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Patients with no history of cardiovascular disease probably derive little-to-no benefit from taking aspirin for primary prevention, physicians argued -- despite recommendation by the U.S. Preventive Services Task Force.

The trials that suggested potential benefits to aspirin "were done decades ago in a very different health care environment (different risk factor profiles, fewer concurrent preventive therapies, and less access to early diagnostic and treatment services)," according to Michael Pignone, MD, MPH, of the University of Texas' Dell Medical School in Austin, and Darren DeWalt, MD, MPH, of the University of North Carolina School of Medicine in Chapel Hill.

"The current environment, in which more attention is given to cardiovascular prevention and care, may reduce the benefits of aspirin -- or simply decrease overall risk and hence affect the benefit–harm ratio," they said in an opinion piece published online in the .

Recently, the large ASPREE and ASCEND trials offered mixed data on the effects of aspirin in these patients, Pignone and DeWalt recalled.

ASPREE showed that aspirin was no better than placebo and actually increased bleeding risk (with cancer mortality also on the rise, unexpectedly) in patients 70 or older. ASCEND found that aspirin was tied to a modest reduction in cardiovascular events during more than 7 years of follow-up among patients 40 or older with diabetes, but bleeding was again a safety concern.

In 2016, the U.S. Preventive Services Task Force issued a for daily aspirin use in adults ages 50 to 59 at increased 10-year cardiovascular disease risk, meaning "high certainty that the net benefit [of aspirin in primary prevention] is moderate or there is moderate certainty that the net benefit is moderate to substantial," according to the Task Force's definitions. Pignone was a Task Force member at the time of the recommendation.

"Among middle-aged adults with or without diabetes, we believe that an approach based on cardiovascular risk still holds. Aspirin can be offered as an additional risk-reducing therapy for those younger than 70 years if other such therapies have been used appropriately and the patient still has elevated cardiovascular risk (>1% per year) and no increased bleeding risk," Pignone and DeWalt wrote.

"In most adults older than 70 years with or without diabetes, aspirin therapy should not be initiated for primary prevention. The absolute risk for bleeding increases, and current evidence does not support net benefit," they continued.

And as for those who have already started taking aspirin for primary prevention, the evidence does not point in a direction for or against withdrawing it at age 70, the editorialists noted.

Until there is more definitive data to help inform the benefit-risk equation, they argued, the net magnitude of benefit of aspirin is likely small for those without cardiovascular disease.

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