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News from the Womens Health Study: Aspirin Can Reduce the Risk of Stroke, but Not Heart Attack

June 10, 2008 - 7:30am
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News from the Women’s Health Study: Aspirin Can Reduce the Risk of Stroke, but Not Heart Attack

Every minute of every day, one woman dies of cardiovascular disease (CVD). This translates to 60 women per hour, 1,440 women per day, and half a million women every year. These startling statistics make CVD the number one killer of women in the United States. Cardiovascular diseases affect the arteries that supply blood and oxygen to tissues throughout the body.

The most well-known types of CVD are heart attack and stroke , which most often occur when a clot forms in the arteries that nourish these organs. In the case of stroke, there are two main types. The more common type—ischemic—results from a blocked artery in the brain. A hemorrhagic stroke, which accounts for just 12% of all strokes, but is more likely to cause death, occurs when a vessel bursts and bleeds into the brain.

Preventing blockages is one way to reduce the risk of CVD. Aspirin’s status as a blood thinner makes it a good candidate for this job. Aspirin interferes with the ability of platelets to adhere to one another, which makes the formation of large clots more difficult. Clinical studies have found aspirin to be so effective at reducing blockages that the American Heart Association recommends aspirin therapy for people who have had a major cardiovascular event—heart attack, unstable angina , ischemic stroke or transient ischemic attack (“mini-stroke”)—to help prevent a second such event. This recommendation carries an important caveat: as a blood thinner, aspirin increases the risk of bleeding most anywhere in the body, including the stomach or brain. People at risk for bleeding complications should not take aspirin.

Previous studies have also found a decrease in the risk of heart attack when healthy individuals at risk for CVD take aspirin. However, very few women were enrolled in these trials. The Women’s Health Study set out to determine if giving aspirin therapy to healthy, symptom-free women would lower their risk of having a heart attack, stroke, or dying from CVD. In this study, published in the March 31, 2005 issue of the New England Journal of Medicine , the research team reports that the aspirin-takers had a lower risk of stroke, but no change in their risk for heart attack.

About the Study

The researchers recruited 39,876 women working in the health professions for this study. The women, who were healthy and age 45 or older at the beginning of the study, were randomly assigned to the aspirin or placebo group. All received identical-looking pills so they would not know which group they were in. Those in the aspirin group took a low-dose (100 milligrams) of aspirin every other day, while those in the placebo group took an inactive sugar pill every other day.

The women followed their assigned regimen for ten years. Each year, they were asked about side effects, risk factors, and cardiovascular events. The researchers wanted to see if aspirin takers would have a lower risk of a “first major cardiovascular event”—a nonfatal heart attack, nonfatal stroke, or death from any cardiovascular cause.

The Findings

The researchers found the risk of any first major cardiovascular event was the same whether a woman was taking aspirin or placebo. However, when the events were analyzed individually, aspirin use significantly reduced the risk of stroke. Specifically, aspirin lowered the risk of transient ischemic attacks, ischemic strokes, and all nonfatal strokes. It slightly, but nonsignificantly, raised the risk of hemorrhagic stroke.

The most benefit was seen in women age 65 and older. The aspirin takers in this age group experienced a decreased risk of heart attacks, ischemic strokes, and major cardiovascular events overall.

Bleeding-related side effects occurred more often in the aspirin group than the placebo group. Women taking aspirin were 22% more likely to have gastrointestinal (GI) bleeding and 32% more likely to develop stomach ulcers. This means that six extra women, out of 1,000, would be expected to develop GI bleeding if they took aspirin, and eight extra women, out of 1,000, would be expected to develop stomach ulcers if they took aspirin.

How Does This Affect You?

Even though low-dose aspirin therapy did not effectively lower the risk of heart attack in this large study, it appears to be a valuable tool in reducing a woman’s chance of having a stroke. Does this mean all women should pop an aspirin every-other day? Not quite. Aspirin therapy is not without risks. Internal bleeding occurred slightly more often in women using aspirin.

Before taking aspirin on a regular basis, have a thorough discussion about your risk of cardiovascular disease with your doctor. If your risk is deemed low to average, the adverse effects of aspirin may outweigh its benefits. However, if you fall into the high-risk category, or if you’ve already had a heart attack or ischemic stroke, the benefits of low-dose aspirin may outweigh its harm. If you are a woman age 65 or older, the benefits appear to extend to heart attack as well as stroke.

In addition to considering aspirin, all women (and men) of any age can safely help minimize their risk of cardiovascular disease by:

  • Eating a heart healthy diet
  • Engaging in regular physical activity
  • Achieve and maintaining a healthful weight
  • Not smoking

Additionally, most women (particularly older women) can benefit from regular screening tests for cholesterol, blood pressure, and blood sugar.


American Heart Association

American Stroke Association

National Heart, Lung, and Blood Institute


American Heart Association. Aspirin in heart attack and stroke prevention. Available at: http://www.americanheart.org/presenter.jhtml?identifier=4456 Accessed March 9, 2005.

American Stroke Association. Heart disease and stroke statistics – 2005 update . Available at: http://www.americanheart.org/downloadable/heart/1105390918119HDSStats2005Update.pdf Accessed March 9, 2005.

Ridker PM, Cook NR, Lee I, et al. A randomized trial of low-dose aspirin in the primary prevention of cardiovascular disease in women. New England Journal of Medicine . 2005;352.

Statement on the findings of the Women’s Health Study from Elizabeth G. Nabel, MD, Director of the National Heart, Lung, and Blood Institute of the National Institutes of Health. Available at: http://www.nhlbi.nih.gov/new/press/05-03-07.htm Accessed March 9, 2005.

Last reviewed Mar 11, 2005 by Richard Glickman-Simon, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.



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