Colonoscopy is associated with lower colorectal cancer occurrence and mortality in the older population: A population-based cohort study

Background and study aims: We aimed to evaluate the association between colonoscopy (CS) and colorectal cancer (CRC) occurrence and related mortality in an older population. Patients and methods: This retrospective, nationwide, population-based cohort study used data of adults aged ≥40 years from the Health Insurance Review and Assessment Service database. After excluding CS within 6 months of CRC diagnosis during enrollment, CRC occurrence and related mortality were compared between CS and non-CS groups using a time-dependent Cox proportional hazard model. Sub-group analysis was conducted among four age groups: young, middle age, old, and very old. Results Among 748,989 individuals followed for 9.64±0.99 years, the CS group had a 65% lower CRC occurrence (adjusted hazard ratio [HRa]: 0.35, 95% confidence interval [95%CI]: 0.32–0.38) and 76% lower CRC-related mortality (HRa: 0.24, 95%CI: 0.18–0.31) after 5 years than the non-CS group. CS was associated with the most significant reduction in CRC occurrence in the middle age group (HRa: 0.32, 95%CI: 0.29–0.35) and CRC-related mortality in the young age group (HRa: 0.04, 95%CI: 0.01–0.33); the very old age group had the least reduction in both CRC occurrence and CRC-related mortality (HRa: 0.44, 95%CI: 0.33–0.59 and HRa: 0.28, 95%CI: 0.15–0.53, respectively). Conclusion We found a significant association between colonoscopy and reduction in CRC occurrence and CRC-related mortality in adults aged ≥ 40 years after 5 years of follow-up; however, these associations were weaker in the very old group. Research is needed on the association between colonoscopy and older age.