In individuals with no known cardiovascular disease (CVD), the use of aspirin for at least 12 months is associated with a reduced risk for cardiovascular events. Major bleeding risk, however, is increased in these patients. This is according to findings from a meta-analysis published in JAMA.
Using PubMed and Embase databases, researchers from the United Kingdom searched for randomized controlled trials that enrolled ≥1000 participants who did not have CVD. Selected studies were required to have a follow-up of ≥12 months and a comparative analysis between aspirin use vs no aspirin use, the latter of which could include either placebo or no treatment.
A composite of cardiovascular mortality, nonfatal myocardial infarction, and nonfatal stroke comprised the primary cardiovascular outcome. Additionally, researchers defined a primary bleeding outcome, which included any major bleeding.
In the 13 trials selected for inclusion, the pooled cohort consisted of 164,225 individuals without CVD. Approximately 19% (n = 30,361) had diabetes, and there was a 9.2% (range, 2.6%-15.9%) median risk for the primary cardiovascular outcome at baseline.
A total of 5983 events were reported for the primary cardiovascular outcome in 11 studies, with fewer events occurring in patients randomly assigned to aspirin (2911 [57.1/10,000 participant-years]) vs no aspirin (3072 [61.4/10,000 participant-years]).
Aspirin use was associated with a reduction in the composite cardiovascular outcome (hazard ratio [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). Additionally, a total of 2029 bleeding events were reported in 11 studies, with more events occurring in the aspirin groups (1195 [23.1/10,000 participant-years]) vs the no-aspirin groups (834 [16.4/10,000 participant-years]).
Overall, the use of aspirin was associated with an increased risk for major bleeding (HR, 1.42; 95% CrI, 1.30-1.56), intracranial bleeding (HR, 1.33; 95% CrI, 1.13-1.57), and major gastrointestinal bleeding (HR, 1.57; 95% CrI, 1.38-1.79).
A limitation of the meta-analysis included the variation in aspirin doses among studies (range, 50 mg-500 mg), which may preclude the ability to identify an exact effective dose that might be generalizable across the population.
Findings from this study “may inform discussions with patients about aspirin for primary prevention of cardiovascular events and bleeding.”
Zheng SL, Roddick AJ. Association of aspirin use for primary prevention with cardiovascular events and bleeding events: a systematic review and meta-analysis. JAMA. 2019;321(3):277-287.