A systematic review of large trials found that among those with no known history of cardiovascular disease, regular aspirin use was associated with a 11% lower risk of CV events but also with a 43% increase in major bleeding episodes. No effect was seen with on new cancer diagnoses or deaths.
The systematic review from scientists at King’s College London, King’s College Hospital and Imperial College London looked at the overall effects on patients who did not have known cardiovascular disease. They found that while it was associated with a lower risk of heart attacks and other cardiovascular events, it did lead to an increased risk of major bleeding.
While aspirin is known to reduce risks for those who have previously suffered strokes and heart attacks, the evidence of the role of aspirin in the initial prevention of cardiovascular events, is uncertain.
This study looked at the outcomes of trials enrolling more than 1,000 participants with no known history of cardiovascular diseases and which included a follow-up after twelve months. Participants included ones who took aspirin and other who took a placebo or had no treatment at all.
The results showed that: aspirin use was associated with an 11% lower risk of cardiovascular events; approximately 250 patients needed to be treated with aspirin for 5 years to prevent a single heart attack, stroke or cardiovascular death; aspirin use was associated with a 43% increase of major bleeding events, compared to those who did not take it; approximately one in 200 people treated with aspirin would have a major bleed; and no effect was seen with aspirin on new cancer diagnoses or deaths.
Lead author, Dr Sean Zheng, academic clinical fellow in cardiology at King’s College London said: “This study demonstrates that there is insufficient evidence to recommend routine aspirin use in the prevention of heart attacks, strokes and cardiovascular deaths in people without cardiovascular disease.
“There has been more uncertainty surrounding what should be done in patients who are at higher risk of cardiovascular disease and in patients with diabetes. This study shows that while cardiovascular events may be reduced in these patients, these benefits are matched by an increased risk of major bleeding events.
“Aspirin use requires discussion between the patient and their physician, with the knowledge that any small potential cardiovascular benefits are weighed up against the real risk of severe bleeding.”
Importance: The role for aspirin in cardiovascular primary prevention remains controversial, with potential benefits limited by an increased bleeding risk.
Objective: To assess the association of aspirin use for primary prevention with cardiovascular events and bleeding.
Data Sources: PubMed and Embase were searched on Cochrane Library Central Register of Controlled Trials from the earliest available date through November 1, 2018.
Study Selection: Randomized clinical trials enrolling at least 1000 participants with no known cardiovascular disease and a follow-up of at least 12 months were included. Included studies compared aspirin use with no aspirin (placebo or no treatment).
Data Extraction and Synthesis: Data were screened and extracted independently by both investigators. Bayesian and frequentist meta-analyses were performed.
Main Outcomes and Measures: The primary cardiovascular outcome was a composite of cardiovascular mortality, nonfatal myocardial infarction, and nonfatal stroke. The primary bleeding outcome was any major bleeding (defined by the individual studies).
Results: A total of 13 trials randomizing 164 225 participants with 1 050 511 participant-years of follow-up were included. The median age of trial participants was 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 associated with significant reductions in the composite cardiovascular outcome compared with 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). Aspirin use was associated with an increased risk of major bleeding events compared with 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).
Conclusions and Relevance: The use of aspirin in individuals without cardiovascular disease was associated with a lower risk of cardiovascular events and an increased risk of major bleeding. This information may inform discussions with patients about aspirin for primary prevention of cardiovascular events and bleeding.
Sean L Zheng, Alistair J Roddick