Zheng SL, et al. - In this systematic review and meta-analysis, researchers evaluated data from 13 trials with 164,225 participants without cardiovascular disease to see how aspirin use for primary prevention relates with cardiovascular events and bleeding. Findings revealed that aspirin use in those without cardiovascular disease correlated with a lower risk of cardiovascular events and a higher risk of major bleeding.

Methods

• PubMed and Embase were searched from the earliest available date to November 1, 2018 in the Cochrane Library Central Register of Controlled Trials.
• Included were randomized clinical trials with at least 1,000 participants without known cardiovascular disease and a follow-up of at least 12 months that evaluated the use of aspirin vs aspirin (placebo or treatment).
• By both investigators, data were screened and extracted independently.
• Bayesian and frequentist meta-analyses have been carried out.
• A composite of cardiovascular mortality, nonfatal myocardial infarction, and nonfatal stroke was the primary cardiovascular outcome.
• Any major bleeding (defined by the individual studies) was the primary bleeding outcome.

Results

• A total of 13 trials were included, randomizing 164,225 participants with 1,050,511 participant-years of follow-up.
• Trial participants had a median age of 62 years (range, 53-74), 77,501 (47%) were men, 30,361 (19%) had diabetes, and the median baseline risk of the primary cardiovascular outcome was 9.2% (range, 2.6%-15.9%).
• Aspirin use was related to significant reductions in the composite cardiovascular outcome vs no aspirin (57.1 per 10,000 participant-years with aspirin and 61.4 per 10,000 participant-years with no aspirin) (hazard ratio [HR], 0.89 [95% credible interval, 0.84-0.95]; absolute risk reduction, 0.38% [95% CI, 0.20%-0.55%]; number needed to treat, 265).
• Investigators found that aspirin use was linked to an increased risk of major bleeding events vs no aspirin (23.1 per 10,000 participant-years with aspirin and 16.4 per 10,000 participant-years with no aspirin) (HR, 1.43 [95% credible interval, 1.30-1.56]; absolute risk increase, 0.47% [95% CI, 0.34%-0.62%]; number needed to harm, 210).