For the study, researchers looked at data from more than 500,000 adults ages 40 to 60 from the U.K. Biobank, a large biomedical database and research resource of anonymized genetic, lifestyle, and health information. Study participants regularly provided blood, urine, and saliva samples, and detailed information about their lifestyle, including how often they partook in daytime napping. The study took place from 2006 to 2019. Participants were divided into groups based on self-reported napping frequency: never/rarely, sometimes, or usually. Compared with people who never napped, usual daytime napping was associated with a 12 percent higher risk of developing high blood pressure and a 24 percent higher risk of having a stroke compared with those who never napped. “These results are especially interesting since millions of people might enjoy a regular, or even daily nap,” E Wang, PhD, MD, a professor and chair of the department of anesthesiology at Xiangya Hospital Central South University in Changsha, China, and the study’s corresponding author, said in a press release. The results also showed that if napping frequency increased, say a person moved from the “never/rarely” category to the “sometimes” category, the risk of high blood pressure increased by 40 percent.
Too Soon to Hit the Snooze on Naps
But before canceling your siestas, it’s important to know that these are not blanket findings applicable to everyone. The study found that a higher percentage of people in the usually napping group had lower education and income levels, smoked cigarettes, drank alcohol daily, had insomnia, snored, or claimed to be an “evening person.” Each of these factors alone can affect the duration and quality of a person’s sleep at night, which can affect your health. So much so that the AHA recently added “sleep duration” as one of its metrics for optimal heart health. “I would worry about people who are taking lots of naps and are sleepy during the day because either they’re not sleeping well at night, or there’s something else that’s making them feel really fatigued, says Kristen L. Knutson, PhD, associate professor of neurology at Northwestern Medicine Feinberg School of Medicine in Chicago, who was not involved in the study. So is it the naps, or what is causing the naps? After all, planned naps can increase alertness, according to the Centers for Disease Control and Prevention (CDC), and plenty of countries have siesta cultures that revolve around midday naps. Ultimately, the study does not give a firm answer on what constitutes a nap — the duration or the quality. In lieu of a definition given by the study authors, Dr. Knutson says that naps should be broken down into two categories — intentional and unintentional. Intentional naps may be classified as one of those siestas, a quick sleep that is part of your schedule. Unintentional naps, like dozing off on the couch or while at work, are more problematic and symptomatic of other issues and are likely what this study is trying to address. Still, Knutson hesitates to tell people to stop napping, because the study does not show what biological mechanisms would lead to a nap causing a stroke. “If someone is otherwise healthy and likes to nap, I wouldn’t suddenly tell them to stop napping without a better understanding of the association,” she says. “But if someone is taking frequent naps because they feel they’re not getting restorative sleep or they’re very sleepy during the day, then those individuals should discuss this with their physician to try to determine why and make sure they don’t have a sleep disorder.”
