Gender Gap in Risk of Incident Myocardial Infarction
Is the risk of incident myocardial infarction (MI) different between men and women?
The Tromsø study was a population-based prospective study from Norway, which included adults (both men and women), aged ≥20 years, during 1979-2008. Primary exposures of interest included sex, age, birth cohort, serum lipid levels, blood pressure, lifestyle factors, and diabetes. The primary outcome of interest was incident MI. Diagnostic information including dates of MI were assessed retrospectively by linking to information from the local hospital discharge register and the national Cause of Death Registry by means of unique personal identification numbers.
A total of 33,997 adults (51% women) were included. Median follow-up duration was 17.6 years, during which time 2,793 adults experienced an MI. Women experienced 886 of these MI events. With increasing age, the incident rate of MI increased for both sexes. However, lower rates of MI were observed among women compared to men until the age of 95 years. After adjusting for age and birth cohort, the overall incident rate ratio (IRR) was 2.72 (95% confidence interval [CI], 2.50-2.96) for men versus women. Adjustment for high-density lipoprotein cholesterol and total cholesterol had the strongest impact on risk estimates for sex, followed by diastolic blood pressure and smoking. Sex remained a significant factor in risk for MI (IRR, 2.07; 95% CI, 189-226). Men had a higher risk throughout life, but the IRRs decreased with age.
The investigators concluded that the observed sex contrast in risk of MI cannot be explained by differences in established coronary heart disease risk factors. The gender gap persisted throughout life, but declined with age as a result of a more pronounced flattening of risk level changes in middle-aged men. The minor changes in IRs when moving from premenopausal to postmenopausal age in women make it unlikely that changes in female hormone levels influence the risk of MI.
These data suggest that risk of MI related to MI for women is not simply related to changes in hormones (i.e., menopausal status). Furthermore, gender differences in MI appear to not be fully explained by traditional risk factors. Given the increase in morbidity and mortality among women with MI, we clearly need to improve our understanding of the gender-related differences related to MI.
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