Association between BMI and WalkScore, Dining and Drinking Score and Grocery Score in a multi-city sample of adults: A cross sectional mediation analysis
Obesity is a complex, multi-factorial health epidemic in North America and is a leading public health concern. No single theory explains all of the factors that are associated with obesity but built environmental factors may be an important contributor. In this study, we aim to understand the mediation effect of the food environment, specifically Grocery Score and Dining and Drinking Score, in the relationship between walkability and BMI. We further study whether SES is an effect modifier in our hypothesized mediation pathway.
Data were collected using a quasi-experimental non-equivalent group design via an online panel survey with participants recruited in Boston, Chicago, Detroit, Montréal, New York, Toronto, Philadelphia, and Vancouver. Our analysis sample included 20,459 respondents from the 8 cities. We used mediation analyses within a causal framework using the R package “mediation.”
The analysis for Grocery Score showed that average causal mediation effect (ACME) was present but that the estimated effect was small. In models accounting for covariates, the average effect of a 10-unit increase in walkability on BMI that operates through Grocery Score was a 0.13 (95% CI: 0.07 to 0.20) greater BMI. The direct effect of a 10-unit change on walkability on BMI accounting for Grocery Score was a -0.16 (95% CI: -0.22 to 0.10) lower BMI. The total effect (ADE + ACME) of walkability and grocery score was not meaningfully associated with BMI, -0.03 (95% CI: -0.07 to 0.00). Overall, there were no mediated associations between walkability, DiningandDrinkingScore, and BMI.
Our results show that greater walkability is associated with lower BMI values. However, the association between walkability and BMI is strongly mediated by grocery score. The indirect effect of walkability mediated by grocery stores is positively associated with BMI. Walkability was not associated with Dining and drinking scores and no mediation was present
See the full analysis and results here https://github.com/walkabillylab/mediation_walkability_food_bmi/blob/main/Thesis_Analysis.md