The study was conducted by researchers at Washington University School of Medicine in St. Louis, Indiana University School of Medicine and other institutions and will appear in the March 1 issue of the American Journal of Epidemiology.
"Our study shows that it's not just who you are or what you do, but where you live that affects your well-being," says lead author Mario Schootman, Ph.D., assistant professor of medicine in the Division of Health Behavior Research. "It also suggests that the effort to revitalize inner-city neighborhoods can have the added benefit of improving the health of individuals living there."
The study is an outgrowth of a larger health study of African-Americans. In that study members of the research group investigated the factors responsible for the excess health problems experienced by late middle-aged and older African-Americans living in St. Louis. It revealed a high level of disability risk among older African-Americans living in St. Louis.
For the current study, the researchers rated neighborhoods based on noise, air quality and the condition of houses, streets, yards and sidewalks. Such elements as broken windows, faulty siding, cracks and holes in sidewalks and high levels of industry or traffic noise lowered a neighborhood's rating.
The St. Louis neighborhoods studied included a poor, inner-city area and a less-impoverished, suburban area with a variety of socioeconomic conditions. The scientists assessed limitations in lower-body function in 563 African American men and women, age 50 to 64, living in the neighborhoods.
Good lower-body function is critical for maintaining independence and avoiding disability, according to study authors. A person was considered to have a lower-body functional limitation if he or she had difficulty walking a short distance, climbing a short flight of stairs, standing, stooping, crouching, kneeling or lifting 10 pounds. Many of these functions are influenced by respiratory health as well as lower-body strength and mobility.
After three years, the researchers retested the physical abilities of the same people. They found that those that had been living in neighborhoods with four or five conditions rated fair or poor were three times more likely to have developed limitations in lower-body function than people in neighborhoods that had one or no fair or poor ratings. Street and road quality and air quality had the greatest effect on disability development.
"Very few studies have examined the influence of neighborhood conditions on physical disabilities," Schootman says. "We found the quality of the neighborhood had a very high impact on lower-body function in the people we surveyed."
The study took into account a variety of factors that could influence health including weight, smoking, alcohol use, marital status and education. None showed a significant relation to the development of lower-body problems.
Interestingly, although an earlier study suggested poor neighborhood conditions might increase functional disabilities by creating barriers to health services, the current study demonstrates that lack of access to health care did not affect the development of lower-body functional limitations.
Other studies have proposed that a lack of physical activity fostered by bad streets and sidewalks could lead to disabilities, but again the present study rules out lack of physical activity as a factor in disability development.
"Right now the reason for the association between poor neighborhood conditions and physical disabilities is unclear," says senior author Douglas K. Miller, M.D., professor of medicine at Indiana University School of Medicine. "It's possible that people in neighborhoods where the sidewalks are hard to navigate and the streets are noisy are more apt to stay indoors instead of walking or going out to see friends. The social isolation such people experience can have a strong negative impact on health. In addition, staying indoors could give them greater exposure to indoor hazards including allergens."
Having eliminated some explanations for the link between poor neighborhoods and disabilities, the research group is planning further studies to uncover what causes the association.
"This study of neighborhood conditions is especially important because it has investigated a relatively older population," Schootman says. "Older people are much more sensitive to their environment. They rely on aspects of their immediate surroundings--how easy it is to get to the doctor or the grocery store or go for a walk--much more than younger people do."
"The U.S. currently is trying to reduce disparities in health status among subgroups in the population," Miller says. "Our work suggests that this will be impossible to accomplish without understanding the impact of a person's environment on health and reversing any adverse effects."
Schootman M, Andresen EM, Wolinsky FD, Malmstrom TK, Miller JP, Miller DK. Neighborhood conditions and risk of incident lower-body functional limitations among middle-aged African Americans. American Journal of Epidemiology 2006 Mar 1;163(5):450-458.
Funding from the National Institutes of Health supported this research.
Washington University School of Medicine's full-time and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children's hospitals. The School of Medicine is one of the leading medical research, teaching and patient care institutions in the nation, currently ranked third in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children's hospitals, the School of Medicine is linked to BJC HealthCare.
Journal
American Journal of Epidemiology