COMMENTARY

Aspirin for Primary Prevention: 2016 USPSTF Recommendations

Kenneth W. Lin, MD, MPH

Disclosures

April 14, 2016

Editorial Collaboration

Medscape &

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

Taking aspirin after a heart attack or a stroke can literally be lifesaving. The benefits of daily low-dose or "baby" aspirin, 81 mg, to prevent a second cardiovascular event are also well established. A more challenging question in primary care is: Who should take aspirin for primary prevention—that is, to prevent a first heart attack or stroke? The issue at stake here is that even if aspirin reduces the relative risk for initial cardiovascular events (which it appears to do), in a patient with low absolute risk for heart attack or stroke, the small preventive benefit can easily be outweighed by the increased risk for gastrointestinal bleeding.

Since 2009, the US Preventive Services Task Force (USPSTF) has recommended that we encourage men age 45-79 years and women age 55-79 years without known heart disease to use preventive aspirin when the potential benefit of a reduction in myocardial infarctions or ischemic strokes outweighs the potential harm of bleeding.[1] In practice, I have found this recommendation very challenging to implement. It requires using one of two different calculators to estimate 10-year heart attack or stroke risk, then consulting a table that compares cardiovascular events prevented to bleeding harms by age group. Some patients will have comparable offsetting risks, which then requires clinicians to use shared decision-making to determine whether to start aspirin on the basis of a patient's values and preferences.

Even family physicians who are willing to spend the time to have this complicated discussion with patients about the benefits and risks of aspirin may be concerned by recent analyses that have appeared to contradict the Task Force's guidance. A 2013 meta-analysis[2] contended that the absolute benefits of aspirin for primary prevention were small and generally outweighed by the increased bleeding risk. In 2014, the US Food and Drug Administration advised the general public against using aspirin for primary prevention of heart attack or stroke.[3] Nonetheless, more than one third of Americans age 40 years or older reported taking daily aspirin in a recent national survey, 97% for primary prevention purposes.[4]

Last September, the USPSTF signaled that it was preparing to update its 2009 recommendations on aspirin for the primary prevention of cardiovascular events and include an updated assessment of the benefits of long-term aspirin use in preventing colorectal cancer.[5] The recently finalized recommendations[6] should be much easier to follow. This time around, the Task Force narrowed the age range of patients for whom clinicians should consider preventive aspirin to 50-69 years and removed the previous distinction between men and women, recognizing newer evidence that both sexes benefit from reductions in heart attacks and strokes, as well as a decreased incidence of colorectal cancer. The USPSTF recommends that adults in their 50s start low-dose aspirin if they have a 10% or greater 10-year cardiovascular disease (CVD) risk, do not have bleeding risk factors, and are willing to take aspirin for at least 10 years. Adults in their 60s with similar CVD risk can also consider starting low-dose aspirin but are at higher risk of bleeding and so are less likely to benefit overall. The Task Force found insufficient evidence to assess the balance of benefits and harms of starting aspirin for primary prevention in adults younger than 50 or older than 69.

Some other important points are that preventive aspirin only reduces the future risk for cardiovascular events and colorectal cancer but doesn't appear to affect the numbers of deaths from those conditions. Taking aspirin does not modify the need for adults age 50-75 years to undergo regular colorectal cancer screening. And once a patient decides to start taking aspirin for primary prevention, his or her CVD and bleeding risk factors should be periodically reassessed to make sure that it still makes sense to continue.

Although many patients take aspirin on the advice of their doctors, there are also many adults who start taking aspirin on their own. Some may consider aspirin to be more along the lines of a vitamin supplement and neglect to mention it when asked what medications they are taking. Because only a limited group of patients should use preventive aspirin, family doctors should view the new USPSTF recommendations as an opportunity to make sure that our patients' aspirin use is consistent with the likelihood of health benefits.

This has been Dr Kenny Lin for Medscape Family Medicine. Thank you for listening.

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