Depression status as a reliable predictor of functional decline among Japanese community-dwelling older adults: a 12-year population-based prospective cohort study

Objective This study aimed to examine a longitudinal relationship between depression status and functional decline among Japanese community-dwelling older adults, using a 12-year population-based, prospective cohort study design. Method A total of 710 men and women, aged 65 years and over, participated in the study. Katz's Index and the Tokyo Metropolitan Institute of Gerontology Index of Competence were used to measure the functional capacities of basic activities of daily living (BADL) and higher-level competence, respectively. For the purpose of analysis, a decline in each subscale of functional capacity during the follow-up period were used as outcome variables; depression status assessed by the Japanese version of the 30-item Geriatric Depression Scale (GDS), with a cut-off of 11, was used as an independent variable; and age, gender, education level, history of chronic disease, hospitalization, smoking, physical activity, living alone, hearing problems, physical pain, dietary habits, and usual walking speed at baseline were used as covariates. Results Use of the multivariate Cox proportional hazards model adjusted for potential confounders showed that depression status was significantly and independently associated with BADL decline (risk ratio (RR) = 1.46, 95% confidence interval (CI): 1.13–1.89) and with higher-level competence decline (RR = 1.56, 95% CI: 1.18–2.04). Conclusion Our study found an independent relationship between depression status and longitudinal change in functional capacity among community-dwelling older individuals, suggesting that depression status is a reliable predictor of functional decline (both of BADL decline and higher-level competence decline) in older adults. Copyright © 2009 John Wiley & Sons, Ltd.