PREVALENCE, DETERMINANTS, AND MISCLASSIFICATION OF MYOCARDIAL-INFARCTION IN THE ELDERLY

We evaluated the prevalence, determinants, and misclassification of di fferent types of myocardial infarction in 3,272 men and women age 55 y ears or older. We defined self-reported myocardial infarction with ele ctrocardiographic evidence as ''typical myocardial infarction.'' We de fined self-reported myocardial infarction without electrocardiographic evidence, but verified with additional clinical information, as ''non -Q-wave myocardial infarction.'' Finally, we defined myocardial infarc tion detected by electrocardiogram that was not self-reported as ''sil ent myocardial infarction,'' after verification of absence of symptoms . Overall, the prevalence of typical myocardial infarction was 4.1% [9 5% confidence interval (CI) = 3.5-4.9], of non-Q-wave myocardial infar ction 2.8% (95% CI = 2.2-3.4), and of silent myocardial infarction 3.9 % (95% CI = 3.2-4.5). Silent myocardial infarction was more prevalent in women, hypertensives, cigarette smokers, and those with higher post -load blood glucose. Self-reported myocardial infarction without elect rocardiographic characteristics could be verified as myocardial infarc tion by means of additional clinical information in 56% of the cases. We conclude that myocardial infarction occurs frequently in the elderl y without typical symptoms or electrocardiographic changes. As all the se manifestations of myocardial infarction convey an increased risk of symptomatic heart disease or death, they require further attention. M isclassification due to limited sources of information can be consider able and should be taken into account in the design and interpretation of epidemiologic studies.