[Epidemiology and risk factors of inflammatory bowel diseases]

Inflammatory bowel diseases (IBD) are a public health problem in developed countries as 1 per 1000 people suffers from these diseases. Most of affected people are young adults. The incidence of IBD has increased considerably in western countries since the Second World War and it is beginning to level off. On the other hand, incidence is still rising in low incidence areas such as Eastern Europe, Asia and developing countries. Differences in incidence across age, time, and geographic areas suggest that environmental factors are acting in IBD but so far cigarette smoking and appendectomy are the only risk factors which have been consistently demonstrated. An important role for genetic factors in IBD was first suggested by epidemiological studies showing familial aggregation of IBD and by twin studies. In 2001, the first CD susceptibility gene, NOD2/CARD15 on chromosome 16, has been characterized. Other susceptibility genes have been localized. Their identification should help to understand the complex interaction between the environment and the intestinal immune system from which IBD are originating.