Risk Factors for Early Myocardial Infarction in South Asians Compared With Individuals in Other Countries
Prashant Joshi, MD; Shofiqul Islam, MSc; Prem Pais, MD; Srinath Reddy, MD; Prabhakaran Dorairaj, MD; Khawar Kazmi, MBBS; Mrigendra Raj Pandey, MBBS; Sirajul Haque, MBBS; Shanthi Mendis, MD; Sumathy Rangarajan, MSc; Salim Yusuf, MD, DPhil
JAMA. 2007;297:286-294.
Context:
South Asians have high rates of acute myocardial infarction (AMI) at younger ages compared with individuals from other countries but the reasons for this are unclear.
Objective:
To evaluate the association of risk factors for AMI in native South Asians, especially at younger ages, compared with individuals from other countries.
Design, Setting, and Participants:
Standardized case-control study of 1732 cases with first AMI and 2204 controls matched by age and sex from 15 medical centers in 5 South Asian countries and 10 728 cases and 12 431 controls from other countries. Individuals were recruited to the study between February 1999 and March 2003.
Main Outcome Measure:
Association of risk factors for AMI.
Results:
The mean (SD) age for first AMI was lower in South Asian countries (53.0 [11.4] years) than in other countries (58.8 [12.2] years; P<.001). Protective factors were lower in South Asian controls than in controls from other countries (moderate- or high-intensity exercise, 6.1% vs 21.6%; daily intake of fruits and vegetables, 26.5% vs 45.2%; alcohol consumption ≥once/wk, 10.7% vs 26.9%). However, some harmful factors were more common in native South Asians than in individuals from other countries (elevated apolipoprotein B100 /apolipoprotein A-I ratio, 43.8% vs 31.8%; history of diabetes, 9.5% vs 7.2%). Similar relative associations were found in South Asians compared with individuals from other countries for the risk factors of current and former smoking, apolipoprotein B100 /apolipoprotein A-I ratio for the top vs lowest tertile, waist-to-hip ratio for the top vs lowest tertile, history of hypertension, history of diabetes, psychosocial factors such as depression and stress at work or home, regular moderate- or high-intensity exercise, and daily intake of fruits and vegetables. Alcohol consumption was not found to be a risk factor for AMI in South Asians. The combined odds ratio for all 9 risk factors was similar in South Asians (123.3; 95% confidence interval [CI], 38.7-400.2] and in individuals from other countries (125.7; 95% CI, 88.5-178.4). The similarities in the odds ratios for the risk factors explained a high and similar degree of population attributable risk in both groups (85.8% [95% CI, 78.0%-93.7%] vs 88.2% [95% CI, 86.3%-89.9%], respectively). When stratified by age, South Asians had more risk factors at ages younger than 60 years. After adjusting for all 9 risk factors, the predictive probability of classifying an AMI case as being younger than 40 years was similar in individuals from South Asian countries and those from other countries.
Conclusion:
The earlier age of AMI in South Asians can be largely explained by higher risk factor levels at younger ages.
Author Affiliations: Department of Medicine, Government Medical College, Nagpur, India (Dr Joshi); Population Health Research Institute, McMaster University and Hamilton Health Sciences, Hamilton, Ontario (Mr Islam, Ms Rangarajan, and Dr Yusuf); Department of Medicine, St John’s Medical College, Bangalore, India (Dr Pais); All India Institute of Medical Sciences, New Delhi, India (Drs Reddy and Dorairaj); Department of Cardiology, Aga Khan Univer sity, Karachi, Pakistan (Dr Kazmi); Nepal Hypertension Society, Nepal (Dr Pandey); Department of Cardiology, Bangabandhu Sheikh Medical University, Bangladesh (Dr Haque); and World Health Organization, Geneva, Switzerland (Dr Mendis).
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