WASHINGTON -- The common assumption that old age in the United States brings with it unremitting deterioration is being challenged by a new study that shows disability rates among the elderly decreasing during the 1980s.
Findings by three Duke University researchers -- Kenneth G. Manton, Larry S. Corder and Eric Stallard -- being published in the forthcoming issue of the Journal of Gerontology, have generated a whirlwind of discussion. Demographers were taken aback by the extent to which the disability rates had shifted.
While many researchers said they were waiting to see the work duplicated by other demographers, they also said that the shift rTC makes sense, particularly in light of the increase in commonplace surgical techniques -- like cataract removal and joint replacement -- that allow older people to resume the normal activities of daily life.
Another factor in the decline in disability rates may be the higher educational levels of those now entering retirement. Several studies, including those by a University of Pennsylvania sociologist, Samuel Preston, have found that higher levels of education go hand in hand with higher incomes, which are associated with better nutrition and health care.
"Education has lifelong implications, from having access to medical care to likelihood that you will take good care of yourself throughout your life," said Cynthia Taeuber, a demographer specializing in the elderly for the U.S. Census Bureau.
Eileen Crimmins, a professor of gerontology at the University of Southern California, said that while it would be important to replicate the Manton group's findings, there is an emerging belief that the idea of old age as a time of steady deterioration should be replaced by the notion that the health of old people, like that of young people, goes through phases, for better or worse.
"Now more and more people believe there's an ongoing change in both directions," she said. "Sometimes people get better, sometimes worse. Some things can get better while others get worse."
The Manton study showed that while the population of those past their 65th birthday increased by 14.7 percent between 1982 and 1989 -- from 26.9 million to 30.9 million -- the chronically disabled elderly population increased by just 9.2 percent.
Overall, the proportion of the elderly population reporting no disabilities rose from 76.3 percent in 1982 to 77.4 percent in 1989.
The new findings, which have been circulated in academic forums for more than a year, have obvious relevance to the discussions under way in President Clinton's Task Force on National Health Care Reform, several experts said.
"Manton's research findings are quite germane to the question of how many Americans will need long-term care in the future," said Alan Garber, an associate professor of medicine and economics at Stanford University.
Until recently, he said, it was assumed that elderly people whose lives were prolonged by medical intervention would live longer but that the extra time would mostly be spent in a disabled and dependent state.
Mr. Garber and others say the Manton study modifies that thinking somewhat. As baby boomers age, Mr. Garber said, "no matter what, we'll need more long-term care." But lower disability rates among the elderly may slow the increase in demand for costly nursing home care.
A companion study by the Duke researchers, just published in the journal Gerontology, shows that the number of elderly people requiring personal assistance declined by 10 percent between 1982 and 1989 even as the number of elderly was increasing. At the same time, the number of people using mechanical aids but living independently without personal assistance increased by 5 percent.
Richard Suzman, director of demographic studies at the National Institute of Aging, said that "the general consensus" among gerontologists once was that increased life expectancy would mean that an individual could expect that a longer fraction of the years after retirement would be spent dependent on someone else for basic needs like taking a bath, getting dressed or using the toilet.
The extent of an older person's disability is usually gauged by measuring how many such tasks, known as Activities of Daily Living, a person can manage independently.
Another commonly used scale, for those with less drastic impairments, measures how many Instrumental Activities of Daily Living, like shopping or managing finances, the person can perform.
The new findings, which are based on raw data from Mr. Suzman's National Long-Term Care Survey, are particularly surprising, he said, because "we find that the improvement in health seems to be greatest for those 75 and over and as great at 85 and over as it is 75 and over. This is a big change in terms of expectations."
Mr. Manton cautioned that his findings did not change the underlying facts about aging or mean that future elderly populations can expect to be as healthy, on average, as their children or grandchildren.
But, he said, the study indicated a substantial possibility for increasing older people's activity.
"For a lot of people with problems primarily related to joints, vision or sensory function, you could have biomedical intervention or nutrition therapy and have a larger potential for improvement," Mr. Manton said.
Mr. Suzman said it was impossible to say whether the decline in disability rates would be enduring.
"We won't know till be get more data. There were three points in time in this study," he said, referring to the survey dates -- 1982, 1984 and 1989. "The effect seems to be stronger in the 1984 to 1989 period."
The most important parts of the study, Mr. Suzman said, were the suggestions that disability was not an inevitable part of aging and that it might be possible to find a way to slow such loss of function.