Increased frequency of daytime napping may correspondingly increase the risk for hypertension and ischemic stroke, according to study findings published in Hypertension.
Researchers conducted a prospective cohort study to determine the association between daytime napping and incidence of hypertension and stroke/ischemic stroke. They used data on 358,451 participants from the United Kingdom (UK) Biobank for an observational analysis.
To validate the results from the observational study, the researchers performed 2-sample Mendelian randomization. They used data from the FinnGen Biobank to analyze daytime napping and hypertension and data from the MEGASTROKE project to analyze daytime napping and stroke/ischemic stroke.
Next, they completed a 1-sample Mendelian randomization using data from 407,025 participants from UK Biobank to measure exposures and outcomes in 1 data set.
Participants self-reported day napping frequency, answering either “never/rarely”, “sometimes”, “usually”, or “prefer not to answer” (categorized as missing data).
Out of 358,451 participants in the prospective cohort, hypertension occurred in 50,507, while stroke occurred in 4333 participants (with 3621 ischemic strokes) over a median of 11.16 years.
Compared with “never napping”, “sometimes napping” increased risk for hypertension by 7%, stroke by 12%, and ischemic stroke by 9%, while “usually napping” increased the risk for hypertension by 12%, stroke by 24%, and ischemic stroke by 20%.
The 2-sample Mendelian randomization revealed a potential causal effect of increased nap frequency on hypertension (P =.018) and ischemic stroke (P =.023). The 1-sample Mendelian randomization predicted a 40% increased risk for hypertension for every 1-unit increase (never, sometimes, and usually) in the nap frequency category; however, it revealed no significant association between nap frequency and ischemic stroke unlike the 2-sample Mendelian randomization and the prospective cohort study.
“Prospective observational and [Mendelian randomization] analyses provided evidence that increased daytime nap frequency may represent a potential causal risk factor for essential hypertension,” the researchers stated. “The potential causal association of increased nap frequency with ischemic stroke was supported by 2-sample [Mendelian randomization] and prospective observational results.”
Study limitations included data only regarding frequency of napping without attention to duration, subjective reporting of nap frequency instead of objective measures, non-quantifiable measure of nap frequency using descriptive terms instead of numbers or percentages, and generalizability only to middle-aged or older adults in Europe.
The researchers concluded, “Our study, along with previous clinical studies, suggests that further examination of the mechanistic basis of the association between a healthy sleep pattern, including daytime napping, and cardiovascular disease is necessary.”
Yang MJ, Zhang Z, Wang YJ, 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. Published online July 25, 2022. doi:10.1161/HYPERTENSIONAHA.122.19120