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Revisiting the USPSTF Recommendations on Aspirin

Due to a technical glitch, I’m republishing this post from two days ago.

Aspirin is a unique drug, the prototypical two-edged sword of pharmaceuticals. It has the capability of stopping platelets, the sticky elements in our blood, from forming clots that cause strokes and heart attacks when arterial plaques rupture, but it increases the risk of serious bleeding into the brain or from the GI tract. Despite these powerful properties, aspirin is available over the counter and is very cheap, thus anyone can take it in any dosage they want.

In 2014 the skeptical cardiologist wrote a post entitled “Should I take aspirin to prevent stroke or heart attack?”,  it pointed out that although Dr. Oz had recently told almost all middle-aged women to take a baby aspirin and fish oil, there was, in fact no evidence to support that practice.

In 2018 I revisited (Revisiting Who Should Take Aspirin) my aspirin recommendation after the publication of the ASPREE (Aspirin in Reducing Events in the Elderly) trial results were published in the New England Journal of Medicine and concluded:

The ASPREE study confirms what I advised in 2014 and hopefully will further reduce the inappropriate consumption of aspirin among low risk individuals.
I’ve taken more patients off aspirin since 2014 than I’ve started on aspirin and what I wrote then remains relevant and reflects my current practice. Especially in light of the increase cancer risk noted in ASPREE, patients should only take aspirin for good reasons.

Yesterday, I received an email from the USPSTF which indicates their recommendations for aspirin in primary prevention will be substantially modified in light of ASPREE and other data which have emerged in the last 3 years. These are draft comments and the USPSTF is inviting public review and comment:

The big change was in individuals 60 years and over without clinical evidence of cardiovascular disease (primary prevention) with a recommendation against initiating aspirin therapy in this group:

These recommendations have generated extensive media coverage including a featured NY Times article this morning. It’s good to see the USPSTF revising ASA recommendations and hopefully this will further reduce the inappropriate use of aspirin in low-risk individuals. I wonder if Dr. Oz will recant his spurious advice now.

Optimal Aspirin Usage in Primary Prevention

In my practice, the answer to the question of who should or should not take aspirin is based on whether my patient has or does not have significant atherosclerosis.

If they have had a clinical event due to atherosclerotic cardiovascular disease (stroke, heart attack, coronary stent, coronary bypass surgery, documented blocked arteries to the legs) I recommend they take one 81 milligram (baby) uncoated aspirin daily.

If my patient has not had a clinical cardiovascular event but we have documented advanced subclinical atherosclerosis by imaging such as :

  • vascular screening (significant carotid plaque)
  • Abnormally high coronary calcium score
  • Incidentally discovered significant plaque in the aorta or peripheral arteries (found by CT or ultrasound done for other reasons)

then I recommend a daily baby aspirin (assuming no high risk of bleeding).

I have been using a coronary calcium score >100 as a guide for who benefits from aspirin since a study entitled “The Use of Coronary Artery Calcium Testing to Guide Aspirin Utilization for Primary Prevention: Estimates from the Multi-Ethnic Study of Atherosclerosis” was published in 2015.

This study found

Individuals with CAC ≥ 100 had an estimated net benefit with aspirin regardless of their traditional risk status (estimated NNT5 of 173 for individuals <10% FRS and 92 for individuals ≥ 10% FRS, estimated NNH5 of 442 for a major bleed). Conversely, individuals with zero CAC had unfavorable estimations (estimated NNT5 of 2,036 for individuals <10% FRS and 808 for individuals ≥ 10% FRS, estimated NNH5 of 442 for a major bleed)

Randomized trials testing this approach are needed but in the next few years several large aspirin trials will be completed and hopefully, we will get a more refined understanding of who benefits most from aspirin for primary prevention.
Until then remember that aspirin is a powerful drug with the potential for good and bad effects on your body. Only take it if you and your health care provider have decided the benefits outweigh the risks after careful consideration of your particular situation.

Acetylsalicylically Yours,

N.B. Some other skepcard posts relevant to aspirin

Does aspirin have a role in stroke prevention related to atrial fibrillation?

Thoughts on prolonged bleeding whilst taking baby aspirin.

Which kind of baby aspirin should I take?

N.B. 2 The inclusion criteria for ASPREE define significant cardiovascular disease as follows a past history of cardiovascular or cerebrovascular event or established CVD, defined as myocardial infarction (MI), heart failure, angina pectoris, stroke, transient ischemic attack, >50% carotid stenosis or previous carotid endarterectomy or stenting, coronary artery angioplasty or stenting, coronary artery bypass grafting, abdominal aortic aneurysm


13 thoughts on “Revisiting the USPSTF Recommendations on Aspirin”

  1. Hello Dr. P. Thanks for your very informative website. I have read that as little as 30 mg. of aspirin per day is sufficient to slow coagulation. One of my cardiologists states that the lowest effective dosage for aspirin has not been established. Would lower dosage cause fewer side effects? Your thoughts please.

    Best wishes,
    T. D. Murray

    • T.D.
      After scanning the literature I have concluded that you are correct. This review article (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1073805/)from 2016 mentions a Dutch TIA trial showing no difference in efficacy between 30 mg and 283 mg aspirin and less bleeding at the lower dosage.
      “In the group assigned to receive 30 mg of aspirin, the frequency of death from vascular causes, nonfatal stroke, or nonfatal myocardial infarction was 228 of 1555 (14.7 percent), as compared with 240 of 1576 (15.2 percent) in the group assigned to receive 283 mg. The age- and sex-adjusted hazard ratio for the group receiving the lower dose was 0.91 (95 percent confidence interval, 0.76 to 1.09). There were slightly fewer major bleeding complications in the 30-mg group than in the 283-mg group (40 vs. 53), and significantly fewer reports of minor bleeding (49 vs. 84). Fewer patients receiving 30 mg of aspirin reported gastrointestinal symptoms (164 vs. 179) and other adverse effects (73 vs. 90).”
      There aren’t a lot of studies with that low a dosage and I haven’t found any comparing 30 to what has become the standard-81 mg

  2. The question of the daily aspirin is confusing me. I am a 69 year old female. At age 64 I had a CAC scan with a result of 98, putting me in the 82nd percentile for my age. At the time my cholesterol was 242, HDL 71, LDL 154. My doctor put me on 10 mg of Pravastatin and later increased it to 20 mg. Cholesterol is now 186, HDL 67, LDL 96. I visited a cardiologist after the CAC scan and she recommended a low-dose aspirin daily. I am 5′ 1″ tall and weigh 114 lbs. In your opinion, and in light of the recent research, would the low-dose aspirin still be advised? Should I repeat the CAC scan?

    • Kathy,
      Given that your score was at 98 5 years ago there is no doubt that you are now significantly >100.
      I intend to write a post separately on repeat CAC scans but for individuals with a nonzero CAC score I do not recommend a repeat CAC.
      Dr P

    • Cathy,
      Good question. Off the top of my head I would say we should not recommend ASA for every diabetic, rather we should be looking more closely at the ASCVD risk. Calcium scan is one way of assessing risk. Using a risk estimator like the MESA calculator is another
      I’ll research this further and write a post shortly.
      Dr P

  3. Do you normally recommend medicines with such a High NNT ~ 92, or only for meds with extremely low chance of side effects. To me any NNT > 40 seems too high for an individual to consider taking. Population recommendation yes, but an individual choice not for me. What is your take here?

    • VT,
      Your question implies you find a benefit to thinking about drugs using the NNT concept. I’ve never been convinced this enhances my patient’s understanding of treatment risks/benefits
      As I answered another reader
      NNT=number needed to treat
      NNH=number needed to harm
      FRS most likely Framingham Risk Study

      Some experts feel that NNT is a better way to present info to patients on risks/harms of a proposed treatment.
      See the logic here. https://www.thennt.com/thennt-explained/#anchor-basicidea

      If we are talking death prevention, then if our treatment provides a 2% absolute risk reduction then NNT is 50, greater than 40 and likely worthwhile if risks are acceptable.
      I’m putting together a post on NNT and look forward to generating a discussion on the topic.
      Dr P

  4. What about the diabetic patients who don’t have CAD history or other vascular diseases… do u recommend aspirin ?


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