Although naps may not be unhealthy, frequent napping could reflect poorer sleep at night.
Frequent daytime napping in adults was associated with a 12% higher risk of developing high blood pressure as well as a 24% higher risk of stroke, compared to adults who never take daytime naps, according to a study published in Hypertension.
For the study, researchers in China examined whether frequent or usual napping could be a potential causal risk factor for high blood pressure or stroke. This was the first study to use observational analysis of participants over a long period of time as well as Mendelian randomization, which is a genetic risk validation, to investigate potential links.
“These results are especially interesting since millions of people might enjoy a regular, or even daily, nap,” said corresponding author E. Wang, PhD, MD, a professor and chair of the department of anesthesiology at Xiangya Hospital Central South University in China, in a press release.
The research team used data from UK Biobank, a large biomedical database and research resource containing anonymized genetic, lifestyle, and health information from more than 500,000 UK participants. The database recruited participants between 40 and 69 years of age who lived in the United Kingdom between 2006 and 2010. They provided regular blood, urine, and saliva samples, as well as detailed lifestyle information. The daytime napping frequency survey occurred 4 times between 2006 and 2019 in a small proportion of UK Biobank participants.
Wang’s research team then excluded records of individuals who had already had a stroke or experienced hypertension before the start of the study. This left approximately 360,000 participants to analyze the association between napping and first-time reports of stroke or high blood pressure, with an average follow-up of about 11 years. Participants were divided into groups based on their self-reported napping frequency, including “never/rarely,” “sometimes,” or “usually.”
According to the study, a higher percentage of the “usual” nappers were men, had lower education and income levels, and reported cigarette smoking, daily drinking, insomnia, snoring, and being an evening person compared to participants who said they never or sometimes napped. Compared to individuals who reported never taking a nap, individuals who usually nap had a 12% higher likelihood of developing high blood pressure and 24% higher likelihood of having a stroke.
Furthermore, participants younger than 60 years of age who usually napped had a 20% higher risk of developing high blood pressure compared to individuals the same age who never napped. After 60 years of age, usual napping was associated with a 10% greater risk of high blood pressure compared to those who reported never napping. Approximately three-fourths of participants remained in the same napping category throughout the study.
Finally, the Mendelian randomization result showed that if napping frequency increased by one category (from never to sometimes, or from sometimes to usually), high blood pressure risk increased by 40%. Higher napping frequency was related to the genetic propensity for high blood pressure risk.
“This may be because, although taking a nap itself is not harmful, many people who take naps may do so because of poor sleep at night,” sleep expert Michael A. Grandner, PhD, MTR, said in the press release. “Poor sleep at night is associated with poorer health, and naps are not enough to make up for that.”
The authors recommended further examination of the associations between a healthy sleep pattern, including daytime napping, and heart health. They also noted that they only collected data on daytime napping frequency, not duration, which could be a limitation.
Additionally, nap frequency was self-reported without any objective measurements, making estimates nonquantifiable. The results also may not be generalizable based on the study population.
“This study echoes other findings that generally show that taking more naps seems to reflect increased risk for problems with heart health and other issues,” Grander concluded in the press release.
Study shows link between frequent naps and high blood pressure. Press release. American Heart Association; July 25, 2022. Accessed August 4, 2022. https://newsroom.heart.org/news/study-shows-link-between-frequent-naps-and-high-blood-pressure