American Heart Association study shows link between frequent naps and high blood pressure.
- Frequent or usual daytime napping in adults was associated with a 24% high risk of having a stroke and a 12% higher risk of developing high blood pressure compared to never napping.
- Experts say napping, though not unhealthy, could be a sign of poor sleep quality.
- A higher percentage of frequent nappers were men, had lower education and income levels, and reported daily drinking, cigarette smoking, insomnia, snoring, and being an evening person compared to people who reported napping sometimes or never.
- The Mendelian randomization result shows that if napping frequency increased by one category (from never to sometimes or sometimes to usually) high blood pressure risk increased by 40%.
According to new research published on July 25, 2022, in Hypertension, an American Heart Association journal, napping on a regular basis is associated with higher risks for high blood pressure and stroke.
For the research, scientists in China investigated whether frequent naps could be a potential causal risk factor for high blood pressure and/or stroke. It is the first study to investigate whether frequent napping was associated with high blood pressure and ischemic stroke using both observational analyses of participants over a long period of time and Mendelian randomization – a genetic risk validation.
“These results are especially interesting since millions of people might enjoy a regular, or even daily nap,” says E Wang, Ph.D., M.D., a professor and chair of the Department of Anesthesiology at Xiangya Hospital Central South University, and the study’s corresponding author.
For the study, researchers used information from UK Biobank. This large biomedical database and research resource contains anonymized genetic, lifestyle, and health information from half a million UK participants. Between 2006 and 2010, UK Biobank recruited more than 500,000 participants between the ages of 40 and 69 who lived in the United Kingdom. The participants regularly provided blood, urine, and saliva samples, as well as detailed information about their lifestyles. The daytime napping frequency survey occurred 4 times from 2006 – 2019 in a small proportion of UK Biobank participants.
Wang’s team excluded records of people who had already had a stroke or had high blood pressure before the start of the study. This left about 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 three groups based on self-reported napping frequency: “never/rarely,” “sometimes,” or “usually.”
The study found:
- A higher percentage of usual-nappers were men, had lower education and income levels, and reported daily drinking, cigarette smoking, snoring, insomnia, and being an evening person compared to never- or sometimes-nappers;
- People who usually nap had a 12% higher likelihood of developing high blood pressure and 24% higher likelihood of having a stroke compared to people who reported never taking a nap;
- Participants younger than age 60 who usually napped had a 20% higher risk of developing high blood pressure compared to people the same age who never napped. After age 60, usual napping was associated with a 10% higher risk of high blood pressure compared to those who reported never napping;
- About three-fourths of participants remained in the same napping category throughout the study;
- The Mendelian randomization result showed that if napping frequency increased by one category (from never to sometimes or sometimes to usually) high blood pressure risk increased 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. Poor sleep at night is associated with poorer health, and naps are not enough to make up for that,” said Michael A. Grandner, Ph.D., MTR, a sleep expert and co-author of the American Heart Association’s new Life’s Essential 8 cardiovascular health score, which added sleep duration in June 2022 as the 8th metric for measuring optimal heart and brain health. “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 is director of the Sleep Health Research Program and the Behavioral Sleep Medicine Clinic and associate professor of psychiatry at the University of Arizona in Tucson.
The researchers recommend further examination of the associations between a healthy sleep pattern, including daytime napping, and heart health.
Several important limitations of the study should be considered. Scientists only collected daytime napping frequency, not duration, so there is no information on how or whether the length of nap affects blood pressure or stroke risks. In addition, nap frequency was self-reported without any objective measurements, making estimates nonquantifiable. Furthermore, the research participants were mostly middle-aged and elderly with European ancestry, so the results may not be generalizable. Finally, scientists have not yet discovered the biological mechanism for the effect of daytime napping on blood pressure regulation or stroke.
Reference: “Association of Nap Frequency With Hypertension or Ischemic Stroke Supported by Prospective Cohort Data and Mendelian Randomization in Predominantly Middle-Aged European Subjects” by Min-jing Yang, Zhong Zhang, Yi-jing Wang, Jin-chen Li, Qu-Lian Guo, Xiang Chen and E. Wang, 25 July 2022, Hypertension.
Co-authors are Min-jing Yang, M.D.; Zhong Zhang, Ph.D., M.D.; Yi-jing Wang; M.D.; Jin-chen Li, Ph.D.; Qu-lian Guo, Ph.D., M.D.; Xiang Chen, Ph.D., M.D.
The National Key Research and Development Program of China financially support this research.
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