WEDNESDAY, Aug. 16 (HealthDay News) -- Even a little extra income can make a big difference in helping middle-class people ward off disability, a new study finds.
"The surprise was at the upper end," said Meredith Minkler, an author of a report on the study in the Aug. 17 issue of the New England Journal of Medicine. "We always knew there was a major gap between the very poor and the very rich. To find that the middle class was at a substantial disadvantage to slightly wealthier folks was a surprise."
The study was sponsored by the U.S. National Institute on Aging (NIA), which requires the information to help it prepare for the health needs of aging baby boomers -- 8,000 of them per day -- who are now reaching the age of 60.
The study used data on 335,000 people 55 and older collected as part of the Census 2000 American Community Survey. In that survey, pollsters asked older Americans about disabilities that affected basic activities such as walking, reaching and lifting.
Respondents were classified into nine household income levels, starting with poverty ($8,259 for someone 65 or older living alone in 2000, $17,761 for a family of four) and going up to 700 percent of that figure -- $124,327 or over.
As expected, disability increased with age. While 16.2 percent of men aged 55 to 64 reported disability, the incidence for men 85 and older was 47.5 percent. Among women aged 55 to 64, the incidence of disability was 17.2 percent, compared to 57.9 percent for those aged 85 and older.
The difference between making a good income and making a very good income turned out to be important, the researchers said. For example, men aged 65 to 74 in the "600-699 percent" income group ($49,544 single-person income) had a 44 percent higher odds of disability than those in the "700 percent" group, where single-person income topped $57,813 per year. For women aged 55 to 64, that income difference translated to a 16 percent greater incidence of disability.
There are several possible explanations for the income-linked differences, said Dr. Jack Guralnik, chief of the NIA laboratory of epidemiology, demography and biometry, and a member of the research team.
"Health behaviors explain some of this," Guralnik said. "Also, people with lower incomes tend to have less access to medical care."
But, Guralnik said, "There's something going on here that is not easy to understand, something related to what is going on in life at lower income levels."
The NIA will continue to look at differences in disability, he said. "Better understanding of why income status has an impact on health can lead to better interventions," Guralnik noted.
"One of the things we can conjecture is that people who are upper class have slightly better medical care, a better environment in which to live and fewer hassles," said Minkler, a professor of health and social behavior at the University of California at Berkeley School of Public Health.
Money can also help reduce disability though improvements in the home, she said. "You can widen doorways and put in ramps," Minkler said. "Ultimately, that can make the difference between living at home and being in an institution."
While the United States has "the best-educated, best cared-for population in the history of the world," she said, an increase in disability is inevitable as the number of older people increases. "It's important to find out whether slight increments in income make a difference," Minkler said.
A resource guide for people with disabilities is available from the University of Buffalo.