High risk of MS in Iranian immigrants in Gothenburg, Sweden.

BACKGROUND: In this study we investigated the risk of multiple sclerosis (MS) in migrants who had moved from Iran to Gothenburg, Sweden. METHODS: Patients born in Iran were retrieved from a population-based cohort, which included 534 MS and clinically isolated syndrome patients, born 1959-1990, aged 10-39 years at disease onset in Gothenburg. The expected versus observed number of migrants from Iran was calculated. RESULTS: The MS risk in the Iranian migrants in Gothenburg was several times higher than in Isfahan, Iran (hazard ratio 3.88, 95% confidence interval 2.17-6.40). Compared with the general population of Gothenburg, the observed number of 17 Iranian patients was higher than the expected value of 9.89 (hazard ratio 1.72, 95% confidence interval 1.00-2.75). CONCLUSION: Migration from a medium-risk to a high-risk area may increase the MS risk to that of the high-risk area