An aspirin a day: will it help or hurt you?
For people with cardiovascular disease—coronary heart disease, stroke, or peripheral artery disease—taking aspirin regularly can help prevent a future heart attack or stroke. However, it has been unclear whether regular aspirin therapy reduces the risk of heart attack and stroke in people without cardiovascular disease.
On the negative side, taking aspirin regularly may increase the risk of bleeding in the stomach and intestines (gastrointestinal bleeding). And to complicate matters more, aspirin appears to have different effects on different types of strokes: reducing the risk of stroke due to blockage of blood vessels in the brain (ischemic stroke) but increasing the risk of stroke due to bleeding in the brain (hemorrhagic stroke).
The authors of a recent study published in the Annals of Internal Medicine analyzed several studies on the subject (meta-analysis) in an effort to weigh the benefits and risks of aspirin therapy in people without known cardiovascular disease.
About the study
Researchers from the University of North Carolina and the Research Triangle Institute searched the U.S. National Library of Medicine's MEDLINE database for two types of studies:
- Studies of aspirin's ability to prevent cardiovascular events (i.e., heart attack and stroke)
- Studies of the adverse effects of regular aspirin therapy (i.e., hemorrhagic stroke and gastrointestinal bleeding)
Before analyzing the studies, the researchers assessed the quality of the studies in terms of:
- How participants were selected and assigned to treatment groups
- If a placebo (inactive pill) was used in the control group
- If participants and researchers knew which participants were taking aspirin
- How the data was analyzed
- How many participants failed to complete the study
Only studies deemed to be of good quality were analyzed for this meta-analysis. The researchers analyzed five studies of aspirin's effectiveness in preventing cardiovascular events and nine studies of aspirin's effect on the risk of hemorrhagic stroke and gastrointestinal bleeding.
After analyzing the data from all the studies, the researchers used statistical modeling techniques to estimate the risks and benefits of aspirin therapy in people with varying degrees of risk of coronary heart disease.
Overall, the pooled data suggest that aspirin therapy reduced the risk for coronary heart disease by 28%. However, aspirin therapy did not seem to have an effect on the risk of stroke.
Analysis of the pooled data also suggest that people taking regular aspirin therapy were 1.5 to 2 times more likely to experience gastrointestinal bleeding. In addition, aspirin therapy may have increased the rate of hemorrhagic stroke by up to 40%.
The study authors explain that based on the type of people in the studies they analyzed, these results are most applicable to men between the ages of 50 and 65 who are taking low-dosage aspirin of 162 mg per day or less. Note: 162 mg is one-half of a regular aspirin tablet (325 mg each) or two baby aspirin tablets (81 mg each) or one Halfprin tablet (162 mg each).
There are several limitations to this study. First, it is a meta-analysis, meaning that the researchers collected data from several studies and analyzed it together in an attempt to derive an overall estimate of risk or benefit. Because studies are designed differently, meta-analyses lack a certain degree of precision, though they do help to synthesize data from many similar studies. Second, because very few strokes occurred in these studies, the estimates of stroke risk are less reliable than those of coronary heart disease and gastrointestinal bleeding. Third, the majority of the participants in these studies were men between the ages of 40 and 75, so these findings may not apply to women and people older than 75. Although older people may gain more benefit from aspirin therapy, they may also be at higher risk of bleeding.
How does this affect you?
Based on the findings of this study, the U.S. Preventive Services Task Force recommends that adults at higher risk for coronary heart disease consider regular aspirin therapy. Because taking aspirin regularly may increase your risk of gastrointestinal bleeding and hemorrhagic stroke, regular aspirin therapy is not recommended for adults at low risk for coronary heart disease. In this situation, the potential risks of aspirin may outweigh the potential benefits.
How do you know if you are at risk for coronary heart disease? Your health care provider can estimate your risk for coronary heart disease using a number of risk assessment tools. In assessing your risk, your health care provider will consider factors such as your age, sex, cholesterol levels, blood pressure, family history of coronary heart disease in younger adults, smoking status, and whether or not you have diabetes.
Should you take a low dose of aspirin each day to prevent heart disease? According to the U.S. Preventive Services Task Force, regular aspirin therapy is only recommended for people known to have cardiovascular disease. Before beginning regular aspirin therapy, or any therapy for that matter, ask your health care provider to help you assess the risks and benefits for your specific situation.
Hayden M, et al. Aspirin for the Primary Prevention of Cardiovascular Events: A Summary of the Evidence for the U.S. Preventive Services Task Force.
Annals of Internal Medicine . January 15, 2002;136(2):161-172.
U.S. Preventive Services Task Force. Aspirin for the Primary Prevention of Cardiovascular Events: Recommendations and Rationale.
Annals of Internal Medicine . January 15, 2002;136(2):157-160.
Last reviewed Jan 29, 2002 by ]]>Richard Glickman-Simon, MD]]>
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