title: Geographical variations in sex ratio trends over time in multiple sclerosis.
abstract: BACKGROUND
  A female/male (F/M) ratio increase over time in multiple sclerosis (MS) patients was demonstrated in many countries around the world. So far, a direct comparison of sex ratio time-trends among MS populations from different geographical areas was not carried out.
  
  
  OBJECTIVE
  In this paper we assessed and compared sex ratio trends, over a 60-year span, in MS populations belonging to different latitudinal areas.
  
  
  METHODS
  Data of a cohort of 15,996 (F = 11,290; M = 4,706) definite MS with birth years ranging from 1930 to 1989 were extracted from the international MSBase registry and the New Zealand MS database. Gender ratios were calculated by six decades based on year of birth and were adjusted for the F/M born-alive ratio derived from the respective national registries of births.
  
  
  RESULTS
  Adjusted sex ratios showed a significant increase from the first to the last decade in the whole MS sample (from 2.35 to 2.73; p = 0.03) and in the subgroups belonging to the areas between 83° N and 45° N (from 1.93 to 4.55; p<0.0001) and between 45° N to 35° N (from 1.46 to 2.30; p<0.05) latitude, while a sex ratio stability over time was found in the subgroup from areas between 12° S and 55° S latitude. The sex ratio increase mainly affected relapsing-remitting (RR) MS.
  
  
  CONCLUSIONS
  Our results confirm a general sex ratio increase over time in RRMS and also demonstrate a latitudinal gradient of this increase. These findings add useful information for planning case-control studies aimed to explore sex-related factors responsible for MS development.
authors.affiliation: Department of Neuroscience and Sense Organs, University of Bari, Bari, Italy. mtrojano@neurol.uniba.it
authors.forename: Maria
authors.initials: M
authors.lastname: Trojano
authors.forename: Guglielmo
authors.initials: G
authors.lastname: Lucchese
authors.forename: Giusi
authors.initials: G
authors.lastname: Graziano
authors.forename: Bruce V
authors.initials: BV
authors.lastname: Taylor
authors.forename: Steve
authors.initials: S
authors.lastname: Simpson
authors.forename: Vito
authors.initials: V
authors.lastname: Lepore
authors.forename: Francois
authors.initials: F
authors.lastname: Grand'maison
authors.forename: Pierre
authors.initials: P
authors.lastname: Duquette
authors.forename: Guillermo
authors.initials: G
authors.lastname: Izquierdo
authors.forename: Pierre
authors.initials: P
authors.lastname: Grammond
authors.forename: Maria Pia
authors.initials: MP
authors.lastname: Amato
authors.forename: Roberto
authors.initials: R
authors.lastname: Bergamaschi
authors.forename: Giorgio
authors.initials: G
authors.lastname: Giuliani
authors.forename: Cavit
authors.initials: C
authors.lastname: Boz
authors.forename: Raymond
authors.initials: R
authors.lastname: Hupperts
authors.forename: Vincent
authors.initials: V
authors.lastname: Van Pesch
authors.forename: Jeannette
authors.initials: J
authors.lastname: Lechner-Scott
authors.forename: Edgardo
authors.initials: E
authors.lastname: Cristiano
authors.forename: Marcela
authors.initials: M
authors.lastname: Fiol
authors.forename: Celia
authors.initials: C
authors.lastname: Oreja-Guevara
authors.forename: Maria Laura
authors.initials: ML
authors.lastname: Saladino
authors.forename: Freek
authors.initials: F
authors.lastname: Verheul
authors.forename: Mark
authors.initials: M
authors.lastname: Slee
authors.forename: Damiano
authors.initials: D
authors.lastname: Paolicelli
authors.forename: Carla
authors.initials: C
authors.lastname: Tortorella
authors.forename: Mariangela
authors.initials: M
authors.lastname: D'Onghia
authors.forename: Pietro
authors.initials: P
authors.lastname: Iaffaldano
authors.forename: Vita
authors.initials: V
authors.lastname: Direnzo
authors.forename: Helmut
authors.initials: H
authors.lastname: Butzkueven
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016208:Databases, Factual; D005060:Europe; D005260:Female; D005843:Geography; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000175:diagnosis* / Q000453:epidemiology*; D020528:Multiple Sclerosis, Chronic Progressive / Q000175:diagnosis / Q000453:epidemiology; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000175:diagnosis / Q000453:epidemiology; D009520:New Zealand; D012042:Registries; D012044:Regression Analysis; D012737:Sex Factors; D012744:Sex Ratio; D013997:Time Factors