Researchers at Duke University estimate that 1.2 million fewer older people were disabled in 1994 than would have been expected based on disability rates observed in 1982. The number of older people with functional problems in 1994 stood at 7.1 million, not the 8.3 million who would have been impaired if health had not improved over the last few years.
The report by Kenneth G. Manton, Ph.D., Larry Corder, Ph.D., and Eric Stallard, A.S.A., M.A.A.A., of Duke University appears in the March 18, 1997, Proceedings of the National Academy of Sciences. It follows a groundbreaking April 1993 analysis by the same team, which discovered a surprising fall in disability rates during the 1980s. Both surveys and analyses were funded by the National Institute on Aging (NIA).
"This is one of the most important findings in demography that I've seen in many years. The trend is very powerful," Richard M. Suzman, Ph.D., director of the NIA's Office of the Demography of Aging, said.
"Many factors, including better public health measures and nutrition, higher levels of education, improved economic status, and medical advances, may be involved in the decline in disability. Now, in order to maintain and accelerate the decline, we need to pinpoint how each of these factors is contributing to the improved health of older people."
The researchers looked at disability among people 65 and older between 1982 and 1994. The data come from the National Long Term Care Surveys, which followed the health status and disability in national samples of approximately 20,000 people in 1982, 1984, 1989, and 1994. The number of disabled people in 1994 was compared with what it would have been had 1982 disability rates remained unchanged. The calculations were adjusted to account for the growth in the older population and the increasing age of the elderly over that period.
It was expected that some 24.9 percent of older people would have been disabled if rates had remained at 1982 levels. Instead, the proportion of older people chronically disabled in 1994 was 21.3 percent, a reduction of 3.6 percentage points, or 1.2 million fewer disabled older people than would have been expected without better health. That represents a relative decline of some 14.5 percent.
In addition, Manton found, the decrease in disability is accelerating. About 47 percent of the reduction occurred in the 5 years
between 1989 and 1994, while 53 percent occurred in the 7 years from 1982 to 1989. By this measure, the annual declines in disability between 1989 and 1994 were greater than those of the 1980s.
Disability among older people with functional problems also may be less severe. The researchers assessed how many problems people had with "activities of daily living (ADLs)" such as eating, dressing, or bathing and "instrumental activities of daily living" like shopping or using the telephone, for 3 months or more.
The proportion of people who had problems with 3 or more activities of daily living, for example, dropped 1 percent for people ages 65-74, 2.5 percent at ages 75-84, and 2.4 percent for those age 85 and older. Such '3+ADL' impairment is often required before many older people can receive benefits from private long term care insurance, the scientists pointed out.
Manton offered some possible explanations for why older people are doing better. Improvements to date are likely due to better nutrition and public hygiene, coupled with lifestyle changes such as reduced cigarette smoking. In addition, he notes, the public is better educated than it has ever been, and higher education levels have been associated with better health.
The research was conducted by Duke University at its NIA-sponsored Center for the Demography of Aging. The Duke center is one of nine across the U.S. established in 1994 to improve and promote demographic research on health, economics, and aging. The NIA, a component of the National Institutes of Health (NIH), funds and conducts research into the biomedical, social, and behavioral aspects of aging.
The 1982 and 1984 waves of the surveys, and components of later waves, were supported by the Assistant Secretary for Policy and Evaluation and the Health Care Financing Administration, which, along with the NIH, are part of the Department of Health and Human Services.