Is the “South Asian Phenotype” unique to South Asians?

Abstract

Background: In the context of rising obesity in South Asia, it is unclear whether the “South Asian phenotype” (described as high glucose, low high-density lipoprotein cholesterol and high triglycerides at normal ranges of body weight) continues to be disproportionately exhibited by contemporary South Asians relative to other race/ethnic groups. Objectives: We assessed the distinctiveness of the South Asian cardiometabolic profile by comparing the prevalence of combined high glucose, high triglycerides and low high-density lipoprotein cholesterol (combined dysglycemia and dyslipidemia) in resident South Asians with 4 race/ethnic groups in the United States (Asians, black persons, Hispanics and white persons) overall and by Body Mass Index (BMI) category. Methods: South Asian data were from the 2010 to 2011 Center for Cardiometabolic Risk Reduction in South Asia Study, representative of Chennai and New Delhi, India and Karachi, Pakistan. U.S. data were from the 2011 to 2012 National Health and Nutrition Examination Survey, representative of the U.S. population. Combined dysglycemia and dyslipidemia was defined as fasting blood glucose ≥126 mg/dl and triglyceride/high-density lipoprotein cholesterol ratio >4. Logistic regression was used to estimate the relative odds and 95% confidence intervals of combined dysglycemia and dyslipidemia associated with each race/ethnic group (referent, U.S. white persons). Models were estimated among adults aged 20 to 79 years by sex and BMI category and accounted for age, education and tobacco use. Data from 8,448 resident South Asians, 274 U.S. Asians, 404 U.S. black persons, 308 U.S. Hispanics and 703 U.S. white persons without previously known diabetes were analyzed. Results: In the normal body weight range of BMI 18.5 to 24.9 kg/m², the prevalence of combined dysglycemia and dyslipidemia among men and women, respectively, was 33% and 11% in resident South Asians, 15% and 1% in U.S. Asians, 5% and 2% in U.S. black persons, 11% and 2% in U.S. Hispanics and 8% and 2% in U.S. white persons. Compared with U.S. whites persons, South Asians were more likely to present with combined dysglycemia and dyslipidemia at all categories of BMI for men and at BMI 18.5 to 29.9 for women in adjusted models. The most pronounced difference between South Asians and U.S. white persons was observed at normal weight (adjusted odds ratio: 4.98; 95% confidence interval: 2.46 to 10.07 for men) (adjusted odds ratio: 9.09; 95% confidence interval: 2.48 to 33.29 for women). Conclusions: Between 8% and 15% of U.S. men and 1% and 2% of U.S. women of diverse race/ethnic backgrounds exhibited dysglycemia and dyslipidemia at levels of body weight considered “healthy,” consistent with the cardiometabolic profile described as the “South Asian Phenotype”. Urban South Asians, however, were 5 to 9 times more likely to exhibit dysglycemia and dyslipidemia in the “healthy” BMI range compared with any other U.S. race/ethnic group.