Season of birth and multiple sclerosis in Sweden

Acta Neurol Scand. 2010 Jul;122(1):70-3. doi: 10.1111/j.1600-0404.2010.01396.x.


Objective: To estimate the risk of multiple sclerosis (MS) by month of birth in Sweden.

Materials and methods: Cases (n = 9361) were obtained from the Swedish MS Registry. All births in Sweden 1900-2007 served as controls (n = 12,116,853). The risk of MS was analyzed for each month of birth separately compared with birth during the other 11 months.

Results: More (11%) cases with MS than expected were born in June. Fewer (8% and 10%) cases with MS than expected were born in December and January (non-significant after correction for multiple analyses). More (5%) cases with MS than expected were born in February-July as compared with August-January.

Conclusions: This study supports previous results suggesting an association between the risk of MS and the season of birth. Decreased exposure to sun in the winter leading to low vitamin D levels during pregnancy is a possible explanation that needs further research.

Publication types

  • Corrected and Republished Article
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Child
  • Child, Preschool
  • Female
  • Humans
  • Infant
  • Male
  • Middle Aged
  • Multiple Sclerosis / epidemiology*
  • Multiple Sclerosis / etiology
  • Parturition*
  • Risk Factors
  • Seasons*
  • Sweden
  • Vitamin D
  • Young Adult


  • Vitamin D