People who regularly take aspirin over several years may be less likely to develop colon cancer, researchers say.
They found that regular aspirin use for several years was tied to a lower risk of cancer in general, but that was mainly due to a reduced risk of colon cancer.
"We did find that aspirin reduced someone's risk of developing cancer overall," said senior author Dr. Andrew Chan, of Massachusetts General Hospital. "Much of that reduced risk is of cancers of the gastric system."
Aspirin reduces inflammation throughout the body, which may influence cancer risk. Additionally, Chan told Reuters Health, aspirin may affect prostaglandins, natural compounds with a role in the development of colon cancer.
In 2015, the government-backed U.S. Preventive Services Task Force said people taking aspirin for at least 10 years to prevent cardiovascular disease may also have a reduced risk of colon cancer.
Previous research also suggested that routine aspirin use is linked to a reduced risk of overall cancer, Chan and his colleagues write in JAMA Oncology.
For their new work, the researchers used data on 88,084 women and 47,881 men participating in two large studies.
Women were between ages 30 and 55 when they enrolled in 1976, and men were between ages 40 and 75 when they enrolled in 1986.
During about 32 years of follow up, there were 20,414 cancers among women and 7,571 among men.
Overall, people who took aspirin regularly were about 3 percent less likely to develop cancer than those who didn't regularly take aspirin.
Aspirin use was not tied to a decreased risk of breast, advanced prostate or lung cancers.
Instead, the lower risk was mostly due to a 15 percent reduced risk of gastrointestinal tract cancers, which was itself mostly due to a 19 percent reduced risk of colon cancers.
The new study suggests aspirin use may compliment colon cancer screening and lead to benefits among people who don't follow recommendations to get screened, write Karen Colbert Maresso and colleagues of the University of Texas MD Anderson Cancer Center in Houston, in an editorial.
They write that about 17 percent of colon cancers could be prevented with regular aspirin use among people who don't get colonoscopies. About 9 percent of colon cancers could be prevented with regular aspirin use among people who do get screened.
In the study, the reduced risk of gastrointestinal cancers was tied to taking 0.5 to 1.5 aspirin tablets per week for at least six years.
"What it looks like is even reasonably low doses like a baby aspirin a day has some benefit," Chan said. "What's unclear is if higher doses have more of an effect. I think that question is still open."
The researchers warn that more information is needed on the cost-effectiveness of using aspirin for prevention and the possibility of side effects, including an increased risk of gastric bleeding.