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One more way the rich are different . . .
They have the money to act on their healthiest impulses. Differences in disability rates are evident even at higher rungs of the socioeconomic ladder, a new public-health study shows

| 24 August 2006

Numerous studies have already established the link between extreme poverty and poor health, but a new study led by a Berkeley public-health researcher has found that health disparities exist even among those with higher incomes.


Meredith Minkler (Peg Skorpinski photo)
 

"What was unusual was that we found that people in the middle class were still at a disadvantage compared with those at just a slightly higher income," says Meredith Minkler, professor of health and social behavior at the School of Public Health and lead author of the study, published in the Aug. 17 issue of the New England Journal of Medicine. "The fact that there's a significant difference between people [living] at 600 and 700 percent above the poverty level was a striking finding of this study."

Previous studies have shown that wealthier people in society are healthier and live longer than the poorest, Minkler notes. "Less settled is whether you see this gradient with respect to disability, and whether it plays out among older people," something this new research focuses on.

One in four suffer functional limitation

The researchers looked at data from 335,000 respondents (age 55 and older) to the Census 2000 American Community Survey. They compared poverty-level status with the rate of functional limitation, defined as a long-lasting condition that substantially limits one or more basic physical activities, such as walking, reaching, or lifting. They chose functional limitation as a variable over death or illness, since many chronic diseases affect functional status.

Of the respondents surveyed, 80,791 (nearly 25 percent) had functional limitations. Not surprisingly, the prevalence of functional limitation increased with age. Among men 55 to 64 years old, 16.2 percent reported some level of functional limitation compared with 47.5 percent of those 85 years and older. Among women between 55 and 64 years old, 17.2 percent had functional limitation, compared with 57.9 percent of those 85 and over.

The researchers found the biggest differences among the younger age group, those 55 to 64. In that group, people who were living in poverty were six times more likely to report functional limitation than people in the same age group who were living at or above 700 percent of the poverty level, with very little difference between men and women.

"These findings underscore that poverty is one of the major risk factors for disability," says report co-author Esme Fuller-Thomson of the University of Toronto.

For this study, household income was categorized into nine levels, from less than 100 percent of the poverty level to 700 percent and higher. In 2000 the poverty threshold for a person living alone who was 65 or older was $8,259 per year; it was $17,761 for a four-person household. A single 65-year-old living at 600 percent of poverty would therefore earn $49,544 per year in income, while someone at 700 percent of poverty would earn $57,813. A four-person household at 600 percent of poverty would take in $106,566 per year, while the comparable annual income at 700 percent is $124,327.

The researchers found significant differences in the rates of limitations even among those in the upper income brackets. Even 55- to 74-year-olds at 600-699 percent of the poverty level had elevated odds of having a disability compared to those at 700 percent and higher. For example, women in that age group in the 600-699 percent category had 16 percent higher odds of disability than women in the 700 percent bracket, while their male peers had 44 percent higher odds than men in the 700 percent group.

The authors point to a number of possible explanations for the social gradient in health. The upper class has lower rates of smoking, and may have less stress, better access to health coverage, and healthier environments, including safer neighborhoods that encourage walking and have less pollution, even when compared with those living comfortable middle-class lives.

"We know that Americans 55 and above today are relatively health-conscious compared to prior generations. But it may be that the wealthiest Americans have the greatest edge in acting upon their motivations to stay healthy," says Minkler. "For instance, wealthier adults with problems walking can afford to renovate their homes to make them more accessible to wheelchairs. This could include widening doorways and installing ramps in the home's front entrance."

The researchers point out that while the rate of disability has been declining slowly but steadily over the past two decades, the aging of the baby-boomer generation means that the number of people with disabilities is going to increase.

"There are now almost 8,000 people turning 60 every day in the U.S.," says Minkler. "It's therefore important for us to understand all of the factors that affect disability rates. Social class is a badly neglected determinant of health and illness. This study highlights that socioeconomic status operates independently of such factors as race, ethnicity, and health behaviors. Although researchers often control for social class, it warrants much more focused attention."

The complete study, "Gradient of disability across the socioeconomic spectrum in the United States," is online at content.nejm.org/content/vol355/issue7.