Aspirin Prophylaxis Cuts Strokes in Healthy Women

By Mitchell Zoler

ORLANDO -- Among women at least 65 years old, a regimen of 100 mg of aspirin every other day cut the incidence of ischemic stroke, MI, and all major cardiovascular disease (CVD) events, while causing a small number of adverse events, according to the Women's Health Study. Among women younger than 65, the benefit was limited to cutting the risk of ischemic strokes, and the reduction was so modest that aspirin prophylaxis will have to be targeted to a select group of women.

"For women 65 and older, the risk and benefit balance may tip toward benefit, but for women younger than 65, patients and physicians will need to look very carefully," Julie E. Buring, Sc.D., said at the annual meeting of the American College of Cardiology.

The Women's Health Study highlighted differences in how CVD plays out in women, compared with men. Strokes were more common in women than MIs, and aspirin's benefit was largely in stroke prevention. In contrast, prior studies in healthy men, including the similarly designed Physicians' Health Study, showed MIs were the primary threat and aspirin prophylaxis was greatest for MI prevention.

"The results show the danger of generalization," said Paul M. Ridker, M.D., Brigham and Women's Hospital in Boston and co-principal investigator for the study along with Dr. Buring.

For example, in 2002, American women had 373,000 new strokes and 345,000 new MIs, said Dr. Buring, a professor of epidemiology at Harvard School of Public Health, Boston. In contrast, men had 520,000 new MIs and 323,000 new strokes.

The study enrolled 39,876 healthy, female health professionals during the early 1990s who reported their baseline health data by returning a questionnaire. In general, these women had few CVD risk factors. As rated by the Framingham Risk Score, 84% of the enrollees had a less than 5% risk of coronary heart disease in the ensuing 10 years, 12% had a 5%-9.9% risk, and 4% had a risk that was 10% or greater for developing coronary heart disease during the 10 years after they entered the study. The women were randomized to the aspirin regimen or placebo, over an average follow-up of 10.1 years. During follow-up, 999 participants had a first, major cardiovascular event: nonfatal MI, nonfatal stroke, or death from cardiovascular causes.

The rate of major cardiovascular events, the study's primary end point, was about 2.4% in the women who took aspirin and about 2.6% in those who didn't, a relative risk reduction of 9% that failed to reach significance. But the rate of ischemic stroke was cut by aspirin use by a relative rate of 24%, which was significant, Dr. Ridker reported. Concurrent with the meeting, results were published in the New England Journal of Medicine