Inflammatory bowel disease (IBD) affects about 7 million people worldwide, and the numbers are growing. A 2022 Danish study found that the prevalence of IBD doubled between 1995 and 2016. The most significant increase was seen among adults ages 40 years or older with ulcerative colitis (UC). Environmental factors are suspected of playing a role in the increasing prevalence of IBD, including ulcerative colitis. Antibiotic exposure has been linked to IBD development in children, but it is unclear whether antibiotic use is associated with an increased risk of IBD in adults.

In a study published earlier this year in the journal Gut, Adam S. Faye, M.D., of an IBD specialist at NYU Langone Health in New York and an assistant professor at NYU Grossman School of Medicine, and colleagues conducted a population-based cohort study to investigate the impact of antibiotic use on the risk of IBD in individuals ages 10 years and older.

Using data gathered from the Danish Civil Registration System, Faye and his colleagues identified over six million individuals, ages 10 years and older, with no previous IBD history between January 1, 2000, and December 31, 2018. About 90% had received at least one course of antibiotics during the study time. Antibiotic classes included broad spectrum and narrow spectrum penicillin, nitrofurantoin, sulfonamides, tetracyclines, and macrolides. Nitroimidazoles, such as metronidazole, and fluoroquinolones were included due to their common use in treating gastrointestinal (GI) infections.

The researchers found that antibiotic exposure increased the risk of IBD in all age groups, but the greatest increase was seen among adults ages 40 years and older. The risk of IBD increased with each subsequent course of antibiotics, with the highest risk observed in individuals who received five or more courses of antibiotics. The highest risk for developing IBD was seen one to two years after antibiotic use. The and the risk declined with each subsequent year after that.

Nitrofurantoin was the only antibiotic not associated with an increased risk of developing IBD. The classes with the strongest association were those typically used to treat GI infections, nitroimidazoles and fluoroquinolones.

Faye and colleagues conclude that antibiotic exposure is associated with an increased risk of developing IBD, especially among adults ages 40 years and older. “The association between antibiotic exposure and the development of IBD underscores the importance of antibiotic stewardship as a public health measure and suggests the gastrointestinal microbiome as an important factor in the development of IBD, particularly among older adults,” they wrote.