Antibiotic exposure early in life is associated with an increased risk for developing inflammatory bowel disease (IBD), according to study results published in Gut.

Researchers conducted a national cohort and case-control study using data from the Danish Civil Registration system to identify antibiotic usage amongst residents. They identified a specific cohort who were not been previously diagnosed with IBD and were started on a course of antibiotics. Utilizing datasets of all hospitalizations and outpatient visits, individuals with a new diagnosis of IBD were identified using disease specific International Classification of Diseases, Eighth Revision or International Classification of Diseases, Tenth Revision codes (ICD-8/10).

A total of 6,104,245 individuals aged older than 10 years of age were included in the cohort, and were followed up for at least 5 years of antibiotic exposure. A total of 90.9% received at least 1 course of antibiotics. There were 36,017 new cases of UC and 16,881 new cases of CD reported during follow-up.

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Exposure vs nonexposure to antibiotics was associated with increased IBD risk. This association was observed among individuals across all age groups, including in those aged 10 to 40 years (incidence rate ratio [IRR], 1.28; 95% CI, 1.25-1.32), 40 to 60 years (IRR, 1.48; 95% CI, 1.43-1.54), or 60 years and older (IRR, 1.47; 95% CI; 1.42-1.53).

Each additional course of antibiotics further increased risk, which led to a positive dose-response relationship. The highest risk was in participants who received 5 or more courses of antibiotics among those aged 10 to 40 years (IRR, 1.69; 95% CI, 1.61-1.76), 40 to 60 years (IRR, 2.12; 95% CI, 2.01-2.23), and 60 years and older (IRR, 1.95; 95% CI, 1.85-2.04).

Timing of antibiotic exposure played a crucial role in the development of IBD. Participants in all age groups showed the highest risk of developing IBD 1 to 2 years after antibiotic exposure, and each subsequent year resulted in a lower risk for all age groups. Participants aged 10 to 40 had an IRR of 1.4 (95% CI, 1.35-1.44) 1 to 2 years after antibiotic exposure as compared with an IRR of 1.13 (95% CI 1.08 to 1.20) 4 to 5 years after exposure.

Similarly, participants aged 40 to 60 years had an IRR of 1.66 (95% CI, 1.59-1.73) 1 to 2 years after antibiotic exposure compared with an IRR of 1.21 (95% CI, 1.13-1.29) 4 to 5 years after exposure. Those aged 60 years and older had an IRR of 1.63 (95% CI, 1.57-1.70) 1 to 2 years after antibiotic exposure compared with an IRR of 1.22 (95% CI, 1.14-1.31) 4 to 5 years following antibiotic exposure.

Limitations of the study include the possibility of reverse causality (ie, infection drove development of IBD vs antibiotic use).

The researchers conclude, “The risk of IBD was greatest among individuals aged 40 years and older, increased with each subsequent antibiotic course, and was highest following exposure to antibiotic groups commonly prescribed to treat gastrointestinal pathogens.”


Faye AS, Allin KH, Iversen AT, et al. Antibiotic use as a risk factor for inflammatory bowel disease across the ages: a population-based cohort study. Gut. Published online January 9, 2023. doi:10.1136/gutjnl-2022-327845

This article originally appeared on Gastroenterology Advisor