Printed in U.S.A. Epidemiology of Aging

The last quarter of the 20th century has seen the formal coming of age of the study of the health, dis-eases, and disabilities of older adults, as well as of aging itself. Epidemiologic research on aging devel-oped out of groundbreaking gerontologic studies that have been carried out since the 1940s, the establish-ment of the National Institute on Aging in 1974 (an outgrowth itself of the first White House Conference on Aging in 1961), and the maturation of programs in gerontology and geriatrics. The 1980s brought recog-nition that the US population was aging and the initi-ation of the first cohort studies that assessed older adults longitudinally, including a report by Branch et al. (1) showing that older adults could and would par-ticipate in epidemiologic cohort studies. Following this, the National Center for Health Statistics raised the age of the population studied in the Health Interview Survey to 75 years (2), and the National Institute on Aging funded the EPESE studies [Established Populations for the Epidemiologic Study of the Elderly] (3), the first multicenter prospective cohort studies designed specifically to study adults aged 65 years and older. At the same time, cohorts in established epidemio-logic studies such as the Framingham Heart Study (4) had aged, permitting an expansion of such studies' focus to the epidemiology of disease and disability in older adults. Subsequently, it was demonstrated that older adults can be recruited to participate in intensive physiologic and clinical evaluations in cohort studies, with 4- to 6-hour examinations carried out in both cen-tralized and home locations (5-7), and that long term retention in such studies is high. For example, after 10 years of annual examinations, the rate of cohort reten-tion for adults aged 65 years or more in the multicen-Received for publication August 10, 1999, and accepted for pub