Longitudinal associations of neighborhood-level racial residential segregation with obesity among Blacks: The Coronary Artery Risk Development in Young Adults (CARDIA) Study

Previous research has suggested larger social processes like racial residential segregation may contribute to obesity by constraining resources available for physical activity or healthy eating. However, prior studies relating segregation to obesity are cross-sectional and use self-reported outcomes. In this study we examined the longitudinal relationship between change in neighborhood-level racial residential segregation and obesity among 2,316 Black CARDIA participants living in Birmingham, AL; Chicago, IL; Minneapolis, MN; and Oakland, CA at baseline (1985) and followed for 25 years (5 follow-up exams). We hypothesized that Blacks living in more segregated neighborhoods would be more likely to become obese over time. Racial residential segregation was measured at each exam using the G_i^* statistic, a z-score measuring the extent to which the racial composition of a given neighborhood (census tract) deviates from the composition of the larger surrounding metropolitan area. A higher score indicates greater segregation. Body mass index (BMI) was measured (weight [kg]/height[m], squared). Logistic mixed modeling was used to estimate odds ratios (OR) for obesity (BMI ≥30) over time. At baseline, the median G_i^* statistic score was 6.38 and 16.7% of participants were obese. By the fifth exam, the median G_i^* statistic score was 4.33 and the prevalence of obesity increased to 55.7%. Each unit increase in segregation was associated with a 3% increase (95% Confidence Interval: 1.01, 1.04) in the odds of obesity after adjusting for age, exam year, field center, sex, marital status, physical activity level, current smoking status, and neighborhood poverty. The relationship between segregation and obesity did not statistically significantly differ across years in the study period (p=0.30). In summary, segregation was associated with obesity, even after controlling for individual and neighborhood characteristics.  These findings support previous cross-sectional studies and highlight the important contributions of social environment to obesity.