The mediating effect of activities of daily living (ADL) disability on the association between depressive symptoms and cognitive impairment in older adults: a National study.

Background: Numerous studies have demonstrated a correlation between depressive symptoms and a higher likelihood of cognitive impairment among older adults. Little is known about the underlying pathway connecting these two conditions.

Objective: This study aimed to investigate whether activities of daily living (ADL) disability potentially mediate the relationship between depressive symptoms and cognitive function.

Methods: This study is a cross-sectional design. A total of 6623 Chinese older adults aged 65 years and above from the 2018 China Longitudinal Healthy Longevity Survey (CLHLS) were included in this study. Multiple linear regression was conducted to examine the relationships among depressive symptoms, ADL disability and cognitive function, while accounting for all confounding factors. Mediation analyses were performed to examine whether ADL disability mediated the relationship between depressive symptoms and cognitive function via PROCESS macro version 4.0.

Results: The results indicated that the relationship between depressive symptoms and cognitive function was significantly mediated by ADL disability (estimated indirect effect = -0.040, bootstrapped SE = 0.020, bootstrapped standard 95% CI= -0.083 - -0.007), with ADL disability accounting for 7.5% of the total effect. Moreover, the mediating role of ADL disability was moderated by gender, as the interaction between depressive symptoms and gender on ADL disability was found to be significant (β=-0.102, p = 0.033, IMM: 0.005, 95%CI: 0.001-0.011). When stratified by gender, the mediating effect of ADL disability was observed exclusively in males (estimated indirect effect= -0.055, bootstrapped SE = 0.031, bootstrapped standard 95% CI= -0.123 - -0.004), with a relative proportion of 9.7%.

Limitations: The causal relationship was not able to certain because of the cross-sectional design.

Conclusion: This study revealed that ADL disability may partially mediate the relationship between depressive symptoms and cognitive function in older adults. Furthermore, the mediating effect of ADL disability was moderated by gender, and the effect was observed exclusively in males when analyzed hierarchically.