Aspirin Might Help Reduce Your Colon Cancer Risk

Key Takeaways

• Regular aspirin use appeared to lower the risk of developing colorectal cancer in a new study.
• The benefits were most pronounced for people with lifestyle risk factors like smoking, poor diet, and inactivity.
• Daily aspirin use does increase the risk of gastrointestinal bleeding, though, especially for adults over 60.

Aspirin might help reduce the risk of colorectal cancer in people with lifestyle factors like smoking, heavy drinking , and physical inactivity, which make them more apt to develop these tumors, a new study suggests.

Researchers followed more than 100,000 men and women for three decades starting when subjects were 49 years old on average. Scientists compared colorectal cancer rates among regular aspirin users - defined as those taking two or more standard 325 milligram doses per week or a daily low-dose 81 milligram pill - and individuals who didn't regularly take aspirin.

Overall, the cumulative 10-year colorectal cancer incidence was 1.98 percent among regular aspirin users, compared with 2.95 percent among those who didn't routinely take aspirin, according to study findings published in JAMA Oncology .

However, aspirin didn't appear to have the same degree of risk reduction for everyone in the study. Among participants with the least healthy lifestyles - based on risk factors like smoking, drinking, inactivity, poor diet, and obesity - aspirin was associated with a bigger benefit. Among this group, the 10-year cumulative colorectal cancer incidence was 2.12 percent with regular aspirin use, compared with 3.4 percent without it.

By contrast, the risk reduction was minimal for people with the healthiest lifestyles who had the lowest risk of developing colorectal cancer. In these individuals, the 10-year colorectal cancer incidence was 1.5 percent with regular aspirin use, versus 1.6 percent without it.

"Aspirin still reduces risk of colorectal cancer in those with the healthiest lifestyle," says senior study author Andrew Chan, MD, MPH , a gastroenterologist and director of epidemiology at the Massachusetts General Hospital Cancer Center and a professor at Harvard Medical School in Boston. "However, the absolute total benefit is not as strong because they were at low risk to begin with."

How Aspirin Might Prevent Cancer

While the study wasn't designed to prove whether or how aspirin might directly prevent colorectal cancer, there are several possible ways this medication might help, Dr. Chan says.

For one thing, aspirin reduces inflammation, which is known to promote tumor growth, Chan says. Aspirin also appears to block signaling pathways within cells that cause them to grow and spread, which can prevent the spread of cancer. In addition, aspirin may boost the immune system's response to cancer and block the development of blood vessels that supply nutrients to growing tumors, Chan adds.

"Aspirin may have a more pronounced benefit in individuals with less healthy lifestyles, for example, because they probably have higher levels of inflammation," Chan says.

One limitation of the study is that it didn't assess the potential side effects of daily aspirin use, such as bleeding. The risk of gastrointestinal bleeding was part of what influenced the U.S. Preventive Services Task Force in 2022 to revise its previous recommendation that many adults in their fifties take daily aspirin to prevent cardiovascular events and colorectal cancer.

The revised aspirin recommendations don't include colorectal cancer and note that its potential to prevent a first heart attack or stroke may be too small to justify the risk.

Risks of Regular Aspirin Use

Minor risks of regular aspirin use can include easy bruising, longer bleeding time if you cut yourself, heavier menstrual cycles for premenopausal women, and upset stomach, says Michael Hall, MD , chairman of the clinical genetics department and co-leader of the cancer prevention and control program at Fox Chase Cancer Center in Philadelphia. More serious risks include severe gastritis, gastrointestinal bleeding, other forms of bleeding, stroke , and serious kidney malfunction, Dr. Hall notes.

A drawback of the study is that it "unfortunately does not answer for us who are the best candidates for aspirin prevention, and at what risk level for colorectal cancer would they want to consider taking aspirin to lower their risk," says Hall, who wasn't involved in the study.

Because the risk of aspirin use is lower in younger adults, it might make sense for people at high risk for colorectal cancer based on lifestyle factors like obesity, smoking, or inactivity to consider daily aspirin earlier in adulthood, Hall says.

"A 30 year-old with multiple unhealthy lifestyle factors could consider taking preventive aspirin to mitigate future cancer risk while they are at a time in their life when the risk of the using aspirin is low, and when they can safely accrue future protective benefits as they move into their forties and fifties and colorectal cancer risk increases," Hall says. But more research is still needed to pinpoint who is most likely to benefit.

What does seem clear at this point is that the risks of aspirin for cancer prevention increase with age, says Lenard Lichtenberger, PhD , a professor emeritus of integrative biology and pharmacology at the University of Texas Health Science Center at Houston.

People under 60 years old are most likely to benefit, while older individuals are at higher risk for bleeding with regular aspirin use, says Dr. Lichtenberger, who wasn't involved in the new study.

"Aspirin has clear utility in preventing cardiovascular disease events, especially in subjects who have a history of cardiovascular disease," Lichtenberger says. "Therefore, in older subjects it is a balancing act between the cardiovascular and anti-cancer benefits of aspirin versus aspirin-associated gastrointestinal ulceration and bleeding."

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Sources

1. Sikavi DR et al. Aspirin Use and Incidence of Colorectal Cancer According to Lifestyle Risk. JAMA Oncology . August 1, 2024.
2. Aspirin Use to Prevent Cardiovascular Disease: Preventive Medication. U.S. Preventive Services Task Force . April 26, 2022.
3. Aspirin Use to Prevent Cardiovascular Disease and Colorectal Cancer: Preventive Medication. U.S. Preventive Services Task Force . April 11, 2016.

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Lisa Rapaport

Author

Lisa Rapaport is a journalist with more than 20 years of experience on the health beat as a writer and editor. She holds a master's degree from the UC Berkeley Graduate School of Journalism and spent a year as a Knight-Wallace journalism fellow at the University of Michigan. Her work has appeared in dozens of local and national media outlets, including Reuters, Bloomberg, WNYC, The Washington Post, Los Angeles Times , Scientific American , San Jose Mercury News , Oakland Tribune , Huffington Post, Yahoo! News, The Sacramento Bee , and The Buffalo News . See full bio See Our Editorial Policy Meet Our Health Expert Network