Insulin resistance, high prevalence of diabetes, and cardiovascular risk in immigrant Asians

SIR,-We read with interest the findings of Dhawan et al,' who highlighted the importance of hyperinsulinaemia, central obesity, and physical inactivity as risk factors in Asians with angiographically significant coronary artery disease: Both British and Indian Asians were found to share a predisposition to insulin resistance and its associated metabolic abnormalities-and hence a high cardiovascular risk. They conclude that this finding is likely to favour a genetic rather than environmental basis for the recognised high mortality in this ethnic group. However, migrants are not a random sample of the original population,2 and their "selection" is likely to be determined by several health and socioeconomic factors, which are likely to influence their morbidity and mortality. If this environmental effect were a significant determinant of cardiovascular risk, one would not expect to see the high mortality from ischaemic heart disease (IHD) that has been recorded in Asians in South Africa,' Trinidad,4 and Singapore,5 who emigrated over a century ago. We recently reported a survey in which we studied the cardiovascular risk factor profile of all Asian men admitted with acute myocardial infarction during 8 weeks to our city centre district general hospital in Birmingham, England, and to the San Fernando General Hospital, in Trinidad6: 74 patients were studied (55 patients (mean (SEM) age 58-1 (1-4)) in Trinidad (Trinidad group) and 19 in Birmingham (62-1 (2 6)) (UK Group) (table). We also found that mean systolic and diastolic blood pressures were higher in those with hypertension in the Trinidad group (146-6 (16-9)/93.4 (114) mm Hg than in the UK group (120-8 (25 4)/75 0 (13-4) mm Hg, P < 0-05).6 Though Asians in Trinidad have in many ways adapted to the lifestyle of the host population, this does not appear to have reduced their cardiovascular risk profile, because those admitted with acute myocardial infarction had, in fact, a greater prevalence of central obesity, smoking, and higher blood pressures than a similar group in England.6 Central obesity and physical inactivity were common to both communities in England and Trinidad and their relation to insulin resistance may be particularly important in Asians with IHD. Our data support the hypothesis of a genetic predisposition to central obesity and diabetes in Asians that seems to have been retained by