Does Higher Neighborhood Walkability Reduce the Impact of Mobility Limitation on BMI?
Background: Obesity is more prevalent among people with disabilities than those without, especially among people with mobility limitations.1,2 An estimated 31.5 million or 13% of US adults have a mobility limitation.3 Although research has suggested that neighborhood walkability may play an important role in helping to curb the obesity epidemic in the US population4,5, there is no existing research on how neighborhood walkability impacts body weight for people with mobility limitations. Conceptual models of disability suggest that the neighborhood environment could be an important moderator of the effect of mobility limitation on BMI.6

Purpose: The purpose of this study was to examine whether living in more walkable neighborhoods reduces the impact of mobility limitation on BMI. Further, we examine whether these relationships hold in neighborhoods with different levels of poverty.

Methods: We used data from the Weight and Veteran’s Environment Study (WAVES) from 2009-2014. The analytic sample was 842,861 veterans from large, metro counties. Time-varying data on walkability and other measures of the food and physical activity environment within one mile of veterans’ homes came from public and private sources and were developed for the continental US.7 Information on veterans’ health and healthcare, including BMI, and demographics came from the US Department of Veterans Affairs healthcare system. A predictive algorithm, developed in prior work, was used to identify veterans with a mobility limitation (binary variable). We ran individual fixed effects regression models, which strengthen the causal interpretation of findings because they control for all unmeasured/unobserved factors that do not change over time. An interaction between walkability and mobility limitation (lagged 1-year) was used to examine moderation. We conducted stratified analysis by census-tract poverty tertiles, as well as based on having never moved during the study period.

Results: We found that neighborhood walkability moderated the effect of mobility limitation on BMI. For veterans in low-walkability neighborhoods, having a mobility limitation increased BMI [males 0.056 BMI units (p<0.001), females 0.151 BMI units (p<0.001)]. The effect of mobility limitation on BMI decreased as walkability increased and became insignificant in the highest walkability quartile (males: 0.014-units (p=0.166), females 0.010-units (p=0.815). In higher poverty neighborhoods, the effect of mobility limitation on BMI was larger than in low-poverty neighborhoods. However, across neighborhood poverty levels the effect of mobility limitation on BMI decreased as walkability increased. The pattern of moderation also held for those who never moved during the study period.

Conclusion: Findings from this study suggest that living in neighborhoods with higher walkability reduces the impact of mobility limitation on BMI. Low-walkability neighborhoods that are also high in poverty present additional risk for increased BMI among people with mobility limitations. This study overcame several threats to causal interpretation but there were limitations related to time-varying omitted variable bias, use of a binary mobility limitation variable, and generalizability of findings beyond the veteran population. Policy and built environment strategies that improve neighborhood walkability may be an impactful component of strategies to reduce obesity and improve health in populations with mobility limitation.

Presenter: Yochai Eisenberg
Agency Affiliation: Department of Disability and Human Development, University of Illinois at Chicago

Presenter Biographical Statement: [biography]