Aspirin may help reduce the risk of colorectal cancer in unhealthy adults

Just two aspirin a week can help reduce the risk of colorectal cancer in adults who live an unhealthy lifestyle, a new study from Mass General Brigham finds.

Nearly 108,000 health professionals were included in the study – most were around 50 years old.

The researchers recorded their aspirin intake and assigned them a lifestyle score based on their body mass index, alcohol consumption, physical activity, diet and tendency to smoke cigarettes.

Regular aspirin use was defined as two or more standard tablets (325 milligrams each) or at least six low-dose tablets (81 milligrams each) per week.

Participants were followed for more than three decades, with researchers documenting nearly 2,500 cases of colorectal cancer.

They determined that those with unhealthy lifestyles – especially if they were overweight or heavy smokers – enjoyed the greatest benefit from aspirin use compared to their healthier peers.

Unhealthy participants had a 3.4% chance of developing colorectal cancer if they did not take aspirin regularly versus a 2.1% chance if they did.

Among the healthiest participants, the rate of colorectal cancer was 1.5% in the group taking aspirin and 1.6% in the group not taking aspirin.

The findings were published Thursday in JAMA Oncology.

“Our results show that aspirin can proportionally reduce the significantly increased risk in those with multiple risk factors for colorectal cancer,” said Dr. Daniel Sikavi, lead author of the paper and a gastroenterologist at Massachusetts General Hospital.

“In contrast, those with a healthier lifestyle have a lower baseline risk of colorectal cancer and, therefore, their benefit from aspirin was still evident, albeit less pronounced,” Sikavi added.

Colorectal cancer is one of the most common cancers worldwide – according to the Colon Cancer Coalition, about 1 in 24 Americans will get it at some point. It is also one of the obesity-related diseases that is becoming more prevalent in the younger generations.

In 2016, the US Preventive Services Task Force (USPSTF) recommended that adults in their 50s take low-dose aspirin daily for the prevention of heart disease and colorectal cancer.

Researchers say aspirin can help the immune system identify and target cancer cells, inhibit inflammation, a risk factor for colorectal cancer, and promote the growth of beneficial gut bacteria.

However, the USPSTF changed its guideline in 2022 after a study found that older people taking a low daily dose of aspirin actually had a higher risk of advanced cancer and cancer death.

The task force now says that people aged 40 to 59 who are at higher risk for heart disease should decide with their doctor whether to start taking aspirin. Potential downsides include an increased risk of bleeding.

This new study did not assess potential side effects of daily aspirin use, such as bleeding.

However, the researchers hope that “healthcare providers may more strongly consider recommending aspirin to patients who have a less healthy lifestyle.”