Study finds sharp rise in colitis among children

A study of Northern California children finds that diagnoses of the digestive disease ulcerative colitis increased nearly three-fold between 1996 and 2006 - for reasons that are not yet clear.

Ulcerative colitis is one of the two major forms of inflammatory bowel disease (IBD), a group of conditions marked by chronic inflammation in the intestines, leading to symptoms like abdominal pain and diarrhea. The other major form is Crohn's disease.

It's estimated that about 1 million Americans have IBD. However, when it comes to children, relatively little has been known about the epidemiology of IBD - including its incidence rate and how that rate may be changing over time.

In the new study, researchers looked at IBD diagnoses among children age 17 and younger who were members of the large Kaiser Permanente health plan in Northern California.

They found that the rate of colitis increased from 1.8 cases per 100,000 children in 1996, to 4.9 per 100,000 in 2006. There was also an increase in Crohn's disease diagnoses - from 2.2 to 4.3 cases for every 100,000 children - but the difference was not significant in statistical terms.

The study, published in the Journal of Pediatrics, cannot pinpoint the reasons for the colitis increase. But one factor may be the changing demographics of Northern California, according to lead researcher Dr. Oren Abramson, a pediatric gastroenterologist at Kaiser Permanente in Santa Clara.

Over the last 20 years, the region has seen a significant increase in the proportion of Asian and Hispanic residents. In this study, Asian and Hispanic children accounted for a growing share of ulcerative colitis cases over time; and in contrast to white children - who were affected by colitis and Crohn's in roughly equal proportion - Asian and Hispanic children were more likely to have colitis than Crohn's.

In an interview, Abramson said that more studies are needed to see whether the "Westernization" of Asian and Hispanic immigrants is playing a role in children's risk of colitis.

It's not clear how many Asian and Hispanic children in this study were from immigrant families, but immigration in general has accounted for a large share of California's population growth in recent years, Abramson and his colleagues note.

Abramson also pointed out that a few studies have found evidence that certain immigrant groups' risk of IBD goes up after they leave their home countries - including South Asian immigrants to the UK and Mexican immigrants to the U.S.

More studies, Abramson said, are needed to see whether changes in diet, lifestyle or environmental exposures are involved in that trend.

Such research, he added, should help in identifying the environmental factors important in IBD in general.

The precise cause of IBD is not known, but it is thought to involve an immune system overreaction that injures the body's own intestinal tissue. In general, experts suspect that genetic susceptibility, coupled with some type of environmental trigger, cause IBD.