The mediating effect of depressive symptoms on the association between childhood friendship and physical function in middle-aged and older adults: Evidence from the China Health and Retirement Longitudinal Study (CHARLS)

Abstract Purpose This study examines the extent to which depressive symptoms mediate the link between childhood friendship (CF) and physical function among middle-aged and older adults in China. Methods The data originated from the China Health and Retirement Longitudinal Study. The Sobel test and multivariable logistic regression were performed to examine the mediating role of depressive symptoms (measured by the 10-item Center for Epidemiologic Studies Depression Scale) in the association between CF (measured by a standardized retrospective questionnaire) and physical function, which was measured by basic activities of daily living (BADL) disability, instrumental activities of daily living (IADL) disability, and grip strength. Results A total of 12,170 participants aged 45 or older were included in this cross-sectional study. After controlling for covariates, worse CF was associated with an increased prevalence of BADL disability (OR = 1.18; 95% CI = 1.05–1.32), IADL disability (OR = 1.25; 95% CI = 1.12–1.40), and low grip strength (OR = 1.21; 95% CI = 1.09–1.34). The proportion of the mediating effect of depressive symptoms was 49% in CF and BADL, 41% in CF and IADL, and 12% in CF and grip strength. Depressive symptoms and worse CF have a joint effect on BADL disability (OR = 3.30; 95% CI = 2.82–3.85), IADL disability (OR = 3.52; 95% CI = 3.03–4.09), and low grip strength (OR = 1.65; 95% CI = 1.43–1.92). Conclusions Adults with better CF were more likely to have a decreased prevalence of impaired physical function in their later lives. Depressive symptoms acted as a mediator associated with the development of CF. Interventions focusing on the improvement of CF and depression may help improve physical function in adults.