Review
Type 2 diabetes in migrant south Asians: mechanisms, mitigation, and management

https://doi.org/10.1016/S2213-8587(15)00326-5Get rights and content

Summary

South Asians, particularly when living in high-income countries, are at a substantially elevated risk of type 2 diabetes compared with white Europeans, and typically develop the disease 5–10 years earlier and at a lower BMI. Migrant south Asians seem to be more insulin resistant than white Europeans across the life course and potentially experience β-cell exhaustion at a younger age. Differences in adiposity (high percentage of body fat and high proportion of deep subcutaneous and visceral fat) and skeletal muscle (low percentage of lean mass and low cardiorespiratory fitness) are likely to contribute these factors. No clear evidence is available suggesting genetic factors make a major contribution to the increased risk of diabetes in south Asians, but epigenetic factors might have a role. Irrespective of future mechanistic discoveries, south Asians need to be encouraged and helped—by various culturally appropriate methods—to maintain a high physical activity level and low bodyweight across the life course to prevent diabetes. In clinical terms, cardiovascular risks have attenuated over time in migrant south Asians with diabetes but retinopathy and renal complication risks remain high because of the high levels of glycaemia and rapid glycaemic deterioration noted in this population. We review these aspects and suggest areas for future research.

Introduction

South Asians—Pakistani, Indian, Bangladeshi, and Sri Lankan individuals—represent almost a quarter of the world's population. Many south Asians live outside the Indian subcontinent with large populations in the UK (about 3 million people), Canada (1·6 million), South Africa (1·3 million), the USA (3 million), many other European countries, the Middle East, Australia, and several African countries. This Review concentrates on the risk of accelerated type 2 diabetes in migrant south Asian populations; however, many aspects are pertinent to understanding the accelerated type 2 diabetes risk in all south Asians.

Section snippets

How high is diabetes risk in south Asians?

Immigrant south Asians generally have greater prevalence of type 2 diabetes than do the background populations of the countries to which they move.1, 2, 3, 4, 5 Compared with white people of European descent, south Asians living in high-income countries have an age-standardised rate of type 2 diabetes of about two to four times higher, with these risks being highest in Bangladeshis (roughly four times) and lowest in Indians (about two times).2, 6 Of particular note, increased risk for diabetes

Mechanisms: current hypothesis for why south Asians are at increased risk of diabetes

Increased risk of type 2 diabetes in south Asians probably results from the interaction between several innate and environmental factors. Current hypotheses for the mechanisms responsible for the increased diabetes risk in south Asians are described in the section below and summarised in figure 3.

Prevention of type 2 diabetes in south Asians

Few lifestyle intervention trials have been done for the prevention of diabetes in migrant south Asian populations. The PODOSA trial,100 reported a non-significant 28·4% reduction in progression to diabetes in the lifestyle intervention (incorporating dietary change and increased physical activity) compared with control in south Asians with impaired fasting glucose or impaired glucose tolerance, or both, in Scotland, UK, although this trial was powered to address weight loss, rather than

Clinical considerations

There is evidence that migrant south Asians with type 2 diabetes have a more rapid yearly deterioration in HbA1c concentrations than do white Europeans in routine clinical practice, despite greater prescription of oral glycaemic drugs.102 This finding implies an ethnic difference in diabetes progression rates. A helpful review103 has called for ethnic specific guidelines for the prevention, diagnosis, and management of type 2 diabetes in south Asians living on the Indian subcontinent.

Conclusions and future directions

We have emphasised the need for trials addressing treatment targets that are ethnically specific in migrant south Asians. For example, consideration of early use of angiotensin-converting enzyme and angiotensin-receptor blocker in south Asians at the point of type 2 diabetes diagnosis, might be helpful. At present, south Asians with diabetes seem to have low use of antihypertensive drugs early in the course of their disease. Nevertheless, this population's faster progression of retinopathy and

Search strategy

We searched PubMed and Google Scholar using the terms ”South Asian*”, “Asian Indian*”, ”diabetes”, “impaired glucose tolerance”, “insulin*”, “glucose”, “obesity”, “adipose tissue”, “ectopic fat”, “muscle”, “liver”, “lifestyle”, “fitness”, “physical activity”, “gene*”, “early origins”, “fetal programming”, and “diet” and selected relevant papers published in English from January, 1970, to June, 2015. We used our judgment to select representative papers or reviews to show key points and issues

References (123)

  • C Zheng et al.

    Vascular function, insulin action, and exercise: an intricate interplay

    Trends Endocrinol Metab

    (2015)
  • S Raj et al.

    Dietary habits of Asian Indians in relation to length of residence in the United States

    J Am Diet Assoc

    (1999)
  • GJ Miller et al.

    Dietary and other characteristics relevant for coronary heart disease in men of Indian, West Indian and European descent in London

    Atherosclerosis

    (1988)
  • L Sevak et al.

    Relationship of hyperinsulinemia to dietary intake in south Asian and European men

    Am J Clin Nutr

    (1994)
  • RS Bhopal et al.

    Effect of a lifestyle intervention on weight change in south Asian individuals in the UK at high risk of type 2 diabetes: a family-cluster randomised controlled trial

    Lancet Diabetes Endocrinol

    (2014)
  • UE Ntuk et al.

    Ethnic-specific obesity cutoffs for diabetes risk: cross-sectional study of 490,288 UK biobank participants

    Diabetes Care

    (2014)
  • K Sproston et al.

    The health of minority ethnic groups, vol 1. In: Health Survey for England–2004

    (2006)
  • Q Zhang et al.

    Changes in racial/ethnic disparities in the prevalence of Type 2 diabetes by obesity level among US adults

    Ethn Health

    (2009)
  • M Chiu et al.

    Comparison of cardiovascular risk profiles among ethnic groups using population health surveys between 1996 and 2007

    CMAJ

    (2010)
  • AJ Karter et al.

    Elevated rates of diabetes in Pacific Islanders and Asian subgroups: The Diabetes Study of Northern California (DISTANCE)

    Diabetes Care

    (2013)
  • J Hippisley-Cox et al.

    Predicting risk of type 2 diabetes in England and Wales: prospective derivation and validation of QDScore

    BMJ

    (2009)
  • M Chiu et al.

    Deriving ethnic-specific BMI cutoff points for assessing diabetes risk

    Diabetes Care

    (2011)

  • (2) Classification and diagnosis of diabetes

    Diabetes Care

    (2015)

  • Assessing body mass index and waist circumference thresholds for intervening to prevent ill health and premature death among adults from black, Asian and other minority ethnic groups in the UK

    (2013)
  • DA Lawlor et al.

    Pregnancy glycaemia and cord-blood levels of insulin and leptin in Pakistani and white British mother-offspring pairs: findings from a prospective pregnancy cohort

    Diabetologia

    (2014)
  • CS Yajnik et al.

    Adiposity and hyperinsulinemia in Indians are present at birth

    J Clin Endocrinol Metab

    (2002)
  • PH Whincup et al.

    Early evidence of ethnic differences in cardiovascular risk: cross sectional comparison of British South Asian and white children

    BMJ

    (2002)
  • PH Whincup et al.

    British South Asians aged 13-16 years have higher fasting glucose and insulin levels than Europeans

    Diabet Med

    (2005)
  • PH Whincup et al.

    Early emergence of ethnic differences in type 2 diabetes precursors in the UK: the Child Heart and Health Study in England (CHASE Study)

    PLoS Med

    (2010)
  • KL Harron et al.

    Rising rates of all types of diabetes in south Asian and non-south Asian children and young people aged 0-29 years in West Yorkshire, U.K., 1991–2006

    Diabetes Care

    (2011)
  • T Tillin et al.

    Insulin resistance and truncal obesity as important determinants of the greater incidence of diabetes in Indian Asians and African Caribbeans compared with Europeans: the Southall And Brent REvisited (SABRE) cohort

    Diabetes Care

    (2013)
  • NT Raymond et al.

    Comparative risk of microalbuminuria and proteinuria in UK residents of south Asian and white European ethnic background with type 2 diabetes: a report from UKADS

    Curr Med Res Opin

    (2011)
  • B Mukhopadhyay et al.

    A comparison of glycaemic and metabolic control over time among South Asian and European patients with Type 2 diabetes: results from follow-up in a routine diabetes clinic

    Diabet Med

    (2006)
  • RM Anjana et al.

    Incidence of Diabetes and Prediabetes and Predictors of Progression Among Asian Indians: 10-Year Follow-up of the Chennai Urban Rural Epidemiology Study (CURES)

    Diabetes Care

    (2015)
  • AA Motala et al.

    High risk of progression to NIDDM in South-African Indians with impaired glucose tolerance

    Diabetes

    (1993)
  • A Ramachandran et al.

    The Indian Diabetes Prevention Programme shows that lifestyle modification and metformin prevent type 2 diabetes in Asian Indian subjects with impaired glucose tolerance (IDPP-1)

    Diabetologia

    (2006)
  • S Engberg et al.

    Progression to impaired glucose regulation and diabetes in the population-based Inter99 study

    Diabetes Care

    (2009)
  • S Valdés et al.

    Population-based incidence of type 2 diabetes in northern Spain: the Asturias Study

    Diabetes Care

    (2007)
  • WC Knowler et al.

    Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin

    N Engl J Med

    (2002)
  • J Tuomilehto et al.

    Prevention of type 2 diabetes mellitus by changes in lifestyle among subjects with impaired glucose tolerance

    N Engl J Med

    (2001)
  • ZN Sohani et al.

    Does genetic heterogeneity account for the divergent risk of type 2 diabetes in South Asian and white European populations?

    Diabetologia

    (2014)
  • PH Whincup et al.

    Birth weight and risk of type 2 diabetes: a systematic review

    JAMA

    (2008)
  • CM Nightingale et al.

    Birthweight and risk markers for type 2 diabetes and cardiovascular disease in childhood: the Child Heart and Health Study in England (CHASE)

    Diabetologia

    (2015)
  • S Ikehara et al.

    Age trajectories of glycaemic traits in non-diabetic south Asian and white individuals: the Whitehall II cohort study

    Diabetologia

    (2015)
  • AM Kanaya et al.

    Understanding the high prevalence of diabetes in US south Asians compared with four racial/ethnic groups: the MASALA and MESA studies

    Diabetes Care

    (2014)
  • AK Singh

    Incretin response in Asian type 2 diabetes: Are Indians different?

    Indian J Endocrinol Metab

    (2015)
  • M Chandalia et al.

    Insulin resistance and body fat distribution in South Asian men compared to Caucasian men

    PLoS One

    (2007)
  • M Chandalia et al.

    Relationship between generalized and upper body obesity to insulin resistance in Asian Indian men

    J Clin Endocrinol Metab

    (1999)
  • LM Hall et al.

    Fat oxidation, fitness and skeletal muscle expression of oxidative/lipid metabolism genes in South Asians: implications for insulin resistance?

    PLoS One

    (2010)
  • NG Forouhi et al.

    Relation of triglyceride stores in skeletal muscle cells to central obesity and insulin sensitivity in European and South Asian men

    Diabetologia

    (1999)

    • Cited by (168)

    • Call for Cultural and Language-Concordant Diabetes Care, Nutrition Education, and Self-Management for South Asian Individuals Living in the US

      2023, Journal of Nutrition Education and Behavior

    • Epicardial, peripancreatic and other “orthotopic” excessive fat deposition in south Asians and Europeans: Are differences clinically relevant?

      2023, Journal of Diabetes and its Complications

    • Dietary weight-management for type 2 diabetes remissions in South Asians: the South Asian diabetes remission randomised trial for proof-of-concept and feasibility (STANDby)

      2023, The Lancet Regional Health - Southeast Asia

    • Knowledge, attitude, and practice of diabetes in patients with and without sight-threatening diabetic retinopathy from two secondary eye care centres in India

      2024, BMC Public Health

    • “The Critical Services Are Out of Reach”: Diabetes Management and the Experiences of South Asian Immigrants in Ontario

      2024, Journal of Primary Care and Community Health

    • Feasibility of prevention of type 2 diabetes in low- and middle-income countries

      2024, Diabetologia
    View all citing articles on Scopus
    †

    Authors contributed equally

    View full text
    Copyright © 2015 Elsevier Ltd. All rights reserved.