Perceived racism and incident diabetes in the Black Women's Health Study.

AIMS/HYPOTHESIS: Our aim was to assess the association of perceived racism with type 2 diabetes, and the possible mediating influence of diet and BMI. METHODS: The Black Women's Health Study, a follow-up of 59,000 African-American women, began in 1995. Over 16 years 5344 incident cases of diabetes occurred during 576,577 person-years. Cox proportional hazards models were used to estimated HRs and 95% CIs for categories of 'everyday racism' (interpersonal racism in daily life) and 'lifetime racism' (reporting ever treated unfairly due to race with respect to police, housing or work) and incident type 2 diabetes. Models were adjusted for age, questionnaire cycle, marital status, socioeconomic status, education, family history of diabetes, physical activity, alcohol use and smoking status, with and without inclusion of terms for dietary patterns and adult BMI. RESULTS: Compared with women in the lowest quartile of exposure, women in the highest quartile of exposure to everyday racism had a 31% increased risk of diabetes (HR 1.31; 95% CI 1.20, 1.42) and women with the highest exposure to lifetime racism had a 16% increased risk (HR 1.16; 95% CI 1.05, 1.27). Mediation analysis estimated that BMI accounted for half of the association between either the everyday or lifetime racism measure and incident diabetes. CONCLUSIONS/INTERPRETATION: Perceived everyday and lifetime racism were associated with increased risk of type 2 diabetes in this cohort of African-American women and appear to be at least partly mediated by BMI.