Individual and neighborhood disadvantage modifies the association between neighborhood walkability and BMI

Introduction: Walkable environments have been associated with a lower BMI, but the strength of this association may depend on population characteristics. We identified four population characteristics to identify historically underserved individuals and neighborhoods (low educational attainment, low household income, black race, and Hispanic ethnicity) in order to test the hypothesis that disadvantaged populations would be more vulnerable to the constraints of their immediate environment, leading to stronger associations between built environment characteristics and BMI.

Methods: Height and weight were measured for a diverse sample of 13,102 adults living throughout New York City. Each participant's home address was geocoded and surrounded by a circular buffer with a one-kilometer radius. The composition and built environment characteristics of these areas, along with self-reported individual characteristics, were used to predict BMI using generalized estimating equations. Both individual-level and area-based measures of education, income, race, and ethnicity were used to generate stratified results and tests for interactions.

Results: Higher population density, more mixed land use, and more transit access were consistently associated with a lower BMI, but contrary to expectations this association was most consistent among those with more education or higher incomes, and among non-Hispanic whites. Significant interactions were observed for education, income, race and ethnicity.

Conclusions: We found that built environment characteristics were less consistently associated with BMI for disadvantaged groups. This pattern may be explained by disadvantaged groups encountering other barriers to maintaining a healthy weight, or self-selection being stronger among those with more control over selecting their area of residence.