Understanding the high prevalence of diabetes in U.S. south Asians compared with four racial/ethnic groups: the MASALA and MESA studies.
OBJECTIVE
We compared South Asians with four other racial/ethnic groups in the U.S. to determine whether sociodemographic, lifestyle, or metabolic factors could explain the higher diabetes prevalence and whether insulin resistance and β-cell dysfunction occurred at younger ages and/or lower adiposity levels compared with other groups.


METHODS
We performed a cross-sectional analysis of two community-based cohorts, the Mediators of Atherosclerosis in South Asians Living in America (MASALA) study and the Multi-Ethnic Study of Atherosclerosis (MESA); all participants had no known cardiovascular disease and were between 44 and 84 years of age. We compared 799 South Asians with 2,611 whites, 1,879 African Americans, 1,493 Latinos, and 801 Chinese Americans. Type 2 diabetes 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) and β-cell function was measured by the HOMA-β model.


RESULTS
South Asians had significantly higher age-adjusted prevalence of diabetes (23%) than the MESA ethnic groups (6% in whites, 18% in African Americans, 17% in Latinos, and 13% in Chinese Americans). This difference increased further after adjustment for potential confounders. HOMA of insulin resistance (HOMA-IR) levels were significantly higher and HOMA-β levels were lower among South Asians compared with all other racial/ethnic groups after adjustment for age and adiposity.


CONCLUSIONS
The higher prevalence of diabetes in South Asians is not explained by traditionally measured risk factors. South Asians may have lower β-cell function and an inability to compensate adequately for higher glucose levels from insulin resistance.
University of California, San Francisco, San Francisco, CA alka.kanaya@ucsf.edu.
Alka M
AM
Kanaya
Wake Forest University Medical Center, Winston-Salem, NC.
David
D
Herrington
University of California, San Francisco, San Francisco, CA.
Eric
E
Vittinghoff
University of California, San Francisco, San Francisco, CA.
Susan K
SK
Ewing
Northwestern University, Chicago, IL.
Kiang
K
Liu
Johns Hopkins Ciccarone Center for the Prevention of Heart Disease, Baltimore, MD.
Michael J
MJ
Blaha
Northwestern University, Chicago, IL.
Swapna S
SS
Dave
University of California, San Francisco, San Francisco, CA.
Fareeha
F
Qureshi
Northwestern University, Chicago, IL.
Namratha R
NR
Kandula
D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data; D000368:Aged; D000369:Aged, 80 and over; D001213:Asian / Q000706:statistics & numerical data; D050197:Atherosclerosis / Q000453:epidemiology*; D015415:Biomarkers / Q000032:analysis; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology*; D005006:Ethnicity / Q000706:statistics & numerical data*; D005260:Female; D006630:Hispanic or Latino / Q000706:statistics & numerical data; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D044465:White People / Q000706:statistics & numerical data
D015415:Biomarkers