Early Life Oral Antibiotics Are Associated With Pediatric‐Onset Inflammatory Bowel Disease—A Nationwide Study

Objectives: Early‐life environmental triggers are thought to play a larger role in pediatric‐onset inflammatory bowel disease (pIBD) compared to adult‐onset IBD. We aimed to assess the risk of developing pIBD after exposure to oral antibiotics during the first 5 years of life. Methods: In a nation‐wide cohort study, we identified all patients diagnosed with pIBD (<18 years at diagnosis) in Denmark between 1995 and 2018 from the National Patient Registry and matched them with up to 10 reference individuals. Antibiotic exposure was defined as being prescribed antibiotics during first 5 years of life. Data were retrieved from the National Prescription Register. Outcome was developing pIBD. Risk estimates are presented by hazard ratios (HR) with 95% confidence intervals (CI). Results: We identified 1927 pIBD patients and 18,318 reference individuals. Oral antibiotic exposure during the first 5 years of life was associated with a higher risk of developing pIBD (HR = 1.33 [95% CI: 1.2–1.5], P <0.0001). The risk was also increased if patients had ≥4 antibiotic prescriptions compared to no antibiotics (HR = 1.33 [95% CI: 1.2–1.5], P <0.0001). Broad‐spectrum antibiotics increased the risk of pIBD compared to narrow‐spectrum antibiotics (HR = 1.29 [95% CI: 1.2–1.4], P < 0.0001). When stratified by IBD subtypes, only Crohn disease was significantly associated with exposure to antibiotics (HR = 1.37 [95% CI: 1.1–1.7], P = 0.002). Conclusions: In this nationwide registry‐based study, we found that oral antibiotic exposure during first 5 years of life was associated with an increased risk of pIBD. Repeated antibiotic exposures increased risk estimates.