Myocardial infarction (MI) before the age of 55 has traditionally been thought of as a man's disease, but two recent studies of sex-specific trends in heart disease reveal some good news and some bad news for women. Although the gap in hospital mortality after acute MI between younger men and younger women has narrowed (it had been higher in women), middle-aged women are gaining on their male counterparts in terms of prevalence of MI and cardiovascular risk-factor scores.
The investigators in each of the studies attribute the changing patterns to changing trends in risk factors. However, both sets of data confirm that the cardiovascular risk-factor burden (the overall risk profile) is worsening among women.
The bad news: MIs and cardiovascular risk factors in women are increasing. Towfighi and colleagues used data from two phases of the National Health and Nutrition Examination Survey (NHANES) to examine changes in the sex-specific prevalence of MI and in the Framingham coronary risk score (FCRS) among U.S. adults 35 to 54 years old. The first phase of the NHANES was conducted from 1988 through 1994; the second phase, from 1999 through 2004.
Although the prevalence of MI decreased among men, from 2.5% during the first phase of the NHANES to 2.2% during the second phase, it increased among women, from 0.7% to 1.0%, respectively. Among those without a history of MI, the mean FCRS declined in men between the first and second surveys but remained stable in women.
When looking at the individual components that make up the FCRS, only one, the level of high-density lipoprotein (HDL) cholesterol, improved in women. Total cholesterol levels, systolic blood pressure, and the prevalence of smoking remained stable, and the prevalence of both diabetes mellitus and obesity increased. In contrast, men showed improvements in HDL cholesterol, systolic blood pressure, and the prevalence of smoking, but their rates of diabetes and obesity also increased.
One possible explanation for this narrowing gap is a relative inattention to cardiovascular risk factors among younger women, who may believe they're at greater risk for other diseases, such as cancer. In addition, prevention campaigns have largely focused on men because of their historically higher risk of MI, said the study's lead author, Amytis Towfighi. "In the past we thought that this age group of women was protected against heart disease," she said. "Although their rates are still lower than men's, they're going up, so women are not absolutely protected. The take home message is that we have to be more aggressive in identifying and treating cardiovascular risk factors in women."
The good news: mortality after MI is declining in younger women. Meanwhile, hospital mortality after MI is declining more among younger women than among younger men, and this can be largely explained by changes in risk profiles over time, according to a study by Vaccarino and colleagues.
Using data from the National Registry of Myocardial Infarction, a prospectively collected database of patients admitted with acute MI at approximately 1,600 hospitals nationwide, the researchers examined case fatality rates of MI from 1994 through 2006. Hospital mortality rates declined over time in both sexes in all age groups, but the decline was largest (52.9%) in the women younger than 55 and smallest (33.3%) in the men younger than 55. The absolute (unadjusted) decrease in hospital mortality was three times greater in women younger than 55 than in their male counterparts (absolute reductions of 2.7% and 0.9%, respectively).
Women were less likely than men to undergo coronary catheterization and revascularization procedures, so in-hospital treatment could not account for the narrowing of the gap in the mortality rates between younger women and younger men, according to the report. However, most of the change in the rates can be explained by improvements in women's risk status on admission over time.
Noting the worsening risk profiles in both sexes in the study, the report's lead author, Viola Vaccarino, said, "We need to make sure that people at high risk are recognized early enough, so intervention can be started. We need to focus on many behavioral risk factors that are among the strongest risk factors for heart disease," such as a poor diet, a low level of physical activity, poor adherence to medication regimens, and smoking.
Wayne Kuznar