Antibiotic Use Linked to Increased Risk of Inflammatory Bowel Disease, Study Finds

A new study published in the journal Gut highlights a concerning association between frequent antibiotic use and an increased risk of developing inflammatory bowel diseases (IBD), including Crohn’s disease and ulcerative colitis.

Key Findings on Antibiotic Exposure and IBD Risk

Researchers analyzed health records from over 6 million Danish residents aged 10 and older, all initially free of IBD, between 2000 and 2018. Of these, more than 5.5 million individuals were prescribed antibiotics at least once.

During the study period, 36,017 individuals were diagnosed with ulcerative colitis and 16,881 with Crohn’s disease. The analysis revealed that any antibiotic use increased the likelihood of developing IBD, with older adults facing the highest risks.

• IBD Diagnosis Risk Compared to Non-Antibiotic Users:
  • Ages 10–40: 28% increased risk
  • Ages 40–60: 46% increased risk
  • Over 60: 47% increased risk
• Crohn’s Disease Risk:
  • Ages 10–40: 40% higher risk
  • Ages 40–50: 62% higher risk
  • Over 50: 51% higher risk

Cumulative Effect of Antibiotics

The risk of IBD rose with the number of antibiotic courses taken:

• 11% increase after the second round
• 15% increase after the third
• 14% increase after the fourth

Those who underwent five or more courses had the highest risk:

• Ages 10–40: 59% higher risk
• Ages 40–60: Risk nearly doubled
• Over 60: 95% increased risk

Importantly, the researchers noted that the greatest risk appeared one to two years after antibiotic use and gradually decreased over time if no further antibiotics were taken.

• Risk Drop Over Time Without Further Antibiotic Use:
  • Ages 10–40: 40% risk after 1–2 years; down to 13% by 4–5 years
  • Ages 40–60: 66% risk initially; down to 21%
  • Over 60: 63% initially; dropped to 22%

Antibiotic Type Matters

One exception was nitrofurantoin, an antibiotic mainly used for urinary tract infections. It showed no association with IBD risk across all age groups. Experts attribute this to its more targeted action on urinary pathogens, sparing the gut microbiome.

Implications for Gut Health and Microbiome

This research strengthens the hypothesis that disruptions to the gut microbiome play a role in IBD development. Many antibiotics, especially broad-spectrum ones, can alter microbial diversity in the gut—potentially triggering chronic inflammation.

However, the study did have limitations. Researchers relied on prescription data without confirming whether patients completed the treatments or their durations.

Expert Perspectives on Antibiotic Use

While antibiotics remain essential for treating bacterial infections, experts urge more cautious and evidence-based use.

“Antibiotics are lifesaving but can be a double-edged sword with long-term consequences,” noted Dr. Sara Mesilhy, MRCP, a gastroenterologist with the Royal College of Physicians.

“This study shouldn’t be interpreted as a call to avoid antibiotics altogether,” added Dr. Adam Faye of NYU Grossman School of Medicine. “It emphasizes the importance of antibiotic stewardship—not only to curb resistance but also to potentially reduce IBD development, especially in older adults.”

Understanding Inflammatory Bowel Disease (IBD)

IBD includes Crohn’s disease and ulcerative colitis, both chronic conditions marked by inflammation in the gastrointestinal tract. Symptoms can include:

• Persistent diarrhea
• Abdominal pain
• Rectal bleeding
• Weight loss
• Fatigue

The exact cause of IBD remains unclear, but it likely involves a mix of genetic, environmental, and immunological factors. Antibiotic exposure now appears to be an additional contributing factor.

“In younger patients, family history often plays a larger role, whereas in older patients, environmental triggers—such as antibiotic use—are more significant,” Dr. Mesilhy added.