The more antibiotics that seniors take, the greater their risk of inflammatory bowel disease (IBD), a new study suggests.
The findings could help explain some of the increase in Crohn’s disease and ulcerative colitis (common types of IBD) among older adults, according to the study authors.
“In older adults, we think that environmental factors are more important than genetics,” says lead researcher Dr. Adam Faye. He is an assistant professor of medicine and population health at NYU Grossman School of Medicine in New York City.
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“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,” Faye said in a news release from the upcoming Digestive Disease Week meeting.
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What Are Antibiotics?
Antibiotics are medications that kill or stop the growth of bacteria. They don’t directly reduce inflammation but target infections that may trigger or worsen inflammation in the body. By altering the gut microbiome (the balance of bacteria in the intestines), antibiotics can sometimes help manage IBD symptoms — though they also carry risks.
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Examples of antibiotics used in IBD treatment include metronidazole and ciprofloxacin, which are available as oral medications or injections.
The Study: Antibiotics and IBD Risk in Seniors
For the study, Faye and his colleagues analyzed prescribing records for 2.3 million adults aged 60 and older in Denmark who were newly diagnosed with IBD between 2000 and 2018.
The researchers found a clear link between antibiotic use and higher rates of IBD, with the risk rising significantly with each additional course of antibiotics:
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1 course → 27% higher risk
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2 courses → 55% higher risk
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3 courses → 67% higher risk
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4 courses → 96% higher risk
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5+ courses → 236% higher risk
The highest risk was seen in patients who had taken antibiotics within the previous one to two years, but the risk remained elevated for up to five years.
Interestingly, the increased risk was found for nearly all antibiotic classes except nitrofurantoin, which is commonly prescribed for urinary tract infections. Antibiotics used for gastrointestinal infections showed the strongest association with new IBD diagnoses.
Who Are Antibiotics Used For in IBD?
Antibiotics are not a standard first-line treatment for mild IBD, but are often prescribed to manage complications such as:
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Abscesses
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Perianal fistulas
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Pouchitis (inflammation of an internal pouch created after surgery)
They may also be prescribed when the immune system cannot clear bacterial infections on its own.
Effectiveness of Antibiotics in IBD
Research suggests:
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Ulcerative Colitis (UC): Antibiotics can help induce remission during active disease, but no particular class is universally recommended. They are not proven to prevent relapse in inactive UC.
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Crohn’s Disease (CD): Antibiotics are effective for inducing remission, reducing fistula drainage, and helping prevent relapse in inactive disease. Again, no single antibiotic is considered superior.
Side Effects and Risks of Antibiotics
While often necessary, antibiotics carry risks. Common side effects include:
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Nausea, vomiting, diarrhea
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Yeast infections in women
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Clostridium difficile infection, a serious intestinal infection
Specific risks:
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Metronidazole may cause constipation, metallic taste, or — with long-term use — numbness in hands/feet affecting balance. Alcohol use with metronidazole can trigger nausea, flushing, and weakness.
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Ciprofloxacin may cause rare nausea and diarrhea, insomnia, vivid dreams, and (in rare cases) tendonitis. It also prolongs caffeine effects.
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Should You Be Taking Antibiotics?
The study highlights the importance of cautious antibiotic use — not only to prevent antibiotic resistance, but also to lower the risk of IBD in seniors.
“Antibiotic stewardship is important; but avoiding antibiotics at all costs is not the right answer either,” Faye says. “If patients are coming in with clear infections, and they need antibiotics, they should not be withheld because of these findings.”
If you are concerned about the side effects of any antibiotics you are prescribed, speak with your doctor. In some cases, alternative treatment methods may be available.
