Incidence of myocardial infarction in women. A cohort study of risk factors and modifiers of effect

STUDY OBJECTIVE: To assess whether the increased incidence of myocardial infarction and death associated with smoking, hypertension, hyperlipidaemia and diabetes varies significantly between groups defined in terms of occupation, education and marital status. SETTING: Malmo, Sweden. PARTICIPANTS: 9351 women, aged 28-55, with a mean follow up of 10.7 years. MAIN RESULTS: Smoking, hypertension (> or = 160/95 mm Hg or treatment), hyperlipidaemia (cholesterol > or = 6.5 mmol/l or triglycerides > or = 2.3 mmol/l), diabetes, low occupation and education levels were significantly more common among women who experienced a fatal or nonfatal myocardial infarction during the follow up (n = 104) than in other women (n = 9247). Exposure to smoking, hypertension and hyperlipidaemia showed substantial differences between groups defined in terms of education, occupation and marital status. The association between low occupation and myocardial infarction remained statistically significant after adjustments for several potential confounders (RR = 2.6, 95% CI 1.1, 6.0). Single women had similarly higher adjusted mortality rates than married women (RR = 1.4, 95% CI 1.1, 1.8). When other major risk factors were taken into account, the relative risk for mortality and myocardial infarction associated with smoking was 2.6 (95% CI 2.0, 3.4) and 7.8 (95% CI 4.4, 13.9), respectively. CONCLUSION: In this urban female population, short education and low occupation level were both associated with an increased prevalence of smoking, hypertension, hyperlipidaemia and diabetes. Low occupation level increases the rate of cardiac events caused by exposure to these four risk factors.