Antibiotic linked to bowel disease risk

Babies treated with antibiotics for middle-ear and other infections have a higher risk of developing inflammatory bowel disease later in childhood.

Both colitis and Crohn's disease are marked by chronic inflammation in the intestines, leading to symptoms like abdominal pain and diarrhoea. The conditions are thought to arise from an immune-system overreaction that injures the body's own intestinal tissue, but the underlying reasons for the aberrant immune response are unclear. There is a genetic component to inflammatory bowel disease (IBD) since the conditions can run in families. However, experts believe that environmental triggers - such as diet, an infection, or exposure to tobacco smoke - likely combine with genetic susceptibility to cause IBD in some people.

In theory, early antibiotic use could create an imbalance in the potentially beneficial and potentially harmful bacteria that establish residence in the gut during the first year of life. If the composition of the intestinal microflora is altered, the immune system may begin to react abnormally to some of the bacteria.

Researchers analysed medical records for 36 children diagnosed with either ulcerative colitis or Crohn's between 1996 and 2008, at an average age of 8 years in Canada. Each child was compared with 10 IBD-free children of the same age, sex and area of residence. It was found that 58 percent children with IBD were prescribed an antibiotic during the first year of life - most commonly for middle-ear infections, but also for respiratory and other types of infection. In contrast, only 39 percent of 360 IBD-free children studied for comparison had taken antibiotics during their first year.

Overall, antibiotic use in infancy was linked to a tripling of the risk of IBD relative to children who had no antibiotic prescriptions in their first year of life. While that relative increase in risk is large, any one child's absolute risk of developing IBD from antibiotic use - if the medications are, in fact, to blame - would be small.

The findings do not prove that early antibiotic use causes IBD in some children. But they support the theory that factors affecting the early-life balance of good and bad bacteria in the intestines may contribute to IBD. Therefore, larger studies, as well as lab research into the effects of common antibiotics on different types of intestinal bacteria, are still needed.

It is still possible that factors other than the antibiotics themselves explain the link between early use of the medications and IBD risk. The above findings offer a reminder to avoid indiscriminate use of antibiotics. Parents should be aware that antibiotics are often unnecessary for upper respiratory infections; in fact, the majority are caused by viruses and do not need nor respond to antibiotics, which target bacteria.