Meta-analysis: aspirin for primary prevention is tied to reduced CV event risk but increased bleeding risk

  • Zheng SL & al.
  • JAMA
  • 22 Jan 2019

  • curated by Emily Willingham, PhD
  • Clinical Essentials
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  • Controversy over aspirin for primary cardiovascular (CV) disease prevention continues.
  • Meta-analysis finds protection against CV events but increased major bleeding risk.

Why this matters

  • Results follow on high-profile reports that aspirin does not keep CV disease at bay in older adults. 
  • 2 other major studies reached similar conclusions
  • They are all in agreement about the increased bleeding risk, however.
  • Editorial: use of aspirin for primary prevention requires careful patient selection.

Key results

  • With aspirin use vs no use, decreased risk for composite CV outcome:
    • 57.1/10,000 vs 61.4/10,000 participant-years;
    • HR, 0.89 (95% credible interval [CrI], 0.84-0.95); 
    • Absolute risk reduction, 0.38% (95% CI, 0.20%-0.55%); 
    • Number needed to treat, 265;
    • Low heterogeneity: I2=0%; and
    • Risk also decreased for ischemic stroke and myocardial infarction.
  • With aspirin use vs no use, increased major bleeding risk:
    • 23.1 vs 16.4/10,000 participant-years;
    • HR, 1.43 (95% CrI, 1.30-1.56); 
    • Absolute risk increase, 0.47% (95% CI, 0.34%-0.62%); and
    • Number needed to harm, 210.
  • No reductions in all-cause, CV mortality with aspirin.

Study design

  • Meta-analysis, 13 randomized trials; n=164,225; 1,050,511 participant-years of follow-up.
  • Main outcomes: CV composite (mortality, nonfatal myocardial infarction, nonfatal stroke); major bleeding.
  • Funding: None disclosed.


  • Related to those of included trials.

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