U.S. Department of Health and Human Services
Measuring the Activities of Daily Living Among the Elderly: A Guide to National Surveys
Joshua M. Wiener and Raymond J. Hanley
The Brookings Institution
This report was prepared for the Forum on Aging-Related Statistics by the Committee on Estimates of Activities of Daily Living in National Surveys. For additional information, you may visit the DALTCP home page at http://aspe.hhs.gov/daltcp/home.htm or contact the Office of Disability, Aging and Long-Term Care Policy, Room 424E, H.H Humphrey Building, 200 Independence Avenue, SW, Washington, DC 20201. The e-mail address is: webmaster.DALTCP@hhs.gov. The DALTCP Project Officer was Robert Clark.
The "activities of daily living" or ADLs are the basic tasks of everyday life, such as eating, bathing, dressing, toileting and transferring (i.e., getting in and out of a bed or chair). Although persons of all ages may have problems performing the ADLs, disability prevalence rates are much higher for the elderly than for the nonelderly. Within the elderly population, disability rates rise steeply with advancing age and are especially high for persons aged 85 and over.
To the casual observer, estimates of the size of the elderly population with activity of daily living disabilities differ substantially across national surveys. There are a number of reasons for this variation, but differences in which ADL items are being measured and in what constitutes a disability account for much of the variation. Other likely explanations are differences in sample design, sample size, survey methodology and age structure of the population at the time the surveys were conducted.
When an effort is made to standardize ADL items for comparison, estimates for the community-based population vary by no more than 3.1 percentage points and for the institutionalized population, with the exception of toileting, by no more than 3.2 percentage points. As small as these differences are in absolute terms, they can be large in percent differences across surveys. For example, the National Medical Expenditure Survey estimates that there are 60 percent more elderly with ADL problems than does the Supplement on Aging.
The main conclusion is that ADL estimates will differ for good reasons and that there is no one "right" estimate. Researchers and policy analysts alike need to be aware that ADL disability rates are simply much "softer" measures than, say, mortality rates. From wording decisions made by persons who design the survey questionnaire, to the analysts who choose a particular ADL question or set of questions to analyze and report, to the programmers who must actually handle multiple question recodes and deal with missing and inconsistent data, each step will influence the final results. Thus, even an extremely large sample could not provide a definitive estimate.
What should policymakers and others make of these differences across surveys? Cost estimates for home care programs or insurance benefits based on one set of ADL prevalences will be substantially different from cost estimates based on a different set of ADL prevalences. This inconsistency will clearly be unsettling to those who must pay the bills. From a research perspective, however, the estimates are remarkably alike. If the policy interest was on the nondisabled, nobody would give the inconsistency of the estimates a second thought. The fact is that, even among the elderly, ADL limitations are relatively rare and some variation in the estimates is inevitable.
|The Full Report is also available from the DALTCP website (http://aspe.hhs.gov/daltcp/home.shtml) or directly at http://aspe.hhs.gov/daltcp/reports/guide.htm.|