Education and risk for acute myocardial infarction in 52 high, middle and low-income countries: INTERHEART case-control study

Objective: To determine the effect of education and other measures of socioeconomic status (SES) on risk of acute myocardial infarction (AMI) in patients and controls from countries with diverse economic circumstances (high, middle, and low income countries). Design: Case-control study. Setting: 52 countries from all inhabited regions of the world. Participants: 12242 cases and 14622 controls. Main outcome measures: First non-fatal AMI. Results: SES was measured using education, family income, possessions in the household and occupation. Low levels of education (<= 8 years) were more common in cases compared to controls (45.0% and 38.1%; p<0.0001). The odds ratio (OR) for low education adjusted for age, sex and region was 1.56 (95% confidence interval 1.47 to 1.66). After further adjustment for psychosocial, lifestyle, other factors and mutually for other socioeconomic factors, the OR associated with education <= 8 years was 1.31 (1.20 to 1.44) (p<0.0001). Modifiable lifestyle factors (smoking, exercise, consumption of vegetables and fruits, alcohol and abdominal obesity) explained about half of the socioeconomic gradient. Family income, numbers of possessions and non-professional occupation were only weakly or not at all independently related to AMI. In high-income countries (World Bank Classification), the risk factor adjusted OR associated with low education was 1.61 (1.33 to 1.94), whereas it was substantially lower in low-income and middle-income countries: 1.25 (1.14 to 1.37) (p for interaction 0.045). Conclusion: Of the SES measures we studied, low education was the marker most consistently associated with increased risk for AMI globally, most markedly in high-income countries.