Abstract
Objectives: This study aims to investigate the mediating role of depression and the moderating effect of gender in the relationship between total sleep time (TST) and instrumental activities of daily living (IADL) in middle-aged and elderly people (aged 45 or above). Methods: The data used in this study is from the China Health and Retirement Longitudinal Study (CHARLS), including a total of 10,460 respondents. Associations between TST, IADL, depression, and gender were analyzed using logistic regression and Karlson, Holm, and Breen (KHB) methods. Results: Short (OR = 1.42, 95% CI = 1.28-1.58 of ≤6 h) and long TST (OR = 1.16, 95% CI = 1.02-1.32 of 8-9 h; OR = 1.35, 95% CI = 1.19-1.54 of >9 h) were both associated with IADL. The mediation effect analyses observed that depression explained 64.80% of the total effect of short TST (≤6 h) and IADL, but was insignificant in long TST (8-9 h and >9 h). Meanwhile, gender has moderating effects on the mediation effect model. Conclusion: The study suggests that health interventions that focused on the dimensions of TST and depression are crucial for preventing functional disability while accounting for gender differences.