However, the researchers found, the major reasons for the risk reduction differed between the sexes. For men, aspirin lowered the risk of a heart attack, while in women, aspirin reduced the risk of a stroke.
The use of aspirin, however, also carries an increased risk of bleeding among both sexes, the study found. The results of the new analysis lead the researchers to recommend that all patients and physicians should discuss the benefits and drawbacks of regularly taking aspirin as a preventative measure against cardiovascular events.
"Aspirin is a drug that has been used for many years ?it is well-understood, effective, inexpensive and widely available," said Duke cardiology fellow Jeffrey Berger, M.D, first author of a paper published Jan. 18, 2006, in the Journal of the American Medical Association. He performed much of the research while at Beth Israel Medical Center, New York, under senior author cardiologist David Brown, M.D.
"This is good news because many of the past studies of the effect of aspirin in preventing cardiovascular events looked only at men, so physicians were reluctant to prescribe aspirin for women because there was little data," Berger continued. "But now, the combined data of recent trials involving women demonstrates that women can benefit just as much from aspirin therapy as men."
Berger emphasized that more healthy men and women who can tolerate aspirin should be taking the medication for the prevention of cardiovascular disease. It is estimated that fewer than five percent of the population suffers from the known gastrointestinal side effects of aspirin or are allergic to it, meaning that many more serious cardiovascular events could be prevented if aspirin was more widely used, Berger said
In his analysis, Berger combined the data from six different randomized clinical trials, which yielded a total of 95,456 patients, none of whom had coronary artery disease. Of that total, 51,342 were women. The trials all involved the comparison of low-dose aspirin versus placebo for the primary prevention of cardiovascular disease.
The analysis revealed that aspirin conferred a 12 percent reduction in risk in cardiovascular events for women, and a 14 percent reduction for men.
"Our findings are particularly noteworthy in that aspirin's main beneficial effects appeared to be the reduction in the risk of stroke for women and reduction in the risk of heart attacks for men," Berger said. "While our analysis showed that aspirin may have different effects in men and women, the relatively small number of heart attacks among women and strokes among men suggest that more research is needed to better understand any differences in cardiovascular responses to aspirin."
Specifically, among the 51,342 women in the analysis, there were 625 strokes and 469 heart attacks. Among the 44,114 men, there were 597 strokes and 1,023 heart attacks.
However, the routine use of aspirin does not come without potential risks, especially in terms of major bleeding episodes. The analysis found that routine aspirin use for an average of 6.4 years would lead to 2.5 major bleeding events per 1,000 women and 3 major bleeding events per 1,000 men.
"For this reason, while we believe that many more people could benefit from taking aspirin, it is important for patients and their physicians to discuss the issue and weigh the benefits and potential drawbacks to this therapy," Berger said. "Also, aspirin should never replace other ways of reducing cardiovascular risks, such eating a proper diet and exercising."
Of the six randomized clinical trials involved in the a nalysis, three enrolled solely men, one included only women, and two enrolled both sexes. The trials were: Physicians Health Study, British Doctor's Trial, Thrombosis Prevention Trial, Hypertension Optimal Treatment Trial, Primary Prevention Project and the Women's Health Study.