LOWER-EXTREMITY FUNCTION IN PERSONS OVER THE AGE OF 70 YEARS AS A PREDICTOR OF SUBSEQUENT DISABILITY

Background. Functional assessment is an important part of the evaluation of elderly persons. We conducted this study to determine whether objective measures of physical function can predict subsequent disability in older persons. Methods. This prospective cohort study included men and women 71 years of age or older who were living in the community, who reported no disability in the activities of daily living, and who reported that they were able to walk one-half mile (0.8 km) and climb stairs without assistance. The subjects completed a short battery of physical-performance tests and participated in a follow-up interview four years later. The tests included an assessment of standing balance, a timed 8-ft (2.4-m) walk at a normal pace, and a timed test of five repetitions of rising from a chair and sitting down. Results. Among the 1122 subjects who were not disabled at base line and who participated in the four-year follow-up, lower scores on the base-line performance tests were associated with a statistically significant, graduated increase in the frequency of disability in the activities of daily living and mobility-related disability at follow-up. After adjustment for age, sex, and the presence of chronic disease, those with the lowest scores on the performance tests were 4.2 to 4.9 times as likely to have disability at four years as those with the highest performance scores, and those with intermediate performance scores were 1.6 to 1.8 times as likely to have disability. Conclusions. Among nondisabled older persons living in the community, objective measures of lower-extremity function were highly predictive of subsequent disability. Measures of physical performance may identify older persons with a preclinical stage of disability who may benefit from interventions to prevent the development of frank disability. (N Engl J Med 1995;332:556-61.) From the Epidemiology, Demography, and Biometry Program, National Institute on Aging, Bethesda, Md. (J.M.G., E.M.S., M.E.S.); the Geriatrics Department, Hospital “I Fraticini,” National Institute for Research and Care of the Elderly (INRCA), Florence, Italy (L.F.); and the Department of Preventive Medicine and Environmental Health, University of Iowa, Iowa City (R.B.W.). Address reprint requests to Dr. Guralnik at the National Institute on Aging, 7201 Wisconsin Ave., Rm. 3C-309, Bethesda, MD 20892. Supported by a contract (N01-AG-0-2106) and a grant (AG-10127-01) from the National Institute on Aging. I N recognition of the importance of both extending life and increasing the number of years during which people are free of disability, the national health objectives for the year 2000 included as an overarching goal an increase in years of healthy life, with a full range of functional capacity at each stage of life. 1 Disability in the older population, and the attendant need for informal and formal care, will increasingly affect older people, their families, and the health care system as the population continues to age. 2 The addition of functional evaluation to the traditional clinical examination provides information that is critical in the comprehensive assessment of elderly persons. 3,4 Disability can be identified accurately through responses to a wide variety of questions about the ability to perform activities ranging from basic self-care to household activities and more strenuous tasks. Increasingly, functional status has also been characterized through the use of measures of physical performance, which are objective tests of subjects’ performance of standardized tasks, evaluated according to predetermined criteria that may include counting repetitions or timing the activity. 5 These measures have been shown to predict outcomes such as falls, institutionalization, and death. 6-12 Nearly all studies involving the use of performance measures have been of groups that included disabled persons. In these populations, performance measures predict adverse outcomes such as institutionalization and death because of their ability to identify subjects with substantial reductions in function. What has not been clearly demonstrated is whether measures of physical performance can provide useful prognostic information about older persons who report little or no disability. In the analyses presented here, we tested the hypothesis that performance measures capture information on the range of functioning in people who are not currently disabled and that such information can be used to predict the subsequent onset of disability. The measures we used assessed general lower-extremity function, and the types of disability we evaluated involve lower-extremity function and have a substantial effect on the ability of older persons to remain independent.