title: Season of birth as a risk factor for multiple sclerosis in Brazil.
abstract: Risk factors for development of multiple sclerosis (MS) are still a matter of debate. Latitude gradient, vitamin D deficiency and season of birth are among the most investigated environmental factors associated with the disease. Several international studies suggest that birth in spring is a substantial risk factor for MS. We investigated the season of birth as a potential risk for MS in different geographical regions of Brazil. We conducted a cross-sectional retrospective study with 2257 clinically definite MS patients enrolled in 13 Brazilian MS clinics in the south, southeast, and northeast regions of Brazil. Demographic and clinical data relating to date of birth and clinical features of the disease were collected and analysed, and subsequently compared with birth date among the general Brazilian population. The distribution of date of birth of MS patients showed an increase in spring and a decrease in autumn, with no difference being observed in the other seasons. In conclusion, season of birth is a probable risk factor for MS in most parts of Brazil. These findings may be related to the role that vitamin D plays in MS pathogenesis.
authors.affiliation: Hospital São Lucas da PUCRS, Porto Alegre, RS, Brazil. jeffersonbecker@hotmail.com
authors.forename: Jefferson
authors.initials: J
authors.lastname: Becker
authors.forename: Dagoberto
authors.initials: D
authors.lastname: Callegaro
authors.forename: Marco Aurélio
authors.initials: MA
authors.lastname: Lana-Peixoto
authors.forename: Maria Lúcia B
authors.initials: ML
authors.lastname: Ferreira
authors.forename: Ailton
authors.initials: A
authors.lastname: Melo
authors.forename: Paulo
authors.initials: P
authors.lastname: Diniz da Gama
authors.forename: Doralina G B
authors.initials: DG
authors.lastname: Souza
authors.forename: Carlos A C
authors.initials: CA
authors.lastname: Teixeira
authors.forename: Damacio Ramón
authors.initials: DR
authors.lastname: Kaimen-Maciel
authors.forename: Marcus Vinícius
authors.initials: MV
authors.lastname: Gonçalves
authors.forename: André P C
authors.initials: AP
authors.lastname: Matta
authors.forename: Ronaldo
authors.initials: R
authors.lastname: Abraham
authors.forename: Luís Edmundo T A
authors.initials: LE
authors.lastname: Furtado
authors.forename: Angelina
authors.initials: A
authors.lastname: Lino
authors.forename: Laura
authors.initials: L
authors.lastname: Hauck
authors.forename: Amilton Antunes
authors.initials: AA
authors.lastname: Barreira
authors.forename: Irenio
authors.initials: I
authors.lastname: Gomes
mesh_terms: D000328:Adult; D001938:Brazil / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000453:epidemiology* / Q000209:etiology; D036801:Parturition; D012016:Reference Values; D012189:Retrospective Studies; D012307:Risk Factors; D012621:Seasons