“When it’s not safe to play outside, kids are more likely to stay inside and play computer games or watch television,” lead author Michael Jerrett, PhD, of the University of California-Berkeley, says in a news release. “These sedentary habits can put them at greater risk for obesity.”
Jerrett and his team of researchers studied nearly 3,000 children aged 9-10 living in and around Los Angeles for about eight years, until they reached age 18. Researchers collected data annually on the children’s height and weight to calculate body mass index (BMI). As expected, BMI increased in the children as they got older, but with children living within 150 meters of traffic, there was a significant increase in BMIs for girls and boys. “This translates into about a 5% increase in attained BMI at age 18,” the authors write. “Although this effect may appear small, the ubiquity of exposure to traffic implies small changes in the BMI in response to traffic may be associated with impacts on overweight and obese status in the population.”
The team speculates that children living in traffic-clogged areas may not walk, bike, or play outside regularly because nearby traffic makes them feel that being outside is risky. They also suggest a second reason for the association between traffic density and increased BMI may be related to air pollution. Because air pollution can negatively impact asthma and lung function, this may play a role in limiting a child’s ability to be physically active.
Jerrett and his colleagues, however, suggest that innovative approaches by city planners could reduce the risk of traffic-related weight gain.
They say measures can and should be taken to increase the “walkability” of neighborhoods, which perhaps would provide some protection against obesity.
The authors conclude that their study “yields the first evidence of significant effects from traffic density on BMI (body mass index) levels at age 18 in a large cohort of children. Traffic is a pervasive exposure in most cities, and our results identify traffic as a major risk factor for the development of obesity in children.”