Abstract
BACKGROUND: This study sought to investigate the effect of changes in depression status on physical disability in older persons receiving home care, examine whether the effect is due to concomitant changes in cognitive status, and test whether affective state and cognitive ability interact to influence physical disability. METHODS: Multilevel analyses were conducted using longitudinal data collected about every 3 months from older participants in Michigan's community-based long-term care programs (N = 13,129). The data set provided an average of nine repeated measures of depressive symptoms, cognitive functioning, and physical disability. We estimated the lag effects of within-person changes in depression and cognitive status, and their interaction, on physical disability measured by activities of daily living (ADL) and instrumental activities of daily living (IADL), controlling for health-related events that occurred in the interim. RESULTS: Changes between not having and having depressive symptoms, including subsyndromal symptoms, are critical to physical disability for home care elders. The effects are independent of concomitant changes in cognitive status, which also have significant adverse effects on physical disability. There is some evidence that improvement of depression buffers the adverse effect of cognitive decline on IADL disability. CONCLUSIONS: Providers should monitor changes in depression and cognitive status in home care elders. Early detection and treatment of subthreshold depression, as well as efforts to prevent worsening of cognitive status in home care elders, may have a meaningful impact on their ability to live at home.