Frequent antibiotic use may increase the risk of inflammatory bowel disease in patients over the age of 40, an analysis of Danish healthcare records shows.

Researchers found the risk seemed to be cumulative and greatest one to two years after antibiotic use.

While antibiotics have been implicated in inflammatory bowel disease in younger age groups, the data on the impact on adults has been limited, the researchers reported in the journal Gut.

Healthcare records from more than six million individuals between 2000 and 2018, which included almost 53,000 new cases of inflammatory bowel disease found antibiotic exposure increased the risk of the condition in all patients but was highest in those aged 40 to 60 years or over 60.

Compared with no antibiotic use, those aged 10-40 were 28% more likely to be diagnosed with IBD after taking the drugs but 40-60-year-olds were 48% more likely to do so, while the over 60s were 47% more likely.

Similar results were seen for both ulcerative colitis and Crohn’s disease and the link was greatest for antibiotics often prescribed for gastrointestinal pathogens – nitroimidazoles and fluoroquinolones – the researchers reported.

Each subsequent course was found to add an extra 11%, 15%, and 14% heightened risk, in those aged 10-40, 40-60 and over 60 years respectively.

The highest risk of all was observed among those prescribed five or more courses of antibiotics, which led to a doubling in risk for 40–60-year-olds and a 95% heightened risk for the over 60s.

Nitrofurantoin was the only antibiotic type not associated with inflammatory bowel disease risk at any age and narrow spectrum penicillins were also associated with developing the condition, although to a much lesser extent.

Plausible explanations for the findings include the natural waning of both the resilience and range of microbes in the gut microbiome associated with ageing, which is likely to be compounded by antibiotic use.

‘With repeated courses of antibiotics, these shifts can become more pronounced, ultimately limiting recovery of the intestinal microbiota,’ the US and Danish researchers concluded.

They suggested that limiting prescriptions for antibiotics may not only help to curb antibiotic resistance but may also help lower the risk of inflammatory bowel disease.

‘This is the first national cohort study providing critical insights into the role that antibiotics play in the development of IBD across the ages.

‘Our results demonstrate a positive dose-response, highlighting the strong association between antibiotic exposure and the development IBD, particularly among adults aged 40 years and older.’

This article first appeared on our sister publication, Pulse.