Changes in racial/ethnic disparities in the prevalence of Type 2 diabetes by obesity level among US adults.

OBJECTIVE: Ethnic minority status and obesity are two independent risk factors for Type 2 diabetes (T2D). There is no clear understanding of how they may have interacted and influenced disparities in T2D prevalence over time. This study examined the trends in racial/ethnic disparities in the prevalence of T2D by weight status among US adults.
METHODS: We used nationally representative data from the National Health and Nutrition Examination Surveys I (1971-1975), II (1976-1980), and III (1988-1994), and 1999-2004 among 49,574 adults aged 20-74 years. The prevalences of diagnosed and undiagnosed T2D were estimated by race/ethnicity groups (non-Hispanic White, non-Hispanic Black, and Mexican American) and body mass index (BMI) groups (normal, 18.5-24.9; overweight, 25-29.9; obese, 30-34.9; severely obese, >or=35). We used logistic regression controlling for age, gender, and education to estimate the odds ratio of T2D across race/ethnicity and BMI groups.
RESULTS: Trends in racial/ethnic disparities in prevalence of diagnosed T2D varied by BMI. Normal weight group saw increasing racial disparities. In the overweight group, ethnic disparities worsened as diabetes prevalence increased 33.3% in Whites, compared to 60.0% in Blacks, and 227.3% in Mexican Americans. Minimal racial/ethnic disparities were observed in obese and severely obese groups over time. In contrast to diagnosed diabetes, overall racial/ethnic disparities in undiagnosed T2D declined in all BMI groups.
CONCLUSIONS: Racial/ethnic disparities in diabetes prevalence have become most pronounced among normal and overweight groups. Eliminating racial/ethnic disparities in diabetes will require prevention efforts not only in obese minority individuals, but also in normal and overweight minority individuals.