Risks of rheumatic diseases in first- and second-generation immigrants in Sweden: A nationwide followup study

Objective. To examine whether there is an association between country of birth in first-generation immigrants and first hospitalization for a rheumatic disease, and to study whether any such association remains in second-generation immigrants. Methods. In this followup study, the Swedish MigMed database at the Karolinska Institute in Stockholm was used to identify all primary hospital diagnoses of rheumatic diseases in first- and second-generation immigrants in Sweden between January 1, 1964 and December 31, 2004. Incidence ratios, standardized with regard to age, geographic region, and socioeconomic status, were estimated by sex in first- and secondgeneration immigrants. Results. First-generation immigrants from Iraq had a higher risk of rheumatoid arthritis than did subjects in the native-born Swede reference group, and the risk of systemic lupus erythematosus was increased in immigrants from Iraq and Africa; these raised risks persisted in the second generation. The lower risk of rheumatoid arthritis in some first-generation immigrants disappeared in the second generation. In groups of second-generation immigrants, the risk of ankylosing spondylitis was similar to the risk in the corresponding parental groups. Polish-born immigrants and second-generation Yugoslavs and Russians showed a significantly increased risk of systemic sclerosis. The raised risk of systemic sclerosis did not persist in the second generation, but was clustered in groups involved in certain blue collar occupations. Conclusion. Country of birth affected the risk of rheumatic disease. These findings indicate that both genetic and environmental factors are involved in the etiology of specific rheumatic diseases.