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Aspirin is too often used to prevent stroke and other cardiovascular risks in people for whom guidelines suggest no net benefit, examination of a national registry of cardiology practices suggested.

Fully 11.6% of aspirin use in primary prevention by cardiologists was among people below the recommended 6% 10-year baseline risk threshold, , of the Michael E. DeBakey VA Medical Center in Houston, and colleagues found.

That rate ranged from as low as 0% in some practices to as high as 71.8% in others (median 10.1%, interquartile range 6.4%), they reported in the Jan. 20 issue of the Journal of the American College of Cardiology.

The variation across practices was so significant that a patient would be 63% more likely to get aspirin inappropriately at one randomly-selected office than an identical patient at another randomly-chosen practice.

"Our findings suggest that there are important opportunities to improve evidence-based aspirin use for the primary prevention of cardiovascular disease," the group concluded.

In patients with low cardiovascular disease risk and no prior events, "aspirin use has not been associated with reduced cardiovascular events," commented journal editor . "In fact, in this primary prevention population, the increased risk of gastrointestinal bleeding and hemorrhagic stroke associated with aspirin use outweighs any potential benefit in cardiovascular risk reduction."

Emphasizing that lack of benefit, a randomized trial among Japanese seniors recently showed no impact of daily low-dose aspirin on cardiovascular and stroke risk over 5 years.

The FDA issued an advisory last year warning that its of aspirin for primary prevention of heart attack and stroke, added Fuster, of the Icahn School of Medicine at Mount Sinai in New York City.

The U.S. Preventive Services Task Force recommended use if the 5-year coronary heart disease risk is 3% or greater (10-year risk 6% or greater), while the American Heart Association and American College of Cardiology recommend use if the 10-year cardiovascular disease risk is at least 6% to 10%.

Virani's analysis used that threshold of at least 6% risk over 10 years by the Framingham risk assessment tool to examine practice in cardiology offices participating in the prospective ACC National Cardiovascular Disease Registry's Practice Innovation and Clinical Excellence (PINNACLE) registry.

In the analysis of 68,808 unique patients receiving aspirin for primary prevention at 119 U.S. practices, the inappropriate use group averaged a 4.00% 10-year Framingham risk compared with 24.5% in the appropriate group (P<0.001).

The trend in primary prevention with aspirin for low-risk patients declined over time, from 14.5% in 2008 but still remained common at 9.1% in 2013.

Notably, the majority of inappropriate use was in women (79.7%), for whom inappropriate use accounted for 16.6% of all aspirin use compared with 5.3% among men.

Inappropriate use was also typically at a younger age, with an average of 50 versus 66 among appropriate use patients.

Subgroup analysis showed consistent results in terms of inappropriate use after excluding women ages 65 and older, for whom the AHA/ACC guideline recommends aspirin if the benefit is likely to outweigh risks, and after excluding patients with diabetes, for whom the American Diabetes Association recommends use after age 40 when there are additional risk factors (inappropriate aspirin use 15.2% and 13.9%, respectively).

The level of inappropriate primary prevention use of aspirin in a given cardiology practice wasn't tied to overall frequency of aspirin use or use in secondary prevention.

An accompanying editorial by Freek W.A. Verheugt, MD, of Nijmegen Medical Centre in Amsterdam, pointed out several limitations of the study.

"The study was performed in cardiology practices, in which more than 70% of the records were missing at least one component of the Framingham risk score," he wrote. "Because the evidence of aspirin's benefit came from other practices, the results may be biased in that the population seen by cardiologists usually differs from those in general practice."

One confounding factor could be the statin use that often accompanies aspirin in primary prevention, he suggested. Statins change a patient's baseline risk profile, theoretically nearly eliminating the potential benefit of aspirin, he explained.

Analysis eliminating the statin users in the database showed similar findings, with a nearly 15% rate of inappropriate aspirin use.

From the American Heart Association:

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