Relationship of Frailty Markers and Socioeconomic Status to Incidence of Depressive Symptoms in a Community Cohort

Objectives This study aimed to examine the relationship between frailty markers and socioeconomic status (SES) to incidence of depressive symptoms using a nationally representative sample of middle-age and older adults. Design Cohort study with a 4-year follow-up; 89.1% of the participants were followed for 2 years and 73.4% for 4 years. Setting and Participants A total of 6641 participants from the China Health and Retirement Longitudinal Study (CHARLS) were included in the analyses. Methods The outcome was incident depressive symptoms. Educational level and occupational status were used to assess SES. Physical frailty status was evaluated using 2 frailty markers, namely weakness and slowness. Two-item questionnaire was used to assess social frailty. Cox regression models were used to examine the relationship between frailty markers and SES to incidence of depressive symptoms, with sociodemographic characteristics, lifestyle information, self-rated health status, medical histories, and depressive symptoms score at baseline adjusted. Results Infrequent social activity [hazard ratio (HR) 1.09, 95% confidence interval (CI) 1.00‒1.19], weakness (HR 1.15, 95% CI 1.03‒1.28), and slowness (HR 1.19, 95% CI 1.01‒1.41) were associated with incidence of depressive symptoms. SES was associated with depressive symptoms not only through social frailty (β = 0.01, 95% CI 0.002‒0.011) and physical frailty (β = 0.01, 95% CI 0.001‒0.012) separately but also through social frailty and physical frailty sequentially. Furthermore, the effect of weakness and slowness on depressive symptoms occurred in participants with lower educational level and doing agricultural work, while the effect of infrequent social activity occurred in participants with higher educational level and doing nonagricultural work. Conclusions/Implications SES is associated with depressive symptoms, in which frailty partly mediates the association. The effect of frailty on depressive symptoms varied across SES. Integrated and comprehensive intervention strategies, including assessing socioeconomic circumstances as well as improving frailty, are suggested in prevention of depressive symptoms.