title: Prevalence of multiple sclerosis among immigrants in Norway.
abstract: BACKGROUND
  Multiple sclerosis (MS) prevalence is unevenly distributed worldwide. Immigration to Norway from countries with a lower MS prevalence is increasing. The aim of this study was to investigate MS prevalence in different immigrant populations in Norway and evaluate the effect of migrating from low- to high-risk regions of MS.
  
  
  METHODS
  First- and second-generation immigrants from the largest immigrant populations were identified from the 2012 Norwegian prevalence study. Prevalence of MS in different ethnic groups was compared using the standardized prevalence ratio (SPR).
  
  
  RESULTS
  European and North-American immigrants had the highest prevalence of MS, whereas African and Asian immigrants had the lowest. The prevalence of first-generation Iranian immigrants was not significantly different from the total Norwegian population (SPR 0.70, 95% CI: 0.46-1.03). Second-generation immigrants from Pakistan (SPR 1.62, 95% CI: 0.88-2.76) had a strong increase in prevalence compared to the first generation (SPR 0.13, 95% CI: 0.05-0.28).
  
  
  CONCLUSIONS
  MS prevalence among immigrants in Norway in general reflects the uneven distribution worldwide. The sharp increase in prevalence in immigrants seen in one generation suggests strong environmental factors affecting the MS risk in Norway.
authors.affiliation: Department of Neurology, Oslo University Hospital, Norway/Institute of Clinical Medicine, University of Oslo, Norway pberghansen@gmail.com.
authors.forename: Pål
authors.initials: P
authors.lastname: Berg-Hansen
authors.affiliation: Department of Neurology, Oslo University Hospital, Norway.
authors.forename: Stine M
authors.initials: SM
authors.lastname: Moen
authors.affiliation: Section of Epidemiology and Biostatistics, Oslo University Hospital, Norway.
authors.forename: Leiv
authors.initials: L
authors.lastname: Sandvik
authors.affiliation: Department of Neurology, Oslo University Hospital, Norway/Institute of Clinical Medicine, University of Oslo, Norway.
authors.forename: Hanne F
authors.initials: HF
authors.lastname: Harbo
authors.affiliation: Norwegian Institute of Public Health, Norway.
authors.forename: Inger J
authors.initials: IJ
authors.lastname: Bakken
authors.affiliation: Norwegian Institute of Public Health, Norway/Department of Public Health and Primary Health Care, University of Bergen, Norway.
authors.forename: Camilla
authors.initials: C
authors.lastname: Stoltenberg
authors.affiliation: Department of Neurology, Oslo University Hospital, Norway.
authors.forename: Elisabeth G
authors.initials: EG
authors.lastname: Celius
mesh_terms: D000293:Adolescent; D000328:Adult; D000349:Africa / Q000208:ethnology; D000368:Aged; D000369:Aged, 80 and over; D001208:Asia / Q000208:ethnology; D002648:Child; D054242:Emigrants and Immigrants / Q000706:statistics & numerical data*; D005060:Europe / Q000208:ethnology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000208:ethnology*; D009656:North America / Q000208:ethnology; D009664:Norway / Q000208:ethnology; D015995:Prevalence; D012042:Registries / Q000706:statistics & numerical data*; D055815:Young Adult
keywords: Epidemiology; ethnicity; migration; multiple sclerosis; prevalence