Epidemiology and determinants of type 2 diabetes in south Asia

Summary

Type 2 diabetes has rapidly developed into a major public health problem in south Asia (defined here as Bangladesh, Bhutan, India, Nepal, Pakistan, and Sri Lanka) in recent decades. During this period, major lifestyle changes associated with economic transition, industrialisation, urbanisation, and globalisation have been key determinants in the increasing burden of non-communicable diseases. A decline in nutrition quality, reduced physical activity, and increased sedentary behaviours are reflected in the increasing prevalence of type 2 diabetes and related risk factors in the region. The International Diabetes Federation 2017 estimates of the prevalence of diabetes in adults in the region range from 4·0% in Nepal to 8·8% in India. The prevalence of overweight ranges from 16·7% in Nepal to 26·1% in Sri Lanka, and the prevalence of obesity ranges from 2·9% in Nepal to 6·8% in Sri Lanka. An increasing proportion of children, adolescents, and women are overweight or obese, leading to a heightened risk of type 2 diabetes. Ethnic south Asians present with greater metabolic risk at lower levels of BMI compared with other ethnic groups (referred to as the south Asian phenotype), with type 2 diabetes often developing at a younger age, and with rapid progression of diabetic complications. Because of the presence of multiple risk factors and a body composition conducive to the development of type 2 diabetes, south Asians should be aggressively targeted for prevention. In this Series paper, we detail trends in the prevalence of diabetes in the region and address major determinants of the disease in the context of nutrition and physical activity transitions and the south Asian phenotype.

Introduction

The development of type 2 diabetes as a major public health problem has been particularly rapid in much of south Asia since the 1990s.¹ In this period, the region has experienced pronounced demographic, epidemiological, and socioeconomic changes,² with important consequences for population health. Type 2 diabetes results from an interplay between genetics and the environment—in the context of the increasing prevalence in south Asia, environmental factors include a combination of increased energy intake and decreased energy expenditure, plus a genetic susceptibility to such lifestyle changes.³ South Asian people have several distinct features with respect to type 2 diabetes compared with other ethnic groups, including an earlier onset of disease and complications, occurrence at a lower BMI, and increased β-cell dysfunction, insulin resistance, and ectopic fat deposition.⁴ The rapid increase in the prevalence of type 2 diabetes in south Asia underscores the challenge facing policy makers and clinicians with respect to prevention and management. The burden of the diabetes pandemic has important consequences for individuals, families, and communities, and is a major challenge with respect to health-care resources and productivity in the region.

This is the first in a Series of three papers about type 2 diabetes in south Asia. The second paper focuses on clinical management⁵ and the third on public health and health systems in the south Asian context.⁶ Here, we describe trends in the prevalence of diabetes in south Asia, and address the major determinants of the disease in the context of nutrition and physical activity transitions. We also consider the concurrent influence of overweight and obesity and the south Asian phenotype.