title: Fluctuations of MS births and UV-light exposure.
abstract: BACKGROUND
  Patients with multiple sclerosis (MS) are more frequently born in spring when compared to autumn. Fluctuation of UV-light has been hypothesized to drive this phenomenon.
  
  
  OBJECTIVE
  To assess the correlation between fluctuation of sunlight and birth season in persons with MS.
  
  
  METHODS
  For this record-linkage study, we collected from the international MSBase and the Italian MS iMed-web databases the dates of birth of 11,415 patients with MS from 36 centres from 15 countries worldwide and compared these to dates of live-births from national registries. From all participating sites, we collected data on UV-light fluctuation and assessed its correlation with seasonal fluctuation in MS births.
  
  
  RESULTS
  Compared with the reference cohort, an increased proportion of persons with MS were born in spring and a decreased proportion in autumn (odds ratio (OR) to be born in spring versus autumn = 1.158, χ² = 36.347, P < 0.001). There was no significantly increased fluctuation of MS births with increased quartile of ambient UV-light fluctuation (Ptrend = 0.086).
  
  
  CONCLUSIONS
  Seasonal fluctuation of MS births as found in this worldwide cohort of patients with MS did not correlate with variation in seasonal fluctuation of UV-light. Most likely, it results from a complex interplay between fluctuation of sunlight, behavioural factors, other environmental factors and (epi)genetic factors.
authors.affiliation: Groene Hart Ziekenhuis, Gouda, The Netherlands. freekverheul@me.com
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mesh_terms: D016208:Databases, Factual; D005260:Female; D014943:Global Health; D006801:Humans; D008297:Male; D009103:Multiple Sclerosis / Q000453:epidemiology*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012042:Registries; D012307:Risk Factors; D012621:Seasons; D013472:Sunlight; D014466:Ultraviolet Rays