Sun, Sleep, and Satisfaction: Mediating Role of Depression and Source of Endogeneity among Middle-aged and Older Adults in China

PurposeTo examine: (i) depression as a mediator in effects of sleep duration and quality on life satisfaction (LS), (ii) source of endogeneity in self-reported data on sleep, and (iii) predictive power of sleep duration and quality on LS. MethodsPanel data of 22,674 observations from the China Health and Retirement Longitudinal Survey (2015 & 2018) was used. Sleep was assessed with self-reported duration and quality. Depression was measured by the 10-question version of the Center for Epidemiological Survey - Depression. LS was rated by five scales. Fixed-effects ordered logit models were used to determine the effect of sleep duration and quality on life satisfaction and the mediating role of depression. We used instrumental variable strategy to explore the source of endogeneity. Information value and random forest model were used to examine the predictive power of sleep measures duration and quality. ResultsSleep duration and quality were found to improve life satisfaction via lower depression score. Non-agricultural employed population with urban hukou (household registration) accounted for the endogeneity, but the instrument variable sunset failed the weak instrument test. Sleep measures were found to predict life satisfaction, especially for the lower life satisfaction groups. ConclusionOur findings suggest the importance of sleep and the study of the associations between solar cues, social schedules, and sleep. Policy makers of social care of older adults might consider sleep intervention among this population.