Antibiotic use as a risk factor for inflammatory bowel disease across the ages: a population-based cohort study

Background There is an increasing incidence of inflammatory bowel disease (IBD) for which environmental factors are suspected. Antibiotics have been associated with development of IBD in earlier generations, but their influence on IBD risk in adults is uncertain. Objective To assess the impact of antibiotic exposure, including dose-response, timing and antibiotic class, on the risk of IBD in all individuals aged ≥10 years. Design Using Denmark nationwide registries, a population-based cohort of residents aged ≥10 years was established between 2000 and 2018. Incidence rate ratios (IRRs) for IBD following antibiotic exposure were calculated using Poisson regression. Results There were a total of 6 104 245 individuals, resulting in 87 112 328 person-years of follow-up, and 52 898 new cases of IBD. Antibiotic exposure was associated with an increased risk of IBD as compared with no antibiotic exposure for all age groups, although was greatest among individuals aged 40-60 years and ≥60 years (age 10-40 years, IRR 1.28, 95% CI 1.25 to 1.32; age 40-60 years, IRR 1.48, 95% CI 1.43 to 1.54; age ≥60 years, IRR 1.47, 95% CI 1.42 to 1.53). For all age groups a positive dose-response was observed, with similar results seen for both ulcerative colitis and Crohn's disease. The highest risk of developing IBD was seen 1-2 years after antibiotic exposure, and after use of antibiotic classes often prescribed to treat gastrointestinal pathogens. Conclusion Antibiotic exposure is associated with an increased risk of IBD, and was highest among individuals aged 40 years and older. This risk increased with cumulative antibiotic exposure, with antibiotics targeting gastrointestinal pathogens and within 1-2 years after antibiotic exposure.