Assessing Aspirin's Strengths and Weaknesses in Cancer Prevention

Many advanced-age people at high risk for heart disease take daily aspirin to keep their condition from getting worse, but aspirin’s benefits might extend well beyond cardiology. According to a new study, aspirin use three or more times per week was associated with a reduction in deaths from cancer in patients aged 65 and older.

To arrive at this association, researchers led by Holli Loomans-Kropp, PhD, MPH, of the Division of Cancer Prevention at the National Institute of Health, evaluated aspirin use among more than 120,000 patients aged 65 years and older between 1993 and 2008.

Compared with no use, taking aspirin one to three times per month was associated with a reduced risk of all-cause death and death from cancer. Additionally, aspirin use three times per week was associated with a reduced risk of all-cause death, death from cancer, and more specifically, death from gastrointestinal (GI) cancer and colorectal cancer (CRC).

Overall, the most striking benefit was found for CRC — patients who took aspirin three or more times per week saw the greatest reductions in CRC mortality.

While these effects are notable, Loomans-Kropp and colleagues found that the degree to which a patient would see preventative benefits from aspirin was associated with an individual patient’s body mass index (BMI). Participants who were underweight (those having a BMI less than 20) had no observable benefit associated with aspirin use, while those with a BMI of 20 or higher saw reduced risk of death, particularly with aspirin use three or more times per week. Moreover, reduced risk of death from CRC was only associated with people who had a BMI between 20 and 29.9 who reported aspirin use three or more times per week.

>> Interested in calculating your BMI? Try this calculator from the US Centers for Disease control and Prevention.

This is not the first study to find an association between aspirin use and decreased cancer risk. A 2016 systematic analysis of cardiovascular prevention trials found reduced rates of CRC between 10 and 19 years following the start of an aspirin regimen. In 2011, a systematic analysis of eight clinical trials found that daily aspirin use was associated with reduced risk of death from several types of cancer, with increased benefit associated with long-term use. A third study in veterans from 2018 also found that aspirin users were associated with reduced risk of CRC death compared with nonusers.

While this evidence is promising, it does not suggest that aspirin is a cancer prevention cure-all, or that people with cancer, or at high risk for cancer should begin taking aspirin without first consulting their doctor.

In fact, recent evidence has triggered an update in prescribing guidelines that limits the amount of people who should be taking daily aspirin, and the amount of aspirin people should take. Taking a daily baby aspirin was once a standard recommendation for healthy older adults, because it was understood to be a simple and cost-effective way to prevent heart attacks and strokes. But taking daily aspirin could bring on unwanted effects, like increased risk for bleeding in the stomach and brain.

In March 2019, the American Heart Association and the American College of Cardiology recommended against the use of low-dose (81-mg) aspirin in people older than 70 who do not have existing heart disease and haven’t had a stroke, or in people of any age who have an increased risk for bleeding, according to Harvard Health Publishing.

“Although aspirin use is associated with benefits as a cancer preventive agent, the changing characteristics of the global population may alter its efficacy and must be considered along with age and risk of bleeding before recommending aspirin for cancer prevention,” the authors wrote in conclusion.