Characterising urban green space density and accessibility in models of BMI
Abstract Background : While exposure to urban green spaces has been associated with various physical health benefits, the evidence linking these spaces to lower BMI, particularly among older people, is mixed. We suggest that dimensions of urban green space accessibility, which are generally unobserved in the existing literature, may be a source of this volatility in results. The aim of this study is to add to the literature on the association between urban green space and BMI by considering alternative measures of urban green space that incorporate measures of footpath availability. Methods: We conduct a cross-sectional study combining data from The Irish Longitudinal Study on Ageing and detailed land use information. We proxy respondents’ exposure to urban green spaces at their residential addresses in network buffers, which are adjusted to account for the density of local footpaths. Generalised linear models are used to test the association between exposure to accessible urban green space and BMI. Results: Relative to the third quintile, exposure to the lowest quintile of urban green space, as measured within a 1600m accessible network buffer, is associated with slightly higher BMI (marginal effect: 0.80; 95% CI: 0.16-1.44). The results, however, are not robust to small changes in how green space is measured and no statistically significant association between urban green spaces and BMI is found under other variants of our regression model. Conclusion : The relationship between urban green spaces and BMI among older adults is highly sensitive to the characterisation of local green space. Our results suggest that there are some other unobserved factors, other than footpath availability, that mediate the relationship between urban green spaces and weight status.