Emigration to western industrialized countries: A risk factor for developing inflammatory bowel disease.

BACKGROUND A higher incidence of inflammatory bowel disease (IBD) in industrialized areas has been previously reported, but the effect of emigrating to western industrialized countries for a period of time and returning to the country of origin is unknown. Aim of the study was to evaluate the effect of emigrating to another country and returning to the place of origin on the risk of IBD. METHODS A prospective case-control study was performed. Inclusion criteria were all patients >18 years diagnosed with Crohn's disease (CD) or ulcerative colitis (UC) in the last 10 years. Healthy, unrelated controls, matched by sex, age and smoking habits, with no family history of IBD were included. All patients and controls were interviewed and emigration was defined as living for at least one year in another country. RESULTS 242 consecutive patients with IBD (105 CD and 137 UC) and 242 controls were included. Patients who had previously emigrated developed more frequently IBD than controls (OR 1.93, 95%CI 1.19-3.15, p<0.01). Patients who emigrated to European countries developed more frequently IBD than controls (OR 1.91, 95%CI 1.07-3.47, p=0.02), but not those who had emigrated to Latin America (OR 1.48, 95%CI 0.67-3.27, p=0.32). Emigration plays a significant role in the development of UC (OR 2.24, 95%CI:1.29-3.88, p<0.01), but not in CD (OR 1.56, 95%IC:0.83-2.92, p=0.15). CONCLUSIONS People who emigrate to westernised countries have a higher risk for developing IBD, especially UC. Environmental factors related with industrialization seem to play an important role in the pathogenesis of these diseases.