Epidemiological studies of international variations in disease incidence have helped to generate and test hypotheses about the relative importance of genetic, environmental, social, and cultural factors in causing cardiovascular diseases.1 Studies of racial and ethnic variation within countries have also contributed in advancing such understanding. Indian, Bangladeshi, and Pakistani people born on the Indian subcontinent (henceforth called South Asian) but living in England and Wales have a 40–50% higher mortality from coronary heart disease than the population average.2 ,3 The prevailing hypothesis explaining this excess is the insulin resistance hypothesis. Coronary heart disease, paradoxically, is comparatively low among Afro-Caribbeans,4 who share with South Asians a high prevalence of insulin resistance.

Another paradox concerns hypertension, one of the major coronary risk factors, as ethnic variations in blood pressure do not parallel variations in coronary heart disease. Prevalence of hypertension among the Afro-Caribbean and African populations is high, but their risk of death from coronary heart disease is low.4 ,5 There is conflicting evidence over whether hypertension is more common in South Asian groups. One study found diastolic blood pressure among South Asian (predominantly Punjabi) men in Glasgow was higher than in the general population, but this was not so for South Asian women, or for systolic blood pressure in South Asian men.6 South Asian groups in Newcastle, particularly Bangladeshis, were found to have lower blood pressure than Europeans.7 Paradoxically Bangladeshis have the highest mortality from …