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Daily aspirin had little if any net benefit in cardiovascular primary prevention across two trials, while omega-3 supplements flopped in one of them, too.

These findings from the two-by-two factorial ASCEND trial with aspirin and omega-3 fish oil pills in diabetes patients and ARRIVE trial with aspirin in patients without diabetes were reported online along with presentations at the European Society of Cardiology meeting in Munich.

ASCEND

In this trial, reported online in two papers in the , 100-mg aspirin reduced the composite of myocardial infarction (MI), stroke, transient ischemic attack (TIA), or death from non-intracranial hemorrhage vascular causes by a relative 12% compared with placebo in adults with diabetes of any type (8.5% versus 9.6% at a mean of 7.4 years, P=0.01).

But major bleeding was increased by 29%. In patients with under a 5% predicted 5-year risk, that meant prevention of six vascular events at the cost of three major bleeds per 5,000 person-years; those at a 10% or greater predicted risk had 11 vascular events prevented at the cost of 10 major bleeds per 5,000 person-years.

"There was no group in which the benefits clearly outweighed the risks," the study's lead author, Jane Armitage, FRCP, FFPH, of the University of Oxford in England, said at a press conference. The trial included 15,480 British patients ages 40 and older with any diabetes and no baseline cardiovascular disease.

In the other portion of the trial, daily 1-g capsules of omega-3 fatty acids didn't reduce non-fatal MI or stroke, TIA, or cardiovascular death compared with an olive-oil placebo (8.9% versus 9.2%, RR 0.97, 95% CI 0.87-1.08), reported Louise Bowman, MD, also of Oxford.

Adding arterial revascularization to the composite did not shift the findings. All-cause mortality and non-fatal serious adverse events likewise were similar between groups.

ARRIVE

The ARRIVE trial included 12,546 patients targeted to be at moderate risk based on being age 55 or older for men, 60 and older for women and having major cardiovascular disease risk factors but no diabetes, prior vascular events, or high risk of gastrointestinal or other bleeding.

For the primary endpoint, 100-mg aspirin did not have an impact on the first occurrence of cardiovascular death, MI, unstable angina, stroke, or TIA at a median of 60 months in 4.29% of participants versus 4.48% of those receiving placebo (HR 0.96, P=0.6038).

Accounting for the nearly 40% noncompliance rate in the underpowered trial, the per-protocol analysis was more on par with that of ASCEND, with a 19% relative reduction in the primary endpoint, albeit still not significant (3.40% versus 4.19%, P=0.0756), J. Michael Gaziano, MD, MPH, of Brigham and Women's Hospital in Boston, and colleagues reported in

Again as expected, GI bleeding was more than twice as common in those on daily aspirin (0.97% versus 0.46%, P=0.0007), although overall serious adverse events and mortality were similar between the study arms.

But with a "much lower than expected" event rate "probably reflective of contemporary risk management strategies," the researchers cautioned that they couldn't really address the impact of aspirin in a moderate risk population.

"I think if you are well managed with diabetes, you've got your other risk factors under control, I think you need to consider very carefully whether or not for you the benefits of aspirin do outweigh the risks, and I think that's a decision that will have to [be made] between patient and doctor," Armitage said at the press conference.

While calling it "a challenging calculus" to integrate ischemic, bleeding, and cancer risk, Gaziano said he believes there are patients whose risk is sufficient to warrant use of aspirin as part of the treatment armamentarium.