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06-06-2012 | Cardiology | Article

Aspirin bleeding risk ‘higher than expected’ in primary prevention


Free abstract

MedWire News: A new analysis of aspirin use for primary prevention of cardiovascular disease suggests it is associated with higher risks for gastrointestinal or cerebral bleeding episodes than previously thought.

The study also found that patients with diabetes have a high rate of bleeding irrespective of aspirin use, however, which the authors say was unexpected and could mean that the efficacy of antiplatelet therapy is reduced in this group.

Antonio Nicolucci (Consorzio Mario Negri Sud, Italy) and team note that the incidence of major bleeding events they observed in their "real-world" study is much higher than that recorded in randomized clinical trials, and, furthermore, five times higher than was estimated in a meta-analysis conducted by the Antithrombotic Trialists' Collaboration.

The authors furthermore point out that the excess number of major bleeding events associated with aspirin use in their study was equal to the number of major cardiovascular events that would be avoided in the primary prevention setting in individuals with a 10-year risk of 10-20%.

The population-based cohort study, published in JAMA included 186,425 patients who were treated with low-dose aspirin (≤300 mg) and 186,425 controls who did not use aspirin between January 2003 and December 2008.

During a median follow-up period of 5.7 years, the incidence of hemorrhagic events was 5.58 per 1000 person-years for aspirin users versus 3.60 per 1000 person-years for non-aspirin users, corresponding to an incidence rate ratio (IRR) of 1.55.

Aspirin use was associated with a significantly greater risk for major bleeding in most of the subgroups investigated, including gender, age, and hypertension. However, it was not associated with a significantly increased risk for bleeding in diabetes patients.

Moreover, the baseline risk for bleeding in the absence of aspirin therapy was higher among individuals with diabetes than those without diabetes, at 5.35 versus 3.32 events per 1000 person-years, whereas aspirin use was associated with a significantly higher bleeding risk in diabetes patients only (IR for gastrointestinal bleeding 1.08, intracranial bleeding 1.01).

The authors say that the lack of an excess bleeding risk in patients with diabetes "deserved additional consideration."

"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 populations," they remark.

"Diabetes might represent a different population in terms of both expected benefits and risks associated with antiplatelet therapy," Nicolucci et al conclude.

In a related editorial, Jolanta Siller-Matula (Medical University of Vienna, Austria) states that Nicolucci and team's study reinforces European guidelines for aspirin use.

She adds: "Future studies investigating the risks and benefits for individual patients appear to be mandatory to help physicians appropriately make recommendations about aspirin use for primary prevention."

By Piriya Mahendra

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