Adults and Aspirin

Does Every Adult Patient Need Aspirin?

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Your patients are likely to ask you about a meta-analysis just published in the Archives of Internal Medicine showing that while aspirin may reduce the risk of heart attack in middle-aged adults without known heart disease, the benefits are only modest.[1] In addition, aspirin appeared to confer no significant protection against stroke or fatal heart attack, and the benefits against a nonfatal heart attack were offset by clinically important bleeding events.

The meta-analysis included nine randomized placebo-controlled trials with a total of 102,621 participants without a prior history of cardiovascular disease (CVD) or stroke. During a mean follow-up of six years, treatment with aspirin reduced total cardiovascular events by 10%, which was driven primarily by a 20% reduction in nonfatal heart attacks. There was no significant reduction in cardiovascular deaths or cancer mortality. However, there was a 70% increased risk of bleeding events, 30% of which were considered “nontrivial.” The number needed to treat to prevent one nonfatal heart attack was 162, compared with a number needed to harm of 73 for causing a nontrivial bleed. In other words, for every two patients that take aspirin to prevent a nonfatal myocardial infarction (MI), two patients will have a significant bleeding episode.

Of note is that this study found no association between aspirin and chemoprevention. This contradicts the findings from a 2011 meta-analysis showing that aspirin has a protective effect against several different kinds of cancer.[2] This may be due to the length of follow-up in the nine studies included in this new meta-analysis not being long enough to detect any major effect on cancer prevention or that this new meta-analysis included far fewer patients who developed cancer than did the earlier meta-analysis.

What can you tell patients?

Low-dose aspirin has become a mainstay of therapy for the prevention of CVD in people with a history of cardiovascular events. However, its role in primary prevention has been less clear. This study strikes a cautionary note in that more people were likely to experience a bleeding episode than to be protected from a cardiovascular event. Therefore, the authors call for careful deliberation between you and your patients to discuss the risk versus the benefit of aspirin use and to encourage patients to make lifestyle changes that focus on reducing blood pressure and smoking cessation.

To date, the data argue against the routine use of aspirin for primary prevention of CVD for individuals at low absolute risk of CVD. As the current guidelines recommend, it is reasonable to consider using aspirin for primary prevention in higher-risk individuals without known CVD if they are deemed to have a greater benefit to risk ratio and after taking into account patient preferences. Or, you might consider exploring every-other-day dosing. And remember that the Centers for Medicare & Medicaid Services has now expanded coverage of CVD prevention to include intensive behavioral counseling in addition to evaluating the individual benefit-risk ratio for aspirin use in primary prevention.

Published January 31, 2012


  1. Seshasai SR, Wijesuriya S, Sivarkumaran R, et al. Effect of aspirin on vascular and nonvascular outcomes: meta-analysis of randomized controlled trials [published online ahead of print January 9, 2012]. Arch Intern Med. doi:10.1001/archinternmed.2011.628.
  2. Rothwell PM, Fowkes FG, Belch JF, et al. Effect of daily aspirin on long-term risk of death due to cancer: analysis of individual patient data from randomised trial. Lancet. 2011;377(9759):31-41.