A dose‐dependent increase in the risk of inflammatory bowel disease after exposure to broad‐spectrum antibiotics: A national population study in Korea

Summary Background The association between antibiotic use and risk of inflammatory bowel disease (IBD), particularly among adults, remains unclear. Furthermore, there is a scarcity of data among non‐Western countries. Aims To investigate the association and dose–response relationships between antibiotic use and subsequent IBD risk across all ages Methods This population‐based case–control analysis used data from the Korean National Health Insurance Service database (2004–2018). We compared 68,633 patients with new‐onset IBD to matched controls ( n = 343,165) using multivariable conditional logistic regression analysis. We also examined the dose–response relationship using non‐linear regression analysis, and separately analysed childhood‐onset IBD (aged ≤14 years) risk following early‐life antibiotic exposure. Results The mean age at diagnosis was 45.2 ± 16.8 years. Antibiotic prescriptions between 2 and 5 years before diagnosis significantly increased the odds of developing IBD (adjusted odds ratio [OR], 1.24; 95% confidence interval [CI]: 1.21–1.27). Additionally, sensitivity analysis revealed an elevated risk up to 9 years before diagnosis. Broad‐spectrum antibiotics increased IBD risk, independent of gastroenteritis. A distinct dose–response relationship was observed irrespective of the IBD subtype and study population (all p < 0.001). Furthermore, antibiotic exposure within the first year of life was linked with the risk of childhood‐onset IBD (OR, 1.51; 95% CI: 1.25–1.82). Conclusions Broad‐spectrum antibiotics dose‐dependently increased the risk for IBD in the Korean population. Our findings provide a fundamental epidemiological basis for identifying antibiotic use as a significant risk factor for IBD across different environmental backgrounds.