Social isolation mediates association between depressive symptoms and cognitive function: Evidence from China health and retirement longitudinal study

Background Depressive symptoms and cognitive decline are common in older adults, but the direction of their relationship remains unclear. Social isolation is linked to both, and we hypothesized it mediates the connection between depressive symptoms and cognitive function. This study investigates whether social isolation mediates this relationship. Methods A total of 9220 participants aged >= 45 years were recruited from the China Health and Retirement Longitudinal Study. Center for Epidemiologic Studies Depression Scale was used to assess the depressive symptoms. Social isolation was measured by the four dimensions (being unmarried, living alone, having less contact with children, and reduced social activities). Cognitive functioning was measured by the Mini Mental State Examination. Variables significantly associated with cognitive function in the multiple linear regression analysis were included as covariates. Cross-lagged panel mediation was used to determine the associations between depressive symptoms, social isolation, and cognitive function. Results After adjusted for covariates, depressive symptoms were significantly associated with subsequent social isolation (beta = 0.042, SE = 0.009, p < .001); Social isolation was significantly associated with subsequent cognitive function (beta = -0.055, SE = 0.010, p < .001). Social isolation mediated the depressive symptoms on cognitive function, accounting for 3.1 % of the total effect (beta = -0.002, 95 % CI [-0.004, -0.001], p < .001). Conclusion The association between depressive symptoms and cognitive function can be partially mediated by social isolation. Public health initiatives targeting depressive symptoms in older adults could reduce social isolation and help maintain cognitive health in middle-aged and older adults in China.