Aspirin use is associated with a reduced risk of cardiovascular events among adults without cardiovascular disease, but this protection comes with a similarly increased risk for bleeding, according to data from a meta-analysis that included more than 1 million participant-years of follow-up.
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“The uncertain role of aspirin in primary prevention of cardiovascular events is reflected in contrasting recommendations offered by guideline bodies,” and has led to a decline in prescribing aspirin for primary prevention of such events, wrote Sean L. Zheng, MRCP, of Imperial College London (England) and his colleagues.
In a systematic review and meta-analysis published in JAMA, the researchers examined 13 randomized trials altogether including 164,225 participants and 1,050,511 participant-years of follow-up.
Overall, aspirin use significantly reduced a composite of cardiovascular outcomes, compared with no aspirin (hazard ratio, 0.89). The composite outcome included cardiovascular mortality, nonfatal myocardial infarction, and nonfatal stroke, and it occurred in 57.1 per 10,000 participant-years in aspirin users versus 61.4 per 10,000 participant-years among individuals who did not use aspirin. The absolute risk reduction was 0.38%.
The median age of the study participants was 62 years, and roughly half (47%) were male.
However, the risk of major bleeding events was significantly higher among aspirin users, compared with nonusers (23.1 per 10,000 participant-years and 16.4 per 10,000 participant-years, respectively), with a HR of 1.43 and an absolute risk increase of 0.47%.
Aspirin use was not associated with several secondary outcomes, including reductions in all-cause mortality or cardiovascular mortality, compared with no aspirin, but it was associated with a reduced risk specifically of myocardial infarction and ischemic stroke. Few deaths related to bleeding were reported.
The number needed to treat (265) and the number needed to harm (210) were similar, which emphasizes the need for an individual approach to treatment, the researchers noted.
“Consequently, the decision to use aspirin for primary prevention may need to be made on an individual basis, accounting for the patient’s risk of bleeding and their views on the balance of risk vs. benefit,” they concluded.
The researchers had no financial conflicts to disclose.
SOURCE: Zheng SL et al. JAMA. 2019;321(3):277-87.