The Daily Aspirin That Bled Through Its Own Alibi

The Claim

Aspirin has had an excellent publicist for more than a century. Small, inexpensive, familiar. The little tablet looks reassuringly incapable of causing trouble.

Unfortunately, platelets do not read advertisements.

Aspirin makes platelets less likely to form clots. That can be lifesaving after a heart attack, certain strokes, or a coronary stent. But should a generally healthy person take it daily to prevent a first cardiovascular event?

What The Trials Found

In the ASPREE randomized trial, 19,114 older adults without established cardiovascular disease were assigned 100 mg aspirin daily or placebo. Most were at least 70; some US Black and Hispanic participants were eligible from age 65. Over a median 4.7 years, cardiovascular events occurred at 10.7 versus 11.3 per 1,000 person-years, respectively. That difference was not statistically significant. [1,2]

Major bleeding, however, occurred at 8.6 versus 6.2 per 1,000 person-years. The tablet did something. Just not enough of the thing its supporters had hoped for. [1]

What about diabetes? In the ASCEND trial, 15,480 adults with diabetes but no known cardiovascular disease took 100 mg aspirin daily or placebo for an average 7.4 years. Serious vascular events affected 8.5% versus 9.6%. Major bleeding affected 4.1% versus 3.2%. Approximately 11 fewer vascular events and nine additional major bleeds per 1,000 people over that follow-up. These are different outcomes, not interchangeable harms and benefits, and the decision is personal. [3]

Who Should Start Aspirin?

This is why the US Preventive Services Task Force, in April 2022, recommended against starting aspirin at age 60 or older solely to prevent a first heart attack or stroke. For adults 40–59 with a 10% or greater estimated ten-year cardiovascular risk, starting it is an individual decision, with only a small average net benefit. [4] The 2019 ACC/AHA guideline similarly discourages routine primary-prevention aspirin while allowing selected higher-risk adults after bleeding-risk assessment. [5]

The Exceptions

Now the crucial exception. Do not stop aspirin on your own if it was prescribed after a heart attack, ischemic stroke, stent or bypass surgery. That is a different problem, called secondary prevention, with a different evidence base. Other specialist indications, including some pregnancy-related prevention plans, also require individualized advice. [6]

What We Do About It

Before starting or stopping, ask why you are taking it, what bleeding risks you have, and whether treatment of smoking, blood pressure or cholesterol offers more benefit. Blood in vomit, black stools, sudden weakness or a severe unusual headache merit urgent assessment.

The Verdict

The Shit List is not a list of bad drugs. It is a list of bad reflexes.

Sources and receipts

1. [1] McNeil JJ et al. “Effect of Aspirin on Cardiovascular Events and Bleeding in the Healthy Elderly.” N Engl J Med. 2018. DOI 10.1056/NEJMoa1805819. — Source cited in the reviewed article
2. [2] McNeil JJ et al. “Effect of Aspirin on Disability-free Survival in the Healthy Elderly.” N Engl J Med. 2018. DOI 10.1056/NEJMoa1800722. — Source cited in the reviewed article
3. [3] American College of Cardiology, ASCEND trial summary and absolute outcomes, updated 2024: — Source cited in the reviewed article
4. [4] US Preventive Services Task Force. “Aspirin Use to Prevent Cardiovascular Disease: Preventive Medication.” April 26, 2022: — Source cited in the reviewed article
5. [5] 2019 ACC/AHA Guideline on Primary Prevention. Aspirin section: — Source cited in the reviewed article
6. [6] American College of Cardiology, “New USPSTF Recommendation on Aspirin in CVD: No For Primary Prevention, Yes For Secondary Prevention.” April 27, 2022: — Source cited in the reviewed article