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Study: Low-Dose Daily Aspirin May Accelerate Cancer Progression in Older Adults

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Key Takeaways

  • Taking low-dose daily aspirin is a common (and often doctor-approved) practice for older adults.
  • A new study has found that low-dose daily aspirin might increase the risk of aggressive cancers in some people.
  • Experts say that the recommendation to take daily aspirin should be individualized to each patient with consideration of their risk factors.

A new study has found that taking a low-dose aspirin every day might increase the risk of cancer progression and spread in some people. These findings are putting the common practice of taking low-dose daily aspirin among older adults into question.

The study, which was published in the Journal of the National Cancer Institute in August, included 19,114 Americans and Australians age 70 and older with no cardiovascular disease, dementia, or physical disability. The participants were followed for almost five years.

The study was randomized, placebo-controlled, and double-blind. Some participants received a daily 100-milligram dose of aspirin and the others got a placebo.

During the study period, 981 people who took a daily, low-dose aspirin developed cancer. Among the participants who took a placebo, 952 people developed cancer. While there was no statistically significant difference in the development of cancer, the researchers found that the participants in the aspirin group had a higher risk of having cancer that had metastasized (spread) or was stage 4 at diagnosis. They also had a higher risk of death.

“This finding was so unexpected and in contrast with prevailing views on aspirin that we spent a lot of time checking and reanalyzing before we submitted it for publication,” lead study author John McNeil, PhD, a professor in the department of epidemiology and preventive medicine at Monash University in Australia, tells Verywell.

Why Some Older Adults Take Aspirin

For many years, a daily dose of aspirin was thought to help prevent a heart attack, stroke, or other cardiovascular events. However, more recent research has changed that opinion. In 2019, the American Heart Association (AHA) released its updated cardiovascular disease prevention guidelines which advised against the practice of low-dose daily aspirin unless someone already has heart disease and their provider recommends the regimen.

The AHA cited research that found that the benefits of taking daily low-dose aspirin were offset by the danger of internal bleeding and other side effects in people who were considered to be at low or moderate risk for heart disease.

The U.S. Preventive Services Task Force (USPSTF) recommends a low-dose aspirin regimen for adults aged 50 to 59 years old with a 10-year risk of developing cardiovascular disease that is over 10%. The USPSTF recommends that for older adults, the decision to take daily low-dose aspirin should be individual.

“Low dose daily aspirin is usually used to prevent the formation of clots,” Jamie Alan, RPH, PharmD, PhD, an assistant professor of pharmacology and toxicology at Michigan State University, tells Verywell. However, Alan adds that "aspirin can be hard on your stomach, although daily aspirin is at a lower dose. Individuals are still at risk for a gastrointestinal bleed and also at risk for drug interactions while on aspirin.”

Daily Aspirin and Aggressive Cancer

McNeil says there are lots of theories as to why low-dose aspirin might be linked to aggressive cancer, but the exact reason is unknown. One theory the authors of the study posed is that aspirin might suppress anti-tumor inflammatory or immune responses that are important in controlling later-stage growth and spread of cancers.

John McNeil, PhD

A doctor should give you a good reason why you should be taking low-dose aspirin.

— John McNeil, PhD

"Such an effect may be particularly evident among an older population for which underlying anti-tumor immunity may already be compromised,” wrote McNeil and his co-authors.

That said, McNeil stresses that the findings do not mean that people should stop taking daily aspirin. “If you have had a heart attack, stroke, angina, or a transient ischemic attack, you should be taking low-dose aspirin regularly because the benefit in preventing a second heart attack, stroke, etc., is pretty strong."

If you’re otherwise healthy, though, it might be best to avoid the drug. “A doctor should give you a good reason why you should be taking low-dose aspirin,” McNeil says.

Overall, Alan says it’s really best to talk to your healthcare provider. “The potential risk may very well be minimal compared to some proven benefits.”

What This Means For You

If you’re considering taking low-dose daily aspirin, talk to your healthcare provider. You might not need to take it and, in some cases, it could do more harm than good.

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  1. McNeil JJ, Gibbs P, Orchard SG, Lockery JL, Bernstein WB, Cao Y, et al. Effect of aspirin on cancer incidence and mortality in older adultsJNCI: J Natl Cancer Inst. August 2020. doi:10.1093/jnci/djaa114

  2. Arnett DK, Blumenthal RS, Albert MA, Buroker AB, Goldberger ZD, Hahn EJ, et al. 2019 ACC/AHA guideline on the primary prevention of cardiovascular disease: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice GuidelinesCirculation. 2019;140(11). doi:10.1161/cir.0000000000000678‌

  3. The United States Preventive Services Taskforce. Recommendation: Aspirin Use to Prevent Cardiovascular Disease and Colorectal Cancer: Preventive Medication. Updated April 11, 2016.