Taking aspirin can cut the risk of cardiovascular disease in both sexes - but seems to work differently for men and women, research suggests.
Aspirin has many beneficial effects
An analysis by Duke University in North Carolina of more than 95,000 patients found aspirin can cut the risk of heart attack and stroke in healthy people.
However, the drug seemed particularly to cut the risk of heart attack in men, and stroke in women.
The study features in the Journal of the American Medical Association.
It also found that the use of aspirin carries an increased risk of internal bleeding among both sexes, but only in a small minority of cases.
Lead researcher Dr Jeffrey Berger said much of the previous studies into the beneficial effects of aspirin on the cardiovascular system had looked only at men.
As a result, he said, some doctors had been reluctant to prescribe the drug for women because there was such little data.
"But now, the combined data of recent trials involving women demonstrates that women can benefit just as much from aspirin therapy as men."
The Duke researchers examined data from six clinical trials including a total of 95,456 patients, of which 51,342 were women.
The analysis revealed that aspirin conferred a 12% reduction in risk in cardiovascular events for women, and a 14% reduction for men.
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.
Dr Berger said: "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.
"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."
The analysis also found 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.
Belinda Linden, of the British Heart Foundation, said: "Aspirin helps to stop platelets in our blood from sticking together and so prevents clots from forming.
"There are clear benefits from taking aspirin if you have, or are at high risk of having, heart and circulatory disease."
Ms Linden said there had been increasing interest in whether aspirin could also benefit people without any obvious heart and circulatory disease.
She said research had produced conflicting results, suggesting aspiring was not beneficial enough to merit wider use among the general population.
"Although we must always be aware of new research in this important area, it should be noted that aspirin can occasionally lead to bleeding or an allergic reaction and therefore should only be prescribed when its benefits clearly outweigh the risks."