Analysis of change in self-reported physical function among older persons in four population studies.

Change in self-reported physical function was examined using baseline and 5 years of follow-up data between 1982 and 1991 from the four Established Populations for Epidemiologic Studies of the Elderly studies. In East Boston, Massachusetts (n = 3,809), Iowa and Washington Counties, Iowa (n = 3,673), New Haven, Connecticut (n = 2,812), and North Carolina (n = 4,163), noninstitutionalized persons aged 65 years and older were asked a series of questions to assess their physical function: a modified Katz Activities of Daily Living (ADL) scale, three items from the Rosow-Breslau Functional Health Scale, and questions on physical performance, adapted from Nagi, as well as information on demographic, social, and health characteristics. Longitudinal statistical analyses (random effects and Markov transition models) were used to evaluate improvement, stability, and deterioration in functional ability at both an individual and a population level over multiple years of data. The average decline in physical function associated with age was found to be greater than previous cross-sectional studies have suggested, and the rate of decline increased with increasing age. Considerable individual variation was evident. Although many people experienced declines, a smaller but substantial portion experienced recovery. Women reported a greater rate of decline in physical function and were less likely to recover from disability.