Physical Function and Depression in Late Life: A Longitudinal Analysis

Yang Yang, Duke University

This paper tries to address how physical functions are related to depression in the rapidly aging population in the U.S. by examining the dynamic relationship between functional disabilities and depressive symptoms using two waves of longitudinal data, 1986 and 1992, from the Duke University site of the Established Populations for Epidemiological Studies of the Elderly. The results of zero-inflated negative binomial regressions show that (1) both baseline disability status and change in disability are significantly related to change in depressive symptoms over time, with the deteriorated functions having the strongest effect; and (2) the effects of functional disability on depressive symptoms vary by different types and/or severity of functional declines. Transitions into major disabilities as represented by ADLs and minor disabilities as indicated by Nagi and Rosow-Breslau scales have significantly more harmful effects on depression than changes into IADLs and no changes in functions. Only improvement in ADL functions significantly decreases depression in the elderly.