Overuse of antibiotics may trigger inflammatory bowel disease (IBD), new research suggests.
Among folks who were 40 or older, a new study found that antibiotics may increase the risk for bowel diseases, such as Crohn's and ulcerative colitis, for one to two years after use. And the greatest risk was posed by two classes of antibiotics — nitroimidazoles and fluoroquinolones — often used to treat gut infections.
The researchers said these drugs indiscriminately target all bacteria, not just those that cause disease.
"Antibiotics may impact the development of IBD through alteration of the microbiome," said lead researcher Dr. Adam Faye. He is an assistant professor at New York University's Grossman School of Medicine, in New York City.
To reduce your risk for IBD, Faye advises using antibiotics only when needed and not for viral diseases such as colds, flu or other respiratory and gastrointestinal illness.
"We want patients to improve quickly, so we may be more apt to prescribe an antibiotic in some of these settings, but in addition to exacerbating bacterial resistance patterns, this is another reason to practice antibiotic stewardship," Faye said. "In other words, use antibiotics when needed, but be cautious about prescribing them for an infection that will likely be self-limiting or is more likely viral."
Overuse of antibiotics can alter the bacterial balance in the gut, called the microbiome, with serious consequences, Faye warned.
This study, however, doesn't prove that antibiotics cause inflammatory bowel disease, only that there appears to be a connection.
For the study, Faye's team used a Danish national medical database from 2000 to 2018 of more than 6.1 million Danes who had not been diagnosed with IBD. In all, 91% were prescribed at least one course of antibiotics during the study period.
From 2000 to 2018, more than 36,000 people were diagnosed with ulcerative colitis and nearly 17,000 with Crohn's disease.
Faye's team found that among people who had taken antibiotics, those between 10 and 40 years of age were 28% more likely to be diagnosed with IBD, as were 48% of 40- to 60-year-olds, and 47% of those in their 60s or older.
The risk was a little higher for Crohn's disease than for ulcerative colitis: 40% among those aged 10 to 40; 62% among 40- to 60-year-olds; and 51% among those in their 60s or older.
The researchers noted that the risk rose with each course of antibiotics — adding 11% to the risk for the youngest group, and 14% for the oldest.
Those who took five or more courses of antibiotics had the highest risk of developing an IBD: For those aged 10 to 40, risk jumped 69%. It doubled for those between 40 and 60, and was 95% higher for those in their 60s or older.
How much time had passed since taking antibiotics was also a factor. It was as much as 66% higher in the first two years, dropping to as little as 13% after four or five years.
Dr. Bethany DeVito, associate chief of ambulatory clinical gastroenterology at Northwell Health in Great Neck, N.Y., noted that the gut microbiome is very complex.
"Any alterations in the microbiome can lead to diseases in, especially, the GI tract with irritable bowel syndrome," she said, after reviewing the findings. "There's talk about it being a factor in causing inflammatory bowel disease, because of the inflammation that can come about from altering the microbiome."
Antibiotics can alter the microbiome and cause diarrhea, gas and bloating. So, DeVito said, the link with IBD is not surprising.
"Only use antibiotics if you have a clear indication for it," she advised. "Many patients want antibiotics for all sorts of illnesses and doctors may find it hard to resist prescribing them."
These requests can be annoying, and doctors must hold their ground and say no, DeVito said.
"Everyone's looking for a magic pill without realizing that there are consequences to that magic," she said.
The study was published online Jan. 9 in the journal Gut.
There's more about inflammatory bowel disease at the U.S. Centers for Disease Control and Prevention.
SOURCES: Adam Faye, MD, assistant professor, department of population health, NYU Grossman School of Medicine, New York City; Bethany DeVito, MD, associate chief, ambulatory clinical gastroenterology, Northwell Health, Great Neck, N.Y.; Gut, Jan. 9, 2023, online