Antibiotics identified as culprit for older-onset IBD

Antibiotic use appears to be harmful for older adults, with a recent study showing that regardless of class, the drugs raise the risk of developing inflammatory bowel disease (IBD).

In an analysis that involved more than two million individuals aged ≥60 years, any antibiotic use contributed to a 64-percent increase in the rate of a new diagnosis of Crohn’s disease or ulcerative colitis (incidence rate ratio [IRR], 1.64, 95 percent confidence interval [CI] 1.58–1.71), said lead researcher Dr Adam Faye, assistant professor of medicine and population health at NYU Grossman School of Medicine, New York, US, in a presentation at the Digestive Disease Week (DDW) 2022.

There was a notable dose-response effect, in which increasing exposure to antibiotics was associated with increasing rates of incident IBD, ranging from a 1.27-fold increase for those exposed to a single course to a 2.35-fold increase for those exposed to five courses or more. The corresponding IRRs were 1.27 (95 percent CI, 1.21–1.33) for one course of antibiotics, 1.54 (95 percent CI, 1.46–1.63) for two courses, 1.66 (95 percent CI, 1.67–1.77) for three courses, 1.96 (95 percent CI, 1.83–2.09) for four courses, and 2.35 (95 percent CI, 2.24–2.47) for five or more courses. [DDW 2022, abstract 400]

Faye noted a higher rate of new IBD diagnoses when antibiotics were prescribed 1–2 years prior (IRR, 1.87, 95 percent CI, 1.79–1.94). The rate slightly decreased but remained elevated for antibiotic prescriptions in the period 2–5 years before diagnosis (IRR, 1.42, 95 percent CI, 1.36–1.48).

“Additionally, all antibiotic classes were associated with the development of IBD, including those not used to treat gastrointestinal infections,” he said.

Fluoroquinolones had the highest rate of incident IBD (IRR, 2.27, 95 percent CI, 2.08–2.48), followed by nitroimidazoles (IRR, 2.21, 95 percent CI, 1.95–2.50) and macrolides (IRR, 1.74, 95 percent CI, 1.64–1.84). The associations persisted in an analysis stratified by IBD type, although the effect estimates were slightly higher for Crohn’s disease than for ulcerative colitis.

“Older adults are the fastest growing subpopulation of patients with IBD, with approximately 15 percent diagnosed after 60 years of age… In [this group], we think that environmental factors are more important than genetics,” Faye pointed out.

“When you look at younger patients with new diagnoses of Crohn’s disease and ulcerative colitis, there’s generally a strong family history. But that is not the case in older adults, so it’s really something in the environment that is triggering it,” he added.

For the study, Faye and colleagues used data from Denmark nationwide registries and included 2,327,796 individuals aged 60–90 years, yielding 22,670,484 person-years of follow-up. A total of 10,773 new cases of ulcerative colitis and 3,825 new cases of Crohn’s disease occurred during the follow-up period.

Faye stressed the value of weighing the risk, saying that while antibiotic stewardship is important, avoiding antibiotics altogether is not the way to go either.

“If you’re not sure what you are treating, I would be cautious. If patients are coming in with clear infections, and they need antibiotics, they should not be withheld because of these findings,” he added.