The Rand Corp. study — published in the journal Health Affairs — said the health of young Americans is getting worse. It found the number of people ages 30-49 who could not care for themselves or do other routine tasks increased by more than half from 1984 to 2000. Meanwhile, the elderly have become less likely to suffer such disabilities.
"We've always had the assumption that medical science is advancing and that people are getting healthier, but that is not the case," said Darius Lakdawalla, lead author of the study.
For those 30- to 39-years-old, the number reporting disabilities increased from 118 per 10,000 people to 182 per 10,000 people from 1984 to 1996. Among those 40- to 49-years-old, the number rose from 212 per 10,000 to 278 per 10,000 in the same period.
There were smaller but still significant increases for people ages 18 to 29 as well as those 50 to 59, the study found.
However, disability declined by more than 10 percent for those 60 to 69, the study said.
The leading causes of disability are mental illness and musculoskeletal problems — such as chronic back pain — which are linked to obesity.
The number of cases stemming from musculoskeletal problems and diabetes grew more rapidly than those from other problems during the length of the study. The proportion that were diabetes-related doubled. Obesity is a major factor in the development of diabetes.
"People today find it's very cheap to eat and expensive to exercise," Lakdawalla said.
The ballooning obesity problem isn't the only culprit, the study said.
The growth in disability could be the result of increased incentives to report disability and could be linked to advancing medical technology, the report said. Medical advances have saved people who normally would have died, but many end up needing help and going on disability.
Researchers warned that the increase in the disability rate could mean higher health care costs in the future.
The Rand Corp., a nonprofit research group, studied people between the ages of 18 and 69 using data from the National Health Interview Survey which gathers information from about 36,000 households annually. The data covered the years 1984 to 2000.
Support for the study was provided by the Centers for Medicare and Medicaid Services and the National Institute on Aging.