Relationships between social disadvantage and environmental exposures are complex and vary by geographic context and outcomes. However, few population-based studies have data to test these differences. The overarching goal of this study was first to examine the associations between cumulative socio-environmental stress and ambient air pollution with lung function then with body mass index (BMI) and examine how relationships differ in urban and rural contexts. Using data from 2400 adult participants of the Survey of the Health of Wisconsin, an additive socio-environmental stress index (SESI) was created from self-reported estimates of six social and built environment factors including self reported stress, poor neighborhood aesthetics, maintenance, presence of garbage and litter, limited safety from crime and lifetime discrimination. Three-year chronic air pollution exposure was estimated using USEPA's Bayesian space-time downscaler model for PM2.5. Both BMI and lung function were objectively measured during an exam visit. After careful adjustments, results showed no association between the non-chemical SESI and lung function in the overall study population. In contrast, three-year chronic air pollution was associated with reduced lung function (p<.03). In fully adjusted models of chronic air pollution and lung function that tested for potential mediation by SESI, associations were slightly attenuated but remained significant. In stratified analyses, air pollution was only associated with reduced lung function in urban populations. Repeating analyses with body mass index as the primary outcome found opposite associations. Exposure to SESI but not chronic air pollution was a predictor of increased BMI (p<.001). Stratified analyses revealed associations persisted in rural but not urban areas. Results highlight the importance of context in teasing out complex relationships between chemical and social environmental factors impacts on population health.
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