Abstract MP74: Understanding the Higher Diabetes Prevalence in South Asians Compared to Four U.S. Racial/Ethnic Groups: The MASALA and MESA Studies

Abstract

Background: South Asians (SA) have a high prevalence of diabetes (DM) which may be due to differences in insulin resistance (IR) or beta-cell function. We compared the prevalence of DM, IR, and beta cell function between SA and four race/ethnic groups. We also determined whether the association between age and adiposity with IR and beta cell function differed by ethnicty. Methods: We conducted a cross-sectional analysis of two cohorts aged 44-84 years without CVD: the Mediators of Atherosclerosis in South Asians Living in America (MASALA) study and the Multi-Ethnic Study of Atherosclerosis (MESA). We compared 799 SA with 2,611 Whites, 1,879 African Americans (AA), 1,493 Latinos and 801 Chinese Americans (CA). DM was classified by fasting plasma glucose ≥126 mg/dL or use of a diabetes medication. Insulin resistance was estimated by the homeostasis model assessment (HOMA)-IR and beta cell function by the HOMA-ß model. Spline curves displayed the effect of age and waist with HOMA-IR and HOMA- ß stratified by ethnic group among those not on diabetes medications. Results: SA had significantly higher age-adjusted prevalence of DM (23%) compared to each MESA group (6% Whites; 18% AA; 17% Latino; 13% CA, p<0.001 each compared to SA), which were further enhanced after adjusting for all covariates of DM. Median HOMA-IR was higher and HOMA-β was lower in SA compared to other groups. Patterns of insulin resistance and ß cell function with age and waist circumference differed by ethnic group (Figure). SA had higher HOMA-IR to age 65, and lower HOMA-ß across the all ages compared to other groups. SA had higher HOMA-IR and lower HOMA-β after adjusting for waist circumference compared to other groups. Conclusions: There are ethnic differences in IR and beta cell that vary by age and adiposity. South Asians may have lower innate beta cell function and an inability to compensate adequately for high levels of IR with increasing adiposity. Longitudinal follow-up can assess whether IR and beta cell function explain the higher diabetes rates in South Asians.