by Eric Pryne
January 26, 2006
Residents of King County’s less-walkable neighborhoods – can you say sprawl? – are more likely to be overweight, a recently completed study concludes.
Another related study has found, perhaps not surprisingly, that people who live and work in those neighborhoods generate more auto-related air pollution, another potential threat to health.
The two studies’ findings are summarized in the winter edition of the peer-reviewed Journal of the American Planning Association. The authors, who collaborated in their research, say their work constitutes the most comprehensive look yet at the link between urban-development patterns and human health in a single metropolitan area.
Earlier research has raised the possibility of a connection between sprawl, obesity and other health problems. The King County results suggest “current laws and regulations are producing negative health outcomes,” the authors warn.
“None of this is saying suburbia is bad,” said Lawrence Frank, an urban-planning professor at the University of British Columbia and co-author of both studies. “It just says these are the relationships you get … and they should be taken into account.”
A top aide to King County Executive Ron Sims said the county already has adopted some changes as a result of the studies and is planning more.
The research isn’t likely to end the debate over sprawl and health.
“If you’re listing things that impact obesity, neighborhood design would be maybe 10th on my list,” said Tim Attebury, King County manager for the Master Builders Association of King and Snohomish Counties. “I would put McDonald’s and too much TV way in front of neighborhood design.”
But Frank and co-author James Sallis, a health psychologist at San Diego State University, said the two new studies go beyond previous work in showing that development patterns can have a significant impact on health even when taking into account other variables such as age, income, education and ethnicity.
The walkability factor
For both studies, researchers ranked neighborhoods using a “walkability index” that included such factors as residential density, the number of street connections, and the mix of homes, stores, parks and schools. All are believed to influence how much people walk.
In one study, funded by the National Institutes of Health, researchers surveyed and monitored about 75 adults in each of 16 King County neighborhoods. Eight neighborhoods, including Upper Queen Anne and White Center, scored high on the walkability index; the other eight, including Kent’s East Hill and part of Sammamish, scored low.
Each group of eight included four wealthier and four lower-income neighborhoods.
On average, researchers found, the Body Mass Index – a measure of height and weight – of residents of the more walkable neighborhoods was lower, and they were more likely to get the U.S. Surgeon General’s recommended 30 minutes of daily exercise.
In the second study, funded by the Federal Transit Administration, King County and other local governments, researchers estimated the auto-related pollution generated by about 6,000 King County residents who kept detailed records of their travel for two days in 1999 as part of another study.
Again, people who lived and worked in more walkable neighborhoods produced fewer pollutants associated with smog, the study found.
After subjecting the data to statistical analysis, Frank said, researchers were surprised to learn that even small changes in neighborhood design can make a difference.
A 5 percent increase in a neighborhood’s walkability index, for instance, was associated with a 0.23-point drop in Body Mass Index. For someone 6 feet tall, that’s a difference of less than 2 pounds, but Frank said bigger changes in a neighborhood’s walkability would be expected to produce greater differences in weight.
The presence or absence of stores, parks, schools and other destinations within a quarter- to a half-mile of home appears to be the most important factor in how much people walk, he said.
Karen Wolf, a senior policy analyst in Sims’ office, said that as a result of the studies, the county already has amended the policies that guide its planning to make health a priority.
County officials also are working on a checklist to rate development projects’ impact on health, she said.
In White Center, one of three neighborhoods that Frank and other researchers studied in detail, Wolf said the county has rezoned property to encourage “mixed-use” development that allows both housing and shops, and is seeking a grant to develop an inviting walkway between a redeveloped housing project and the community’s business district.
“The whole idea is to make walking something you don’t even think about,” she said. “It’s part of your everyday life.”