A Study of Risk Factors for First Myocardial Infarction in 52 Countries and Over 27,000 Subjects - INTERHEART
The goal of the study was to evaluate risk factors associated with the development of first myocardial infarction (MI) in a worldwide population.
Patients Enrolled: 29,972
The study was an international, case-control study of patients with first MI (cases; n=15,152) compared with patients without MI (controls; n=14,820), matched on gender and age. Patients were evaluated in 52 countries worldwide. Evaluation included a questionnaire on demographics, lifestyle, health history, psychosocial factors and medications; physical assessment of blood pressure, heart rate, height, weight, and waist and hip circumference; and nonfasting blood samples for measurement of lipid profiles.
Mean age of MI was lower in men compared with women by a median of nine years. Nine risk factors were identified to be associated with MI in cases compared with control, the strongest of which was the highest quintile of apolipoprotein B/A-1 ratio (20.0% in controls vs. 33.5% in cases, adjusted odds ratio [OR] 3.25) and cigarette smoking (26.8% vs. 45.2%, OR 2.87).
Other risk factors identified included self-reported hypertension (21.9% vs. 39.0%, OR 1.91), diabetes (7.5% vs. 18.4%, OR 2.37), abdominal obesity (33.3% vs. 46.3%, OR 1.62), stress (OR 2.67), lack of daily consumption of fruits and vegetables (42.4% vs. 35.8%, OR 0.70), and lack of daily exercise (19.3% vs. 14.3%, OR 0.86). These factors predicted 90% of the risk of MI. Having all nine factors was associated with an OR of 129.2, although the frequency of having all nine factors would be relatively uncommon. Both Apo B/A-1 ratio and amount of cigarettes smoked were associated with a stepwise increase in MI, with an increased risk associated with even 1-5 cigarettes smoked per day (OR 1.38).
Risk factor prevalence differed by region, but the association with MI was consistent across region and ethnicity. When risk factors were evaluated by young and older age groups, smoking, diabetes, Apo B/A-1 ratio, and hypertension were even more strongly associated with MI in young patients.
Among an international study population, nine risk factors were identified that predicted 90% of the risk of MI in this case-control study. Smoking and nonfasting Apo B/A-1 ratio were the two factors most strongly associated with MI.
Most risk factors in the present study are both easily identified during a general screening. Importantly, the risk factors are modifiable, especially smoking. As the presenter suggested, these risk factors can be used to guide prevention strategies to lower the frequency of MI and subsequent mortality worldwide.
Yusuf S, Hawken S, Ounpuu S, et al. Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): case-control study. Lancet 2004;364;937-52.
Yusuf S. INTERHEART: a study of risk factors for first myocardial infarction in 52 countries and over 27,000 subjects. Paper presented at the European Society of Cardiology Congress 2004, 29 August-1 September, Munich, Germany.
Keywords: Odds Ratio, Obesity, Abdominal, Life Style, Myocardial Infarction, Blood Pressure, Risk Factors, Heart Rate, Smoking, Case-Control Studies, Surveys and Questionnaires, Diabetes Mellitus, Hypertension
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