Type 2 Diabetes and Risk of Early-Onset Colorectal Cancer.

Background and Aims: Early-onset colorectal cancer (CRC) is increasing in many developed countries. Type 2 diabetes mellitus has increased substantially in younger adults; however, its role in early-onset CRC remains unidentified. Methods: We conducted a claims-based nested case-control study using IBM MarketScan Commercial Database (2006-2015). Incident early-onset CRC diagnosed at ages 18-49 was identified by the International Classification of Diseases, ninth Revision, Clinical Modification diagnosis code, and the first coded diagnostic pathology date was assigned as the index date. Controls were frequency matched with cases. Type 2 diabetes, stratified by severity, was identified through International Classification of Diseases, ninth Revision, Clinical Modification using the Klabunde algorithm. Multivariable logistic regressions were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Results: A total of 6001 early-onset CRC and 52,104 controls were included. Type 2 diabetes was associated with an increased risk of early-onset CRC (5.0% in cases vs 3.7% in controls; OR = 1.24, 95% CI: 1.09-1.41). The positive association was more pronounced for uncontrolled (OR = 1.37; 95% CI: 1.12-1.67) or complicated (OR = 1.59, 95% CI: 1.08-2.35) type 2 diabetes compared with controlled diabetes (OR = 1.13, 95% CI: 0.94-1.36). Conclusion: Individuals with type 2 diabetes have a higher risk of early-onset CRC, with stronger associations for uncontrolled diabetes and complicated diabetes. The rising prevalence of type 2 diabetes among younger adults may partially contribute to the increasing incidence of early-onset CRC.