Certain Risk Factors Carry Higher MI Risk in Women Than in Men

Although men are more likely than women to experience myocardial infarction at any age, certain risk factors appear to carry a higher risk of heart attack for women than they do for men, new research shows.

Researchers say the findings underscore the importance of optimized preventive medicine in women, while also raising the possibility for MI rates to equalize between men and women with time, as lifestyle-associated risk factors continue to rise.

“The clinical implications could go in either direction,” one of the study authors, Sanne Peters, PhD (University of Oxford, England), told TCTMD. “The MI rates are still higher in men, but given that diabetes, smoking, and also hypertension, seem to increase the risk of MI more in women than in men, you might argue there is more to gain [in women], given those relative risks increase to a greater extent in women than in men."

Peters continued: "What we took away from this study is that certain risk factors . . . increase [MI] rates to a greater extent in women than in men, but despite that, men still have higher rates of CV events. So, from a population perspective, one might argue that you would still may be better off treating men, given that they have a higher risk overall, but there are also certain low-risk women, such as those with diabetes and those who smoke, who had a much higher risk of MI compared to their nonsmoking and nondiabetic counterparts, than men. It’s a double-edged sword.”

Peters, with first author Elizabeth Millett, PhD, and senior author Mark Woodward, PhD (University of Oxford), reported the results of their study earlier this month in the BMJ.

MI Across the Ages

Previous studies addressing sex differences in cardiovascular disease have established that MI rates are typically lower in women than in men and tend to strike men at a younger age, with this gap narrowing later in life. How risk factors interact with MI risk at different ages, and how these differ between the sexes, has not been as well studied.

To address these questions, investigators dug into the UK Biobank, a prospective registry of more than half a million men and women in the United Kingdom recruited between 2006 and 2010, then linked this information with nationwide hospital admissions data as well as mortality records. They zeroed in on the 5,081 subjects (29% women) who were free of cardiovascular disease at baseline but who had an MI during the 7 years’ mean follow-up.

As previous work has shown, rates of MI were higher in men than in women, occurring at a rate of 24.35 per 10,000 person-years for men and 7.76 per 10,000 person-years for women. Hypertension, smoking, elevated body mass index, and presence of diabetes were associated with an increased MI risk for both men and women, but in an important new finding, the presence of each of these risk factors was linked with a higher hazard ratio (HR) for MI in women than in men.

For example, compared with women with no diabetes, women with type 1 diabetes had an eightfold higher risk of MI, which was also three times higher than the HR in men. Type 2 diabetes, on the other hand, carried roughly the same degree of risk for both men and women. The HR associated with smoking, as compared with no smoking, was also greater for women than for men, especially among people smoking 20 or more cigarettes per day. In these heavy smokers, the HR for MI was twice as high in women than in men. Lastly, elevated blood pressure was associated with a more than 80% higher relative risk in women than in men.

“Even though diabetes, smoking, and hypertension had a greater relative impact on the risk of MI in women than in men, at an absolute level, women still had lower rates of MI compared with men,” explained Peters. “So the relative risks for MI associated with certain risk factors are greater among women, but even when women had all the adverse risk factors—smoking, diabetes, and hypertension—they still had a lower absolute rate of CVD.”

In another novel finding, the excess risk conferred by these risk factors in women was similar across age groups, “and that’s something we hadn’t seen before,” Peters said.

Risk Factor Control

The analysis did not look at levels of HbA1c: diabetes was assessed as a yes/no in the database. Investigators also did not have information on LDL or total cholesterol to be able to determine whether risk factor control for either of these two variables differed between men and women. Speaking with TCTMD, Peters noted that she and her co-authors would ideally like to repeat their analysis with this additional information.

What’s already established from randomized controlled trials, however, is that primary prevention medications work, regardless of patient sex.

“If you take the example of statins,” said Peters, “there’s no evidence whatsoever that men benefit more from statins as compared with women and the same is true for diabetes and blood pressure lowering medications.” That said, she continued, “women and men generally show up with a different risk factor profile and that might have an impact, first of all, on whether or not they are treated and, second of all, the benefits they might have.”

A wealth of earlier studies suggest that women are not as aggressively treated as men, she pointed out.

“This paper shows that regardless of the greater relevance of certain risk factors in women, women still have lower rates of MI than men, but it doesn’t mean that women shouldn’t be treated at least equally,” she said. “The main message from this paper is that women should be treated as aggressively as men and certain risk factors should be followed more intensively.”