Incidence and pathophysiology of diabetes in South Asian adults living in India and Pakistan compared with US blacks and whites

• Authors: Kabayam Venkat Narayan, Emory University; Dimple Kondal, Public Health Foundation of India; Natalie Daya, Johns Hopkins University; Unjali Gujral, Emory University; Deepa Mohan, Madras Diabetes Research Foundation; Shivani Patel, Emory University; Roopa Shivashankar, Public Health Foundation of India; Ranjit Mohan Anjana, Madras Diabetes Research Foundation; Lisa Staimez, Emory University; Mohammed Ali, Emory University; Howard Chang, Emory University; Masood Kadir, Aga Khan University; Dorairaj Prabhakaran, Emory University; Elizabeth Selvin, Johns Hopkins University; Viswanathan Mohan, Madras Diabetes Research Foundation; Nikhil Tandon, All India Institute of Medical Sciences
• Journal Title: BMJ OPEN DIABETES RESEARCH & CARE
• Volume: Volume 9, Number 1
• Publisher: BMJ PUBLISHING GROUP | 2021-01-01
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1136/bmjdrc-2020-001927
• Subjects: Health Sciences, Public Health; Health Sciences, Epidemiology; Sociology, Ethnic and Racial Studies
• Keywords: Science & Technology; Life Sciences & Biomedicine; Endocrinology & Metabolism; diabetes mellitus; type 2; epidemiology; ethnic groups; India

Abstract

Introduction We compared diabetes incidence in South Asians aged ≥45 years in urban India (Chennai and Delhi) and Pakistan (Karachi), two low-income and middle-income countries undergoing rapid transition, with blacks and whites in the US, a high-income country. Research design and methods We computed age-specific, sex-specific and body mass index (BMI)-specific diabetes incidence from the prospective Center for Cardiometabolic Risk Reduction in South Asia Study (n=3136) and the Atherosclerosis Risk in Communities Study (blacks, n=3059; whites, n=9924). We assessed factors associated with incident diabetes using Cox proportional hazards regression. Results South Asians have lower BMI and waist circumference than blacks and whites (median BMI, kg/m 2: 24.9 vs 28.2 vs 26.0; median waist circumference, cm 87.5 vs 96.0 vs 95.0). South Asians were less insulin resistant than blacks and whites (age-BMI-adjusted homeostatic model assessment of insulin resistance, μIU/mL/mmol/L: 2.30 vs 3.45 vs 2.59), and more insulin deficient than blacks but not whites (age-BMI-adjusted homeostasis model assessment of β-cell dysfunction, μIU/mL/mmol/L: 103.7 vs 140.6 vs 103.9). Age-standardized diabetes incidence (cases/1000 person-years (95% CI)) in South Asian men was similar to black men and 1.6 times higher (1.37 to 1.92) than white men (26.0 (22.2 to 29.8) vs 26.2 (22.7 to 29.7) vs 16.1 (14.8 to 17.4)). In South Asian women, incidence was slightly higher than black women and 3 times (2.61 to 3.66) the rate in white women (31.9 (27.5 to 36.2) vs 28.6 (25.7 to 31.6) vs 11.3 (10.2 to 12.3)). In normal weight (BMI <25 kg/m 2), diabetes incidence adjusted for age was 2.9 times higher (2.09 to 4.28) in South Asian men, and 5.3 times (3.64 to 7.54) in South Asian women than in white women. Conclusions South Asian adults have lower BMI and are less insulin resistant than US blacks and whites, but have higher diabetes incidence than US whites, especially in subgroups without obesity. Factors other than insulin resistance (ie, insulin secretion) may play an important role in the natural history of diabetes in South Asians.