Study Assesses Ethnic Relationships Between Metabolic Risk Factors and CHD

Morbidity and mortality from coronary heart disease (CHD) are elevated in South Asians, and lower in African Caribbeans compared to European origin populations, according to a new study in the Journal of the American College of Cardiology.

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The study, possibly the largest to assess cardiovascular risk factors in 2,049 Europeans; 1,517 South Asians; and 630 African Caribbeans primarily in their early fifties, found that the incidence of CHD was more prevalent in South Asians, and less prevalent in African Caribbeans, compared to Europeans. South Asians were also more likely to be centrally obese and dyslipidaemic than Europeans, while African Caribbeans were less likely. The authors also noted that, "the [African Caribbean] vs. European age and sex adjusted subhazard ratios (SHRs) of 0.64(0.52, 0.79), p<0.001 remained significant when adjusted for HDL and LDL cholesterol (0.74(0.60, 0.92),p=0.008)."

While the differences between the ethnic populations were "not explained by conventional risk factors measured in mid-life … factors across the life course, in particular the mismatch between early and later life environments in migrant cohorts may be key," the authors said. They also suggested that urban-rural differences may be factors. "As in the west, CHD is a consequence of industrialisation, associated with reduced physical activity and adverse diet," they note. "Genetic factors alone are unlikely to have acted this rapidly."

Meanwhile, the study did find that baseline diabetes prevalence was over three times greater in South Asians and African Caribbeans than in Europeans. The likelihood of stroke was also greater in South Asians and African Caribbeans than Europeans. According to the study authors, this differential was more marked in those with diabetes (age adjusted SHRs: 1.97(1.16,3.35), interaction p=0.038) and 2.21(1.14, 4.30), interaction p=0.019).

"The apparently greater association between diabetes and stroke risk in [South Asians] and [African Caribbeans] compared with Europeans merits further study," the authors said.

In an accompanying editorial comment, Prakash Deedwania, MD, FACC, agreed, saying that the study underscores the "urgent need to devote adequate resources" towards diabetes and CHD research and to "implement appropriate public health measures in order to prevent the oncoming tsunami of chronic debilitating and deadly disorders like diabetes and cardiovascular disorders across the world."  To date, diabetes and CHD have become the "leading causes of death and disability in the minority populations and various ethnic cohorts across the world often affecting younger people in many developing nations like India," he writes.

However, he notes that a major limitation of the study is that the evaluation for diabetes mellitus and other metabolic risk factors was only made at the beginning of the study, and data regarding any likely changes that may have occurred during the long follow-up period of 20 years is not available. "The lack of information regarding the treatment received by the study subjects for important risk factors such as diabetes, hypertension, and dyslipidemia also makes it difficult to put these data in proper perspective," he writes.

Keywords: Ethnic Groups, Stroke, Cholesterol, LDL, Caribbean Region, European Continental Ancestry Group, Coronary Disease, Risk Factors, Developing Countries, Prevalence, Cause of Death, Incidence, Dyslipidemias, Public Health, India, Motor Activity, Diet, African Continental Ancestry Group, Hypertension, United States, Diabetes Mellitus

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