AIMS: To investigate the association of estimated total daily sleep duration and daytime nap duration with deaths and major cardiovascular events.
METHODS AND RESULTS: We estimated the durations of total daily sleep and daytime naps based on the amount of time in bed and self-reported napping time and examined the associations between them and the composite outcome of deaths and major cardiovascular events in 116 632 participants from seven regions. After a median follow-up of 7.8 years, we recorded 4381 deaths and 4365 major cardiovascular events. It showed both shorter (≤6 h/day) and longer (>8 h/day) estimated total sleep durations were associated with an increased risk of the composite outcome when adjusted for age and sex. After adjustment for demographic characteristics, lifestyle behaviours and health status, a J-shaped association was observed. Compared with sleeping 6-8 h/day, those who slept ≤6 h/day had a non-significant trend for increased risk of the composite outcome [hazard ratio (HR), 1.09; 95% confidence interval, 0.99-1.20]. As estimated sleep duration increased, we also noticed a significant trend for a greater risk of the composite outcome [HR of 1.05 (0.99-1.12), 1.17 (1.09-1.25), and 1.41 (1.30-1.53) for 8-9 h/day, 9-10 h/day, and >10 h/day, Ptrend < 0.0001, respectively]. The results were similar for each of all-cause mortality and major cardiovascular events. Daytime nap duration was associated with an increased risk of the composite events in those with over 6 h of nocturnal sleep duration, but not in shorter nocturnal sleepers (≤6 h).
CONCLUSION: Estimated total sleep duration of 6-8 h per day is associated with the lowest risk of deaths and major cardiovascular events. Daytime napping is associated with increased risks of major cardiovascular events and deaths in those with >6 h of nighttime sleep but not in those sleeping ≤6 h/night.
C. Wang, Bangdiwala, S. I., Rangarajan, S., Lear, S. A., AlHabib, K. F., Mohan, V., Teo, K., Poirier, P., Tse, L. Ah, Liu, Z., Rosengren, A., Kumar, R., Lopez-Jaramillo, P., Yusoff, K., Monsef, N., Krishnapillai, V., Ismail, N., Seron, P., Dans, A. L., Kruger, L., Yeates, K., Leach, L., Yusuf, R., Orlandini, A., Wolyniec, M., Bahonar, A., Mohan, I., Khatib, R., Temizhan, A., Li, W., and Yusuf, S., “Association of Estimated Sleep Duration and Naps with Mortality and Cardiovascular Events: a Study of 116 632 People from 21 Countries”, Eur Heart J, vol. 40, no. 20, pp. 1620-1629, 2019.