Aspirin for Primary Prevention of Strokes and Heart Attacks
Henry I. Bussey, Pharm.D., FCCP, FAHA
April, 2009
The March 17, 2009 issue of Annals of Internal Medicine contains three important articles for those weighing the risks and benefits of taking aspirin for the prevention of heart attacks and stroke. The three articles are summarized briefly below:
First of Three articles:
Wolff T, Miller T, Ko S. Aspirin for the primary prevention of cardiovascular events : An update of the evidence for the U.S. Preventive Services Task Force. Annals of Internal Medicine. 2009; 150(6):405-410.
This publication reviews the literature and reaches the conclusion that aspirin reduces the risk for myocardial infarction in men and the risk for ischemic stroke in women; but the authors also conclude that aspirin increases the risk of serious bleeding. Closer scrutiny also indicates that aspirin increases the risk of hemorrhagic stroke in men by about 69%, but the increase in hemorrhagic stroke in women was only 29%, which was not statistically significant.
Second of Three articles:
U.S. Preventive Services Task Force. Aspirin for the prevention of cardiovascular disease: U.S. Preventive Services Task For Recommendation Statement. Annals of Internal Medicine. 2009; 150(6): 396-404.
The summary recommendations of this report are that:
- Men 45 to 79 years of age be "encouraged" to take aspirin "when the potential benefit of a reduction in myocardial infarction outweighs the potential harm of an increase in gastrointestinal hemorrhage."
- Women age 55 to 79 years be "encouraged" to use of aspirin when the potential benefit of a reduction in ischemic strokes outweighs the potential harm of an increase in gastrointestinal hemorrhage.
- Evidence is insufficient to make recommendations for men or women over 80 years of age.
- Use of aspirin not be encouraged in women younger than 55 years and men younger than 45 years.
Although the summary of the recommendations does not address the increased risk of hemorrhagic stroke related to aspirin, the body of the article contains a nice table that allows one to exam the number needed to help (based on 10-year risk of a cardiovascular event) vs. the number needed to harm (based on gastrointestinal hemorrhage and hemorrhagic stroke risk due to aspirin). The risk of developing cardiac disease can be quickly calculated online at http://healthlink.mcw.edu/article/923521437.html. Because the risk of harm from major bleeding increases with age and the potential for benefit with aspirin increases with higher 10-year cardiovascular risk, the point at which the risk and benefit are similar can be approximated (see table).
Age and cardiovascular risks at which the benefits and risks approximate each other (increasing age leads to increased risk of bleeding while increased 10-year cardiovascular risk leads to increased benefit of aspirin).
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Men
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Women
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Age groups
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% 10-yr Card. risk
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Age groups
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% 10-yr Card. risk
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45 - 59 yrs
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> 4
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55 - 59 yrs
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> 3
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60 - 69 yrs
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> 9
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60 - 69
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> 8
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70 - 79 yrs
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> 12
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70 - 79
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> 11
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For any age group, a 10-year card. risk profile greater than the figure listed in the table would favor aspirin therapy. Adapted from USPSTF report. Ann Intern Med 2009; 150:396-404.
Third of Three articles:
Mehta SR. Aspirin for prevention and treatment of cardiovascular disease. Annals of Internal Medicine 2009; 150(6):414-416
This editorial reviews the recommendations for aspirin use described and provides further insight into the analysis. For instance, the author questions the wisdom of making recommendations based on gender when conclusions are based on post-hoc analysis and a limited number of studies that included women. Also examined is the issue of personal preference in weighing different potential end points. For example, would a patient prefer to have a myocardial infarction (MI) or a gastrointestinal bleed? If the bleed is favored, how many bleeds would one be willing to trade for one MI. Alternatively, a hemorrhagic stroke may be more devasting than an MI or an ischemic stroke.
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