Aspirin and women — age matters

Aspirin can help healthy women over age 65 prevent both strokes and heart attacks. For younger women, the hazards of aspirin outweigh the benefits.

(This article was first printed in the May 2005 issue of the Harvard Heart Letter. For more information or to order, please go to www.health.harvard.edu/heart.)

Ever since a landmark trial in male physicians revealed in 1988 that aspirin helps prevent a first heart attack in men, the question “Does aspirin work for women, too?” has been crying out for an answer.

The search for that answer began almost immediately. The research team at Harvard-affiliated Brigham and Women’s Hospital that led the Physicians’ Health Study convinced the National Heart, Lung, and Blood Institute that a similar trial in women was vitally important. Thus was born the Women’s Health Study.

Principal investigator Julie E. Buring and her colleagues recruited almost 40,000 female health professionals who were at least 45 years old for a 10-year trial. Half the women took a tablet containing 100 milligrams (mg) of aspirin every other day. The other half took an identical, equally bitter-tasting placebo. (In an effort to kill two birds with one stone, the study also included vitamin E. On the days the women didn’t take the aspirin or the aspirin look-alike, half of each group took vitamin E and half took an identical placebo.)

Over the course of the trial, national recommendations and guidelines generally took a conservative approach, urging women to hold off until the results were in from the Women’s Health Study. That wasn’t easy, given aspirin’s strong benefit in men. Millions of women, figuring what’s good for the gander is good for the goose, took aspirin to prevent a heart attack.

Waiting might have been a better option.

The results, please

The findings from the Women’s Health Study weren’t the crystal-clear slam-dunk the investigators had been hoping for. In a nutshell, the study showed that aspirin may affect women’s hearts differently than men’s, and that age really matters.

Let’s look at results from the entire 40,000 women first. Aspirin had no effect on heart attacks, nor did it influence deaths from heart disease or stroke. It did prevent some strokes, reducing the risk by 17%. That’s an important finding, since more women have strokes each year than heart attacks. This is the reverse of what studies have shown in men — that aspirin prevents heart attacks but seems to have little effect on stroke.

Most of the volunteers were under age 65 when the trial began. In these younger women, the small benefit of aspirin was counterbalanced by the risk of bleeding problems.

Here’s where the story gets more interesting. About 10% of the volunteers were age 65 or older when the trial started. In this group, aspirin prevented a significant number of strokes and heart attacks. In fact, the impact on heart attack was in the same ballpark as it was for men in the Physicians’ Health Study.

Aspirin is so cheap that if it were a completely safe drug, it wouldn’t matter much who took it. If it helped, fine. If it didn’t, nothing would be lost. Unfortunately, that’s not the case.

Aspirin’s dark side

When it comes to the heart, aspirin’s magic is in its ability to prevent blood clots. These clumps of red blood cells, platelets, and stringy proteins can block blood vessels feeding the heart and brain. Yet allowing blood to clot less readily increases bleeding, and so can harm as well as help.

Taking aspirin can cause bleeding in the gut and elsewhere. It has also been linked with an increased risk of bleeding (hemorrhagic) strokes. Results from the Women’s Health Study outline the hazards of aspirin specifically for women.

There were slightly more hemorrhagic strokes among women who took aspirin. Gastrointestinal bleeding, sometimes serious enough to require a transfusion, happened significantly more often among aspirin takers than placebo takers. Nosebleeds, blood in the urine, and easy bruising were reported by women in both groups but were more common in the aspirin group.

What it all means

In the most general terms, an aspirin a day is a good idea for some healthy women over age 65, but not for most younger women. Again, keep in mind that we are talking about primary prevention here — efforts designed at preventing a heart attack or stroke in people who do not have heart disease. Aspirin is recommended for most women (and men, for that matter) with heart disease or characteristics nudging them toward it.

Is aspirin right for you? Many factors influence whether aspirin will probably help you, harm you, or have little effect. Your age is one of the most important. Other factors that enter into the calculation include your risk for heart disease and stroke, prior gastrointestinal bleeding, and other lifestyle and clinical factors.

“This is an individual decision that must be made by sitting with your doctor or health care provider and weighing the chances of having a stroke or heart attack against the risks of taking aspirin on a regular basis,” cautions Dr. Buring.

Another report from the Women’s Health Study, presented at the American Academy of Neurology meeting in early April 2005, offers another way to prevent stroke — clean living. The stroke rate among women in the study who exercised at least four times a week, didn’t smoke, maintained a healthy weight, ate a heart-healthy diet, and had an alcoholic drink a day was almost half that among women without these healthful habits. And they didn’t face the side effects of aspirin.

(This article was first printed in the May 2005 issue of the Harvard Heart Letter. For more information or to order, please go to www.health.harvard.edu/heart.)

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