Nighttime sleep, midday napping, and mortality in Chinese older adults: A China Health and Retirement Longitudinal...

ObjectiveTo evaluate the independent and combined associations of nighttime sleep duration and midday napping duration with all-cause mortality and premature death in Chinese older adults and to examine potential sex-specific differences.MethodsThis longitudinal cohort study analyzed 11,054 adults aged ≥60 years from the China Health and Retirement Longitudinal Study 2018-2020. Sleep is a key factor in the health of older adults, but prior research has focused on nighttime sleep in Western populations, with limited attention to the culturally common practice of midday napping in China and no systematic analysis of sex differences. Nighttime sleep and daily midday napping durations were collected using standardized questionnaires. Two-year all-cause mortality and premature death were tracked as the primary outcomes. Cox regression, restricted cubic spline analysis, and multiple sensitivity analyses were performed. The proportional hazards assumption was verified using Schoenfeld residuals (all p > 0.05).ResultsAfter adjustment for covariates (age, sex, education level, marital status, smoking, alcohol consumption, and number of chronic diseases), daily napping ≥60 min was independently associated with a higher risk of all-cause mortality (overall hazard ratio = 1.289, p = 0.013; males: hazard ratio = 1.298, p = 0.049). The "long sleep + long nap" pattern (>8 h nighttime sleep + ≥60 min nap) was associated with the highest risk of all-cause mortality (hazard ratio = 3.048, p < 0.001). Males with 8-10 h of nighttime sleep had an elevated risk of all-cause mortality (hazard ratio = 3.095, p = 0.001), whereas females with 4-6 h of nighttime sleep had a lower risk of premature death (hazard ratio = 0.522, p = 0.039). Restricted cubic spline analysis confirmed a nonlinear U-shaped association between nighttime sleep duration and all-cause mortality.ConclusionsIn Chinese older adults, prolonged daily napping (≥60 min) was associated with a higher risk of mortality after adjustment for covariates. Sex-specific differences were observed, although the formal interaction test did not reach statistical significance (p = 0.112). Nighttime sleep of 6-8 h and avoiding daily napping ≥60 min may be associated with a lower risk of mortality; however, as this was an observational study, causal inference cannot be established.