Associations between air pollution indicators and prevalent and incident diabetes in an African American cohort, the Jackson Heart Study.

Background: Diabetes is especially prevalent among African Americans. Prior studies suggest that long-term exposure to ambient air pollution may be associated with greater incidence of diabetes, but results remain heterogeneous. Few studies have included large numbers of African Americans.

Methods: We assessed diabetes status and concentrations of 1- and 3-year fine particulate matter (PM_2.5) and ozone (O₃) among African American participants of the Jackson Heart Study at visits 1 (2000-2004, N = 5128) and 2 (2005-2008, N = 2839). We used mixed-effect modified Poisson regression to estimate risk ratios (RRs) and 95% confidence intervals (CIs) of incidence of diabetes by visit 2 and prevalence ratios (PRs) of the association between air pollution exposure and prevalent diabetes at visits 1 and 2. We adjusted for potential confounding by patient characteristics, as well as inverse probability weights of diabetes at visit 2, accounting for clustering by census tract.

Results: We observed associations between incident diabetes and interquartile range increase in 1-year O₃ (RR 1.34, 95% CI = 1.11, 1.61) and 3-year O₃ (RR 0.88, 95% CI = 0.76, 1.02). We observed associations between prevalent diabetes and 1-year PM_2.5 (PR 1.08, 95% CI = 1.00, 1.17), 1-year O₃ (PR 1.18, 95% CI = 1.10, 1.27), and 3-year O₃ (PR 0.95, 95% CI = 0.90, 1.01) at visit 2.

Conclusions: Our results provide some evidence of positive associations between indicators of long-term PM_2.5 and O₃ exposure and diabetes. This study is particularly relevant to African Americans, who have higher prevalence of diabetes but relatively few studies of environmental pollution risk factors.