HealthDay News — Daily low-dose aspirin use to prevent heart disease is associated with an increased risk of major gastrointestinal (GI) or cerebral bleeding, Italian researchers found.

Daily prescribed aspirin was associated with a 55% relative increase in the risk for major bleeding, or an excess of two bleeding cases per 1,000 patients treated each year, Giorgia De Berardis, from Consorzio Mario Negri Sud in S. Maria Imbaro, Italy, and colleagues reported online in the Journal of the American Medical Association.

“Weighing the benefits of aspirin therapy against the potential harms is of particular relevance in the primary prevention setting, in which benefits seem to be lower than expected based on results in high-risk patients,” the researchers wrote.

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Although aspirin’s benefit as a secondary prevention strategy in patients with moderate to high risk for cardiovascular events, it’s role in primary prevention has been controversial. So De Berardis and colleagues conducted a population-based cohort study involving 186,425 individuals with new prescriptions for low-dose aspirin (≤300 mg) and 186,425 propensity-matched controls, identified from January 2003 to December 2008. Hospitalization for major gastrointestinal bleeding or cerebral hemorrhage was compared among the two groups.

During a median 5.7 year follow-up period, overall incidence of hemorrhagic events was significantly higher for aspirin users than for those without aspirin use (5.58 vs. 3.60 per 1,000 person-years; incidence rate ratio [IRR], 1.55). The researchers observed an excess risk of both GI (IRR 1.55; 95% CI:1.46-1.65) and intracranial bleeding (IRR 1.54; 95% CI: 1.43-1.67). 

In addition to aspirin use, the bleeding risk increased with age and was higher in men; individuals treated with antihypertensive agents; patients taking prescription nonsteroidal anti-inflammatory drugs (NSAIDs); and patients taking other antiplatelet and antithrombotic agents.

In most of the subgroups investigated, aspirin use correlated with an increased risk of major bleeding, with the exception of individuals with diabetes (IRR, 1.09; 95% CI: 0.97-0.22). Diabetes correlated independently with an increased risk of major bleeding, regardless of aspirin use (IRR, 1.36).

“In this population-based cohort, aspirin use was significantly associated with an increased risk of major bleeding, but this association was not observed for patients with diabetes,” the authors write. “In this respect, diabetes might represent a different population in terms of both expected benefits and risks associated with antiplatelet therapy.”

In an accompanying editorial, Jolanta Siller-Matula, MD, PhD, of the Medical University of Vienna in Austria, wrote that this study highlights the importance of assessing bleeding risk when deciding on interventions for patients at risk for cardiovascular events.

“There is only a thin line between efficacy and safety, and the reduction in ischemic events comes at the cost of increased major bleedings,” she wrote and called for more studies to assess individual risk-versus-benefits to help primary care clinicians make recommendations about aspirin use for primary prevention.

Study limitations included lack of data on lifestyle factors such as obesity, smoking, alcohol consumption, or the use of over-the-counter NSAIDS or over-the-counter aspirin, which are not typically collected in claims databases. Several researchers disclosed financial ties to the pharmaceutical industry.

De Berardis G et al. JAMA. 2012; 307(21): 2286-2294.

Siller-Matula JM. JAMA. 2012; 307(21): 2318-2320.