Introduction: Recent guidelines suggest colorectal cancer (CRC) screening for individuals under 50, but data on the clinical benefits for those 40-49 are scarce. This cohort study using a national database assessed CRC risk in this age group according to colonoscopy status. Methods: Using diagnostic and procedural codes from the Korean National Health Insurance System claims data from 2004 to 2007, we constructed a 1:2 propensity score-matched (PSM) colonoscopy cohort (CsC) and non-colonoscopy cohort (NCsC) of patients aged 40–49 years and followed them through 2020. CRC risk was evaluated after PSM between the CsC and NCsC based on age, sex, income, alcohol consumption, smoking, and the presence of metabolic syndrome. Results: Among 557,638 patients in the CsC and 1,115,276 patients in the NCsC aged 40–49 years at baseline, 4,672 (0.8%) and 14,424 (1.3%) cases of CRC, respectively. The study showed a lower cumulative incidence of CRC in patients who underwent colonoscopies: 0.7% versus 1.0% in their early 40s and 1.0% versus 1.5% in their late 40s. Compared with the NCsC, the adjusted hazard ratio for CRC development in the CsC was 0.62 (95% CI, 0.57–0.67) in men and 0.79 (95% CI, 0.73–0.85) in women in their early 40s and 0.57 (95% CI, 0.54–0.60) in men and 0.74 (95% CI, 0.69–0.78) in women in their late 40s. Discussion: Colonoscopy was associated with a 21%–43% lower CRC risk among individuals in their 40s, with the greatest risk difference observed in men in their late 40s. These findings highlight the importance of age and sex-specific screening guidelines.
Kim et al. (2026) studied this question.