Associations between the built environment and body mass index among a residentially stable cohort of mid-older aged adults in Brisbane, Australia (2007-2016)

Understanding the relationship between neighbourhood design and health is important for designing communities that facilitate ageing in place. This study examined trends in body mass index (BMI) across levels of neighbourhood built environment exposure, as well as associations between changes in the built environment and changes in BMI among ageing adults. The sample included 11,035 participants aged 40-65 years at baseline from the HABITAT study, residing in Brisbane, Australia. Data were collected over five waves. Self-reported height and weight were used to calculate BMI. Built environment measures (dwelling density, street connectivity, land use mix) were derived spatially. Models were adjusted for education, occupation, household income, residential self-selection, and neighbourhood disadvantage. Analyses used mixed-effects hybrid models that decomposed time-varying neighbourhood exposures into within- and between-individual components. Most participants experienced an increase in dwelling density and street connectivity. Greater dwelling density was associated with lower BMI. Participants with greater street connectivity had greater BMI increases over time. No association between changes in neighbourhood built environment characteristics and BMI was found. This study showed limited evidence for changing BMI by the neighbourhood built environment among residentially stable adults. However, supportive neighbourhood design remains important for supporting other health behaviours and outcomes.