Does Aspirin Benefit Men and Women Differently?

Jan. 17, 2006 — -- It's no secret that aspirin may reduce the risk of heart attacks and strokes for some men and women, but a new study reveals it may help them in different ways.

Aspirin therapy was associated with a 17 percent reduction in strokes among women and a 32 percent reduction in heart attacks among men, according to a new comprehensive analysis of research published in this week's Journal of the American Medical Association.

"The specific types of benefits differ in important ways ... in women, by reducing the risk of ischemic stroke, and in men, by reducing the risk of heart attack," said Dr. David L. Brown, director of cardiovascular medicine at State University New York-Stony Brook and an author of the study.

Interestingly, "among women, aspirin had no significant effect on the risk of [a heart attack]," according to the authors of the study, which analyzed data from six past clinical trials. When totaled together, the data included more than 95,456 patients -- including 51,342 women -- with no previous heart problems.

Many experts said the findings are unlikely to change how doctors currently prescribe aspirin, but Brown said it may influence the way doctors use risk calculators, a formula that physicians use to predict the chance that an individual will develop a heart attack over the next decade of his or her life.

"It does not make intuitive sense in women to use risk calculators for heart attacks when in fact aspirin is not going to affect that risk," he said. "We need to develop a risk calculator for risk of first stroke in women and then apply that information to whether an individual woman should take an aspirin."

Dr. Jeffrey S. Berger, the main author of the study and a cardiology fellow at Duke University, added that the sex difference needs further investigation.

"We know that men and women have different metabolic responses to aspirin," he said.

Also, he said a greater reduction in strokes among women and heart attacks among men could be because statistically a greater proportion of women have strokes and men have heart attacks.

But, "the numbers of people in the meta-analysis are so high that this is likely not the only reason," Berger said.

However, Dr. Charles H. Hennekens, a research professor of biomedical science at the Center of Excellence at Florida Atlantic University, said the gender-difference findings could be questioned.

Hennekens noted that a majority of the women in the studies were younger than 65, and so were not as prone to heart attacks as women of that age but were still at risk for strokes. He also said that in previous trials women who were older than 65 had a reduction in heart attack risk similar to men's.

"We simply need more [data]," he said.

The study did find that aspirin could increase the risk of major bleeding regardless of sex. So the decision to start taking an aspirin a day is to be made between patients and their physicians, Berger said.

Dr. Rajesh V. Swaminathan is a resident at Massachusetts General Hospital.