Association between Type 2 Diabetes and Gastrointestinal Bleeding: A Nationwide Population-Based Cohort Study in South Korea

Type 2 diabetes mellitus (T2DM) is linked to an elevated risk of gastrointestinal bleeding (GIB), but the effects of diabetes duration and severity remain unclear. We investigated these associations in a nationwide Korean cohort. This retrospective cohort study used the Korean National Health Insurance database from individuals who underwent national health screening between 2009 and 2015. Participants were classified as having normal glucose, impaired fasting glucose (IFG), new-onset diabetes, diabetes <5 years, or diabetes ≥5 years. GIB was defined by fulfilling all three: hospitalization, red blood cell transfusion, and ICD-10 GIB codes. Because hemoglobin A1c data were unavailable, insulin treatment served as a surrogate for diabetes severity. Kaplan-Meier and Cox proportional hazards models were applied to estimate cumulative incidence and adjusted hazard ratios (aHRs), adjusting for medications and comorbidities. Upper GIB risk increased progressively with diabetes duration: aHR 1.081 (95% confidence interval [CI], 1.008 to 1.159) for IFG; 1.265 (1.128 to 1.418) for new-onset diabetes; 1.561 (1.392 to 1.751) for diabetes <5 years; and 1.738 (1.578 to 1.915) for diabetes ≥5 years. Elevated risk was also observed among those receiving insulin. In contrast, diabetes duration was not significantly related to lower GIB: aHR 0.949 (95% CI, 0.830 to 1.085) for IFG; 1.150 (0.902 to 1.468) for new-onset diabetes; 1.202 (0.944 to 1.531) for diabetes <5 years; and 0.984 (0.792 to 1.224) for diabetes ≥5 years. Longer duration and greater severity of T2DM are associated with increased risk of upper GIB, whereas no significant association was found for lower GIB.