Aspirin To Prevent Cardiovascular Disease In Women — Is The Picture Any Clearer?

The Women’s Health Study published in the New England Journal of Medicine on March 31, 2005 , has helped clarify the effect of aspirin on the prevention of cardiovascular disease (heart attack or stroke) in older women. Preventing a first heart attack or stroke is called primary prevention. The prevention of a second serious outcome in people who have already had a heart attack or stroke is known as secondary prevention.

Aspirin is approved by the Food and Drug Administration (FDA) for the secondary prevention of heart attack and stroke. The U.S. Preventative Services Task Force presented solid evidence in 2002 suggesting that aspirin is beneficial in the primary prevention for patients at a high risk of these serious events. However, before the release of the Women’s Health Study, the recommendations for the use of aspirin as primary prevention in women were based on limited data.  

The Women’s Health Study is the first randomized clinical trial designed specifically to evaluate the effect of aspirin for primary prevention of cardiovascular disease in women 45 years of age and older. Randomized controlled trials are the scientific “gold standard” for drug research. The study evaluated over 39,000 female health professionals in the U.S.over a 10 year period. The women in the study were generally healthy. Only 2.6 percent of women in the placebo group experienced a major cardiovascular event during the 10-year period they were followed.

A commentary published in the June 7, 2005 Annals of Internal Medicine reviewed the results of the Women’s Health Study and placed in context the extent to which this study has helped in understanding the effect of aspirin in women.

The Women’s Health Study showed that aspirin might not affect the incidence of heart attack, reduces the incidence of a type of stroke that results from reduced blood flow in the brain known as ischemic stroke, and probably has little or no effect on death from all causes. Women over 65 years of age benefited more from aspirin than did younger women. In this age group, aspirin reduced the risk of both ischemic stroke and heart attack. Adverse effects included a possible increased risk for hemorrhagic stroke (stroke due to bleeding) and a definite increased risk for major gastrointestinal (GI) bleeding.

Overall, the women in the study were at a low risk for a cardiovascular event. The finding that aspirin was more effective at preventing heart attacks among older women supports the assumption that benefits of aspirin may be greater in women with higher risk of cardiovascular disease.

This table summarizes the results of the study:

Low-dose aspirin had little or no effect on death from all causes in the 1,000 healthy women who took it over a ten-year period. Evidence for a benefit for the heart is also unclear. With regards to the question of stroke prevention, patients must balance the potential benefit of aspirin — ischemic strokes prevented — versus its potential harm — increased risk of hemhorragic strokes and GI bleeding. At best, two to three women and at fewest one to two women per 1,000 could receive a net benefit from the drug.

The study did suggest that women 65 years of age and older who are presumably at a higher baseline risk for cardiovascular disease may benefit more from aspirin than younger women. The adverse effects of aspirin include GI bleeding, the possibility of hemorrhagic stroke (an uncommon form of stroke), easy bruising, nosebleeds, and blood in the urine.

Early aspirin primary prevention studies done in the 1980s and 1990s were conducted primarily in men. These studies found that aspirin reduced heart attacks but had little effect on ischemic stroke. Because few women were included in these studies, the results were inconclusive about whether aspirin affected men and women differently.

The Women’s Health Study does provide valuable information, but it does not conclusively prove that the effects of aspirin in men and women are different. At similar levels of risk, women are more likely to have strokes than heart attacks. Men exhibit an opposite pattern, suffering from more heart attacks than strokes. At this time, there is little evidence to favor a difference in aspirin’s effectiveness based on gender.

The primary prevention of cardiovascular events through the use of a pharmaceutical in large, healthy populations always presents the possibility of harm — even with an old, well-understood over-the-counter drug like aspirin. For healthy women there is a non-pharmacological option to reduce the risk of cardiovascular disease — dietary and life-style changes.

What You Can Do

If you are healthy, you should not undertake aspirin treatment for the primary prevention of cardiovascular disease without consulting your physician about whether you are at high enough risk to benefit.