Younger immigrants at higher risk of developing inflammatory bowel disease

The younger a person is when they immigrate to Canada, the higher their risk of developing inflammatory bowel disease (IBD), and its major subtypes Crohn's disease and ulcerative colitis, according to a study by researchers at the University of Ottawa, the Institute for Clinical Evaluative Sciences (ICES) and the Children's Hospital of Eastern Ontario (CHEO). Canada has one of the highest rates in the world of IBD and while immigrants to Canada have lower rates of IBD compared to Canadian-born residents, that risk goes up in immigrants who are younger at arrival to Canada. In addition, Canadian-born children of immigrants from some regions have a higher risk of developing IBD.

While their parents were at lower risk of developing IBD, once they arrive the children of immigrants from the Middle East, North Africa and South Asia had the same incidence of IBD compared with the children of non-immigrants. In fact, there is a 14 per cent increased risk per younger decade of life at immigration. However, the children of immigrants from East Asia, Eastern Europe, Central Asia, Latin America and the Caribbean had lower incidence of IBD compared with the children of non-immigrants.

"These findings suggest an increased risk of IBD when there is early-life exposure to the Canadian environment in immigrants from some regions," said Dr. Eric Benchimol, adjunct scientist with ICES, and pediatric gastroenterologist at CHEO.

The study, published today in American Journal of Gastroenterology, is the first population-based study to demonstrate the increased risk in the children of immigrants to Canada. This indicates that the environment plays an important role in IBD pathogenesis.

"IBD is a disease of Westernized nations, with high rates in North America and Europe, and low rates in Asia, Africa, and South America. Rates increased dramatically in Eastern Europe in recent decades and are increasing in other nations as Western lifestyle becomes more prevalent," added Benchimol.

Canada has some of the highest rates of IBD (Crohn's disease and ulcerative colitis) in the world with 240,000 Canadians affected. Ontario has a very high rate of IBD (1/160 people), and the fastest growing group of new diagnoses is children under 10-years-old. The recent rapid increase in IBD suggests environmental risk factors.