title: [Seasonal variations in the outbreaks in patients with multiple sclerosis].
abstract: BACKGROUND
  It has been suggested that there is an environmental factor at play in the aetiology and pathogenesis of multiple sclerosis (MS) that acts as an essential component of the disease process, and a number of studies also point to a relationship between the seasons of the year and the appearance of outbreaks.
  
  
  OBJECTIVE
  Our aim was to study the possible relation between seasonal variations and the appearance of outbreaks in patients with relapsing-remitting forms of MS.
  
  
  METHODS
  We studied 31 patients over the period between 1997 and 2002 and calculated the monthly and quarterly rate of incidence of outbreaks. The statistical evaluation of the results was performed by applying the Chi-squared test.
  
  
  RESULTS
  We observed a higher incidence of outbreaks in the summer months (more in June) and a lower incidence in winter (less in December), with statistically significant differences.
  
  
  CONCLUSIONS
  In our patients, outbreaks of MS are related to seasonal variations, with a higher number in the warmer months and fewer in the colder months.
authors.affiliation: Servicio de Neurología, Hospital Clínico Universitario de Santiago de Compostela, A coruña, Spain. javiabella@hotmail.com
authors.forename: J
authors.initials: J
authors.lastname: Abella-Corral
authors.forename: J M
authors.initials: JM
authors.lastname: Prieto
authors.forename: D
authors.initials: D
authors.lastname: Dapena-Bolaño
authors.forename: S
authors.initials: S
authors.lastname: Iglesias-Gómez
authors.forename: M
authors.initials: M
authors.lastname: Noya-García
authors.forename: M
authors.initials: M
authors.lastname: Lema
mesh_terms: D000328:Adult; D004196:Disease Outbreaks; D004777:Environment; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D009103:Multiple Sclerosis / Q000453:epidemiology*; D012621:Seasons; D013030:Spain / Q000453:epidemiology