of around 2 hours could be a sign of an underlying problem that should be checked by a sleep specialist if these problems persist. Naps should be intentional, 15- to 30-minute periods.

"We don't want to use a nap as a mechanism to compensate for poor sleep ," said Dashti.

2023 PG Publishing Co. Distributed by Tribune Content Agency, LLC.

Explore further

Feedback to editors

New cancer treatment slows progression of aggressive neuroendocrine tumors, study finds

7 hours ago

Why schizophrenia and apathy go hand in hand

8 hours ago

Study: Women veterans at higher risk for repeat suicide attempts

9 hours ago

Childhood obesity tied to double the risk of dengue hospitalization

Financial incentives found to double smoking cessation rate for people with socioeconomic challenges

10 hours ago

Study discovers connection between between heart and brain in KBG syndrome

Clinical trial could lead to new 'gold standard' test for prostate cancer detection

11 hours ago

Serendipity reveals new method to fight cancer with T cells

The path to Parkinson's disease: All roads lead to the nigrosome

12 hours ago

Researchers discover a new face-detecting brain circuit

Related stories.

Regular napping linked to larger brain volume

Jun 20, 2023

Q&A: Is there a wrong way—or time—to nap?

Jul 14, 2023

How to get the most out of napping

Mar 10, 2023

Sleep dysregulation ups risk for inflammatory bowel disease

Nov 18, 2022

Short night-time sleep linked with nearly doubled risk of clogged leg arteries

Mar 15, 2023

Sleep problems? You may have an increased risk of stroke

Apr 6, 2023

Recommended for you

Group prenatal care shows promise in reducing maternal health disparities

13 hours ago

Bacteria detected in tattoo and permanent makeup inks

14 hours ago

Researchers find that gratitude is a useful emotional tool in reducing desire to smoke

Jul 1, 2024

Prolonged exposure to pollution can lead to loss of independence in later life, study suggests

Blood test can help predict risk of obstructive sleep apnea

Pandemic newborns in India more likely to have lower birth weight, shows study

Let us know if there is a problem with our content.

Use this form if you have come across a typo, inaccuracy or would like to send an edit request for the content on this page. For general inquiries, please use our contact form . For general feedback, use the public comments section below (please adhere to guidelines ).

Please select the most appropriate category to facilitate processing of your request

Thank you for taking time to provide your feedback to the editors.

Your feedback is important to us. However, we do not guarantee individual replies due to the high volume of messages.

E-mail the story

Your email address is used only to let the recipient know who sent the email. Neither your address nor the recipient's address will be used for any other purpose. The information you enter will appear in your e-mail message and is not retained by Medical Xpress in any form.

Newsletter sign up

Get weekly and/or daily updates delivered to your inbox. You can unsubscribe at any time and we'll never share your details to third parties.

More information Privacy policy

Donate and enjoy an ad-free experience

We keep our content available to everyone. Consider supporting Science X's mission by getting a premium account.

E-mail newsletter

Napping may be beneficial for your brain – here’s how

Assistant Researcher in the MRC Unit for Lifelong Health and Ageing, UCL

Instructor in Anaesthesia Medicine, Harvard University

Senior Research Fellow in Genetic Epidemiology, UCL

Disclosure statement

Victoria Garfield receives funding from the Diabetes, Research and Wellness Foundation; the British Heart Foundation; and Diabetes UK.

Hassan S Dashti and Valentina Paz do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.

University College London provides funding as a founding partner of The Conversation UK.

View all partners

Sleep plays an important role in keeping the brain healthy, which is why people are advised to get at least 7-9 hours each night . When people have difficulties with sleep, for example, they usually feel more stressed. This is because a lack of sleep activates the body’s stress response , which affects different brain and body systems. This could lead to stress-related disorders.

Napping also appears to be beneficial to the brain – with research showing that even brief naps of 5-15 minutes can instantly improve how well you perform mentally. But could frequent napping have long-term benefits for our brains? Our latest study shows that they might – we found that habitual naps may help preserve brain health .

Our study aimed to uncover the potential causal relationship between daytime napping, cognitive function and brain volume. We focused on reaction time and memory because these cognitive abilities tend to decline as we get older . We also examined the hippocampus (an important brain structure for memory) and total brain volumes because they play a significant role in explaining differences in memory and overall thinking skills .

To conduct our study, we used a technique called Mendelian randomisation . This uses genetic markers to assess the relationship between exposures and outcomes (such as certain traits or diseases). We analysed data from 378,932 people aged 40-69 who had participated in the UK Biobank study (a large-scale biomedical database) We only studied people with white European ancestry, as they accounted for more than 80% of the participants of the Biobank study.

We looked at genetic variations previously discovered to be associated with daytime napping, based on the question “Do you have a nap during the day?” with possible responses: “never or rarely”, “sometimes” and “usually”. We used structural magnetic resonance imaging (MRI) data to study brain volumes and the results of computerised games that involved identifying matches of cards to test cognitive abilities.

We discovered that people who had genetic variations associated with napping also had larger total brain volume on average.

• Brain volume

Our brains naturally shrink gradually as we age. But this process is accelerated in people with neurodegenerative diseases such as Alzheimer’s. Some studies have also shown that people with cognitive impairment may experience a decrease in brain volume .

Additionally, previous research has indicated a connection between sleep problems and reductions in brain volume in various regions of the brain, which can be linked to cognitive decline. However, it’s important to note that these findings have been inconsistent across different studies, with some studies not finding any associations between sleep disruptions and structural brain changes. But overall this suggests that poor sleep may decrease brain volume – subsequently affecting brain health.

Our findings demonstrate a larger total brain volume with more frequent napping. This suggests that regular napping may act as a safeguard, compensating for inadequate sleep and preserving brain health.

Surprisingly, we did not find evidence to suggest that napping has an impact on reaction time, visual memory or the volume of the hippocampus. We speculate that different people’s napping experiences – such as nap duration and timing – and the tests employed to study cognitive abilities may have influenced our results. Moreover, these discoveries hint at the possibility that frequent daytime napping may affect other brain regions and mental skills, like alertness, which should be explored in future studies.

Our findings help clarify the impact of daytime napping on brain health, which may limit cognitive decline as a person ages. In the future, it would be valuable to investigate these associations in other ancestries and age groups. Moreover, it is important to replicate these findings by using different data sets and research methods. But, as far as we know right now, taking a brief nap in the early afternoon may be restorative and re-energising for those who need it – and may also be beneficial to brain health.

• Cognitive function
• Brain health

Lecturer in Indigenous Health (Identified)

Social Media Producer

Lecturer in Visual Art

PhD Scholarship

Senior Lecturer, HRM or People Analytics

Login to your account

If you don't remember your password, you can reset it by entering your email address and clicking the Reset Password button. You will then receive an email that contains a secure link for resetting your password

If the address matches a valid account an email will be sent to __email__ with instructions for resetting your password

Access provided by

Download started.

• PDF [1 MB] PDF [1 MB]
• Figure Viewer
• Download Figures (PPT)
• Add To Online Library Powered By Mendeley
• Add To My Reading List
• Export Citation
• Create Citation Alert

Is there an association between daytime napping, cognitive function, and brain volume? A Mendelian randomization study in the UK Biobank

• Victoria Garfield, PhD Victoria Garfield Affiliations MRC Unit for Lifelong Health & Ageing, Institute of Cardiovascular Science, University College London, London, UK Search for articles by this author
• • Whether daytime napping is causally associated with brain health remains elusive.
• • We studied the causal role of daytime napping on cognitive and neuroimaging outcomes.
• • We found a modest causal link between habitual napping and larger total brain volume.

Conclusions

• Mendelian randomization
• Visual memory
• Reaction time
• Brain health

Introduction

• Scopus (46)
• Google Scholar
• Milner C.E.
• Scopus (260)
• Scopus (30)
• Kocevska D.
• Koopman-Verhoeff M.E.
• Luijk M.P.C.M.
• Scopus (186)
• Scopus (144)
• Leong R.L.F.
• Chee M.W.L.
• Blazer D.G.
• Karlawish J.
• Scopus (91)
• Scopus (116)
• Ritchie S.J.
• Dickie D.A.
• Scopus (59)
• Tiemeier H.
• Scopus (24)
• Scopus (3291)
• Katsoulis M.
• Scopus (72)
• Andrews S.J.
• Fulton-Howard B.
• O’Reilly P.
• Scopus (66)

Grover S., Sharma, M. Sleep, pain, and neurodegeneration: a Mendelian Randomization Study. Frontiers in Neurology. 2022; 13. https://doi.org/10.3389/fneur.2022.765321 .

• Cárcel-Márquez J.
• Gallego-Fábrega C.
• Scopus (19)
• Anderson E.L.
• Richmond R.C.
• Scopus (26)

Participants and methods

• Gallacher J.
• Scopus (5349)

• Open table in a new tab

Study design

Genotyping and quality control (qc) in ukb.

• Scopus (3710)

Cognitive function measures

• Allerhand M.

Neuroimaging parameters

• Littlejohns T.J.
• Holliday J.
• Gibson L.M.
• Scopus (263)

Selection of genetic instruments

Main daytime napping genetic instrument.

• Dashti H.S.
• Scopus (83)
• Thompson S.G.
• Scopus (1226)

Additional daytime napping genetic instruments

Statistical analyses, main analyses.

Burgess S, Bowden J. Integrating summarized data from multiple genetic variants in Mendelian randomization: bias and coverage properties of inverse-variance weighted methods ArXiv151204486 Stat 2015. http://arxiv.org/abs/1512.04486 . Accessed August 31, 2021.

• Davey Smith G.
• Scopus (3882)
• Haycock P.C.
• Scopus (3484)

Sensitivity analyses

• a. To ensure that our results were robust, we performed all of our MR analyses additionally using a 47- and 86-SNP daytime napping instrument, as described earlier. We confirmed a priori before implementing our analyses that these instruments were of adequate strength (via F-statistics).

Testing of MR assumptions

• a. Associations between the genetic instrument and exposure instrumented (GWAS robust): this assumption was met, as the daytime napping variants that we instrumented here have been robustly associated with this phenotype in a recent very large-scale GWAS.
• b. No evidence of horizontal pleiotropy (no association between genetic instruments and the outcome, other than via the exposure under study): we tested this assumption by implementing MR-Egger and WME sensitivity analyses, as detailed above.
• Ancoli-Israel S.
• Scopus (70)

Sample characteristics

Main mr results, associations between daytime napping and total brain, and hippocampal volumes using a 92-snp genetic instrument.

• View Large Image
• Download Hi-res image
• Download (PPT)

Associations between daytime napping and cognitive function using a 92-SNP genetic instrument

Associations between daytime napping and total brain, and hippocampal volumes using 47- and 86-SNP genetic instruments

Associations between daytime napping and cognitive function using 47- and 86-snp genetic instruments, association between daytime napping and cognitive function using a 17-snp instrument with no sample overlap, testing mr assumption iii, associations between our main 92-snp daytime napping genetic instrument and common confounders.

• Veasey S.C.
• Scopus (34)
• Anderton B.H.
• Scopus (156)
• Van Der Werf Y.D.
• van den Heuvel O.A.
• Van Someren E.J.W.
• Full Text PDF
• Scopus (251)
• Scopus (45)
• Wiltshire J.
• Scopus (38)
• Musiek E.S.
• Holtzman D.M.
• Scopus (480)
• Hedman A.M.
• van Haren N.E.M.
• Schnack H.G.
• Hulshoff Pol H.E.
• Scopus (316)

He J., Farias S., Martinez O., Reed B., Mungas D., DeCarli C. Differences in Brain Volume, Hippocampal Volume, Cerebrovascular Risk Factors, and Apolipoprotein E4 Among Mild Cognitive Impairment Subtypes | Dementia and Cognitive Impairment | JAMA Neurology | JAMA Network. 2009; 66. https://jamanetwork.com/journals/jamaneurology/article-abstract/798403 . Accessed February 28, 2023.

• Eichenbaum H.
• Scopus (735)
• Campabadal A.
• Scopus (32)
• Saint-Martin M.
• Barthélémy J.C.
• Scopus (25)
• Scopus (140)
• Seong J.-K.
• Scopus (48)
• Scopus (106)
• Winkelman J.W.
• Benson K.L.
• Buxton O.M.
• Scopus (85)
• Spiegelhalder K.
• Baglioni C.
• Scopus (88)
• Sørensen Ø.
• Amlien I.K.
• Scopus (40)
• Silva M.V.F.
• Loures C.d.M.G.
• Alves L.C.V.
• de Souza L.C.
• Borges K.B.G.
• Carvalho M.d.G.
• Scopus (389)
• de Cos J.S.
• Montserrat J.M.
• Scopus (55)
• Terpening Z.
• Rogers N.L.
• Scopus (39)
• Peigneux P.
• Leproult R.

Limitations

Acknowledgments, declaration of conflicts of interest, ethics approval, appendix a. supplementary material.

Supplementary material

Article info

Publication history, identification.

DOI: https://doi.org/10.1016/j.sleh.2023.05.002

User license

• Read, print & download
• Redistribute or republish the final article
• Text & data mine
• Translate the article
• Reuse portions or extracts from the article in other works
• Sell or re-use for commercial purposes

ScienceDirect

• Download .PPT

Related Articles

• Access for Developing Countries
• Articles & Issues
• Articles In Press
• Current Issue
• List of Issues
• Special Issues
• Supplements
• For Authors
• Author Information
• Download Conflict of Interest Form
• Researcher Academy
• Submit a Manuscript
• Style Guidelines for In Memoriam
• Download Online Journal CME Program Application
• NSF CME Mission Statement
• Professional Practice Gaps in Sleep Health
• Journal Info
• About the Journal
• Activate Online Access
• Information for Advertisers
• Career Opportunities
• Editorial Board
• New Content Alerts
• Press Releases
• More Periodicals
• Find a Periodical
• Go to Product Catalog

The content on this site is intended for healthcare professionals.

• Privacy Policy   
• Terms and Conditions   
• Accessibility   
• Help & Contact

Session Timeout (2:00)

Your session will expire shortly. If you are still working, click the ‘Keep Me Logged In’ button below. If you do not respond within the next minute, you will be automatically logged out.

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings

Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now .

• Advanced Search
• Journal List
• Int J Environ Res Public Health

Effects of a Short Daytime Nap on the Cognitive Performance: A Systematic Review and Meta-Analysis

Frédéric dutheil.

1 CNRS, LaPSCo, Physiological and Psychosocial Stress, University Hospital of Clermont-Ferrand, CHU Clermont-Ferrand, Occupational and Environmental Medicine, WittyFit, F-63000 Clermont-Ferrand, France

Benjamin Danini

2 Preventive and Occupational Medicine, University Hospital of Clermont-Ferrand, F-63000 Clermont-Ferrand, France; [email protected]

Reza Bagheri

3 Department of Exercise Physiology, University of Isfahan, Isfahan 8174673441, Iran; [email protected]

Maria Livia Fantini

4 NPsy-Sydo, Sleep Disorders, University Hospital of Clermont-Ferrand, CHU Clermont-Ferrand, F-63000 Clermont-Ferrand, France; [email protected]_airam

Bruno Pereira

5 Clinical Research and Innovation Direction, CHU Clermont-Ferrand, F-63000 Clermont-Ferrand, France; rf.dnarreftnomrelc-uhc@arierepb

Farès Moustafa

6 Emergency Department, CHU Clermont-Ferrand, F-63000 Clermont-Ferrand, France; rf.dnarreftnomrelc-uhc@afatsuomf

Marion Trousselard

7 Neurophysiology of Stress, Armies’ Biomedical Research Institute, Armies’ Health Service, F-91220 Brétigny sur Orge, France; [email protected]

Valentin Navel

8 CNRS, INSERM, GReD, University Hospital of Clermont-Ferrand, Ophthalmology, CHU Clermont-Ferrand, Université Clermont Auvergne, F-63000 Clermont-Ferrand, France; [email protected]

Associated Data

All relevant data are within the paper.

Background: Napping in the workplace is under debate, with interesting results on work efficiency and well-being of workers. In this systematic review and meta-analysis, we aimed to assess the benefits of a short daytime nap on cognitive performance. Methods: PubMed, Cochrane Library, ScienceDirect and PsycInfo databases were searched until 19 August 2021. Cognitive performance in working-aged adults, both before and following a daytime nap or under control conditions (no nap), was analysed by time and by type of cognitive function (alertness, executive function and memory). Results: We included 11 studies (all in laboratory conditions including one with a subgroup in working conditions) for a total of 381 participants. Mean duration of nap was 55.4 ± 29.4 min. Overall cognitive performance did not differ at baseline (t0) between groups (effect size −0.03, 95% CI −0.14 to 0.07), and improved in the nap group following the nap (t1) (0.18, 0.09 to 0.27), especially for alertness (0.29, 0.10 to 0.48). Sensitivity analyses gave similar results comparing only randomized controlled trials, and after exclusion of outliers. Whatever the model used, performance mainly improved until 120 min after nap, with conflicting results during the sleep inertia period. Early naps in the afternoon (before 1.00 p.m.) gave better cognitive performance (0.24, −0.07 to 0.34). The benefits of napping were independent of sex and age. Duration of nap and time between nap and t1 did not influence cognitive performance. Conclusions: Despite the fact that our meta-analyses included almost exclusively laboratory studies, daytime napping in the afternoon improved cognitive performance with beneficial effects of early nap. More studies in real work condition are warranted before implementing daytime napping at work as a preventive measure to improve work efficiency.

1. Introduction

Napping in the workplace is under consideration, with putative benefits on work efficiency and well-being of workers [ 1 ]. Interestingly, productivity at work does not increase with working time [ 2 ], with a lack of sleep having a strong negative impact on work productivity [ 3 ]. Even if several countries benefited from the virtues of napping for millennia [ 4 ], rest time at work is still perceived as a waste of time [ 5 , 6 ] or a sign of laziness [ 7 , 8 ] in western countries. For example, the right to nap has been enshrined in the Chinese Constitution since 1949 [ 8 , 9 ]. In Japan, napping is ideologically accepted in the world of work it is even highly recommended by some companies. It is called “inemuri”, which literally means “to be asleep while present” [ 10 ]. Many scientists recommend taking an afternoon nap to increase alertness, specifically after lunch [ 11 ], to stimulate creativity, to strengthen our memory [ 12 , 13 , 14 ] and to improve the performance of complex tasks (executive function) [ 15 ]. The putative detrimental effects of napping at awakening, during the sleep inertia period, lack of data in real work conditions [ 16 ]. Research has demonstrated that a short nap can benefit cognitive performance the most [ 17 , 18 , 19 ], and the recuperative value of a nap is also dependent on when the nap is taken within the day [ 20 ]. World-famous companies, such as Google, NASA, HuffPost or Samsung, provide to their employees rest areas at work or dedicated nap furniture [ 21 , 22 ]. Considering the numerous studies on the effects of napping at work, a meta-analysis would allow us to synthesize all available evidence-based data from the literature. To the best of our knowledge, no meta-analysis assessed the effects of a daytime nap on cognitive performance. Therefore, we hypothesized that (1) napping at work during day time can benefit cognitive performance, (2) all types of cognitive performance (alertness, memory, executive function) can be improved by a nap, (3) duration of benefits may be prolonged with few detrimental effects during sleep inertia, (4) these effects may also be linked with characteristics of napping (duration, time between nap and test, time of the day) and individuals (age, gender), and conditions of realization of studies (real work or laboratory). Thus, we aimed to conduct a systematic review and meta-analysis on the effects of a short daytime nap on cognitive performance.

2.1. Literature Search

All the studies reporting the effects of a daytime nap on cognitive performance compared to a control group without nap were reviewed. The PubMed, Cochrane Library, ScienceDirect and PsycInfo databases were searched until 19 August 2021, with the following keywords: “daytime nap” OR “napping” AND “work” OR “occupation”. Animal studies were excluded. The search was not limited to specific years and no language restrictions were applied. The search strategy included working-age adults (more than 18 years old), working only on daytime hours. Studies related to night shift work were excluded, as studies mentioning the use of therapeutic adjuvant in addition to nap. Studies related to the effect of nap on fatigue were also excluded because we aimed to analyze only cognitive performance. To be included, articles needed to be controlled studies describing our primary outcome, i.e., the assessment of cognitive performance after a short daytime nap. The search strategy is presented in Figure 1 . Two authors (BD and LF) conducted all the literature searches and collated the abstracts. Three authors (BD, LF and VN) separately reviewed the abstracts and decided the suitability of the articles for inclusion based on the selection criteria. A fourth author (FD) was asked to review the articles where consensus on suitability was debated. All authors then reviewed the eligible articles. We followed the PRISMA guidelines ( Supplementary Materials File S1 ).

Search strategy.

2.2. Quality of Assessment

The “Consolidated Standards of Reporting Trials” (CONSORT) [ 23 ] and the “STrengthening the Reporting of OBservational studies in Epidemiology” (STROBE) [ 24 ] statements were, respectively, used for checking the quality of randomised and non-randomised controlled study reporting. One point was attributed per item or sub-item, with a maximal score of 37 and 32, respectively, then converted into a percentage ( Supplementary Table S1 ). The quality of included studies was also assessed using the “Scottish Intercollegiate Guidelines Network” (SIGN) [ 25 ] Methodology checklist. Items assessing internal validity were quoted as “Yes”, “No”, or “Can’t say”. Overall assessment of studies was quoted as “unacceptable”, “acceptable” or of “high quality”. One point was attributed per response “Yes” or “High Quality”, for a maximal score of 10 for randomised controlled trials (RCT) and 7 for non-RCT, then converted into a percentage ( Figure 2 ).

Methodological quality of included articles and summary bias risk. Using the “Scottish Intercollegiate Guidelines Network” (SIGN) Methodology checklist 2 Yes: +; No: − Can’t say: ?; Not applicable: NA; RCT: Randomized controlled trials; * item only for randomized studies.

2.3. Statistical Considerations

Statistical analysis was conducted using Stata software (v15, StataCorp, College Station, TX, USA) [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. Baseline characteristics were summarized for each study sample and reported as mean (standard deviation) and number (%) for continuous and categorical variables, respectively. Heterogeneity in the study results was evaluated by examining forest plots, confidence intervals (CI) and using formal tests for homogeneity based on the I-squared (I 2 ) statistic. I 2 is easily interpretable and the most common metric to measure the magnitude of between-study heterogeneity. I 2 values range between 0% and 100% and are typically considered low for <25%, modest for 25–50%, and high for >50%. This statistical method generally assumes heterogeneity when the p -value of the I 2 test is <0.05. For example, a significant heterogeneity may be due to the variability between the characteristics of the studies such as those of workers (age, sex, etc.), or those of nap (duration, time of the day). Random effects meta-analyses (DerSimonian and Laird approach) were conducted when data could be pooled [ 34 ]. p values less than 0.05 were considered statistically significant. We conducted a meta-analysis on the effects of daytime napping on cognitive performance at work. We first conducted one meta-analysis on cognitive performance at baseline (t0) to verify that groups were comparable before the intervention (nap). Then we conducted a meta-analysis on overall cognitive performance after a nap (t1) between groups (nap vs. no nap), stratified on the type of cognitive functions (alertness, executive functions, and memory) and on the time of the analysis: <30 min after the nap, 31 min to 60, 61 to 120 min, and >121 min. Then, we conducted two separate meta-analyses on the effects of nap versus baseline (t1 vs. t0): one within the nap group, and one within the control group. Finally, we conducted a meta-analysis on changes in performance between groups ((t1 − t0)/t0). We also stratified those meta-analyses on the type of cognitive functions and the time between nap and tests. We described our results by calculating the effect size (ES, standardized mean differences—SMD) of cognitive performance for each dependent variable [ 34 ]. A positive ES denoted improved performance. All meta-analyses were also conducted after the exclusion of non-RCT. For rigor, funnel plots (metafunnels) of these meta-analyses were used to search for potential publication bias. In order to verify the strength of the results, further meta-analyses were then conducted excluding outliers, i.e., studies that were not evenly distributed around the base of the funnel [ 35 ]. When possible (sufficient sample size), meta-regressions were proposed to study the effects of daytime nap on cognitive performance relevant parameters such as the workers’ gender, age, the time of nap beginning, duration of nap, time between test and nap. Results were expressed as regression coefficients and 95%CI.

An initial search on the selected databases found 1002 articles. Once the duplicate articles were removed and using the inclusion criteria, this number was reduced to 17 articles dealing with cognitive performance after a daytime nap, which was included in the systematic review. After a detailed analysis of the articles, three [ 36 , 37 , 38 , 39 ] were excluded because the numerical data were not available to perform a statistical analysis of the results. Another three articles [ 13 , 39 , 40 ] were also excluded due to a lack of baseline (t0) in the protocol which distorts comparability of tests after the nap, and one article [ 39 ] was excluded because of the two previous criteria. The final sample included in our meta-analysis, therefore, reports 11 articles [ 6 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ] ( Figure 1 ). All articles are written in English. The characteristics of included studies were available in Supplementary Table S1 .

3.1. Quality of Articles

The assessment of the quality of the 11 included studies that were included was performed using the CONSORT for the six RCT [ 6 , 43 , 44 , 45 , 46 , 50 ] and STROBE criteria for the five non-RCT [ 41 , 42 , 47 , 48 , 49 ], with, respectively, a mean score of 42.9 ± 8.5%, ranging from 31.4 [ 45 ] to 57.1% [ 46 ] and a mean score of 41.9 ± 6.5%, ranging from 34.4 [ 48 ] to 50% [ 41 ] ( Supplementary Table S1 ). Using the SIGN criteria, RCT had a mean score of 61.7 ± 9.8%, ranging from 50.0 [ 44 ] to 80.0% [ 46 ], and all non-RCT had a score of 83.3% [ 41 , 42 , 47 , 48 , 49 ]. Thus, the total score using SIGN for the 11 studies was 71.5 ± 13.27%, ranging from 50 [ 44 ] to 83.3% [ 41 , 42 , 47 , 48 , 49 ] ( Figure 2 ). Overall, the studies performed best in the Section 1 and worst in the title/abstract and Section 3 . Most studies (9/11, i.e., 81.8%) mentioned ethical approval [ 6 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 50 ].

3.2. Inclusion Criteria of Participants

The main inclusion criteria were to be an adult [ 6 , 42 , 43 , 44 , 45 , 46 , 47 ] or a student [ 41 , 48 , 49 , 50 ], in good health [ 6 , 42 , 43 , 44 , 45 , 46 , 48 , 50 ] or to be a good sleeper [ 46 ]. To be habitual afternoon nappers was necessary for one study [ 43 ]. The main exclusion criteria were night shift workers [ 41 , 44 , 50 ], any sleep disorders [ 6 , 42 , 44 , 45 , 46 ], smokers [ 43 , 45 , 46 ], caffeine and alcohol consumption [ 6 , 42 , 43 , 44 , 45 , 46 , 48 , 49 ], or excessive physical exercise the day of the study [ 42 , 43 ], psychoactive drugs or medication use [ 43 , 45 , 46 , 49 , 50 ], medication that might alter sleep architecture or ability to fall asleep [ 6 , 44 , 48 ], regular nappers [ 45 ], excessive morning-evening type [ 45 ], a short sleep duration per night [ 50 ] or anxiety and depression symptoms [ 50 ].

3.3. Population

3.3.1. sample size.

381 participants were included: 209 in the nap group and 188 in the control group, among which 16 were enrolled in a crossover condition. Mean population size was 34.6 ± 20.0 ranging from 8 [ 42 , 47 ] to 76 [ 50 ]. Mean proportion of subjects in the nap group was 51.7 ± 7.9% ranging from 41.4 [ 48 ] to 66.7% [ 44 ].

Proportion of male in the nap group was 55.5 ± 10.9%, ranging from 45.2 [ 44 ] to 75% [ 42 ], and 46.7 ± 20.1% in the control group, varying from 14.3 [ 44 ] to 75% [ 42 ]. Five studies [ 43 , 45 , 46 , 47 , 49 ] did not report proportion of male.

Mean age in the nap group was 33.7 ± 2.6 years and 29.6 ± 1.8 years in the control group, ranging from 20.1 [ 48 ] to 70.4 years [ 44 ] and from 20.1 [ 48 ] to 73.9 years [ 44 ], respectively.

3.3.4. Other

Other characteristics were seldom reported, such as body mass index which was reported only in one study [ 41 ] and smoking in three studies [ 43 , 45 , 46 ]. The lack of data for those variables precluded further analysis.

3.4. Aims and Outcomes of Included Articles

The primary objective of most studies (10/11, i.e., 90.9%) was to examine the effect of a short midday nap on cognitive performance [ 6 , 41 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. The aim of one study was to investigate the effect of sleep inertia after a daytime nap [ 42 ].

3.5. Study Designs

All included studies were interventional prospective controlled trials, among two studies (18.2%) with a crossover design [ 42 , 47 ] and six were RCT (54.5%) [ 6 , 43 , 44 , 45 , 46 , 50 ].

3.6. Characteristics of Intervention

Duration of nap: Mean duration of nap, i.e., time of sleep duration was 55.4 ± 29.4 min, varying from 15 [ 47 ] to 90 min [ 6 , 44 , 45 , 50 ].

Number of naps per day: All studies evaluated the effect of one nap per day in the early afternoon [ 6 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ].

Time of nap beginning: All studies gave information on the time of the nap. Mean hour time of nap was 1.32 pm (SD = 44.4 min), varying from 12.30 pm [ 47 ] to 14.45 pm [ 43 ].

The study environment took place in a sleep laboratory in all studies [ 6 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. Only one study was also in the usual work environment, i.e., in medical departments of first-year internal medicine residents [ 41 ].

The activity of control group during nap: During the nap of the intervention group, the control group had the opportunity to rest [ 41 , 42 , 44 , 45 , 48 , 50 ] or to do a quiet activity like watching TV [ 6 , 43 , 47 ], reading [ 46 ] or playing a card game [ 45 ].

Time of testing: All studies assessed baseline (t0) cognitive performance before the nap [ 6 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ]. The mean time between baseline testing and the intervention, nap or no-nap, was 86.3 ± 80.4 min, varying from 10 [ 47 ] to 285 min [ 41 ]. Mean time between nap and the repeat test (t1) was 77.0 ± 59.9 min, varying from 1.5 [ 42 ] to 240 min [ 48 ].

3.7. Measurements of Cognitive Performance

Cognitive performance was evaluated with measures of alertness in five studies [ 41 , 42 , 43 , 46 , 47 ], executive functions in six studies [ 41 , 42 , 43 , 48 , 49 , 50 ] and memory in seven studies [ 6 , 43 , 44 , 45 , 48 , 49 , 50 ] (details of test used for measures of cognitive function in Supplementary Materials File S2 ). Alertness was evaluated with seven tests: Electroencephalographic and electrooculographic recording [ 41 ], Conner’s Continuous Performance Test Version 5 [ 41 ], Arrow-orientation task [ 42 ], Test of Attentional Performance [ 43 ], Ball and cup task [ 46 ], Choice reaction time task [ 47 ] and an Alertness scale [ 47 ]. Executive functions were evaluated with five tests: Conner’s Continuous Performance Test Version 5 [ 41 ], Arrow-orientation task [ 42 ], Auditory oddball task [ 46 ], Mirror Tracing Task [ 43 , 48 , 50 ], and Maze learning task [ 49 ]. Memory was evaluated with nine tests: Paired associates learning [ 43 ], Digit span backwards task [ 43 , 48 ], Verbal learning and memory test [ 44 ], Motor adaptation task [ 44 ], Sequential finger-tapping task [ 45 ], Direct associative (face–object) memory [ 6 ], Paired associates task [ 48 ], Semantically unrelated paired associates [ 49 ], and Word-pair task [ 50 ].

3.8. Meta-Analysis on Performance between Groups at Baseline (t0) by Activity

Overall cognitive performance at baseline (t0) did not differ between nap vs. control groups (effect size −0.03, 95% CI −0.14 to 0.07, I 2 = 21.2%), nor after exclusion of outliers [ 41 , 44 , 50 ] (−0.01, −0.10 to 0.09, I 2 = 0.0%), nor after exclusion of non-RCT [ 41 , 42 , 47 , 48 , 49 ] (−0.04, −0.16 to 0.09, I 2 = 17.2%) ( Figures S1 and S2 ). Stratification by cognitive functions (memory, alertness, and executive functions) demonstrated similar results, i.e., no difference between nap and control groups for the overall analyses, as well as after exclusion of outliers [ 41 , 44 , 50 ] and after exclusion of non-RCT [ 41 , 42 , 47 , 48 , 49 ]—except for executive functions that were lower in the nap group compared to the control group but only in the sensitivity analyses with two RCT ( Figures S1 and S2 ).

3.9. Meta-Analysis on Overall Effects of Nap between Groups

Overall cognitive performance improved in the nap group following the nap (t1) compared to the control group (effect size 0.18, 95% CI 0.09 to 0.27, I 2 = 4.3%) ( Figure 3 , Figure 4 , Figures S2 and S3 ). Stratifying analysis by type of cognitive functions, all types of cognitive performance increased or tended to increase after napping compared with controls (memory: 0.11, −0.01 to 0.24, I 2 = 0.0%; alertness: 0.29, 0.10 to 0.48, I 2 = 38.9%; and executive functions: 0.23, 0.00 to 0.47, I 2 = 0.0%). Stratifying analysis by time of analysis, cognitive performance improved less than 30 min (0.22, 0.03 to 0.42, I 2 = 33.6%), 61 to 120 min (0.28, 0.09 to 0.48, I 2 = 1.0%) and more than 120 min after nap (0.20, 0.04 to 0.37, I 2 = 0.0%). Similar results were found after exclusion of outliers [ 47 , 50 ] and after exclusion of non-RCT [ 41 , 42 , 47 , 48 , 49 ], except less than 30 min after nap which was no more significant after exclusion of outliers ( Figure 3 , Figure 4 , Figures S2 and S3 ).

Summary of meta-analysis on cognitive performance between groups (nap vs. control), for each cognitive function: before ( left ), after ( middle ) exclusion of studies not evenly distributed around the funnel plot and ( right ) non-randomised controlled trials. For details of the meta-analysis at each analysis time, please see Figure S3 for meta-analyses t1. For details of the meta-analysis on each cognitive function, please see Figure S1 for meta-analyses at t0, and Figure 4 for t1. For details of the meta-analysis on each group, please see Figure 4 and Figure S4 for the nap group, Figure 5 for the control group. t0: baseline; t1: after intervention (nap or no-nap). Each overall summary of a meta-analysis is represented in the graph by a dot on a vertical line. The black dots represent the overall pooled-effect estimate of individual meta-analyses (pooled effect size—ES), and the length of each vertical line around the dots represents their 95% confidence interval (95CI). Shorter lines represent a narrower 95CI thus higher precision around pooled-ES. Conversely, longer lines represent a wider 95CI and less precision around pooled-ES. The black solid horizontal line represents the null estimate (with a value of 0 for pooled-ES). Vertical lines that cross the null horizontal line represent a non-significant overall summary of the meta-analysis at each time analysed (t0 and t1).

Summary of meta-analyses on cognitive performance stratified on type of cognitive function and on time of analysis at t1 between groups. Each summary of meta-analysis is presented in three conditions: global model with all the studies, after exclusion of outliers (studies not evenly distributed around the funnel plot) and with only randomized controlled trials. Each summary of several meta-analyses is represented in the forest plot by a dot on a horizontal line. The black dots represent the pooled-effect estimate (pooled effect size—ES), and the length of each line around the dots represents their 95% confidence interval (95CI). Shorter lines represent a narrower 95CI thus higher precision around pooled-ES. Conversely, longer lines represent a wider 95CI and less precision around pooled-ES. An overall summary of the results of the meta-analyses pooled-estimate (result of the overall meta-analysis) is represented by a blue lozenge at the end of the graph. The black solid vertical line represents the null estimate (with a value of 0 for pooled-ES). Horizontal lines that cross the null vertical line represent the non-significant overall summary of the meta-analysis. Bold numbers represent the overall result of each meta-analysis.

3.10. Sensitivity Analysis

Meta-analysis on effects of nap within the nap group ( Figure 5 , Figures S2, S4 and S5 ) and meta-analysis on performance change ( Figure 5 and Figure S6 ) between groups demonstrated similar overall effects of napping (effect size 0.34, 95% CI 0.23 to 0.45, I 2 = 35.8%, and 1.26, 0.79 to 1.73, I 2 = 93.3%, respectively). Similar results were demonstrated stratifying by type of cognitive performance and by time, globally, after exclusion of outliers [ 41 , 44 , 45 , 47 , 50 ] and of non-RCT [ 41 , 42 , 47 , 48 , 49 ] ( Figure 5 , Figures S2, S4 and S6 ). Lastly, comparisons of performance at t1 vs. t0 within the control group ( Figure 5 , Figures S2 and S7 ) mostly did not show differences for overall cognitive performance (0.08, −0.03 to 0.19, I 2 = 31.8%), as well as stratifying the analysis by type of cognitive functions and by time, globally, after exclusion of outliers [ 41 , 44 , 45 , 47 , 50 ] and of non-RCT [ 41 , 42 , 47 , 48 , 49 ] ( Figure 5 , Figures S2 and S7 ). Detail text is available in Supplementary Materials File S3, and Supplemental Figures in Figures S2 and S4–S7 .

Summary of sensitivity analysis: meta-analyses on cognitive performance at t1 compared with baseline (t0) within the nap group ( left ), meta-analyses on cognitive performance at t1 compared with baseline (t0) within the control group ( middle ), meta-analyses on changes in performance between t1 and t0 ((t1 − t0)/t0) between nap and control groups ( right ) Each summary of meta-analysis is presented in three conditions: global model with all the studies, after exclusion of outliers (studies not evenly distributed around the funnel plot) and with only randomized controlled trials For details of each meta-analysis, please see Figures S4, S6 and S7 . Each summary of several meta-analyses is represented in the forest-plot by a dot on a horizontal line. The black dots represent the pooled-effect estimate (pooled effect size—ES), and the length of each line around the dots represents their 95% confidence interval (95CI). Shorter lines represent a narrower 95CI thus higher precision around pooled-ES. Conversely, longer lines represent a wider 95CI and less precision around pooled-ES. An overall summary of the results of the meta-analyses pooled-estimate (result of the overall meta-analysis) is represented by a blue lozenge at the end of the graph. The black solid vertical line represents the null estimate (with a value of 0 for pooled-ES). Horizontal lines that cross the null vertical line represent the non-significant overall summary of the meta-analysis.

3.11. Metaregressions

Men tended to have poorer cognitive performance than women at baseline (coefficient −0.02, 95% CI −0.03 to 0.002, p = 0.086), as well as older participants compared to younger ones (0.01, 0.01 to 0.02, p < 0.001). The benefits of napping on changes in performance were independent of sex and age ( p > 0.05). Napping early at the beginning of the afternoon (before 1 p.m.) was more effective on cognitive performance compared with after 1 p.m. (0.28, 0.10 to 0.46, p = 0.003). Duration of nap and time between nap and t1 did not influence cognitive performance ( Figure 6 ).

Summary of meta-regressions: 95%CI: 95% confidence intervals; t0: baseline; t1: after nap (nap group) or rest without nap (control group) Results were presented before ( left ) and after ( right ) exclusion of non-randomized controlled trials The effect of each variable on the outcome is represented in the forest-plot by a dot on a horizontal line. The black dots represent the coefficient for each variable, and the length of each line around the dots represents their 95% confidence interval (95CI). The black solid vertical line represents the null estimate (with a value of 0). Horizontal lines that cross the null vertical line represent non-significant variables on the outcome. Bold numbers represent the significant results ( p < 0.05).

4. Discussion

The main findings were that napping in the afternoon improved cognitive performance, especially for alertness. However, the duration of benefits should warrant further studies, as napping seemed to improve performance within two hours, with conflicting results during the sleep inertia period. An early nap in the afternoon may be beneficial to cognitive performance. Gender and age did not influence cognitive performance, as well as the duration of nap and time between nap and t1. Our meta-analyses included almost exclusively laboratory studies so results were more difficult to transpose in real work conditions.

4.1. Nap and Cognitive Performance

Many people take daytime naps, with the frequency of napping varying considerably depending on the country, from 36% to 80% [ 51 ]. Reasons for napping are multiple: in response to sleep loss (i.e., replacement napping), in preparation for sleep loss (i.e., prophylactic napping), or just for enjoyment (i.e., appetitive napping) [ 52 ]. Our study demonstrated that napping in the afternoon improved all types of cognitive performance. Napping is particularly beneficial to performance on tasks [ 53 ], such as addition, logical reasoning, reaction time [ 54 ], and symbol recognition [ 55 ]. Napping appears beneficial for all types of memory, either procedural [ 56 ], declarative [ 57 ] or short-term memory [ 19 ]. Daytime napping offers various other benefits such as relaxation, reduced fatigue [ 58 ] and improve mood [ 55 ]. Napping can boost creativity [ 59 , 60 ] and productivity [ 61 ], improve physical performance [ 62 ] and help people to cope with fatigue related to shiftwork [ 63 , 64 , 65 ]. Daytime sleep may also offer cardiovascular benefits in the form of greater cardiovascular recovery from psychological stress [ 66 ]. For example, taking a midday nap, occasionally or at least three times per week, was reported to be inversely associated with coronary mortality. This association was particularly evident among working men [ 67 ].

4.2. Duration of Benefits and Sleep Inertia

The literature reports that the benefits of daytime napping may last 2.5 h [ 68 ], with conflicting results during the sleep inertia period, i.e., after awakening [ 55 , 69 ]. These findings were in accordance with results from our study, in which the positive effects of the nap were mainly 30–120 min following awakening. For the 30 min after napping, results were mitigated and variable, depending on sensitivity analyses, reflecting putative effects of sleep inertia [ 16 ]. Even if we did not find an influence on the duration of the nap, the literature suggests that short naps may benefit more on cognitive performance—possibly because napping more than 30 min produces sleep inertia, making nap benefits obvious only after a delay [ 55 ]. Sleep inertia reflects a transition from a sleep state to a waking state [ 19 ] and is characterized by a reduction in the ability to think and perform upon awakening due to sleep [ 55 ]. This period is a state of grogginess, confusion [ 70 ] and lowered arousal [ 71 , 72 ]. The magnitude of sleep inertia is mostly dependent on the quantity of slow-wave sleep contained within the nap [ 73 ]. Sleep inertia is greater following longer naps that typically contain more slow-wave activity than shorter naps [ 11 , 74 , 75 ]. So, to avoid sleep inertia, naps should be short (20–30 min), and should not occur at the bottom of the circadian phase [ 76 , 77 ]. Paradoxically, in older adults [ 78 ] and not in middle-aged workers, napping might both increase morbidity [ 79 , 80 , 81 , 82 , 83 ]—cardiovascular disease, falls and cognitive impairment—and mortality [ 84 , 85 , 86 , 87 ]. Daytime napping could also diminish the quality of sleep at night [ 8 ].

4.3. Environmental and Individual Characteristics

The recuperative value of a nap depends also on the 24-h circadian rhythm. We showed that early nap in the afternoon has greater benefits, in line with the literature [ 88 , 89 ]. Our organism is physiologically programmed to rest in the afternoon. Our biological clock controls a biphasic rhythm with two periods conducive to sleep, varying with body temperature. The first peak of drowsiness occurs between 1 and 5 a.m., the second twelve hours later, i.e., between 1 to 5 p.m. [ 90 ]. The decrease in alertness within the afternoon is wrongly associated with digestion [ 91 ], but is mainly due to our circadian rhythm [ 92 , 93 ]. So it could suggest a night sleep and a nap in the early afternoon, i.e., when we are naturally less vigilant [ 90 ]. However, ideally, workers may also benefit to nap according to their circadian rhythm rather than clock time. Other factors such as individual characteristics (e.g., age, gender) may also influence the benefits of napping [ 55 ]. Elderly nap more frequently than youngers [ 55 , 94 , 95 , 96 ]. Many factors are likely to contribute, such as disturbed night-time sleep [ 97 , 98 ], age-related phase advance of circadian rhythm [ 99 ], comorbidities [ 96 ] or some combination of those [ 57 ]. In our study, gender and age did not influence cognitive performance after a nap. However, literature suggested sex differences in benefits of daytime sleep, for example, greater benefits on memory for women [ 100 ]. A lab environment does not completely duplicate the real world. As our meta-analyses included mainly lab studies, the applicability of our results to real work must be inferred [ 101 ].

4.4. Limitations

Our study has some limitations like all meta-analyses [ 102 ]. Meta-analyses inherit the limitations of the individual studies of which they are composed and therefore are subjected to the bias of included studies. We conducted the meta-analyses on published articles only so there are potentially exposed to the publication bias [ 103 , 104 ]. Studies with positive results are more likely to be published than studies with negative results, which may also lead to this bias. Moreover, we included a limited number of participants. Our results were based on studies with small sample sizes, that typically have low statistical power, and large standard errors [ 105 ]. As a result, a meta-analysis based on these studies can produce effect sizes that are very heterogeneous, and the findings may lead to erroneous inferences [ 102 ]. However, this risk is limited because funnel plots had homogenous distributions [ 106 ]. We limited the influence of extreme results and heterogeneity by reperforming analyses after exclusion of non-randomized studies and of those with results not evenly distributed around the funnel plots. Though there were similarities between the inclusion criteria, they were not identical. Another limitation of our meta-analysis is the quality of the control group. Participants from the control group did not take a nap but realized relaxing activities which are very different from real work. This could minimize our results. Nearly all data were also in laboratory condition, except one study. Consequently, it is hard to make conclusions of the effects of napping on cognitive performance during daytime work, decreasing the external validity [ 107 ] and strongly enhancing the level of evidence for napping at work. The environment differs widely between working conditions and sleep lab rooms in hospitals. Consequently, the final number of patients included in the meta-analysis was not very high and may preclude generalizability.

5. Conclusions

Napping in the afternoon improved cognitive performance and especially alertness, until two hours after the nap, with conflicting results during the sleep inertia period. Early nap in the afternoon was more effective on cognitive performance. However, our meta-analyses included almost exclusively laboratory studies. Before recommending daytime napping at work as a preventive strategy, further studies should evaluate the effects of naps on cognitive performance in real work conditions to make the results more generalizable.

Supplementary Materials

The following are available online at https://www.mdpi.com/article/10.3390/ijerph181910212/s1 . Supplementary Materials File S1: PRISMA Checklist, Supplementary Materials File S2: Details of test used for measure of cognitive functions in included articles; Supplementary Materials File S3. Details text of sensitivity analysis, Supplementary Table S1: Characteristics of included studies; Figure S1: Summary of meta-analyses on cognitive performance for each cognitive function at baseline (t0) between groups, Figure S2: Funnel plot-Meta-analysis on overall performance between groups at baseline (t0), at t1 and on comparison between t1 and t0 for each group (nap and control) and stratified on type cognitive function, Figure S3: Meta-analysis on overall effects of nap within the nap group (t1 vs. t0) stratified on time of analysis, Figure S4: Summary of meta-analyses on cognitive performance at t1 compared with baseline (t0) within the nap group, stratified on type of cognitive function and on time of analysis; Figure S5. Meta-analysis on overall effects of nap within the nap group (t1 vs. t0) stratified on type of cognitive function; Figure S6. Summary of meta-analyses on changes in performance between t1 and t0 between groups; Figure S7. Summary of meta-analyses on cognitive performance at t1 compared with baseline (t0) within the control group, stratified on type of cognitive function and on time of analysis.

Author Contributions

Conceived and designed the study: F.D., B.D., V.N., M.L.F. Conducted the systematic literature search: B.D. Final approval of eligible articles: F.D., B.D., V.N., M.T., R.B. Analyzed the data: B.D., F.D., V.N., B.P. Wrote the first draft of the article: B.D., F.D., V.N., F.M. Critical revision of the article: all authors. Integrity of the data analysis: B.D., F.D., V.N., B.P. All authors have read and agreed to the published version of the manuscript.

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Data availability statement, conflicts of interest.

No conflicting relationship exists for any author.

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

The science of naps

Researchers are working to pinpoint the benefits — and possible drawbacks — of an afternoon snooze.

By Kirsten Weir

2016, Vol 47, No. 7

Print version: page 48

Feeling drowsy? You could pour a cup of coffee or take a brisk walk, but there is a cozier alternative: the nap. Daytime dozing is becoming a workplace trend. Ben & Jerry's, Zappos, Uber and Google have installed dedicated nap spaces in their headquarters, in hopes that some midday shuteye will boost employee productivity and creativity. While company nap rooms might still be an exception rather than a rule, a sizeable fraction of Americans still find a way to squeeze in a nap. According to a 2009 report by the Pew Research Center, a third of U.S. adults nap on any given day.

For people who don't catch enough Zs during the night, daytime naps can improve alertness and motor performance. "Everybody agrees that if you are sleep deprived, you can't learn, perform or think very well," says Jerome Siegel, PhD, director of the Center for Sleep Research at the University of California, Los Angeles.

But for healthy adults who do get a reasonable amount of nighttime sleep, is there any benefit to a midday nap? Signs point to yes, says Kimberly A. Cote, PhD, a psychology professor at Brock University in Ontario. While little work has been done to look at the long-term effects of habitual napping, studies point to a variety of immediate benefits following an afternoon nap. "If you're talking about a healthy adult population, I think just about anyone could benefit from a nap," she says.

Sleep and learning

Even in well-rested people, naps can improve performance in areas such as reaction time, logical reasoning and symbol recognition, as Cote described in a 2009 review ( Journal of Sleep Research , 2009). They can also be good for one's mood.

A study by University of Michigan doctoral student Jennifer Goldschmied and colleagues found that after waking from a 60-minute midday nap, people were less impulsive and had greater tolerance for frustration than people who watched an hourlong nature documentary instead of sleeping ( Personality and Individual Differences , 2015). "Frustration tolerance is one facet of emotion regulation," says Goldschmied. "I suspect sleeping gives us more distance [from an emotional event] — it's not just about the passing of time."

Researchers are only just starting to understand how naps might affect emotion regulation, Goldschmied adds. But the benefits of napping for memory and learning are well described. "Even a brief bit of sleep helps reinforce learned material," she says.

For many types of memory, the benefits of a nap are substantial, says Sara Mednick, PhD, a psychologist at the University of California, Riverside. Take perceptual learning. Previous research demonstrated that people perform better on a visual texture-distinguishing task after a night of sleep than they do immediately after learning it. Further, Mednick and colleagues found people performed just as well on the test after a 60- to 90-minute nap as they did after a full night of slumber ( Nature Neuroscience , 2003).

"What's amazing is that in a 90-minute nap, you can get the same [learning] benefits as an eight-hour sleep period," Mednick says. "And actually, the nap is having an additive benefit on top of a good night of sleep."

In another experiment, Mednick found that an afternoon nap was about equal to a dose of caffeine for improving perceptual learning. But in other ways, a midday doze might trump your afternoon latte. She found people who napped performed better on a verbal word-recall task an hour after waking compared with people who took caffeine or a placebo ( Behavioural Brain Research , 2008). While caffeine enhances alertness and attention, naps boost those abilities in addition to enhancing some forms of memory consolidation, Mednick notes.

A catnap can benefit performance in a variety of other memory domains as well. In one recent example, Axel Mecklinger, PhD, at Saarland University in Germany, and colleagues studied memory recall in volunteers who learned single words as well as meaningless word pairs (such as "milk-taxi"). Half of the participants then took a 90-minute nap, while the others watched a DVD. Then the researchers retested participants' recall.

Both groups remembered about the same number of single words. This was a test of so-called item memory — the type of memory you use when you recall a grocery list. But the nappers remembered significantly more of the word pairs. This type of "associative memory" is involved in remembering things that are linked, such as putting a name with a face. And unlike item memory, the hippocampus plays a strong role in associative memory, suggesting that naps benefit hippocampus-dependent learning ( Neurobiology of Learning and Memory , 2015).

Other research builds the case that the hippocampus benefits from a nap. Matthew Walker, PhD, a professor of psychology at the University of California, Berkeley, and colleagues recruited volunteers to tax their associative memories by learning a long list of name-face pairings.

Half the participants then took 90-minute midday naps. That evening, the participants were given a new round of learning exercises with novel pairings. Those who hadn't napped didn't perform as well on the evening test as they had in the morning. But the nappers did better on the later test, suggesting the sleep had boosted their capacity for learning ( Current Biology , 2011).

Adaptive behavior

Not all the nap research is so glowing, however. Some studies have suggested that excessive sleep and daytime naps are associated with higher levels of C-reactive protein, a marker for systemic inflammation (which has been linked to a host of ills, including cancer, diabetes, depression and heart disease). Yet other research suggests naps can improve immune function. Indeed, a review by Rebecca Spencer, PhD, found the picture is almost comically muddy: Various studies in various populations have found that too much sleep, too little sleep, frequent naps and infrequent naps can all be linked to elevated C-reactive protein. Ultimately, more work needs to be done to understand what patterns of nighttime and daytime sleep are healthy, and for whom ( Sleep Medicine , 2015).

Other concerns about the downside of naps are better established. The biggest concern is that daytime sleep can disrupt nighttime sleep. Sleeping too much during the day can interfere with the ability to fall asleep and stay asleep at night. That's why, says Siegel, "one of the standard instructions at sleep disorder centers is to tell people not to nap."

Siegel admits he's never been a napper himself. His research suggests he's hardly alone in that respect. In a recent study, he and his colleagues tracked the sleep patterns of hunter-gatherer groups in Tanzania, Namibia and Bolivia. These people are thought to live much like our ancestors did some 10,000 years ago. And while nearly all of them took a break from the sun during the heat of midday, none of the 94 individuals they followed took regular naps.

"I'm not saying we should do everything our ancestors did, but it suggests that napping is not a part of the ancient human physiology," Siegel says.

Still, just because Siegel's subjects didn't nap doesn't mean naps have no benefit, says Cote. "Sleep is a behavior, and human behavior is highly adaptable," she says. "We get sleep in many ways. After a certain age, naps are not biologically necessary, but napping does have benefits."

It's likely that some people benefit more than others, though. "A certain percentage of people are regular nappers. If you ask these people, they'll be aware they're getting benefit: They're more alert, have better moods and they're feeling sharper," Cote says.

But others — including Cote — wake up groggy after naps and drag the rest of the day. She believes people who choose to nap regularly are predisposed to get more out of it. Some of her own laboratory research suggests that frequent nappers show greater improvements in performance following a midday nap than people who don't often nap ( Biological Psychology , 2006). "I think we self-select this behavior," she says.

Other research is starting to piece together clues about who benefits from naps, and why. In not-yet-published research, Goldschmied and colleagues found evidence that people who self-identify as night owls tend to show bigger improvements in performance following a nap, compared with their early-bird counterparts.

The way you move through the stages of the sleep cycle may also play an important part in whether you're a born napper or not. Mednick (who loves a nap when she can get it) says people who nap regularly appear to stay in lighter stages of sleep that they can wake from easily, while infrequent nappers often sink into deeper sleep and wake up woozy. "It appears there's a qualitative difference to naps," she says.

Further reading

• Mednick, S., with Ehrman, E. (2006). Take a nap! Change your life . New York, NY: Workman Publishing.
• Milner, C. E., & Cote, K. A. (2009). Benefits of napping in healthy adults: Impact of nap length, time of day, age, and experience with napping. Journal of Sleep Research, 18 , 272–281. doi: 10.1111/j.1365-2869.2008.00718.x
• Studte, S., Bridger, E., & Mecklinger, A. (2015). Nap sleep preserves associative but not item memory performance. Neurobiology of Learning and Memory, 120 , 84–93. doi:10.1016/j.nlm.2015.02.012

Related Articles

• So you want to take a nap?

Letters to the Editor

• Send us a letter

June 26, 2024

Is napping good for you? If you do it the right way, VCU researcher says.

Psychology professor natalie dautovich offers insight on the midday pick-me-up you might have left in childhood., share this story.

• Share on Twitter
• Share on Facebook
• Share on LinkedIn

By Sian Wilkerson

For a typical American toddler, naps are a much-despised part of the prescribed daily routine. As we age, though, naps become rarer – yet more desirable – with each new stage of life.

“Napping is practiced differently in different cultures all around the world,” according to Virginia Commonwealth University professor Natalie Dautovich. “In North America, napping may be less commonly practiced by adults, [but] napping is a common and valued practice in many other areas of the world.”

So, are naps actually good for you – and if so, can you get too much of a good thing?

Dautovich , Ph.D., is an associate professor in the  Department of Psychology  in VCU’s  College of Humanities and Sciences  and the environmental fellow at the National Sleep Foundation. In her  Chronopsychology: Daily Life Research Lab , she examines daily processes, including sleep, that anchor well-being across adulthood. She spoke with VCU News about napping the right way.

Give us the elevator pitch – and a warning sign – about napping.

Napping can have benefits for energy, cognitive functioning and creativity in the short term. Furthermore, napping can be a short-term solution to help improve alertness when individuals are not getting sufficient sleep at night. But the downside to napping is that it can interfere with sleep at night, and you may feel groggier upon awakening.

Let’s say I want to start napping. What should I know?

Napping can be a learned behavior. If you do it consistently, your body can anticipate the nap and learn to fall asleep quickly. A trial-and-error approach can help many individuals determine whether napping is a useful behavior for themselves.

The challenge with napping is finding the right duration and time of day. Naps can happen anywhere that is safe and comfortable. However, aim for midafternoon: There is naturally circadian dip in alertness, yet there is plenty of time to build up the drive to sleep before bed.

Schedule permitting, beginning with a brief afternoon nap of 20 minutes or less, several days a week, can be helpful to assess if napping improves mood or functioning or interferes with nocturnal sleep, and to give your body time to develop a napping routine. To protect night sleep, avoid late-day naps or napping for too long.

You say ‘too long.’ Share more detail about a nap’s duration.

A short nap – less than 20 minutes – in the afternoon can help you feel recharged. A longer nap, between 60 and 90 minutes, may provide more restorative sleep, but it might interfere with sleep at night. And a moderate nap, between 20 and 60 minutes, can cause sleep inertia, which manifests as feeling groggy or a poor mood.

The cause of the grogginess is that with a medium-length nap, you’re more likely to wake during one of your deeper sleep stages. By napping for shorter or longer periods of time, you are more likely to have either not entered deep sleep or have emerged from deep sleep into a lighter stage of sleep.

Is there such a thing as too much napping?

You can nap too much if you find that it interferes with your sleep at night. Sleeping too much during the day or too close to nighttime sleep (e.g., napping in the late afternoon or evening) can interfere with your drive to sleep. As a result, you might have difficulty falling asleep, or your sleep may not be as deep.

Also, greater daytime sleepiness is symptomatic of many health conditions, and napping along with excessive daytime sleepiness may be an indicator of an underlying medical condition. 

Subscribe to VCU News

Subscribe to VCU News at newsletter.vcu.edu and receive a selection of stories, videos, photos, news clips and event listings in your inbox.

Related stories

VCU-led study finds discrimination over time leads to poor sleep

Want better sleep? Less fast food and screen time, and more physical activity may be key.

Rethinking resolutions: VCU faculty share outside-the-box New Year’s resolutions that can help you get the most bang for your buck

Most popular

June 18, 2024

Joseph Seipel, who helped transform VCU and Greater Richmond through the arts, dies at 76

A century ago, 10 women made history at MCV’s segregated school for Black nursing students

June 20, 2024

VCU basketball player Joe Bamisile offers a big assist for mental health

VCU ranked among top 20% of global universities

Latest headlines

July 2, 2024

VCU Breakthroughs Fund provides grants to 10 more faculty-led projects that pursue transformative innovation

Wilder School event explores health policy consequences of Supreme Court’s Dobbs decision

July 1, 2024

Alice Winn wins the VCU Cabell First Novelist Award for ‘In Memoriam’

‘A structure built for wellness’: Pediatrics training program supports work-life balance with tandem schedule

• International edition
• Australia edition
• Europe edition

Calls to make nap part of working day after latest study on brain benefits

Experts say allowing brief doze may help businesses and employees boost productivity as well as health

‘I’m greatly energised afterwards’: readers tell us how they nap

Winston Churchill was a past master, while Salvador Dalí made it an art and Margaret Thatcher allegedly did it in the back of her official car . Napping has long been a habit of the elite, but recent research has led to renewed calls for employees to be allowed to doze on the job, too.

According to a study published this week , habitual napping appears to be associated with a larger brain volume in adults, with scientists suggesting this raised the possibility the practice offers some protection against neurodegeneration – although experts stressed that further research was needed. The work followed previous studies that suggested a brief doze could improve people’s ability to learn .

Arianna Huffington, a co-founder of HuffPost and the founder and chief executive of wellness company Thrive Global, said: “Given the latest science on the effectiveness of napping and the clear link between employees feeling well rested and their productivity, it’s long past time that businesses embrace short naps at work.”

She is not alone. Dr Mattie Toma, an assistant professor in the behavioural science group at Warwick University, said her own research among low-income urban workers in India found half-hour afternoon naps boosted attention, wellbeing and productivity.

“Given the emerging evidence around the benefits of naps, not only for worker wellbeing but also for a company’s bottom line, companies ought to consider offering their employees the chance to nap,” said Toma.

Prof Sara Mednick, of the department of cognitive sciences at the University of California, Irvine, agreed. “We are a sleep-deprived people, which makes us more prone to accidents at work, lower levels of creativity and concentration, and higher levels of irritability,” she said.

“Businesses providing a space to rest will reduce the costs that incur from the lost time and the fatigue-related errors. It also gives the higher-ups the chance to acknowledge the challenges of the 24/7 culture and come up with top-down solutions that encourage workers to take care of themselves in and out of work, which goes a long way in terms of retention.”

Some businesses, including Thrive and HuffPost, have already introduced facilities for employees to take naps, with Google introducing sleep pods as far back as 2014 and companies including Nike and Ben & Jerry’s introducing nap rooms .

The practice has even been adopted by the NHS, with a growing number of hospitals introducing sleep pods for staff in an effort to help them get more rest.

Employees, it seems, are enthusiastic. Sean Greenwood, of Ben & Jerry’s, said: “I think our experience is that rested employees are much more involved and creative, and if a quick nap helps serve that purpose, we’re happy to provide that for our team members.”

There is still work to do to rehabilitate the idea of a doze, however.

Huffington said: “Unfortunately, the practice of napping still suffers from our collective delusion that equates sleep with weakness and laziness, but the performance-enhancing benefits of naps have been no secret to many leaders throughout history.”

While sleep experts stressed that a daytime doze could be beneficial, they said it was crucial to get enough shut-eye at the end of a day.

“Napping per se is not necessary for everyone, but can be helpful for some,” said Colin Espie, a professor of sleep medicine at the University of Oxford. “Importantly, it is often an indication that people are not getting sufficient good quality sleep at night, so they need to catch up.”

The solution, he said, was to encourage good sleep health . Espie’s five principles, developed for the NHS Every Mind Matters campaign, include prioritising sleep, experimenting to discover the best time and duration of sleep, and avoiding influences that can upset sleep – be it caffeinated drinks in the evening, a stuffy bedroom, or the use of phones and tablets at night.

“If people feel the need to sleep regularly during the day, then they should at least consider that they might have a sleep problem, and that it’s more than a lifestyle thing,” he added.

Previous research has also suggested excessive daytime napping may be an early warning sign of declining cognitive health .

after newsletter promotion

Valentina Paz, a co-author of the study published this week into daytime dozing and brain size, said more work was needed to untangle the association between napping and brain health.

“Based on previous findings, we know that taking a short nap in the early afternoon may benefit those needing it,” she said.

However, Paz added: “Previous studies have reported mixed findings regarding the association between napping and brain health, so … further work is needed on this topic.”

How to have a good nap

According to experts, naps are best kept brief – about 20 minutes – and Espie suggested that just five or 10 minutes was enough.

“It should not be like entering a major sleep episode,” he said. “If napping is too long, you wake up feeling worse and suffer sleep inertia.”

As well as sleep inertia – a feeling of grogginess and low performance after waking up – lengthy naps can also cause other problems, with Espie noting they can reduce the drive for sleep at night.

To avoid a nap ruining a good night’s sleep, some experts also recommend avoiding one after 3pm .

One way to boost the impact of a nap is to drink a couple of cups of coffee before falling asleep for 15 minutes or so – an approach recommended to drivers who experience fatigue.

This works because a nap can reduce levels of adenosine – a chemical that causes feelings of sleepiness when it binds to receptors in the brain. As caffeine subsequently kicks in, it blocks these receptors , preventing adenosine from binding to them and inducing sleepiness. This, in turn, boosts neural activity. The upshot is a double whammy, increasing alertness.

However, Dr Carolin Reichert, deputy head of the centre for chronobiology and assistant psychologist at the centre for affective, stress and sleep Disorders at the University Psychiatric Clinics of Basel, said it can take 30 minutes or more for caffeine to be absorbed by the gastrointestinal tract, while animal studies have suggested that clearing of adenosine does not occur in the early stages of sleep, meaning a longer rest may be needed to reap the greatest benefits.

“Most likely, it takes around 20-30 minutes until you enter deep sleep in the afternoon,” she said.

• Health & wellbeing
• Work & careers

More on this story

Naps are healthy, scientists say – so why has Spain given up on the siesta?

Exhausting search for solutions to UK’s sharp rise in tiredness

Less than six hours’ sleep cuts immune response to vaccines, data shows

Sleeping with light on linked to higher risk of heart disease and diabetes

Sleeping longer can help cut calorie intake – study

Keep it short and before 3pm: what the sleep scientists say about naps

National Trust to give staff siestas in summer

Most viewed.

August 5, 2023

Are Naps Good for You?

Here’s the science on whether naps have short- and long-term benefits for your health

By Stephanie Pappas

AN Studio/Getty Images

It’s midafternoon. You’re full from lunch. The day is warm. You’re starting to feel drowsy. Should you give in to the comfort of a nap?

From a health perspective, it may be worth it. Though there is some debate over whether napping benefits everyone, research suggests naps can boost at least some people’s cognitive performance in the short term. And a regular midday snooze might also have longer-term impacts, from a possible improvement in cardiovascular health to a bulwark against the loss of brain volume—potentially a protective factor against dementia.

“If you can fit in a nap of anything up to about 30 minutes, which isn’t really long, there seems to be fairly good evidence that you could be helping your brain age a little bit more healthily,” says Victoria Garfield, an epidemiologist at University College London.

Several studies find that a well-timed nap can provide a short-term boost in brainpower. For example, scientists reviewed past research that focused on healthy participants with regular sleep cycles. That review, published in 2009 in the Journal of Sleep Research, showed that napping improved factors ranging from reaction time to alertness to memory performance . A brief nap can also light the spark of creativity , a 2021 study in Science Advances found. In that research, participants were given math problems that could be solved with an easy shortcut that they weren’t told about. Some participants were encouraged to take a brief, dozy nap before tackling the problems. The researchers found those who napped—and spent even just 30 seconds in the first, lightest phase of sleep—were 2.7 times more likely to figure out the math shortcut than those who stayed awake. But entering a deeper sleep phase had a negative effect on this creative insight. In other words, there may be a “sweet spot” of mental relaxation that clears the way for eureka moments.

The benefits of napping are strongest for people who have sleep debt, meaning they don’t get enough nighttime sleep . Shift workers, new parents and older people with fragmented nighttime sleep all seem to get a boost: a 2014 review of research , for example, showed that taking a nap during one’s night-shift work reduced sleepiness and improved overall performance, even if people were slightly groggy as they came out of their nap—a phenomenon called “sleep inertia.”

Timing your naps right can reduce sleep inertia, says Natalie Dautovich, a psychologist at Virginia Commonwealth University and an environmental fellow at the National Sleep Foundation, which is primarily funded by pharmaceutical and medical device companies. A 20-minute nap is recharging, Dautovich says, and 60 to 90 minutes of sleep can be even more restorative. The nap to avoid is one lasting more than 20 minutes and less than 60 minutes, which, she says, is most likely to lead to sleep inertia.

The short-term benefits of naps are well established, but long-term effects are a little less clear. In particular, there has been debate about whether naps are good or bad for cardiovascular health after mixed epidemiological research was published on the topic. Self-reports of how frequently people nap and for how long are unreliable, Dautovich says, and pinning down the relationship between naps and any specific health outcomes is not always simple.

“The cause-and-effect association between napping and other health conditions is difficult to determine,” she says. “Greater daytime sleepiness is symptomatic of many health conditions, and therefore napping may not necessarily be the cause of these conditions but rather a consequence.”

For example, a 2021 study in the journal Alzheimer’s & Dementia found that long naps in older adults (who had a mean age of 81.4 years) was a risk factor for developing Alzheimer’s disease but that Alzheimer’s also led to longer and more frequent naps.

A 2017 review of research on the long-term health effects of napping, published in Sleep Medicine Reviews, found that studies in midlife adults showed napping to be associated with reduced coronary heart disease, cardiovascular disease and death from cardiovascular conditions . Short naps may lower blood pressure and heart rate and might also reduce the release of hormones such as adrenaline—all factors that could improve cardiovascular health—the review concluded. In adults around age 65 or older, however, some studies found that long naps of an hour or more were linked to a higher risk of cardiac problems. It’s possible these long naps were a symptom of early or undetected disease rather than a cause, the review authors cautioned.

Garfield and her colleagues at University College London have found that regular brief naps seem to improve brain health in the long run. Using data from the U.K. Biobank, which contains genetic and health information on 500,000 healthy people between the ages of 40 and 69, the team found that those who had genetic variations associated with regular napping also had a larger brain volume. All brains lose volume as they age, Garfield says, but greater losses are linked to conditions such as dementia, sleep apnea and higher levels of the stress hormone cortisol. Taking a nap regularly was equivalent to saving yourself between 2.6 and 6.5 years of aging, at least as far as brain volume was concerned, the researchers reported in Sleep Health .

Not everyone can nap, of course, Garfield says. And there are other similarly healthy habits that could fill 30 minutes a day, such as going on a walk or hitting the gym. But if it works for one’s schedule and personal preference, napping seems to be a healthy habit, not a sign of sloth.

“A trial-and-error approach can help many individuals determine whether napping is a useful behavior for themselves,” Dautovich says. “Schedule permitting, beginning with a brief afternoon nap of 20 minutes or less, several days a week, can be helpful to assess if napping improves mood or functioning or interferes with nocturnal sleep and to give your body time to develop a napping routine.”

Appointments at Mayo Clinic

• Adult health

Napping: Do's and don'ts for healthy adults

Unsure whether napping is good for you? Understand the pros and cons and the best way to take a nap.

If you're sleep deprived or just looking for a way to relax, you might be thinking about taking a nap. Napping at the wrong time of day or for too long can backfire, though. Understand how to get the most out of a nap.

What are the benefits of napping?

Napping offers various benefits for healthy adults, including:

• Reduced fatigue
• Increased alertness
• Improved mood
• Improved performance, including quicker reaction time and better memory

What are the drawbacks to napping?

Napping isn't for everyone. Some people simply can't sleep during the day or have trouble sleeping in places other than their own beds, which napping sometimes requires.

Napping can also have negative effects, such as:

• Sleep inertia. You might feel groggy and disoriented after waking up from a nap.
• Nighttime sleep problems. Short naps generally don't affect nighttime sleep quality for most people. But if you experience insomnia or poor sleep quality at night, napping might worsen these problems. Long or frequent naps might interfere with nighttime sleep.

When should I consider a nap?

You might consider making time for a nap if you:

• Experience new fatigue or unexpected sleepiness
• Are about to experience sleep loss — for example, due to a long work shift
• Want to make planned naps part of your daily routine

Could a sudden increased need for naps indicate a health problem?

If you're experiencing an increased need for naps and there's no obvious cause of new fatigue in your life, talk to your doctor. You could be taking a medication or have a sleep disorder or other medical condition that's disrupting your nighttime sleep.

What's the best way to take a nap?

To get the most out of a nap, follow these tips:

• Keep naps short. Aim to nap for only 10 to 20 minutes. The longer you nap, the more likely you are to feel groggy afterward. However, young adults might be able to tolerate longer naps.
• Take naps in the early afternoon. Napping after 3 p.m. can interfere with nighttime sleep. Individual factors, such as your need for sleep, your sleeping schedule, your age and your medication use, also can play a role in determining the best time of day to nap.
• Create a restful environment. Nap in a quiet, dark place with a comfortable room temperature and few distractions.

After napping, give yourself time to wake up before resuming activities — particularly those that require a quick or sharp response.

There is a problem with information submitted for this request. Review/update the information highlighted below and resubmit the form.

From Mayo Clinic to your inbox

Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. Click here for an email preview.

Error Email field is required

Error Include a valid email address

To provide you with the most relevant and helpful information, and understand which information is beneficial, we may combine your email and website usage information with other information we have about you. If you are a Mayo Clinic patient, this could include protected health information. If we combine this information with your protected health information, we will treat all of that information as protected health information and will only use or disclose that information as set forth in our notice of privacy practices. You may opt-out of email communications at any time by clicking on the unsubscribe link in the e-mail.

Thank you for subscribing!

You'll soon start receiving the latest Mayo Clinic health information you requested in your inbox.

Sorry something went wrong with your subscription

Please, try again in a couple of minutes

• Kryger MH, et al., eds. Psychological and behavioral treatments for insomnia II: Implementation and specific populations. In: Principles and Practice of Sleep Medicine. 6th ed. St. Louis, Mo.: Elsevier Saunders; 2017. https://www.clincalkey.com. Accessed Sept. 19, 2018.
• Faraut B, et al. Napping: A public health issue. From epidemiological to laboratory studies. Sleep Medicine Reviews. 2017;35:85.
• Maski K. Insufficient sleep: Evaluation and management. https://www.uptodate.com/contents/search. Accessed Sept. 19, 2018.
• Mantua J, et al. Exploring the nap paradox: Are mid-day sleep bouts a friend or foe? Sleep Medicine. 2017;37:88.
• Tamaki M, et al. Night watch in one brain hemisphere during sleep associated with the first-night effect in humans. Current Biology. 2016;26:1190.
• Your guide to healthy sleep. National Heart, Lung, and Blood Institute. https://www.nhbli.nih.gov/health-topics/all-publications-and-resources/your-guide-healthy-sleep. Accessed Oct. 4, 2018.
• Sleep deprivation and deficiency. National Heart, Lung, and Blood Institute. https://www.nhlbi.nih.gov/health-topics/sleep-deprivation-and-deficiency#More-Information. Accessed Oct. 4, 2018.
• Hilditch CJ, et al. A review of short naps and sleep inertia: Do naps of 30 min or less really avoid sleep inertia and slow-wave sleep? Sleep Medicine. 2017;32:176.
• Tips for better sleep. Centers for Disease Control and Prevention. https://www.cdc.gov/sleep/about_sleep/sleep_hygiene.html. Accessed Sept. 24, 2018.
• Alzheimer's sleep problems
• Can psoriasis make it hard to sleep?
• Hidradenitis suppurativa and sleep: How to get more zzz's
• Sleep guidelines
• I have atopic dermatitis. How can I sleep better?
• Lack of sleep: Can it make you sick?
• Mayo Clinic Minute: Meditation is good medicine
• Mayo Clinic Minute: Sleep Spoiler - Tips for a Good Night's Rest
• Melatonin side effects
• Prescription sleeping pills: What's right for you?
• Antihistamines for insomnia
• OTC sleep aids
• Sleep and psoriatic arthritis
• Sleeping positions that reduce back pain

Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission.

• Opportunities

Mayo Clinic Press

Check out these best-sellers and special offers on books and newsletters from Mayo Clinic Press .

• Mayo Clinic on Incontinence - Mayo Clinic Press Mayo Clinic on Incontinence
• The Essential Diabetes Book - Mayo Clinic Press The Essential Diabetes Book
• Mayo Clinic on Hearing and Balance - Mayo Clinic Press Mayo Clinic on Hearing and Balance
• FREE Mayo Clinic Diet Assessment - Mayo Clinic Press FREE Mayo Clinic Diet Assessment
• Mayo Clinic Health Letter - FREE book - Mayo Clinic Press Mayo Clinic Health Letter - FREE book
• Healthy Lifestyle
• Napping Do s and don ts for healthy adults

Your gift holds great power – donate today!

Make your tax-deductible gift and be part of the cutting-edge research and care that's changing medicine.

• Search Please fill out this field.
• Manage Your Subscription
• Give a Gift Subscription
• Newsletters
• Sweepstakes

• Human Interest
• Human Interest News

Regular Naps Can Benefit the Brain, Scientists Say

"Everybody could potentially experience some benefit from napping," a researcher from University College London said

Taking regular naps can be beneficial for one's brain, a new study says — and make it larger for longer!

According to researchers from University College London and University of the Republic in Uruguay, brain health can be preserved from daytime napping, which also can slow the rate at which one's brain shrinks.

To come to the conclusion, scientists analyzed data from participants between the ages of 40 to 69. The study was published in the journal Sleep Health .

"We are suggesting that everybody could potentially experience some benefit from napping," Dr. Victoria Garfield told BBC , adding that the findings are “very new and very exciting.”

Napping is vital for infant development but decreases as we age. After retirement, around 27% of individuals over 65 nap during the day. While the impact of napping on preventing diseases like Alzheimer’s is uncertain, further research is needed. Brain shrinkage is a natural part of aging, and maintaining good overall brain health is crucial in guarding against dementia, which is associated with poor sleep quality . Researchers propose that inadequate sleep may lead to brain inflammation and disruptions in neural connections over time.

“Therefore, regular napping could protect against neurodegeneration by compensating for deficient sleep,” researcher Valentina Paz said.

Scientists conducted a natural experiment based on our DNA that we inherit at birth. Previous studies have identified 97 bits of our DNA that make us more likely to be nappers or non-nappers. In the UK Biobank project, they analyzed data from 35,000 people from 40 to 69 and compared those who had the genetic “napper” and “non-napper” traits.

"The brains of nappers were 15 cubic centimeters (0.9 cubic inches) bigger than those of non-nappers," the BBC reported, which is equivalent to slowing down aging by three to six years.

“I like short naps on the weekends and this study has convinced me that I shouldn’t feel lazy napping. It may even be protecting my brain,” Prof Tara Spires-Jones, from the University of Edinburgh and the president of the British Neuroscience Association, told the BBC.

She said the study was “interesting” and showed a “small but significant increase in brain volume." She added that it “adds to the data indicating that sleep is important for brain health."

The researchers did not directly study having a big sleep in the middle of the day, but they said the science suggested a limit of half an hour. The advice: take naps, but make them shorter than 30 minutes, as longer naps may have negative effects. 

Dr. Margaret Blattner, clinical instructor, department of neurology at Beth Israel Deaconess Medical Center, previously told PEOPLE that habitual daytime naps can indicate problems with the quality of nighttime sleep or even overall health.

"Frequent or prolonged daytime naps can disrupt healthy nighttime sleep. Napping during the day may make it harder to fall asleep at night or cause nighttime sleep to become fragmented," Blattner said. "Missing out on nighttime sleep — either because busy schedules don't allow sufficient sleep opportunity, or because of a problem with the quality of sleep itself — can cause severe daytime sleepiness."

Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from celebrity news to compelling human interest stories

Quality sleep is healthy and restorative for the body, Blattner said, so a change in sleep habits, either needing more sleep at night or naps during the day, might signal an underlying health problem.

"Often, prolonged naps are less restorative than more brief daytime naps, people often wake up unrefreshed or "groggy" after a long nap," she adds. "Additionally, long daytime naps take away time from other healthy things that people enjoy during the day: spending time with family, enjoying hobbies, and exercise."

Related Articles

• Rest and Relaxation

How to Take the Perfect Nap

A former boss once assigned me to the only office on our floor with a column right down the middle. She apologized, but I quickly sensed my advantage. Positioning my desk behind this eyesore, I could nap after lunch without detection, head angled toward my computer screen in case someone walked in. These covert catnaps were less about laziness than productivity. They transformed me from lunch-laden zombie to fully functional human—and a better employee.

Not everyone is lucky enough to have a personal napping column. But stigma around napping in American workplaces is slowly changing , in light of the growing recognition that sleep (even the daytime kind) can help productivity. One in five Americans now nap on the job. “Napping might be where nighttime sleep was 25 years ago,” says writer Daniel Pink, author of WHEN: The Scientific Secrets of Perfect Timing , which extols the virtues of napping. Some employers are realizing, “maybe napping isn’t a sign of weakness,” Pink says. 

In fact, research suggests your workday siesta builds several strengths, including brain health. In our early 20s, the brain starts shrinking, which increases dementia risk and slows cognition. In nappers, though, brain size is better preserved, according to this 2023 study , possibly because naps can reduce anxiety. “We aren’t sure of the mechanisms, but there’s a strong link between stress and dementia,” says Victoria Garfield, a genetic epidemiologist at the University of Liverpool who co-authored the paper. Research also shows that napping supports heart health and boosts cognition , creativity, and memory. 

Here’s how to perfect your nap to reap the benefits.

Seize the daytime dip

It’s important to time your nap when you start getting tired but well before evening, so it won’t steal any zzz s from your overnight slumber. For most people, this Goldilocks zone is from 1 to 4 p.m . “That’s when we have a natural dip in our alertness,” says Charlene Gamaldo, professor of neurology at the Johns Hopkins School of Medicine.

You may get more benefits from naps when they’re taken consistently—daily, if possible—and at the same time each afternoon, plus or minus 30 minutes, Gamaldo says. This way, you’re more likely to actually sleep during the nap and fall asleep again later that night, as our bodies come to expect this routine. “We’re rhythmic animals,” says Sara Mednick , a sleep researcher at the University of California, Irvine. “Whenever you’re learning an activity, doing it regularly helps.”  And the plusses of daily napping are cumulative for brain health, whereas any one nap has a small effect, Garfield says. 

You could also time your nap before making an important choice. “Naps help us solve problems and make better decisions,” says Arianna Huffington, founder and CEO of Thrive Global and author of The Sleep Revolution . “They’re a tool that every leader should use when needed.”

Find your magic window

Gamaldo recommends napping for 20-40 minutes, which can improve cognitive function and performance. It’ll be a satisfying snooze, yet it’s short enough to avoid deep sleep, which is harder to wake from . She calls this length the “magic” window.

Read More : 4 Signs Your Body Is Telling You It's Time to Take a Break

Some research points to shorter, 15-20 minute naps. The right length may depend on your fatigue level and the unique way your brain shuts down for sleep, Garfield adds.

Mednick thinks longer daytime dozing is underrated. If you rest through the deep-sleep stage, your brain will cycle back to lighter sleep after about 60 minutes. At that point, waking up is easier, you’ll feel more rested with better emotional control , and you won’t sacrifice any sleep later on. “When people regularly take longer naps, their nighttime sleep is similar to non-nappers,” Mednick says—so the extra rest is a bonus, instead of taking away from nighttime shut-eye. She suggests increasing your duration gradually over several weeks to get used to it.

Relax before you rest

Pre-gaming your naps with progressive muscle relaxation can improve the quality of your rest. The technique involves contracting and relaxing muscles throughout the body while focusing on your breathing. 

Autogenic meditation is another approach that could serve as a useful warmup to napping, Mednick says.  With this type of meditation, you conjure mental images that induce peaceful feelings, such as heaviness in your limbs, aimed at destressing the nervous system . “These are ways of slowing down your physiology to help you access a state that is deeply restorative,” says Mednick, who also authored The Power of the Downstate .

Delphine Oudiette, a neuroscientist who researches sleep, dreams, and creativity at the Paris Brain Institute , recommends experimenting over a weekend with different strategies and timeframes. “Just see if you feel regenerated or not,” she says. 

Build a nap pod

Take pride in cultivating the perfect environment for daytime rejuvenation. Many veteran nappers have a dedicated napping couch, which their bodies learn to associate with daytime sleep. Pink wears a sleep mask, earplugs, and sometimes headphones over the earplugs. “It’s my poor man’s nap pod ,” he explains. “I like the full immersion.” Gamaldo advises her patients to “simulate a cool dark cave.”

You may prefer to nap under a soft light, so your body senses it’s still daytime, potentially making the nap less intrusive on evening sleep. Most importantly, keep your ambiance consistent if possible, whether it’s your couch, car or cubicle. “You want similar cues around you each time,” Mednick says.

Read More : Do Less. It's Good for You

Adam Horowitz, a cognitive scientist and visiting research fellow at Outer Coast College who focuses on sleep and dreams, plays thunderstorm recordings as an audio cue that it’s naptime, but you can learn to associate just about any soundtrack with napping. Horowitz used to play his ukulele before sleeping, he told me—and yawned at the thought of it.

Clear your nap area of any gadgets buzzing with afternoon notifications, advises Huffington. At Thrive Global, she encourages employees to use a designated nap room. 

Before putting her phone away, though, Huffington uses it to play her Thrive Reset (a tool on Thrive’s platform) with photos, music, and quotes that bring calm and joy while breathing deeply. “Just 60 seconds of breathing has a dramatic effect” on reducing fight-or-flight mode while nurturing nap mode, she says.

Caffeinate before your nap

Before napping, set yourself up for success afterward. It sounds counterintuitive, but drinking some coffee beforehand can invigorate you when you wake up (especially if combined with zippy wake-up music ). Metabolizing caffeine takes about 30 minutes, the length of a nap, so your rested feeling after waking up will be amplified by the caffeine jolt, according to some research . Pink takes it a step further: drinking coffee right after waking up, in addition to before. “I’ll admit to working both sides of it,” he says. (Experiment to find what works best for you: Avoid afternoon coffee if it disrupts your nighttime sleep.)

Instead of engineering an energy blast when waking up, you may want to just try to ensure you can get to sleep during the nap. Teas with ginseng, blue lotus, or mugwort may help with inducing sleepiness, Horowitz says, though the effects vary from person to person. Avoid spicy foods and sugary carbs; acid reflux and blood glucose crashes don’t make for pleasant wakeups.

Hack your creativity

New research in napping points to an old trick for creativity: Thomas Edison liked to hold a steel ball while napping. As he nodded off, the ball would fall and hit the floor. The sound woke him in a dreamy state, providing unique windows into his subconscious that sparked new ideas. Oudiette, the researcher in Paris, studied this strategy in modern-day nappers. She found that falling asleep for just 15 seconds, before the ball drop, tripled their chances of solving a math problem requiring creative insight.

Read More : Why Your Breakfast Should Start With a Vegetable

But you may not need the ball trick. Just napping with an alarm set for 60 minutes or a bit longer leads to a 40% increase in creativity , Mednick has found. “There’s this space between wake and deep sleep where these interesting ideas are bopping around, and we can maneuver inside there,” she says. An amateur musician, Mednick was recently struggling to write a song. Just before napping, she reviewed the elements she wanted to include. After she got up, the song flowed right out.

In a study last year, Horowitz tested his own technology for nurturing sleep-related creativity. As study participants fell asleep, this device verbally prompted them to dream about trees. Post-nap, they wrote more creative stories about trees, compared to control groups. Napping opens up some helpful distance between you and the problem you’re working on, similar to gleaning insights after taking a walk or shower—but napping is “an intensified form of mind wandering,” Horowitz says. .

Rest to learn, and learn to rest

Studies show that naps can boost memory and learning , regardless of how often you take them . Gamaldo recommends naps when cramming for college exams. Reviewing test materials and then napping “will cement your knowledge,” she advises, especially if you revisit the info after waking up. Naps also help with recalling learned skills .

Not everyone needs to nap. Oudiette doesn’t. “When I’m tired, I just like to close my eyes,” she says. “It’s helpful even for two minutes.” The biggest thing is taking time to rest, no matter how. “You could lie down and stare at the ceiling,” she says, “but you’re not on your laptop or phone. 

More Must-Reads from TIME

• Welcome to the Noah Lyles Olympics
• Melinda French Gates Is Going It Alone
• What to Do if You Can’t Afford Your Medications
• How to Buy Groceries Without Breaking the Bank
• Sienna Miller Is the Reason to Watch  Horizon
• Why So Many Bitcoin Mining Companies Are Pivoting to AI
• The 15 Best Movies to Watch on a Plane
• Want Weekly Recs on What to Watch, Read, and More? Sign Up for Worth Your Time

Contact us at [email protected]

The AI-fueled stock market bubble will crash in 2026, research firm says

• The AI-fueled stock market bubble will burst in 2026, according to Capital Economics.
• The research firm said rising interest rates and higher inflation will weigh down equity valuations.
• "We suspect that the bubble will ultimately burst beyond the end of next year, causing a correction in valuations."

An artificial intelligence-fueled stock market bubble will burst in 2026, according to Capital Economics.

The research firm has said that a stock market bubble, driven by investor excitement towards artificial intelligence, would drive the S&P 500 to as high as 6,500 by 2025, led by technology stocks.

But starting in 2026, those stock market gains should unwind precipitously as higher interest rates and an elevated inflation rate start to weigh down equity valuations.

"Ultimately, we anticipate that returns from equities over the next decade will be poorer than over the previous one. And we think that the long-running outperformance of the US stock market may come to an end," Capital Economics' Diana Iovanel and James Reilly said.

Their bearish stock market call is somewhat counter-intuitive, as the economists expect the growing adoption of AI will spark a boost in economic growth driven by increases in productivity. That economic boost should result in higher inflation than most expect and, in tandem, higher interest rates.

Higher interest rates and inflation are ultimately bad news for stock prices, as evidenced by the recent stock market decline , which was sparked by a surprisingly hot March CPI inflation report.

"We suspect that the bubble will ultimately burst beyond the end of next year, causing a correction in valuations. After all, this dynamic played out around both the dot-com bubble of the late 1990s and early 2000s and the Great Crash of 1929," Iovanel and Reilly said. 

The expected bursting of the stock market bubble should lead to a decade of investment returns that favor bonds over stocks. 

"We expect stronger returns as government bond yields settle at higher levels," Capital Economics said of the fixed-income market. 

Capital Economics forecasts that between now and the end of 2033, US stocks will deliver average annual returns of just 4.3%, which is well below the long-term average return of about 7% after inflation. Meanwhile, Capital Economics said it expects US Treasurys will return 4.5% in the same period, slightly edging out equity gains. 

Those projected returns are in stark contrast to the average annual returns of 13.1% delivered by US stocks over the past decade.

"American exceptionalism may end in the coming years," Iovanel and Reilly said.

But there is one major risk to their outlook, according to the analysts, and that's the inherent difficulty of accurately timing the top of a stock market bubble, and how long the unwinding of the bubble might last.

"When and how the AI-fueled equity bubble bursts is a key risk to our forecast. In particular, one downside risk is that the aftermath of the bursting of the bubble lasts longer than one year, as was the case following the dot com bubble," Iovanel and Reilly said.

This story was originally published in April 2024.

• Main content

Google Introduces Project Naptime for AI-Powered Vulnerability Research

Google has developed a new framework called Project Naptime that it says enables a large language model (LLM) to carry out vulnerability research with an aim to improve automated discovery approaches.

"The Naptime architecture is centered around the interaction between an AI agent and a target codebase," Google Project Zero researchers Sergei Glazunov and Mark Brand said . "The agent is provided with a set of specialized tools designed to mimic the workflow of a human security researcher."

The initiative is so named for the fact that it allows humans to "take regular naps" while it assists with vulnerability research and automating variant analysis.

The approach, at its core, seeks to take advantage of advances in code comprehension and general reasoning ability of LLMs, thus allowing them to replicate human behavior when it comes to identifying and demonstrating security vulnerabilities.

It encompasses several components such as a Code Browser tool that enables the AI agent to navigate through the target codebase, a Python tool to run Python scripts in a sandboxed environment for fuzzing, a Debugger tool to observe program behavior with different inputs, and a Reporter tool to monitor the progress of a task.

Google said Naptime is also model-agnostic and backend-agnostic, not to mention be better at flagging buffer overflow and advanced memory corruption flaws, according to CYBERSECEVAL 2 benchmarks. CYBERSECEVAL 2, released earlier this April by researchers from Meta, is an evaluation suite to quantify LLM security risks.

In tests carried out by the search giant to reproduce and exploit the flaws, the two vulnerability categories achieved new top scores of 1.00 and 0.76, up from 0.05 and 0.24, respectively for OpenAI GPT-4 Turbo.

"Naptime enables an LLM to perform vulnerability research that closely mimics the iterative, hypothesis-driven approach of human security experts," the researchers said. "This architecture not only enhances the agent's ability to identify and analyze vulnerabilities but also ensures that the results are accurate and reproducible."

Continuous Attack Surface Discovery & Penetration Testing

Continuously discover, prioritize, & mitigate exposures with evidence-backed ASM, Pentesting, and Red Teaming.

Cybersecurity Webinars

Secure your digital identity with these 5 must-have itdr features.

Facing identity threats? Discover how ITDR can save you from lateral movement and ransomware attacks.

Why Compromised Credentials Are the #1 Cyber Threat in 2024

From data breaches to identity theft, compromised credentials can cost you everything. Learn how to stop attackers in their tracks.

Democratization of Cyberattacks: How Billions of Unskilled Would-be Hackers Can Now Attack Your Organization

Survey Reveals Compliance Professionals Seek Quality, Efficiency, Trust & Partnership

Securing SaaS Apps in the Era of Generative AI

Patching vs. Isolating Vulnerabilities

Get the latest news, expert insights, exclusive resources, and strategies from industry leaders – all for free.

First Appearance | June 2024

New law enforcement training resource .

NCSL recently updated and expanded the 50-state statutory database on law enforcement training. You can now filter statutes into additional subcategories, including the type of training: continuing education, specialization training or initial academy requirements. The database can also be used to search by filtering common training topics, by state, or by keyword search across statute excerpts.  

NCSL: Law Enforcement Statutory Database 

NCSL Town Hall: Pretrial Policy 

The latest NCSL Town Hall features two recent NCSL Pretrial Policy Fellows program graduates, Illinois Sen. Elgie Sims and Delaware Sen. Brian Pettyjohn. Both talked about how the fellowship program aided them with legislation in their own states. You’ll also hear about pretrial reforms in both states, including Delaware’s pending amendment of the state’s constitution.  

NCSL: The Pretrial Policy Fellows Program 

Policing State Teams Meeting

Lawmakers, legislative staff and law enforcement representatives from seven states recently met in Charleston, S.C., for NCSL’s Policing State Teams Meeting. Attendees covered topics from crisis response and officer wellbeing to clearance rates and recruitment and retention. Teams from each state participated in facilitated discussions with NCSL staff to identify policy goals. 

State Approaches to Sentence Credits

Sentence credits expand the opportunities for and accelerate the timeline of release, reducing the budgetary impacts of incarceration on states. These credits are in place in at least 42 states. NCSL’s new brief provides additional information on state approaches to good time and earned time laws.  

CSG Justice Center | Mind Matters: Building a Justice System That is Inclusive and Responsive to Brain Injury

CSG Justice Center | Expanding First Response National Commission Report

Ideas 42 | Smart Court Appearance Strategies: Grace Periods

Crime and Justice Institute | Behavioral Health Crisis Response Landscape Analysis

Contact NCSL

For more information on this topic, use this form to reach NCSL staff.

• What is your role? Legislator Legislative Staff Other
• Is this a press or media inquiry? No Yes
• Admin Email

• Share full article

Advertisement

Supported by

Scientists in Japan Give Robots a Fleshy Face and a Smile

Researchers at the University of Tokyo published findings on a method of attaching artificial skin to robot faces to protect machinery and mimic human expressiveness.

By Emily Schmall

Engineers in Japan are trying to get robots to imitate that particularly human expression — the smile.

They have created a face mask from human skin cells and attached it to robots with a novel technique that conceals the binding and is flexible enough to turn down into a grimace or up into a squishy smile.

The effect is something between Hannibal Lecter’s terrifying mask and the Claymation figure Gumby.

But scientists say the prototypes pave the way for more sophisticated robots, with an outward layer both elastic and durable enough to protect the machine while making it appear more human.

Beyond expressiveness, the “skin equivalent,” as the researchers call it, which is made from living skin cells in a lab, can scar and burn and also self-heal, according to a study published June 25 in the journal Cell Reports Physical Science.

“Human-like faces and expressions improve communication and empathy in human-robot interactions, making robots more effective in health care, service and companionship roles,” Shoji Takeuchi, a professor at the University of Tokyo and the study’s lead researcher, said in an email.

The research comes as robots are becoming more ubiquitous on factory floors.

There were 3.9 million industrial robots working on auto and electronics assembly lines and other work settings in 2022, according to the International Federation of Robotics.

We are having trouble retrieving the article content.

Please enable JavaScript in your browser settings.

Thank you for your patience while we verify access. If you are in Reader mode please exit and  log into  your Times account, or  subscribe  for all of The Times.

Thank you for your patience while we verify access.

Already a subscriber?  Log in .

Want all of The Times?  Subscribe .

An official website of the United States government Here's how you know

Official websites use .gov A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS A lock ( Lock A locked padlock ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Biden-Harris Administration Announces $1.94 Million for Research to Improve the Transit Customer Experience

WASHINGTON – The U.S. Department of Transportation's Federal Transit Administration (FTA) today announced  $1.94 million in competitive grant funding is now available. This funding will support research conducted by providers of public transportation. The Notice of Funding Opportunity (NOFO) is intended to advance emerging technologies, strategies, and innovations that make transit easier and more accessible for transit riders across the country.

FTA's Enhancing Mobility Innovation program supports research projects that will improve customer convenience, such as creating easier ways to pay for transit and enhancing transit schedules based on rider demand.

FTA will allocate funding to support rider-centered research projects in two categories:

• Innovations that focus on new service delivery models, creative financing, novel partnerships, and integrated payment solutions; and
• Software solutions that improve ways to provide demand-response public transportation service.

"The Enhancing Mobility Innovation program supports transit agencies as they work to strengthen mobility, with a focus on how innovation can improve service delivery and make trains, buses and ferries easier to use and more attractive to riders," said FTA Acting Administrator Veronica Vanterpool . "This funding will help spur innovation so that people can get to their destinations more reliably, comfortably and conveniently."

Eligible applicants include transit agencies; state or local departments of transportation; Indian tribes; private and nonprofit organizations; colleges and universities; and state and local governments, including metropolitan planning organizations.

This is the second round of funding for enhancing mobility innovation. In August 2022, FTA selected nine projects in six states to support mobility and innovation.

Instructions for applying and eligibility information can be found on FTA’s website and at GRANTS.GOV (solicitation number FTA-2024-010-TRI-EMI). Complete proposals must be submitted electronically through the GRANTS.GOV “APPLY” function by August 30, 2024.

Numbers, Facts and Trends Shaping Your World

Read our research on:

Full Topic List

Regions & Countries

• Publications
• Our Methods
• Short Reads
• Tools & Resources

Read Our Research On:

Third-party and independent candidates for president often fall short of early polling numbers

The 2024 presidential campaign stands out as the first presumptive rematch between major-party candidates since 1956. It’s also the first time an ex-president has run to reclaim the White House in more than a century.

Another uncommon feature is the presence of several high-profile alternative candidates, including Democratic-scion-turned-independent Robert F. Kennedy Jr., independent Cornel West and three-time Green Party nominee Jill Stein.

Kennedy, an environmental lawyer and anti-vaccine activist , is currently polling in the mid-single digits nationally. He appears to draw support both from people who might otherwise back President Joe Biden and former President Donald Trump, complicating both men’s campaign calculations. (Bear in mind that accurately gauging support for third-party candidates can be tricky .)

But U.S. political history tells us that third-party and independent candidates usually finish a lot lower than where they start.

We examined preelection polls in six presidential contests that featured significant third-party or independent candidates, then reviewed those candidates’ actual shares of the popular vote in the general election.

Not only did support for third-party and independent candidates tend to decline over the course of their campaigns, but their vote shares often came in lower than polls suggested they might.

Here’s an election-by-election look at underperformance by third-party and independent candidates.

Given the unusual dynamics of the 2024 presidential election – including the presence of several potentially significant third-party and independent candidates – Pew Research Center examined how such candidates fared in past elections.

We focused on the six elections over the past 60 years in which the major-party share of the nationwide popular vote was less than 98%. In each of those elections, an independent or third-party candidate won at least 2% of the vote.

For each of those candidates, we obtained support-level data via iPoll , an online archive of historical survey data maintained by Cornell University’s Roper Center for Public Opinion Research. For 1980 and subsequent elections, we limited our analysis to surveys of registered voters. No such surveys were available for the 1968 election, so in that case we used surveys of the national adult population.

Over the decades, survey modes shifted from predominantly face-to-face interviews to landline telephone interviews, and then to landline-plus-cellphone interviews. By 2016, online surveys were making their first appearances, but most polls were still conducted via phone. To avoid any distortions caused by such different survey modes , we used only surveys conducted by the same mode within a given year. This meant that we only used face-to-face surveys in 1968, and only phone surveys in all other years we analyzed.

We also looked at the wording of each individual question to make sure each survey was asking essentially the same thing in similar ways. In particular, we wanted to ensure that candidates were referred to by name and identified by party (or as “independent” when appropriate).

Once we had assembled a list of comparable questions, we plotted support for third-party and independent candidates on a timeline. The final point on each chart represents the candidate’s share of the total nationwide popular vote. For 1968 through 2000, we used figures from America Votes , a long-running compilation of election data. For the 2016 election, we compiled official returns from all 50 states and the District of Columbia.

With two exceptions, all support figures in this analysis include those who said they would vote for or leaned toward the candidate in question. The exceptions are John Anderson in 1980 (because no surveys with “leaner” questions met our inclusion criteria) and Ross Perot in 1992, during the interim period in which he wasn’t actively campaigning (because surveys did not typically ask “leaner” questions about him during this period).

1968: George Wallace

Fresh off his first term as Alabama’s segregationist governor, George Wallace – running a “law and order”-themed campaign under the American Independent Party banner – saw his support rise in polls over the spring and summer leading up to the 1968 election. In April, around 10% of adults nationally said they supported or leaned toward Wallace. By September, that had doubled to 20%. Wallace appeared within reach of his goal: dividing the field enough to throw the election to the House of Representatives , where he could try to bargain his electoral votes for “concessions” on desegregation, voting rights and other issues.

That fall, Republican Richard Nixon’s campaign began warning conservatives that voting for Wallace would only help Democrat Hubert Humphrey. Meanwhile, Democratic-aligned unions worked to pull their members – whom Wallace had targeted – back into Humphrey’s fold. Wallace’s running mate, retired Air Force Gen. Curtis LeMay , also made headlines at his introductory press conference after saying he’d consider using nuclear weapons in Vietnam.

Wallace’s support in the polls began to slide, reaching the mid-teens in the weeks before Election Day. He ended up with 13.5% of the popular vote and 46 electoral votes – not enough to keep Nixon from winning the White House.

1980: John Anderson

Rep. John Anderson of Illinois was trailing badly in the Republican presidential primaries when, in April 1980, he dropped out and said he would run as an independent instead. Anderson’s candidacy generated considerable public interest: Around 20% of registered voters said they would support him, and he continued to poll around that level throughout the spring.

But Anderson’s nascent campaign had to spend much time and energy that spring and summer simply getting his name on state ballots. Anderson faded from view during that summer’s Democratic and Republican conventions. Incumbent President Jimmy Carter, the Democrat, refused to share a debate stage with him in the fall – though Republican nominee Ronald Reagan did debate Anderson one-on-one.

By October, Anderson’s support in polls had dwindled to the 9%-10% range. In the end, he won 6.6% of the national popular vote.

1992: Ross Perot

Money and visibility weren’t issues for Ross Perot, the billionaire businessman from Texas who mounted a stop-and-go independent campaign against Republican President George H.W. Bush and his Democratic challenger, Arkansas Gov. Bill Clinton.

Perot’s effort, driven initially by volunteers and appearances on Larry King Live , quickly gained momentum. In March, as Perot’s backers began gathering the hundreds of thousands of petition signatures he would need to get on state ballots, Perot was regularly receiving support from 20% or more of registered voters in polls. By May, about a third of registered voters were telling pollsters they’d vote for or were leaning toward Perot. In a few surveys, he led both Bush and Clinton.

Amid sharpening attacks from Republicans and Democrats , though, Perot’s numbers began falling. In mid-July, when his support was below 20% in most polls, Perot abruptly quit the race .

Although Perot was no longer actively campaigning, his name remained on two dozen state ballots, and some never-say-die supporters continued working to gain him ballot access in additional states. Pollsters continued to ask voters about Perot throughout the summer and fall – especially as speculation grew that he might jump back into the race. While Perot’s support declined steadily during this interim period, in late September around 10% of voters still said they preferred him to Bush or Clinton.

Perot reentered the campaign in early October, and within a few weeks his support had climbed back up to around 20%, including leaners. It began to slip again as Election Day neared, falling to around 15%. In the end, Perot won 18.9% of the popular vote – the best showing by a non-major-party candidate since Theodore Roosevelt 80 years earlier .

1996: Ross Perot

Perot wouldn’t come close to that in his second campaign. At the start of the year, when it was still unclear whether he would seek the nomination of the Reform Party (which he had founded the year before), his support among registered voters typically was in the mid-teens.

But Perot’s support declined during the campaign, eventually settling at around 5%-7%, including leaners. His poll numbers did pick up a bit in the run-up to Election Day, when he received 8.4% of the popular vote. Among the minor candidates Perot beat out for third place: consumer advocate Ralph Nader, who took 0.7% representing the Green Party.

2000: Ralph Nader and Pat Buchanan

Nader had a considerably higher profile four years later, when he was again the Green Party’s nominee. Polls taken during that close, contentious campaign regularly found that around 5% of registered voters said they supported or leaned toward Nader.

That was enough to concern Democrats that Nader threatened Vice President Al Gore’s chances of defeating Republican Texas Gov. George W. Bush. (Whether he in fact did so is still hotly debated among political scientists , journalists and other observers .)

In the end, Nader won only 2.7% of the national popular vote. But in several closely divided states – including Florida and New Hampshire, both of which Bush carried – Nader’s share was enough to potentially swing the outcome.

Another third-party candidate in 2000 received a fair amount of public and media attention: Pat Buchanan, the conservative commentator who had captured the nomination of Perot’s Reform Party. Buchanan polled as high as 4% in the spring, but by fall was mostly in the 1%-2% range. He ended up with less than 0.5% of the popular vote, but did well enough in five states to theoretically (or perhaps not so theoretically ) affect the outcome.

2016: Gary Johnson and Jill Stein

Widespread dissatisfaction with Republican Trump and his Democratic opponent, Hillary Clinton, may have caused more voters than usual to look beyond the major parties. Two candidates in particular received considerable attention: former New Mexico Gov. Gary Johnson – the Libertarian Party nominee – and physician and activist Jill Stein of the Green Party. (Both Johnson and Stein had also run in 2012, though with less impact.)

Johnson polled fairly strongly into the fall, with 8%-12% of registered voters routinely saying that they would vote for him or were leaning toward him. But Johnson’s poll numbers began trending downward, and by Election Day his support level was hovering around 5%-6%. Johnson ended up receiving 3.3% of the vote – the 52-year-old Libertarian Party’s best showing in a presidential election to date.

For her part, Stein often received support from 5%-7% of registered voters in polls taken during the spring and summer of 2016. But her support also eroded as the campaign went on, and she eventually received just over 1% of the popular vote – still the party’s best result since Nader in 2000.

• Election 2024
• Political Parties
• U.S. Elections & Voters
• Voters & Voting

Drew DeSilver is a senior writer at Pew Research Center .

Americans’ Views of Government’s Role: Persistent Divisions and Areas of Agreement

6 facts about presidential and vice presidential debates, satisfaction with democracy has declined in recent years in high-income nations, biden, trump are least-liked pair of major party presidential candidates in at least 3 decades, cultural issues and the 2024 election, most popular.

1615 L St. NW, Suite 800 Washington, DC 20036 USA (+1) 202-419-4300 | Main (+1) 202-857-8562 | Fax (+1) 202-419-4372 |  Media Inquiries

Research Topics

• Email Newsletters

ABOUT PEW RESEARCH CENTER  Pew Research Center is a nonpartisan fact tank that informs the public about the issues, attitudes and trends shaping the world. It conducts public opinion polling, demographic research, media content analysis and other empirical social science research. Pew Research Center does not take policy positions. It is a subsidiary of  The Pew Charitable Trusts .

© 2024 Pew Research Center