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

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.

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 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.

"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.”