Who Should, and Who Shouldn't, Take Aspirin for Primary CVD Prevention

Kenneth W. Lin, MD, MPH


November 18, 2021

Editorial Collaboration

Medscape &

Hi, everyone. I'm Dr. Kenny Lin. I am a family physician at Georgetown University Medical Center, and I blog at Common Sense Family Doctor.

Kenneth W. Lin, MD, MPH

Three years ago, after the publication of three large trials suggesting that the harms of daily low-dose aspirin for primary prevention of cardiovascular disease outweighed the benefits, I suggested in a Medscape commentary that it was time for the US Preventive Services Task Force (USPSTF) to reevaluate its 2016 recommendations for liberal use of aspirin in high-risk adults. Others went further: For example, fellow Medscape commentator F. Perry Wilson, MD, declared that "aspirin for primary prevention is dead."

The USPSTF took its time reviewing the new evidence but finally released a draft recommendation statement that narrows the scope of aspirin for primary prevention. They now recommend against starting aspirin for primary prevention in adults aged 60 years or older. In adults aged 40-59 years with a 10% or greater 10-year risk for a cardiovascular event, they state that the net benefit is "small" and recommend individual shared decision-making. However, they did not say what to do about the many patients who are already taking aspirin on the basis of prior guidelines. Nonetheless, it is possible to distill a practical primary care approach from the USPSTF draft guideline and similar 2019 guidance from the American College of Cardiology/American Heart Association.

The easiest patient group to address is adults of any age who have a history of heart attack, stroke, or revascularization and are taking aspirin for secondary prevention. They should continue taking aspirin; the new recommendations don't apply to them. That leaves three groups of patients who may require counseling:

  1. Adults aged 40-59 considering starting aspirin;

  2. Adults aged 40-69 already taking aspirin; and

  3. Adults aged 70 or older already taking aspirin.

In the first group, I would not start aspirin in patients who don't meet the 10% or greater 10-year risk threshold, have a history of gastrointestinal or intracranial bleeding, or regularly take steroids or non-steroidal anti-inflammatory drugs. For the rest, if neither the patient's preference nor your clinical intuition indicate whether to start aspirin, it would be reasonable to estimate the relative risks for major bleeding and a cardiovascular event using an online calculator developed from a primary care study in New Zealand. The caveats are that this risk prediction tool has not been prospectively validated in a US population and includes a "deprivation index" that represents the contribution of social determinants of health.

For adults aged 40-69 who have already been taking aspirin for a number of years, it is probably worthwhile for them to continue if they have had no bleeding episodes and are not at high risk for future bleeding. However, a modeling report performed for the USPSTF suggested that the benefit of continuing aspirin use beyond age 75 was unlikely to offset the increased bleeding risk associated with age. Therefore, I suggest starting the discussion about discontinuing aspirin in patients older than 70.

Some experts have suggested that because the purpose of aspirin use is to prevent a first heart attack or stroke, obtaining a coronary artery calcium score may be a useful "tiebreaker" if patients and physicians are truly undecided. The evidence for this use of coronary artery calcium scoring is as dubious as the supporting evidence for its use in deciding whether to start a statin.

Given the evolution of guidelines on aspirin for primary prevention over the past few decades, it seems unlikely that the draft USPSTF guidance, when finalized, will be the last word on this topic. But it should serve as a reminder to primary care physicians to make sure that our patients who choose to take aspirin have an appropriate reason to do so and recognize the associated risks.

Kenny Lin, MD, MPH, teaches family medicine, preventive medicine, and health policy at Georgetown University School of Medicine. He is deputy editor of the journal American Family Physician.

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