Any lingering doubts are now dispelled. Taking a low-dose aspirin every day is as valuable for middle aged and older women as it is for their male peers…just not in exactly the same way.

In the first major study of women and aspirin, researchers found that middle aged women (45 to 65 years old) who took a low-dose aspirin every day lowered their overall risk of stroke by 17 percent and their risk of stroke caused by blood clots by 24 percent. Among older women (over 65), those taking aspirin had a 30 percent less chance of stroke and a 34 percent reduced chance of heart attack. However, the aspirin had no significant impact on heart attacks in middle aged women.

Studies dating back to the 1980s had previously demonstrated that aspirin protects middle aged and older men from heart attack and, to a lesser degree, from stroke. Though not typically recommended for healthy men (because of possible side effects), aspirin is widely prescribed to prevent recurrence of heart attacks in men who have already suffered one. Over the last decade, many healthy men have adopted the practice as well.

Heart attack and stroke are often caused by blood clots. When clots occur in blood vessels in or around the heart, impeding blood flow to and from that organ, they can cause heart attacks. When they occur in blood vessels in the neck, they affect blood flow to the brain, causing a stroke.

On the basis of a large, 10-year study of female health professionals, researchers at Harvard University demonstrated the positive health affects of aspirin for women. Aspirin reduces the risk of stroke for women of all ages. However, “in contrast to men,” said Dr. Elizabeth Nable, director of the National Heart, Lung and Blood Institute, “aspirin did not reduce the risk of nonfatal or fatal heart attacks in women of all ages but did so in women over 65.”

Because stroke is a broader problem among women than men and heart attack is more common among men than women, the impact of aspirin in each appears neatly matched to that gender’s greatest need. On the basis of the mounting research and demonstrated results, it seems likely that doctors will increasingly recommend a daily aspirin regiment for all middle aged or older patients who can tolerate the side effects.

The side effects of aspirin are considered minor, but for certain individuals, they can be serious. For the same reason that it helps prevent heart attacks and stroke – in effect, by “thinning” the blood – aspirin can increase the risk of bleeding that is induced by an injury or another disease. It also can cause stomach irritation and, among chronic alcohol users, stomach bleeding. Ringing in the ears, though temporary, is sometimes a problem until aspirin use is discontinued. Also, some people are allergic to aspirin and experience facial swelling and other allergic reactions.

Anyone who thinks they are a candidate for aspirin therapy should consult with their doctor before beginning regular use.