Physical activity and sleep duration as predictors of subsequent depression in older adults: Longitudinal evidence from the China health and retirement longitudinal study (CHARLS)

OBJECTIVES: While extensive research has established significant associations between physical inactivity, abnormal sleep duration, and the development of depressive symptoms in older adults, prior studies have frequently neglected a sleep-centered perspective. Particularly in aging populations, the potential mediating role of sleep duration in the physical activity-depression relationship remains insufficiently investigated. This study therefore examines the longitudinal effects of physical activity and sleep duration changes on subsequent depressive symptoms, with particular emphasis on elucidating the intermediary function of sleep duration. DESIGN: Combining Cross-Sectional and Longitudinal Studies. SETTING AND PARTICIPANTS: From the China Health and Retirement Longitudinal Study (CHARLS) 2015, 2018, and 2020 databases, 4708 participants were tracked. MEASUREMENTS: This study employed generalized estimating equations (GEE) with marginal effects to quantify the associations between physical activity, sleep duration, and depression. Cross-sectional analyses using 2015 China Health and Retirement Longitudinal Study (CHARLS) data applied bootstrap testing to examine potential mediation pathways. Longitudinal analyses incorporated national CHARLS data from 2015, 2018, and 2020, utilizing cross-lagged panel models (CLPM) to delineate directional relationships among physical activity, sleep duration, and depressive symptoms. RESULTS: The study revealed significant dose-response relationships between both physical activity/sleep duration and depressive symptoms among Chinese older adults, with sleep duration demonstrating a robust mediating role in their association. Cross-lagged analyses established a temporal pathway whereby physical activity positively predicted subsequent sleep duration (T₂₀₁₅EX → T₂₀₁₈SE), which in turn significantly predicted later depression development (T₂₀₁₈SE → T₂₀₂₀DP), collectively forming the validated longitudinal mediation pathway "physical activity → sleep duration → depression". CONCLUSION: The onset and progression of depressive symptoms in Chinese older adults demonstrated significant associations with physical inactivity and abnormal sleep duration, exhibiting dose-response relationships with depression severity. The study established a temporal cascade through the "physical activity → sleep duration → depression" pathway, providing directional explanation for previously observed cross-sectional correlations. These findings suggest promising therapeutic strategies for the prevention and clinical management of depression in older adults.