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A Closer Look at Aspirin for Primary Prevention

A meta-analysis of individual patient data from six trials uncovers no clear benefit.

Many consider aspirin to be a miracle drug, but its use for primary prevention of cardiovascular events remains controversial. To synthesize the existing evidence, these investigators pooled patient-level data from major prevention trials comparing aspirin with no aspirin (control).

Six primary-prevention trials involving 95,000 subjects were included in the analysis. During 330,000 person-years, 1671 vascular events occurred in the aspirin group and 1883 in the control group (0.51% and 0.57% per year, respectively; relative risk, 0.88; 95% confidence interval, 0.82–0.94). Aspirin was associated with an 18% proportional reduction in coronary events, with an absolute reduction of 0.06% per year. Stroke incidence was not significantly reduced with aspirin, but a borderline-significant 32% relative increase in hemorrhagic stroke was found, representing an absolute increase of 0.01% per year. Aspirin also increased the incidence of major gastrointestinal and other extracranial bleeding (absolute increase, 0.03%; P<0.0001). Aspirin was not associated with a significant reduction in vascular death (RR, 0.97; 95% CI, 0.87–1.09).

Comment: These findings, the best compilation of evidence from aspirin trials to date, demonstrate the challenges of considering aspirin for primary prevention in a low-risk population. Relative reductions in a few cardiovascular events were achieved at a cost of a small, but important, increase in hemorrhagic events. The balance of risks and benefits did not vary by age, sex, or other clinical characteristics. Moreover, the same factors that increased the risk for occlusive events also increased the bleeding risk; even in individuals at moderate risk for cardiovascular events (5-year risk, 5%–10%), any net benefit of aspirin is likely to be razor thin. These results challenge guidelines that endorse the use of aspirin for primary prevention as a general public health policy and reinforce the need to take each patient’s preferences, goals, and risks into account when deciding whether aspirin therapy is appropriate for cardiovascular risk reduction.

— Harlan M. Krumholz, MD, SM

Published in Journal Watch Cardiology May 28, 2009

Citation(s):

Collins R et al. for the Antithrombotic Trialists’ (ATT) Collaboration. Aspirin in the primary and secondary prevention of vascular disease: Collaborative meta-analysis of individual participant data from randomised trials. Lancet 2009 May 30; 373:1849.

• Medline abstract (Free)

Algra A and Greving JP. Aspirin in primary prevention: Sex and baseline risk matter. Lancet 2009 May 30; 373:1821.

• Medline abstract (Free)

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Review and add to remarks on this article

• What is beyond this metanalysis ?!
  Bassem Zarif Fouad, National Heart Institute ,Egypt, 8 Jun 2009 1:11 PM EST
  I think this meta-anlysis is important in delineating what to in 1ry prevention in low risk patient ?! And it... [more]

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