Study reveals gender differences
Results from a new major study show middle-aged women who take aspirin lowered their risk of having a stroke, but their risk of myocardial infarction (MI) or death from cardiovascular causes was not affected. The therapy, however, did significantly affect the risk of both heart attacks and ischemic strokes in women ages 65 or older. In addition, the study found that taking a vitamin E supplement (600 IU every other day) had no benefit nor added risk for the women.
The Women’s Health Study is the first major trial that focused on the effects of aspirin therapy on women. Previous research had shown that aspirin therapy for men has been associated with a significant reduction in the risk of MI and a nonsignificant increase in the risk of stroke.
The results of the women’s study were published on the web site of the New England Journal of Medicine on March 7 and appeared in the March 31 issue of the journal. The findings also were reported in March at the meeting of the American College of Cardiology in Orlando, FL. The National Institutes of Health’s National Heart, Lung, and Blood Institute and the National Cancer Institute supported the research.
Details of the study
To look at the risk and benefits of low-dose aspirin and vitamin E for women in the “primary prevention of cardiovascular disease and cancer,” researchers in the Women’s Health Study followed almost 40,000 initially healthy women 45 or older. The women received either 100 mg aspirin every other day or placebo. The researchers then monitored the women for 10 years for a first major cardiovascular event.
During follow-up, researchers confirmed 477 major cardiovascular events in the aspirin group and 522 in the placebo, for a nonsignificant risk reduction. There also was a 17% reduction in the risk of stroke in the aspirin group compared to the placebo group. The risk reduction of ischemic stroke was 24%, but the increase in the risk of hemorrhagic stroke was nonsignificant. The aspirin therapy had no significant effect on the risk of fatal or nonfatal MI or death from cardiovascular causes.
Women age 65 or older seemed to benefit most from the aspirin therapy. That subgroup had a 26% risk reduction of major cardiovascular events for those who took aspirin as compared to those who took placebo as well as a 30% risk reduction of ischemic stroke. The subgroup was also the only one in which the women taking aspirin showed a significant reduction in the risk of MI.
The researchers found a greater benefit of aspirin therapy on women who had never smoked or who had quit smoking. The women’s menopausal status, the question of whether the women had used hormone-replacement therapy, or their global cardiovascular-risk status did not change the affect of the aspirin. The women who took the aspirin therapy, however, did experience more side effects related to bleeding and ulcers.
Women in the aspirin group reported 910 instances of gastrointestinal (GI) bleeding, as compared with 751 in the placebo group. Forty percent more women in the aspirin group (127) required transfusions for the bleeding as the placebo group (91).
The benefits of aspirin therapy, even in healthy women age 65 and older, definitely should be weighed against the risks of serious GI bleeding and the potential for increasing hemorrhagic strokes, says Lori Mosca, MD, in a media advisory issued by the American Heart Association (AHA) in Dallas. Mosca is the chair of the association’s writing group for AHA’s evidence-based guidelines for cardiovascular disease prevention in women.
“Many women over the age of 65 have uncontrolled blood pressure, which may increase their risk of hemorrhagic stroke, and this should be taken into consideration,” she explains. “This, along with the GI bleeding risk, may tip the scales against using aspirin therapy in these women. That’s why the decision must be an individual one.”
Mosca also reiterated the steps that women — and men — should follow for reducing their risk of cardiovascular disease: not smoking, eating a healthy diet and being physically active, maintaining a healthy weight, and being sure that their cholesterol and blood pressure levels are controlled optimally. “In diabetics, preventive measures are especially important,” she says.
Why the gender difference?
The differences in the efficacy of aspirin for primary prevention in men and women are not clear and require further study, the researchers say. The finding that aspirin therapy helps reduce the risk of stroke is particularly relevant because women experience a greater proportion of strokes than men. “From a policy perspective, our findings clearly demonstrate the importance of studying women as well as men in major cardiovascular clinical trials,” the researchers say.
The AHA also wants to emphasize that among women with known cardiovascular disease, aspirin therapy is known to be beneficial in reducing heart attacks and strokes. Unless it is contraindicated, those women should receive aspirin therapy, says Alice Jacobs, MD, AHA president. “We want to be sure that these women realize that this study does not apply to them. If they and their doctor have decided that they should be on aspirin, they should continue to take aspirin so they receive the best protection,” she adds.