“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 may raise the risk for cardiovascular disease. But whether napping is good or bad has been unclear.
In the new study, researchers analyzed the sleep patterns of 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, in which she was not involved, 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.
