Midday Napping, Nighttime Sleep, and Mortality: Prospective Cohort Evidence in China / 生物医学与环境科学（英文）

OBJECTIVE@#In developed countries, midday napping and nighttime sleep duration have been linked to long-term survival; however, little is known about such effects in less developed regions. Therefore, this study aimed to assess the associations of midday napping and nocturnal sleep with mortality in middle-aged and older Chinese adults.@*METHODS@#A nationwide cohort of 15,524 adults aged ≥ 45 years was enrolled from 28 provincial regions across mainland China and followed up from 2011 to 2018, using data from the Chinese Health and Retirement Longitudinal Study. Midday napping and nighttime sleep duration were assessed using standardized questionnaires. Cox proportional hazards models with random intercepts for the surveyed provinces were used to estimate hazard ratios ( HRs) of all-cause mortality, adjusting for sociodemographic characteristics, behavioral factors, and health status.@*RESULTS@#A total of 1,745 deaths occurred during a median follow-up of 7.1 years, and the mean (standard deviation) age was 59 (10.1) years at baseline. Compared with non-nappers, over 60 min nappers had a higher risk of all-cause mortality [ HR: 1.35, 95% confidence interval ( CI): 1.17-1.56], while no significant associations were observed among < 30 min nappers. Compared with sleep duration of 6-8 h/night, both short (< 6 h) and long (≥ 8 h) sleep duration were significantly associated with increased mortality, with corresponding HR (95% CI) estimates of 1.21 (1.05-1.38) and 1.26 (1.10-1.44), respectively. We observed significant patterns for greater risks associated with longer nap duration, with a P trend value < 0.001 for all-cause mortality. No significant evidence of an additive interaction was identified between midday napping and nighttime sleep.@*CONCLUSION@#Long midday napping and inappropriate nighttime sleep were independently associated with an increased risk of all-cause mortality in middle-aged and older Chinese populations. Biological studies are needed to validate our findings and clarify the mechanisms underlying this association.

Associations of Daytime Napping with Incident Cardiovascular Diseases and Hypertension in Chinese Adults: A Nationwide Cohort Study / 生物医学与环境科学（英文）

OBJECTIVE@#This study aimed to examine the associations of daytime napping with incident risks of cardiovascular diseases (CVDs) and hypertension (HTN).@*METHODS@#Data for napping and CVD outcomes in 25 provinces were collected from baseline (2010) and three waves of follow-up (2012-2017) investigations of the China Family Panel Studies. Cox frailty models with random intercepts for the surveyed provinces were used to assess the longitudinal effects of daytime napping on CVD and HTN.@*RESULTS@#Compared with non-nappers, 30+ min nappers had higher risks of CVD and HTN, while no significant associations were observed among < 30 min nappers. Incident risks among 30- to < 60-min nappers increased by 22% [hazard ratio (HR) 1.22, 95% confidence interval ( CI) 1.08-1.39] for CVD and 21% (1.21, 1.04-1.41) for HTN, respectively, with corresponding HRs of CVD and HTN of 1.27 (1.09-1.47) and 1.38 (1.16-1.65) among ≥ 60 min nappers. Nap-associated CVD risks varied by subgroups, with stronger associations in participants with lower body mass index (< 24 kg/m 2), physically inactive persons, smokers, and participants with longer nighttime sleep (≥ 7 h/night). Significant effects of daytime napping were observed on rural and northern residents only, highlighting great regional variations in CVD risks associated with napping habits.@*CONCLUSIONS@#This cohort study revealed strong evidence that long daytime napping (≥ 30 min) is associated with an increased incidence of cardiovascular events.