MONDAY, Sept. 27, 2004 (HealthDayNews) -- People who live in sprawling metropolitan areas are paying a health toll for all that time spent sitting in cars instead of walking.

That's the conclusion of a new study by Rand Corp. researchers that appears in the October issue of the journal Public Health.

"More sprawl seems to be associated with more physical, chronic health problems," said Roland Sturm, a senior economist with RAND, and the study's lead author.

The study linked sprawl, in both suburbs and some cities, with a broad range of health problems, including high blood pressure, arthritis, headaches and breathing difficulties. These problems persisted even after the researchers accounted for differences such as age, economic status, race and local environment.

The most obvious way sprawl affects health is by a lack of routine physical activity, the researchers said. Instead of walking to school or the supermarket, suburbanites drive. That lack of exercise has been tied to higher rates of obesity, a risk factor for diseases such as hypertension and heart disease.

Sprawl also leads to more air pollution, the authors said, which may help explain the study's finding of significantly higher rates of breathing difficulties -- from emphysema to chronic lung disease -- in more sprawling areas. Air pollution also may be a factor in the higher rate of headaches seen in spread-out settings, they said.

Reid Ewing, a research professor at the National Center for Smart Growth Research and Education at the University of Maryland, said Sturm's study is the fourth published report to examine the health effects of a so-called "built environment."

"All four studies kind of point in the same direction, and they're all building a body of evidence that these build-environment variables matter," he said.

One weakness with the studies is that all of them took a snapshot in time and didn't control for "self-selection," where people who want to live a more active life can choose to live in places that best accommodate their lifestyle. Some of the studies also suffer from their use of data from very large areas, in which conditions may vary considerably from city to suburb, Ewing said.

To really show that sprawl makes you sick and fat, researchers will have to perform more tightly controlled studies, Ewing said. In fact, some of that work has already begun, with 10 to 15 studies in the works, he said.

For their study, Sturm and his Rand colleague Dr. Deborah Cohen used Ewing's sprawl index. It rates metropolitan areas based on residential density, land use mix, the degree to which development is focused on a region's core, and street accessibility.

A more sprawling area, for example, might have cul-de-sacs instead of streets connected as a grid; shopping, schools, work and residential areas that are far from each other; and a lower population density.

In a previously published study, Ewing showed that people who live in more sprawling areas tend to weigh more and have higher blood pressure. Sturm and Cohen went a step further, using data from Healthcare for Communities, a nationally representative telephone survey, to determine whether the indicators of sprawl are associated with chronic physical or mental health conditions.

The researchers analyzed data from more than 8,600 people in 38 metropolitan areas across the nation.

Overall, more sprawl was associated with a higher prevalence of 14 of the 16 physical conditions studied. In terms of chronic conditions, a 50-point change in the sprawl index is similar to aging four years.

So, for example, an adult living in the relatively high-sprawl city of Atlanta is likely to have a health profile similar to someone four years older but otherwise similar who lives in a more compact city such as Seattle.

The unhealthful affects of sprawling communities also appear to have a disproportionate impact on the poor and the elderly.

In the study, West Palm Beach, Fla., the site with the largest proportion of adults over 65, also had the most chronic medical problems. Los Angeles, which had the fewest older adults, had fewer chronic health problems than average, the study found.

Where you live, of course, isn't the only factor influencing your health. In Ewing's study, age, education and race were more important factors in relationship to a person's health than urban sprawl. Nevertheless, sprawl was a statistically significant factor.

"It's not the main factor, it's not the only factor," Ewing said, "but it may be a factor."

Still, those who live in sprawling metropolitan areas aren't doomed to a less healthy lifestyle. "Individual health habits play an important role," Sturm insisted. "If you live in an area where you cannot walk anywhere, you can go to the gym."

More information

Learn more about the health effects of sprawl by visiting the National Center for Smart Growth Research and Education.

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