In a large-scale study involving over 100,000 individuals, researchers discovered that people who led less healthy lifestyles—characterized by a higher body mass index, increased smoking and alcohol consumption, decreased physical activity, and poor diet quality—experienced a greater reduction in colorectal cancer risk when using aspirin. In contrast, those with a healthier lifestyle had a lower initial risk and thus saw a smaller benefit from aspirin usage. These findings may prompt a more refined approach to recommending aspirin for prevention.
According to a study conducted by researchers at Mass General Brigham, regular aspirin use can potentially lower the risk of colorectal cancer in individuals with higher lifestyle-related risk factors. This study, featured in JAMA Oncology, suggests a more tailored approach to the use of preventive aspirin.
“Our aim was to pinpoint individuals who are more likely to gain from aspirin, assisting in personalized prevention strategies,” explained co-senior author Andrew Chan, MD, MPH, who is the Director of Epidemiology at the Mass General Cancer Center and leads the Young Adult Colorectal Cancer Center at Massachusetts General Hospital (MGH). Colorectal cancer ranks as the second leading cause of cancer deaths in the U.S., as reported by the National Cancer Institute.
The U.S. Preventive Services Task Force had earlier recommended daily low-dose aspirin for preventing cardiovascular issues and colorectal cancer in all adults between the ages of 50 and 59, the group with the highest colorectal cancer risk. However, in 2016, this recommendation was retracted due to concerns regarding aspirin’s potential to increase gastrointestinal bleeding risk.
For their study, researchers examined health data from 107,655 participants from the Nurses’ Health Study and the Health Professionals Follow-Up Study. They compared colorectal cancer rates between those who consumed aspirin regularly and those who did not. Regular use was defined as taking either two or more standard doses (325 mg) of aspirin per week or a daily low-dose (81 mg).
Participants were tracked starting at an average age of 49.4 years. Those who regularly took aspirin had a 10-year cumulative incidence of colorectal cancer of 1.98 percent, in contrast to 2.95 percent in individuals not taking aspirin.
Aspirin’s benefits were most notable among those with unhealthiest lifestyles. Individuals with the lowest healthy lifestyle scores (the unhealthiest group) had a 3.4 percent chance of developing colorectal cancer without regular aspirin use, compared to 2.12 percent with regular use. Meanwhile, in the healthiest group, the rates were 1.5 percent for those taking aspirin regularly and 1.6 percent for those not doing so. This indicates that among the least healthy individuals, treating 78 with aspirin would prevent one case of colorectal cancer over ten years, while for the healthiest group, it would require treating 909 individuals to prevent one case.
“Our study indicates that aspirin can significantly lower the already elevated risk among those with several risk factors for colorectal cancer,” stated lead author Daniel Sikavi, MD, a gastroenterologist at MGH. “Conversely, individuals with a healthier lifestyle have a lower baseline risk for colorectal cancer, thus their aspirin benefit is noticeable, though less impactful.”
Based on the study’s outcomes, “healthcare providers may increasingly consider the recommendation of aspirin for patients exhibiting less healthy lifestyles,” remarked co-senior author Long H. Nguyen, MD, MS, a physician investigator in the Clinical and Translational Epidemiology Unit and Division of Gastroenterology at MGH, and a Chen Institute Department of Medicine Transformative Scholar at MGH.
While the study included participants who took standard-dose (325-mg) aspirin two times a week in the regular-aspirin category, Sikavi emphasized that “historical evidence strongly supports the use of daily low-dose (81-mg) aspirin for prevention.”
Previous research suggests that aspirin may help lower the levels of pro-inflammatory proteins known as prostaglandins, which can facilitate cancer development. It might also hinder signaling pathways that lead to uncontrolled cell growth, affect the immune response against cancer cells, and inhibit the formation of blood vessels that supply nutrients to tumors. “Aspirin likely combats colorectal cancer through a variety of mechanisms,” Chan explained.
The study did not explore possible side effects of daily aspirin use, such as bleeding risks. Additionally, although the researchers attempted to account for numerous risk factors for colorectal cancer, the observational nature of the study means there could be other influencing factors that were not accounted for when comparing the two groups.
