Risk of Inflammatory Bowel Disease in First- and Second-generation Immigrants in Sweden: A Nationwide Follow-up Study

Background: The objective was to analyze whether there is an association between country of birth in first-generation immigrants and first hospitalization for an inflammatory bowel disease, and to study whether any such association remains in second-generation immigrants. Methods: In this follow-up study a nationwide research database at Lund University was used to identify all primary hospital diagnoses of Crohn's disease (CD) and ulcerative colitis (UC) in all first-and second-generation immigrants in Sweden between January 1, 1964, and December 31, 2007. Standardized incidence ratios (SIRs) with regard to age, gender, time period, geographical region, and socioeconomic status were estimated in first-and second-generation immigrants. Results: No increased but some decreased risks for CD and UC were found among first-generation immigrants. These decreased risks partly remained in the second generation. Moreover, second-generation immigrants of Danish, Eastern European, and Iraqi origin had higher risks of CD than the reference group. Second-generation immigrants of Finnish and Iranian origin had higher risks of UC. Conclusions: Decreased risks of CD and UC found in some first-generation immigrant groups partly persisted in the second generation. For some immigrant groups, increased risks of CD or UC emerged in the second generation.