title: Month of birth and level of insolation as risk factors for multiple sclerosis in Poland.
abstract: BACKGROUND
  Many studies have shown that people born in the spring are at a higher risk of developing multiple sclerosis (MS). This may be associated with lower levels of sun exposure, and consequently, lower levels of vitamin D3 during pregnancy. However, these relationships have not been verified thus far in any countries in Central Europe.
  
  
  OBJECTIVE
  The aim of our study was to determine the frequency distribution of births for each calendar month in patients suffering from MS in Poland.
  
  
  METHODS
  We analyzed data for 2574 patients diagnosed with MS (1758 women, 816 men) living in Poland for an extended period. We added corrections resulting from the frequency distribution of births for the years in which the patients were born. We applied the Hewitt test for seasonality with Rogerson modification for 3-, 4-, or 6-month pulses or periods. Moreover, we examined the average number hours of sunshine in every month of the year.
  
  
  RESULTS
  The rank-sums for successive 3- and 4-month segments indicated the period from September to December and from October to December as having a significantly lower incidence (p = 0.027 and p = 0.054, respectively). We did not find a correlation between with hours of sunshine in the first trimester of pregnancy, the child's birth month, and the child developing MS.
  
  
  CONCLUSIONS
  We were able to confirm a seasonal variation in the risk of MS in Poland. However, these findings did not correlate with hours of sunshine during the first trimester of pregnancy.
authors.affiliation: Department of Neurology in Zabrze, Medical University of Silesia, Zabrze, Poland.
authors.forename: Paweł
authors.initials: P
authors.lastname: Dobrakowski
authors.affiliation: Department of Neurology in Zabrze, Medical University of Silesia, Zabrze, Poland.
authors.forename: Michał
authors.initials: M
authors.lastname: Bogocz
authors.affiliation: Department of Neurology in Zabrze, Medical University of Silesia, Zabrze, Poland.
authors.forename: Kamil
authors.initials: K
authors.lastname: Cholewa
authors.affiliation: Department of Neurology in Zabrze, Medical University of Silesia, Zabrze, Poland.
authors.forename: Mateusz
authors.initials: M
authors.lastname: Rajchel
authors.affiliation: Department of Neurology, Medical University of Białystok, Białystok, Poland.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Kapica-Topczewska
authors.affiliation: Department of Neurology, 10th Military Hospital with Policlinic, Bydgoszcz, Poland.
authors.forename: Sławomir
authors.initials: S
authors.lastname: Wawrzyniak
authors.affiliation: Clinical Department of Neurology, Rzeszow State Hospital No 2, Rzeszow, Poland.
authors.forename: Halina
authors.initials: H
authors.lastname: Bartosik-Psujek
authors.affiliation: Department of Neurology, Medical University of Białystok, Białystok, Poland.
authors.forename: Alina
authors.initials: A
authors.lastname: Kułakowska
authors.affiliation: Department of Neurology, Pomeranian Medical University, Szczecin, Poland.
authors.forename: Dorota
authors.initials: D
authors.lastname: Koziarska
authors.affiliation: Department of Neurology in Zabrze, Medical University of Silesia, Zabrze, Poland.
authors.forename: Monika
authors.initials: M
authors.lastname: Adamczyk-Sowa
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000453:epidemiology*; D011044:Poland / Q000453:epidemiology; D012307:Risk Factors