Study: Frequent Use of Antibiotics Shows Link to IBD

Analysis indicates that for individuals older than aged 40 years, the risk is cumulative and greatest 1 to 2 years after use.

Frequent use of antibiotics may heighten the risk of inflammatory bowel disease (IBD), including Crohn disease and ulcerative colitis, among individuals aged 40 or older, according to the results of a study published in Gut.

The findings show that the risk is cumulative and greatest 1 to 2 years after use from antibiotics that target gut infections.

Previous evidence has suggested that environmental factors can contribute to the development of IBD, with 1 of the factors associated with younger individuals is the use of antibiotics. However, previously, it was unclear if the associated applied to those who are older.

Investigators used national medical data from 2000 to 2018 for Danish citizens aged 10 years or older who were not diagnosed with IBD. They wanted to determine if dosing and timing of antibiotics were important factors for the development of IBD, as well as if it varied by antibiotic type and IBD.

More than 6.1 million individuals were included in the study, with 5.5 million prescribed at least 1 course of antibiotics between 2000 and 2018.

During that time, there were approximately 16,881 new cases of Crohn disease and 36,017 new cases of ulcerative colitis diagnosed.

Overall, when compared with no antibiotic use, these drugs were associated with a high risk of IBD, regardless of age. However, investigators found that older age was associated with the highest risk.

Individuals aged 10 to 40 years older were 28% more likely to be diagnosed with IBD, while those aged 40 to 60 years were 48% more likely to be diagnosed. Investigators also found that approximately 47% of individuals aged 60 years or older were more likely.

The risks were slightly higher for Crohn disease compared with ulcerative colitis at 40%, 62%, and 51%, respectively. The risk seemed to be cumulative, with each subsequent course of antibiotics adding an additional 11%, 15%, and 14% higher risk, respectively.

The highest risk was observed among those who were prescribed 5 or more courses of antibiotics, with a 69% heightened risk for individuals aged 10 to 40 years, double the risk for those aged 40 to 60 years, and a 95% heightened risk for those aged 60 years and older.

Investigators also determined that timing mattered, with the highest risk of IBD occurring about 1 to 2 years after antibiotic exposure, with each subsequent year associated with a lower risk.

Among those aged 10 to 40 years, the IBD risk was 40% higher at 1 to 2 years after taking antibiotics compared with 13%, 4 to 5 years later. For those aged 40 to 60 years, the risk was 66% and 21%, respectively, and those aged 60 years, 63% and 22%, respectively.

The highest risk of IBD was associated with fluoroquinolones and nitroimidazoles, broad-spectrum antibiotics typically used to treat gut infections. Nitrofurantoin was the only antibiotic type not associated with IBD risk at any age.

Furthermore, narrow-spectrum penicillin was associated with IBD but to a much lesser extent.

The information available did not include what the drugs were for or how many of them patients took, investigators said.


Frequent use of antibiotics may heighten inflammatory bowel disease risk in over 40s. EurekAlert. News release. January 9, 2023. Accessed January 10, 2023.

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