Racial Differences on Association of Depressive Symptoms With Combined Basic and Instrumental Activities of Daily Living

Background. Depressive symptoms are predictive of multiple degenerative diseases in older age adults. However, the association of depressive symptoms with onset and progression of disability have not been studied. Methods. In a cohort of community-dwelling, older black and white adults, 5,446 initially nondisabled subjects were followed annually for disability between 2000 and 2008. Depressive symptoms were assessed at baseline using a summary measure of 10-item version of the Center for Epidemiologic Survey-Depressive symptoms scale. The disability outcome was based on a summary measure of 13 basic and instrumental activities of daily living, and analyzed using a two-part regression model for onset and progression of disability. Results. During follow-up, 44% of blacks and 35% of whites reported onset of disability. After adjusting for confounders, depressive symptoms were associated with increased odds of disability onset in blacks (odds ratio = 1.12, 95% confidence interval, 1.07-1.18) and whites (odds ratio = 1.21, 95% confidence interval, 1.08-1.36). The odds of disability onset associated with depressive symptoms also increased significantly over time in whites (odds ratio = 1.06, 95% confidence interval, 1.04-1.09), but not in blacks. In addition, depressive symptoms were associated with an increasing rate of progression of disability in whites (rate ratio = 1.08, 95% confidence interval, 1.06-1.09), but not in blacks. Conclusions. Depressive symptoms increased the risk of onset of disability in blacks and whites. This risk tended to increase over time only among whites. A similar race-specific pattern was observed for time-dependent changes due to depressive symptoms in the rate of progression in disability after onset.