According to a study published in the journal Gut, frequent use of antibiotics increases the risk of inflammatory bowel disease (IBD), including Crohn′s disease and ulcerative colitis, in people aged 40 and above. The researchers stated that the risk was a cumulative effect caused by the continuous use of antibiotics, especially those used to treat gut infections, over a period of 1 to 2 years.

In the study, 6.1 million people were enrolled, out of whom 5.5 million were prescribed at least one course of antibiotic between 2000 and 2018. The study′s findings revealed that 36, 017 and 16,881 new cases of ulcerative colitis and Crohn′s disease, respectively, were reported during the same period. It also showed that people in the age groups of 10–40, 40–60, and 60+ were, respectively, 28%, 48%, and 47% more likely to develop IBD.

However, the risk of developing Crohn′s disease was slightly higher than the risk of ulcerative colitis, which was reported at 40% among 10- to 40-yyear-olds, 62% among 40- to 60-year-olds, and 51% among those over the age of 60. The researchers also observed that the frequent usage had a cumulative effect as per the age band, such that it was 11%, 15%, and 14%, respectively.

Additionally, it was seen that the highest risk was among people who were prescribed five or more courses of antibiotics. When the risk was divided by age band, it was reported as a 69% heightened risk for 10- to 40-year-olds, a doubling in risk for 40- to 60-year-olds, and a 95% heightened risk for those over the age of 60. In the 10- to 40-was seen that the highest risk was among people who were prescribed five or more courses of antibiotics. 

When the risk was divided by age band, it was reported as a 69% heightened risk for 10- to 40-year-olds, a doubling in risk for 40- to 60-year-olds, and a 95% heightened risk for those over the age of 60. In the 10- to 40-year-old age group, the risk of IBD was 40% after taking antibiotics for 1-2 years in comparison to taking them for 4-5 years (13%). The equivalent figures for 40- to 60-year-olds were 66% vs. 21%, and for those over 60, they were 63% vs. 22%. 

(Source: https://www.medicalnewstoday.com/articles/frequent-antibiotic-use-increases-risk-of-ibd)