There is substantial evidence that a daily aspirin can reduce risk of colorectal cancer (CRC) in adults up to age 70, but until now there was little evidence about whether older adults should start taking aspirin. Researchers led by Dr Andrew T Chan, a gastroenterologist and chief of the Clinical and Translational Epidemiology Unit at Massachusetts General Hospital (MGH), have found that taking aspirin before the age of 70 lowers CRC risk. The findings¸ ‘Aspirin Use and Risk of Colorectal Cancer Among Older Adults’, published in JAMA Oncology, also reported that people who started regular aspirin use at the age of 70 or older did not seem to reap any benefit.
The researchers carried out a pooled analysis of two large U.S. cohort studies: The Nurses' Health Study (January 1980—June 2014) and the Health Professionals Follow-up Study (January 1986—January 2014). These two studies contributed data on more than 94,500 participants' use of aspirin over about 35 years, offering a unique opportunity to understand the effect of aspirin use across the lifespan on cancer risk.
"There is considerable evidence that aspirin can prevent colorectal cancer in adults between 50 and 70 years old," says Chan. "But it has not been clear whether the effect is similar in older adults. As people get older, if they are not already taking aspirin, a discussion is warranted about whether to start aspirin after weighing the benefits against the risks."
Aspirin is considered the most well-established agent that protects against colorectal cancer (CRC). It is currently recommended by the US Preventive Services Task Force for people aged 50-59 years with specific cardiovascular risk profiles because of its protective effect against heart disease.
However, the recent Aspirin in Reducing Events in the Elderly (ASPREE) trial reported that participants who took a daily low dose of aspirin (100 mg) after age 70 for about five years actually had an unexpected 30% higher risk of death from cancer. The vast majority of the ASPREE participants (89%) had never taken aspirin regularly before joining the study. Chan's team also recently reported that ASPREE participants on aspirin did not experience an increase or decrease in risk of developing a cancer despite having an increase in risk of death from cancer.
The current study confirms that initiating aspirin at an older age was not associated with a lower risk of colorectal cancer. However, importantly, there is a potential benefit of continuing aspirin if is started at an earlier age. These results, the researchers say, "strongly suggest that there is a potential biological difference in the effect of aspirin at older ages which requires further research."