The impact of sleep duration, depressive symptoms, and cognitive function on daily activity among Chinese older adults: a serial multiple mediation model.

Background: Few studies have explained the mechanisms underlying the relationship between sleep duration and the activities of daily living (ADL). We aim to explore the multiple mediating roles of depressive symptoms and cognitive function in this relationship among Chinese older adults.

Methods: A total of 5858 older adults participated in the China Health and Retirement Longitudinal Study, completing the Center for Epidemiologic Studies Depression Scale, the ADL Scale, and the Telephone Interview for Cognitive Status Scale. We performed serial multiple mediation analysis using the Hayes' PROCESS macro.

Results: Sleep duration influenced ADL both directly and indirectly through three significant pathways (P < 0.001). For individuals sleeping 6-8 hours, depressive symptoms accounted for 56.50% of the total effect. In contrast, for those sleeping ≥8 hours, depressive symptoms accounted for 65.50%. Cognitive function contributed to 1.79% of the total effect in the 6-8-hour group, whereas in the ≥8-hour group, cognitive function had a negative mediating effect of -4.60%. Combined mediation by depressive symptoms and cognitive function accounted for 2.42% of the total effect in the 6-8-hour group and 2.76% in the ≥8-hour group. The total mediating effect was 60.70% for the 6-8-hour group and 63.70% for the ≥8-hour group.

Conclusions: The action mechanisms between different levels of sleep duration and ADL differed, but all showed significant effects from sleep duration, depressive symptoms, and cognitive function regarding ADL among older adults. Therefore, promoting sleep education and addressing depressive symptoms and cognitive decline in older adults are essential for the early detection and prevention of ADL impairment.