title: MS prevalence in New Zealand, an ethnically and latitudinally diverse country.
abstract: BACKGROUND
  The prevalence of multiple sclerosis (MS) is not uniform, with a latitudinal gradient of prevalence present in most studies. Understanding the drivers of this gradient may allow a better understanding of the environmental factors involved in MS pathogenesis.
  
  
  METHODS
  The New Zealand national MS prevalence study (NZMSPS) is a cross-sectional study of people with definite MS (DMS) (McDonald criteria 2005) resident in New Zealand on census night, 7 March 2006, utilizing multiple sources of notification. Capture-recapture analysis (CRA) was used to estimate missing cases.
  
  
  RESULTS
  Of 2917 people with DMS identified, the crude prevalence was 72.4 per 100,000 population, and 73.1 per 100,000 when age-standardized to the European population. CRA estimated that 96.7% of cases were identified. A latitudinal gradient was seen with MS prevalence increasing three-fold from the North (35°S) to the South (48°S). The gradient was non-uniform; females with relapsing-remitting/secondary-progressive (RRMS/SPMS) disease have a gradient 11 times greater than males with primary-progressive MS (p < 1 × 10(-7)). DMS was significantly less common among those of Māori ethnicity.
  
  
  CONCLUSIONS
  This study confirms the presence of a robust latitudinal gradient of MS prevalence in New Zealand. This gradient is largely driven by European females with the RRMS/SPMS phenotype. These results indicate that the environmental factors that underlie the latitudinal gradient act differentially by gender, ethnicity and MS phenotype. A better understanding of these factors may allow more targeted MS therapies aimed at modifiable environmental triggers at the population level.
authors.affiliation: Menzies Research Institute, University of Tasmania, Hobart, Australia. bruce.taylor@utas.edu.au
authors.forename: Bruce V
authors.initials: BV
authors.lastname: Taylor
authors.forename: John F
authors.initials: JF
authors.lastname: Pearson
authors.forename: Glynnis
authors.initials: G
authors.lastname: Clarke
authors.forename: Deborah F
authors.initials: DF
authors.lastname: Mason
authors.forename: David A
authors.initials: DA
authors.lastname: Abernethy
authors.forename: Ernie
authors.initials: E
authors.lastname: Willoughby
authors.forename: Clive
authors.initials: C
authors.lastname: Sabel
mesh_terms: D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D009103:Multiple Sclerosis / Q000453:epidemiology*; D009520:New Zealand / Q000453:epidemiology; D015995:Prevalence; D012307:Risk Factors; D012737:Sex Factors