Study finds aspirin reduces risk of colon cancer, but effect varies with lifestyle factors

In a recently published study, JAMA Oncology, Researchers are evaluating the association between aspirin use, lifestyle factors, and risk of colorectal cancer (CRC).

study: Aspirin use and colorectal cancer incidence due to lifestyle risksImage credit: Kmpzzz / Shutterstock.com

Can aspirin prevent colon cancer?

Aspirin is effective in preventing colorectal neoplasia, defined as abnormal cell growth in the colon or rectum. However, the long-term risks associated with chronic aspirin use limit its widespread use. Therefore, individualized recommendations are needed to identify patients most likely to benefit from this treatment.

Several studies have shown that the anticancer effects of aspirin use may vary depending on an individual's diet, body mass index, and smoking habits, therefore, additional research remains needed to refine prevention strategies and understand the impact of aspirin on CRC risk across different lifestyle factors.

About the Research

Study participants were enrolled in two prospective cohort studies, including men from the Health Professionals Follow-up Study (HPFS) and women from the Nurses' Health Study (NHS). The NHS began in 1976 with 121,700 female nurses aged 30 to 55 years, while the HPFS began in 1986 with 51,529 male health professionals aged 40 to 75 years. Study participants with a history of cancer or inflammatory bowel disease before baseline or with missing baseline data were excluded from the study.

Follow-up continued until CRC diagnosis, death, or end of follow-up, which was 30 June 2018 for the NHS and 31 January 2018 for the HPFS. Data analysis was performed between 1 October 2021 and 22 May 2023. More than 90% of study participants completed biennial questionnaires regarding diet, lifestyle, medication use, and disease outcomes, including CRC.

Data on regular aspirin use were collected for the NHS from 1980 and for the HPFS every two years from 1986. Regular aspirin use was defined as taking two or more standard-dose tablets of 325 mg or six or more low-dose tablets of 81 mg every week.

Lifestyle factors such as smoking, BMI, physical activity, alcohol intake, diet, etc. were assessed. Based on these factors, a healthy lifestyle score was created, with scores ranging from 0 to 5, with higher scores indicating a healthier lifestyle.

To assess the absolute benefit of regular aspirin use by lifestyle score, we calculated multivariate-adjusted 10-year cumulative CRC incidence rates. Cox proportional hazards regression models were adjusted for age, lifestyle factors, sex, family history of CRC, and endoscopy.

Absolute risk reductions (ARRs) and numbers needed to treat (NNTs) were calculated, and the potential latent effect of aspirin was also taken into account by assessing the 20-year cumulative CRC incidence.

Cox models estimated hazard ratios for incident CRC due to aspirin use across lifestyle scores, and multiplicative interactions were assessed by likelihood ratio tests.

research result

Among 107,655 study participants (63,957 women from the NHS and 43,698 men from the HPFS), 2,544 incident CRC events were recorded over 3,038,215 person-years. Approximately 41% of study participants were considered to be regular aspirin users. The mean baseline age was 49.4 years with a standard deviation of 9 years.

The 10-year multivariate-adjusted cumulative CRC incidence was 2.95% in nonregular aspirin users compared with 1.98% in regular users, representing an ARR of 0.97% and an NNT of 103.

The ARR associated with regular aspirin use gradually decreased with increasing lifestyle scores: specifically, the 10-year ARR for aspirin users was 1.28% for participants with the unhealthiest lifestyle scores of 0 or 1, 0.61% for participants with a lifestyle score of 2, 0.65% for participants with a lifestyle score of 3, and 0.11% for participants with the healthiest lifestyle scores of 4 and 5.

In the 20-year multivariate-adjusted cumulative incidence of CRC, those who did not take aspirin regularly had a cumulative incidence of 5.56% compared with 4.05% in those who did, resulting in an ARR of 1.51%. The ARR associated with aspirin use decreased with increasing lifestyle score, with an overall ARR of 1.39% in participants with the lowest observed lifestyle score compared with 0.04% in those with the highest score.

Regarding the individual components of the healthy lifestyle score, a higher 10-year ARR was observed in participants who reported a BMI of 25 or more, moderate/heavy smokers, moderate/heavy alcohol drinkers, and low physical activity and adherence to dietary recommendations.

People who took aspirin regularly had an 18% reduced risk of developing CRC compared with people who did not take aspirin regularly. The relative reduction in CRC incidence was consistent across the different healthy lifestyle score groups. Furthermore, supplemental analyses showed that the relative risk reduction varied by BMI and alcohol intake, but not by other factors.

Conclusion

Study participants who lived unhealthy lifestyles experienced the most significant absolute benefits from aspirin use, especially with regard to BMI and smoking.Regular aspirin use was associated with similar reductions in CRC incidence across different lifestyle profiles.

The protective effect of aspirin against CRC may involve several different mechanisms, including suppression of proinflammatory signals and modulation of antitumor responses. Despite previous extensive recommendations, it remains important to identify those who would benefit most from aspirin because of potential side effects of chronic aspirin use.