Neighborhood features and insulin resistance

Little is known about environmental determinants of type 2 diabetes and its precursor, insulin resistance. The primary hypotheses addressed in this dissertation were that insulin resistance is positively related to distance to a high-income area and local neighborhood poverty and negatively related to availability of healthy foods and places to be physically active. Univariate and multivariable spatial interpolation methods were used to smooth area-level data across three mostly-urban study sites in the eastern US. The performance of models predicting neighborhood features was evaluated using cross-validation. Area-level data were derived from a population-based residential survey, an inventory of recreational resources and food stores, and the US Census. Neighborhood features were assigned to a sample of adult residents (aged 45-84 years) for whom health measures were available. The Homeostatic Model Assessment (HOMA) index represented insulin resistance among persons not treated for diabetes. Linear regression was used to estimate associations between area characteristics and insulin resistance, adjusting for age, sex, income, education, and race/ethnicity, and the potential mediators diet, physical activity, and body mass index (BMI). Distance to a high-income area and to a neighborhood with both above-median neighborhood physical activity and healthy foods were positively associated with HOMA index, independent of person-level covariates. These associations were similar in magnitude as the effect of a BMI increase of 1.6 kg/m 2 on HOMA. Associations were reduced after adjustment for potential mediators---physical activity, diet, and BMI. Local neighborhood poverty and residing in a local neighborhood with both above-median physical activity and healthy foods were positively related to HOMA index but 95% confidence intervals included the null value. Living in proximity to resources in high-income areas and in areas with above-median neighborhood physical activity and above-median healthy foods are negatively related to insulin resistance. Diabetes prevention efforts may need to focus on features of residential environments.