Daytime napping for 30 minutes or longer is associated with an increased likelihood of developing atrial fibrillation, according to research presented at ESC Preventive Cardiology 2023, a scientific congress of the European Society of Cardiology (ESC).1
“Our study indicates that snoozes during the day should be limited to less than 30 minutes,” said study author Dr. Jesus Diaz-Gutierrez of Juan Ramon Jimenez University Hospital, Huelva, Spain. “People with disturbed night-time sleep should avoid relying on napping to make up the shortfall.”
Atrial fibrillation is the most common heart rhythm disorder, affecting more than 40 million people worldwide. People with this arrhythmia have a five times greater risk of stroke than their peers. Dr. Diaz-Gutierrez said: “Previous studies have suggested that sleep patterns may play a role in the development of atrial fibrillation, but as far as we know this was the first study to analyse the relationship between daytime napping and risk of the arrhythmia.”
The study used data from the University of Navarra Follow-up (SUN) Project, a prospective cohort of Spanish university graduates. A total of 20,348 participants free of atrial fibrillation at baseline completed a questionnaire every two years. Information was obtained on sociodemographics (age, sex, working hours), medical conditions (high cholesterol, high blood pressure, diabetes, sleep apnoea, cardiovascular diseases including atrial fibrillation), lifestyle (napping, smoking, exercise, coffee intake, binge drinking, adherence to a Mediterranean diet, TV watching), height and weight.
Napping, as well as sleeping too much or too little or having poor sleep patterns, appears to increase the risk for cardiovascular disease in older adults, new research shows.
The study, published Tuesday in the Journal of the American Heart Association, adds to a growing body of evidence supporting sleep’s importance to good health. The American Heart Association recently added sleep duration to its checklist of health and lifestyle factors for cardiovascular health, known as Life’s Essential 8. It says adults should average seven to nine hours of sleep a night.
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“Good sleep behavior is essential to preserve cardiovascular health in middle-aged and older adults,” said lead author Weili Xu, a senior researcher at the Aging Research Center in the department of neurobiology, care sciences and society at the Karolinska Institute in Stockholm, Sweden. “We encourage people to keep nighttime sleeping between seven to nine hours and to avoid frequent or excessive napping.”
Prior research has shown poor sleep may put people at higher risk for a range of chronic illnesses and conditions affecting heart and brain health. These include cardiovascular disease, dementia, diabetes, high blood pressure and obesity. According to the Centers for Disease Control and Prevention, nearly 35% of U.S. adults say they get less than seven hours of sleep, while 3.6% say they get 10 or more hours.
Previous sleep duration studies show that sleeping too much or too little both may raise the risk for cardiovascular disease. But whether napping is good or bad has been unclear.
In the new study, researchers analyzed sleep patterns for 12,268 adults in the Swedish Twin Registry. Participants were an average of 70 years old at the start of the study, with no history of major cardiovascular events.
A questionnaire was used to collect data on nighttime sleep duration; daytime napping; daytime sleepiness; the degree to which they considered themselves a night person or morning person, based on the time of day they considered themselves most alert; and symptoms of sleep disorders, such as snoring and insomnia. Participants were followed for up to 18 years to track whether they developed any major cardiovascular problems, including heart disease and stroke.
People who reported sleeping between seven and nine hours each night were least likely to develop cardiovascular disease, a finding in keeping with prior research. Compared with that group, those who reported less than seven hours were 14% more likely to develop cardiovascular disease, and those who reported more than 10 hours were 10% more likely to develop cardiovascular disease.
Compared with people who said they never napped, those who reported napping up to 30 minutes were 11% more likely to develop cardiovascular disease. The risk increased by 23% if naps lasted longer than 30 minutes. Overall, those who reported poor sleep patterns or other sleep issues – including insomnia, heavy snoring, getting too much or too little sleep, frequent daytime sleepiness and considering themselves a night person – had a 22% higher risk
Study participants who reported less than seven hours of sleep at night and napping more than 30 minutes each day had the highest risk for cardiovascular disease – 47% higher than those reporting the optimal amount of sleep and no naps.
The jury is still out on whether naps affect cardiovascular risk across the lifespan, said Marie-Pierre St-Onge, center director for the Sleep Center of Excellence and an associate professor at Columbia University in New York City. She noted that the new research, which she was not involved in, was restricted to older adults.
Rather than trying to recoup sleep time by napping, people should try to develop healthier sleep habits that allow them to get an optimal amount of sleep at night, St-Onge said. This includes making sure the sleep environment is not too hot or cold or too noisy. Reducing exposure to bright light before going to sleep, not eating too late at night, getting enough exercise during the day and eating a healthful diet also help.
“Even if sleep is lost during the night, excessive napping is not suggested during the day,” Xu said. And, if people have persistent trouble getting enough sleep, they should consult a health care professional to figure out why, she said.
Are you feeling a little guilty about your daily, mid-afternoon snooze? Don’t. Research shows that catching a few ZZZs after lunch can be good for your brain. But keep in mind that the length of your nap matters.
While a 30- to 90-minute nap in older adults appears to have brain benefits, anything longer than an hour and a half may create problems with cognition, the ability to think and form memories, according to the study published in the Journal of the American Geriatrics Society.
“I consider napping to be a good thing, but it needs to be taken in the context of the person and his or her own sleep cycles and body,” says Charlene Gamaldo, M.D., medical director of Johns Hopkins Sleep Disorders Center. For older people, as the study showed, longer naps tend to interfere with cognition, she says.
Napping for a better brain
Researchers looked at data from 2,974 people in China ages 65 and older. Nearly 60 percent of participants reported napping after lunch for about an hour.
How often a person takes daytime naps, if at all, is partly regulated by their genes, according to new research led by investigators at 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, PhD, RD, 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, PhD, 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, PhD, 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. 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 research teams draws a clear conclusion from its study: ‘A short nap at the office or in school is enough to significantly improve learning success. Wherever people are in a learning environment, we should think seriously about the positive effects of sleep,’ says Axel Mecklinger. Enhancing information recall through sleeping doesn’t require us to stuff bulky tomes under our pillow. A concentrated period of learning followed by a short relaxing sleep is all that’s needed.
Generations of school students have gone to bed the night before a maths exam or a vocabulary test with their algebra book or vocabulary notes tucked under their pillow in the hope that the knowledge would somehow be magically transferred into their brains while they slept. That they were not completely taken in by a superstitious belief has now been demonstrated by a team of neuropsychologists at Saarland University, who have shown that even a brief sleep can significantly improve retention of learned material in memory.
Sara Studte, a graduate biologist specializing in neuropsychology, working with her PhD supervisor Axel Mecklinger and co-researcher Emma Bridger, is examining how power naps influence memory performance. The results are clear: ‘Even a short sleep lasting 45 to 60 minutes produces a five-fold improvement in information retrieval from memory,’ explains Axel Mecklinger.
Strictly speaking, memory performance did not improve in the nap group relative…
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