Unrecognized myocardial infarction and the risk of stroke

OBJECTIVE: To investigate the relationship between unrecognized myocardial infarction and the risk of stroke in a population-based cohort study. METHODS: We followed 6,439 participants from the Rotterdam Study for stroke until January 2002. Participants were free from stroke, and presence of myocardial infarction was assessed at baseline (1990-1993). We calculated hazard ratios of stroke for persons with unrecognized or recognized myocardial infarction compared with persons without myocardial infarction. Analyses were adjusted for age, sex, and cardiovascular risk factors. RESULTS: In 52,915 person-years of follow-up, 505 strokes occurred. Recognized myocardial infarction was only borderline associated with an increased risk of stroke. Unrecognized myocardial infarction increased the risk of stroke by 76% (age- and sex-adjusted hazard ratio 1.76, 95% CI 1.31 to 2.37). Stratification by sex showed that the increased risk was only found in men (hazard ratio for men 2.53, 95% CI 1.68 to 3.81; hazard ratio for women 1.27, 95% CI 0.82 to 1.96). After adjusting for cardiovascular risk factors at baseline, the risk remained significantly increased in men (hazard ratio for stroke 2.13, 95% CI 1.35 to 3.36). Subtyping of strokes revealed that unrecognized myocardial infarction was particularly associated with cortical ischemic strokes (hazard ratio for men 3.57, 95% CI 1.79 to 7.12). CONCLUSIONS: Men with unrecognized myocardial infarction have an increased risk of stroke.