BACKGROUND: Depressive symptoms, sleep disturbances, and functional disability are interrelated. However, the bidirectional pathways between depression, sleep disturbances, and disability in instrumental activities of daily living (IADLs) remain underexplored in China.
OBJECTIVE: We aimed to examine the bidirectional longitudinal relationships between depression and disability in IADLs among older Chinese adults, with a focus on elucidating the mediating role of sleep disturbances in this dynamic interplay.
METHODS: The study encompassed 2677 older adults who provided complete data at T1 (2015), T2 (2018), and T3 (2020) for the China Health and Retirement Longitudinal Study (CHARLS). Depressive symptoms were assessed using the 10-item Center for Epidemiological Studies Depression (CESD-10) scale, and a 6-item scale was used to measure disability in IADLs. Sleep disturbances were self-reported. Temporal associations between depressive symptoms and disability in IADLs as well as the longitudinal mediating effect of sleep disturbances were examined using a cross-lagged panel model.
RESULTS: Prior depression significantly predicted subsequent disability in IADLs at T2 (β=0.070, P<.001) and T3 (β=0.074, P<.001), and prior disability in IADL predicted subsequent depression at T2 (β=0.094, P<.001) and T3 (β=0.100, P<.001). Additionally, the indirect effect of prior disability in IADLs on subsequent depression via sleep disturbances was statistically significant (β=0.062, SE=0.010, P<.001), with the mediation effect accounting for 50.41% of the total effect. In contrast, after accounting for this mediation, the direct effect of prior depression on subsequent disability in IADLs was not significant (β=0.009, SE=0.018, P=.61). Consequently, the impact of depression on disability in IADLs was fully mediated through sleep disturbances in this cohort of older Chinese adults.
CONCLUSIONS: Depressive symptoms and disability in IADLs are bidirectionally linked, and sleep disturbances play a longitudinal mediating role in the bidirectional relationship among older Chinese adults. The potential longitudinal bidirectionality highlights the importance of sleep health for interventions on depression and functional disability in older adults.
