PLoS ONE (Jan 2012)

Geographical variations in sex ratio trends over time in multiple sclerosis.

  • Maria Trojano,
  • Guglielmo Lucchese,
  • Giusi Graziano,
  • Bruce V Taylor,
  • Steve Simpson,
  • Vito Lepore,
  • Francois Grand'maison,
  • Pierre Duquette,
  • Guillermo Izquierdo,
  • Pierre Grammond,
  • Maria Pia Amato,
  • Roberto Bergamaschi,
  • Giorgio Giuliani,
  • Cavit Boz,
  • Raymond Hupperts,
  • Vincent Van Pesch,
  • Jeannette Lechner-Scott,
  • Edgardo Cristiano,
  • Marcela Fiol,
  • Celia Oreja-Guevara,
  • Maria Laura Saladino,
  • Freek Verheul,
  • Mark Slee,
  • Damiano Paolicelli,
  • Carla Tortorella,
  • Mariangela D'Onghia,
  • Pietro Iaffaldano,
  • Vita Direnzo,
  • Helmut Butzkueven,
  • MSBase Study Group and the New Zealand MS Prevalence Study Group

DOI
https://doi.org/10.1371/journal.pone.0048078
Journal volume & issue
Vol. 7, no. 10
p. e48078

Abstract

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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.