The effect of aging on functional decline among older Japanese living in a community: a 5-year longitudinal data analysis.

Abstract

Using longitudinal data analyses, we examined the effects of aging on functional decline, based on activities of daily living (ADL) and instrumental activities of daily living (IADL) during a 5-year follow-up among older people living in a community in Japan. The baseline survey in July 1988 involved all elderly residents aged 60 or older in Saku City, Nagano, Japan (N=13418). All survivors of this cohort were asked to participate in follow-up surveys conducted in 1989, 1990, 1991, 1992 and 1993. Five items of ADL and five of IADL were measured on each survey. A generalized estimating equations (GEE) analysis was used to examine the effects of aging on the increase of the proportion of subjects with functional dependence. These results indicated that the proportion of subjects who were dependent in ADL increased during the 5-year period by 2.2 times (p<0.001) and the proportion of those who were dependent in either ADL or IADL increased during the same period by 1.8 times (p<0.001). Gender did not appear to be significantly associated with functional decline. The GEE analysis in this study identified the statistically significant effect of aging on the increase of the proportion of subjects with functional dependence based on ADL and IADL.