Disability as a public health outcome in the aging population.

Improvements in life expectancy in the twentieth century have resulted from major declines in mortality at younger ages, but it is less well recognized that mortality declines at older ages have also played a substantial role in prolonging expectation of life. A person reaching age 65 in 1900 could expect to live an additional 11.9 years. Life expectancy at age 65 rose to 14.4 years by 1960 and then increased by about three years in the next three decades, reaching 17.5 years in 1992 (56, 70). As a greater proportion of the population survives to very old ages, the public health impact of the burden of disease and disability and related utilization of medical care and need for supportive and long-term care has become an important concern. In particular, the ability of the older person to function independently in the community is a critically important public health issue. A growing body of research in the last decade has addressed the measurement of disability, factors related to its onset, consequences of disability, and the potential for preventive interventions. This article summarizes the state of the art in these areas and discusses their public health relevance.