The study, published in the March issue of The Milbank Quarterly, also concluded that the widespread use of common, everyday devices and services—microwaves, cordless phones and direct deposit banking, for example—likely has played an important role in freeing a greater proportion of older Americans from disabilities. Disabilities are defined as a need for help with shopping, preparing meals, and other necessary household activities, or with bathing, dressing and other activities involved in personal care.

So has the use of mobility devices such as canes and walkers and home modifications such as grab bars in the bathroom.

Surprisingly, the study found that reductions in smoking are not among the major reasons that the prevalence of disabilities among the aged has fallen from 22 percent in 1983 to 14 percent in 2005. Although smokers have higher rates of disability than those who never smoked or quit smoking, smoking patterns have not changed that much among the elderly since the early 1980s, so smoking cannot account for the improvements in disability.

"The declining late-life disability prevalence is one of the most significant advances in the health and well-being of Americans in the past quarter century," said University of Michigan economist Robert F. Schoeni, who co-authored the article with Vicki A. Freedman of the University of Medicine and Dentistry of New Jersey and Linda G. Martin of the RAND Corporation.

"Understanding what led to these improvements is much more than an academic exercise. With the first baby boomers turning 65 in 2011, it is imperative that policymakers and clinicians have a clear sense of what led to declining disability rates so they can have the best chance of achieving future reductions that will allow millions of Americans to function independently well into old age," Schoeni said.

"This study is an important step in understanding the factors underlying the trend of chronic disability reductions since 1984 in those age 65 and older," said Richard Suzman, director of the National Institute on Aging's Social and Behavioral Research Program. "While further analyses are needed in a number of areas, we need to begin to explore cost-effective interventions to maintain and perhaps accelerate this trend of improved physical and cognitive functioning in the face of such adverse trends as increasing obesity."

For the study, Schoeni, Freedman and Martin reviewed and analyzed a broad range of data from the National Health Interview Surveys and other studies. They began by analyzing the factors assumed to be most closely linked to disability, including changes in accommodations, in underlying physical, sensory, and cognitive functioning, and in diseases and conditions among non-institutionalized U.S. adults age 70 and older.

They also considered changes in medical care, health behaviors, economic and social factors, and environmental exposures. And they further reviewed the limited existing evidence on mid- and early-life factors that might directly or indirectly influence late-life disability. A recent companion paper appearing in Social Science & Medicine, suggests an important role for mother's education, childhood health, and adult occupation in the late-life disability trends.

Among the key findings of the Milbank Quarterly paper:

• A substantial share of the decline in disability can be accounted for by changes in cardiovascular disease, musculoskeletal conditions, and vision problems. These conditions are less likely to result in disability presumably due to improvements in treatment, especially for the first two conditions, which have become more common among older adults.

• Changes in smoking and obesity did not account for the trends. Smoking rates have not changed substantially among the elderly over this period. However, lifetime smoking of soon-to-be elderly declined considerably and augurs well for future disability. On the negative side, obesity has been increasing in these cohorts.

• Demographic factors, including race, ethnicity, marital status and place of birth—whether in the U.S. or elsewhere—had little effect on the disability rate, accounting for only about 10 percent of the decline.

• Education had a major impact. "Half of the decline in disability can be accounted for by the rise in educational attainment of older Americans," noted Schoeni, "but future educational gains are likely to be smaller as the effects of the post-World War II education boom pass." The data also suggest that improvements in income and declines in poverty contributed to the decline in disability.

While the authors emphasize that no one study is likely to identify definitively all the causes of the drop in old-age disability, the evidence suggests important roles for increased education, use of assistive and mainstream technologies, and the decline in disability due to cardiovascular, musculoskeletal, and vision problems.

"The timing of the improvements in these conditions corresponds to the expansion in treatments for cardiovascular diseases, including medical procedures such as stent insertion and balloon angioplasty, and pharmacologic treatments such as beta blockers, ace inhibitors, anti-cholesterol agents and antihypertensive combinations. Increases in the number of cataract surgeries, and in the number of knee and joint replacements, as well as the use of more medications for arthritic and rheumatic conditions, have also played an important role in reducing the level of disability among older Americans and allowing people to live independently well into their 70s and beyond."

Source: University of Michigan