Is neighbourhood walkability related to body mass index among different age groups? A cross-sectional study of Canadian urban areas

BACKGROUND: Studies of neighbourhood walkability and body mass index (BMI) have shown mixed results, possibly due to biases from self-reported outcomes or differential effects across age groups. Our objective was to examine relationships between walkability and objectively measured BMI in various age groups, in a nationally representative population. METHODS: The study population came from the 2007–2011 Canadian Health Measures Survey, a cross-sectional survey of a nationally representative Canadian population. In our covariate-adjusted analyses, we included survey respondents aged 6–79 who were not pregnant, did not live in rural areas, were not missing data and were not thin/underweight. We used objectively measured height and weight to calculate BMI among adults aged 18–79 and zBMI among children aged 6–17. We categorised respondents into walkability quintiles based on their residential Street Smart Walk Score values. We performed linear regression to estimate differences between walkability quintiles in BMI and zBMI. We analysed adults and children overall; age subgroups 6–11, 12–17, 18–29, 30–44, 45–64 and 65–79; and sex subgroups. RESULTS: The covariate-adjusted models included 9265 respondents overall. After adjustment, differences between walkability quintiles in BMI and zBMI were small and not statistically significant, except for males aged 6–17 in the second-highest walkability quintile who had significantly lower zBMIs than those in the lowest quintile. CONCLUSION: After accounting for confounding factors, we did not find evidence of a relationship between walkability and BMI in children or adults overall, or in any age subgroup with sexes combined. However, post hoc analysis by sex suggested males aged 6–17 in more walkable areas may have lower zBMIs.