Background: Risk factors for development of 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
Objectives: We investigated the season of birth as a potential risk for MS in
different geographical regions of Brazil.
Methods: We conducted a cross-sectional
retrospective study with 2257 clinically definite MSers 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
Results: The distribution of date of birth of MSers showed an
increase in spring and a decrease in autumn, with no difference being
observed in the other seasons.
Conclusion: 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.
The idea in the Northern hemisphere is that if you are born in spring you have a higher risk of developing MS. This study supports that view. However this would not be expected if the vitamin D hypothesis was correct. The closer you are to the equator the less likely there would be a month of birth effect.