Our changing environment may play a role in increasing susceptibility to developing inflammatory bowel disease (IBD), according to evidence from the US.

During all of 2000 and 2001, pediatric gastroenterologists in Wisconsin voluntarily identified all new cases of IBD for children in their care. The demographic and clinical data were sent to a central registry for analysis. The results were extrapolated from a population base of 5.4 million people, where children less than 18 years of age accounted for 26% of the total.

IBD is a term that refers to two diseases of the intestines: Crohn’s disease (CD) and ulcerative colitis (UC). These diseases have a few similarities but are, in fact, significantly different. Both diseases are inflammations of the intestines. UC only involves the large bowel and always starts at the anus. CD can involve any portion of the digestive tract from the mouth to the anus, and is often patchy in presentation.

In UC, the inflammation involves only the inner mucosa; while in CD the inflammation extends right through into the muscle and even into the serosa. The inflammatory process causes dilation of blood vessels with increased warmth, oozing of fluid into the tissue, infiltration with inflammatory cells, and ulceration of the mucosa. Abdominal cramps, weight loss, and bloody diarrhea are common symptoms.

As reported in the October 2003 Journal of Pediatrics, the overall confirmed incidence of IBD in children in this study was 7.05 cases per 100,000, and of these, the specific incidence of CD was 4.56 and UC was 2.14 cases per 100,000. The remaining cases had a confirmed IBD diagnosis that, for various reasons, could not be verified as either CD or UC, and this is called indeterminate colitis (IC).

The overall incidence of IBD was less than 5 per 100,000 until the age of 8, rising to an incidence of 13 per 100,000 by the age of 10. The highest age-related occurrence for IBD was found in the 15-year-old group. The mean age of a CD diagnosis was 13.5 years, and for UC it was 11.8 years.

Studies from Europe have shown that the incidence of IBD in children and adolescents has significantly increased over the last 40 years. These pediatric studies also suggest that there has been a change in the patterns of disease, because the incidence of CD has risen above that of UC.

While previous studies have also suggested that urban populations may be at higher risk for IBD than rural areas, this study did not show a significant difference by geographical location, where sparsely versus densely populated regions were carefully compared. Although the population base was ethnically diverse, the IBD rates were similar among all ethnic groups. Only 11% of the newly diagnosed children had a close family relative with IBD, whereas previous accepted statistics have shown that the onset of CD is associated with a 30% likelihood of a having affected relatives.

In conclusion, the noteworthy results of this large study demonstrate:

  • The highest pediatric IBD incidence reported in the world to date;
  • A twofold predominance in pediatric CD incidence compared with UC;
  • A significantly higher rate of CD diagnosis among boys compared with girls that agrees with studies from the UK (2001) and Canada (1994);
  • A low frequency of patients with IBD positive family histories;
  • No modulatory effect of urbanization on pediatric IBD incidence;
  • Equal distribution of IBD incidence among all ethnic populations, where none of the non-Caucasian children with IBD had family histories of IBD; and,
  • The initial presentation of pancolitis (colitis involving the whole colon) among the majority of newly diagnosed children with UC.

The researchers explained that the pathogenesis of CD and UC is believed to involve the interplay of environmental factors acting on genetically susceptible persons. This study suggests that environmental factors are dominant in changing the pattern of disease because the genetic make-up of the human population does not shift over short periods. A parallel phenomenon pointed out by the researchers is the dramatic increase in asthma during the same period in the West. The concomitant emergence of chronic inflammation in the lung and gut also supports the concept that changing environmental factors play a pivotal role in the increased frequency of these disorders in children.

First published in the Inside Tract® newsletter issue 141 – January/February 2004
S Kugathasan, R H Judd, R G Hoffmann, et al. Epidemiologic and clinical characteristics of children with newly diagnosed inflammatory bowel disease in wisconsin: a statewide population-based study. Journal of Pediatrics. 2003;143(4):525-531