Recognizing the impact of sleep on overall health, the American Heart Association (AHA) recently updated its checklist for a healthy heart and brain and added the dimension of sleep duration as an essential component calling it “Life’s Essential 8”, and replacing the earlier score of “Life’s Simple 7”. It recommends 7-9 hours of sleep daily for optimal cardiovascular health. The other 7 items in the checklist are nicotine exposure, physical activity, diet, weight, blood glucose, cholesterol and blood pressure.

An observational analysis published in the journal Hypertension has now shown that people who nap often during the day are more likely to develop hypertension and suffer a stroke.¹

In this study, Wang et al analysed data of 358,451 participants from UK Biobank to examine a link between frequency of daytime naps and new onset of essential hypertension or incident stroke. None of the study subjects had hypertension and stroke at the time of their enrolment in the present study. Data was gathered from 2006 to 2019. Napping frequency was self-reported as never/rarely, sometimes or usually.

Results show that those who usually napped were mostly men; they were older in age, smokers, consumed alcohol daily and tended to be less educated with lower income. They also reported sleep problems and snoring. They had higher BMI, waist-hip ratio and cholesterol levels and were more likely to have a history of diabetes.

The participants who usually napped were at 12% higher risk of developing essential hypertension with a hazard ratio of 1.12  and 24% more likely to have a stroke (HR 1.24) than those who never took a nap. The risk for ischemic stroke was 20% higher (HR 1.20). People who napped “sometimes” were at a slightly lower risk, which was still higher than those who “never/rarely” took naps during the day.

When the association was analysed according to age, the risk of high BP was 20% higher among the younger participants, below 60 years of age compared to their counterparts who did not sleep during the day. The risk declined a bit among participants older than 60 years, who were at 10% higher risk of high blood pressure compared to those who reported never napping.

A Mendelian randomization was also conducted to investigate the correlation between napping frequency and essential hypertension using the FinnGen Biobank, and stroke and ischemic stroke using the MEGASTROKE consortium. The Mendelian randomization showed that a change in frequency of daytime napping, from never to sometimes or sometimes to usually, increased the risk of essential hypertension in the FinnGen Biobank (OR 1.43) and UK Biobank  (OR 1.4) suggesting a genetic predisposition to high blood pressure. The two-sample Mendelian randomization in the MEGASTROKE also linked daytime napping frequency with increased risk for ischemic stroke (OR 1.29).

A short nap during the day may be invigorating, especially for the sleep-deprived, but it does not make up for regular and adequate sleep at night. This study has linked increased frequency of daytime naps with the risk for essential hypertension and stroke. It has demonstrated a potential causal association, although the mechanisms for the effect of naps on heart health are yet to be elucidated. The study only analysed frequency of daytime naps and not the duration and also it was self-reported, which the authors say are limitations of the study. However, these findings do suggest that clinicians should routinely enquire about daytime napping and accordingly act to modify the risk.

Reference

1. Yang MJ, et al. Association of nap frequency with hypertension or ischemic stroke supported by prospective cohort data and mendelian randomization in predominantly middle-aged European subjects. Hypertension. 2022 Jul 25:101161HYPERTENSIONAHA12219120. doi: 10.1161/HYPERTENSIONAHA.122.19120.