Primary Prevention of Cardio-Vascular Disease in Ethnic South Asians

• Adjusting Framingham Risk Estimate
• Issues to Consider When Adjusting Risk
• Consider Adjusting Risk for Additional Risk Factors by a Factor of 1.5-2.0.

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• South Asians
• The Importance of Conventional Risk Factors in South Asians- The INTER-HEART Study

Assessment and Management of Cardiovascular Risk

Risk Factors in South Asians in the INTER-HEART Study

This large case-control study was published in The Lancet in 2004 suggests that most of the risk of ischaemic cardiac events can be predicted by the measurement of conventional risk factors. These factors seemed to impart the same risk in different populations.

The median age at the time of first infaction was lowest in South Asians, Arabs and Black Africans (median age 52-54 years). The median age for Other Asians (non-South Asians) was about five years higher at 57 years, and the median age for Chinese was (63 years) and similar to those of European ethnic origins (62 years).

This study found that conventional risk factors with the addition of measures of psychosocial stress, alcohol intake, dietary intake and exercise account for almost all of the risk in all regions and in all ethnic groups.

It has been widely reported that the impact of changes in lifestyle due to increased urbanisation and wealth seems to have lead to a shift in the prevalence of various risk factors. Changes in diet and to lifestyle with reduced exercise have caused weight gain and consequently to increased prevalence of hypertension, dyslipidaemia, diabetes and insulin resistance.

Careful review of this study does not explain why, for example, South Asians have myocardial infarcts ten years earlier than European peoples, with the possible exception of the underestimation of the impact of hypertension or diabetes. The population attributable risk of smoking and dyslipidaemia does not account for this difference. The risk of myocardial infarction associated with apo-B/apo-A1 (highest vs lowest quintile) was the same for Western Europeans and South Asians (but higher amongst South East Asians).

Choosing an appropriate upwards adjustment of total estimated risk is vital to ensure there is no undertreatment of ethnic groups that develop first infarction five to ten years before ethnic Europeans. The Framingham based risk calculators will underestimate risk in those populations that have first myocardial infarcts at an earlier age. Until there is consensus on how to adjust risk, not all will accept the NZ guidelines' recommendation to limit upwards risk estimation to five percent. In addition, I suspect practitioners will continue to use other tests in efforts to find more accurate means of identifying those that are at higher risk of future events, this might include measurement of apo-B levels in those likely to have the metabolic syndrome and measurement other emerging risk factors.

Hitesh Patel, Cardiologist
5th September, 2004