Neighborhood density connected to changes in body mass index for children

Study uses geographic data to track change over time

Using data from Kaiser Permanente and King County in Washington state, researchers have found that certain neighborhood features can impact levels of obesity for children and adolescents. Although the effects are small, they may accumulate over time.

The study, published in AJPM Focus, is part of the Moving to Health project, a collaboration between Kaiser Permanente Washington Health Research Institute (KPWHRI) and the University of Washington. The project takes a hyperlocal approach to understanding how aspects of the built environment — including the number of households in an area (residential density), the number and size of parks, and the presence of fast-food restaurants and supermarkets — influence the health of residents in individual neighborhoods. Moving to Health is one of the largest studies of children and adolescents to look at these associations.

The researchers looked at growth patterns of King County children in 3 age ranges, starting at around age 5 years, 9 years, and 13 years. During 3 years of follow-up, they found that greater residential density, which is used as an indicator of a walkable neighborhood, was associated with smaller increases in body mass index (BMI) for girls of all age groups, and for boys in the youngest and oldest age groups.

Body mass index itself is not an indicator of health, but it is used to screen for weight categories that can put a child or teen at higher risk of health complications. Obesity is defined as having a BMI at or above the 95th percentile, which is specific to a child’s age and sex.

“These associations between residential density and BMI were also seen for adults,” said Paula Lozano, MD, MPH, who led the study. “However, the associations were stronger for children and adolescents than they were for adults, which suggests to us that living in a walkable neighborhood has a greater impact for these age groups.”

Adults living in the lowest-density areas gained, on average, 0.28 kg more over 3 years than those in high-density neighborhoods. For girls age 13, the difference was 1.1 kg — almost quadruple that for adults.

“Obesity-related health issues are increasing among children and adolescents, and understanding the different factors that can cause someone to have obesity is a first step toward reducing that health burden,” Lozano said. “Although the associations we found aren’t huge, they are noticeable for all the age groups we looked at, which means they likely influence a child throughout their life, starting when they are young.”

The study was based on medical records for 15,920 children and adolescents in King County who are insured through Kaiser Permanente Washington. (All records were anonymized, which means personally identifiable information was removed.)

Associations between fast-food restaurants and supermarkets and changes in BMI over time were not particularly strong for children and teens, which was consistent with the results for adult age groups.

A baseline analysis showed that children and adolescents who were living in denser neighborhoods, without fast-food restaurants and with more parks nearby, had lower BMI and were less likely to have obesity.

The baseline measure of BMI was also strongly associated with property values, even for the youngest age groups. For children in all age groups living in the lowest property value areas, the prevalence of obesity was more than twice as high as for those living in areas with the highest property values. The relationship between BMI and property value was stronger than that for any of the other factors.

“That connection between property values and BMI is consistent with other studies,” Lozano said. “We know from previous research that household socioeconomic status plays a role in child obesity. Our study suggests that there are factors beyond the built environment that influence that relationship that need to be further explored.”

This study was funded by the National Institutes of Health.

Other KPWHRI authors are Jennifer Bobb, PhD; Maricela Cruz, PhD; Jane Anau, BS; Mary Kay Theis, MS; Andrea Cook, PhD; and David Arterburn, MD, MPH.

By Amelia Apfel