Research: Month of Birth Effect-Brazil

MS Month of birth effect pans out in Brazil as well. Will  it be due to vD deficiency in pregnancy? #MSBlog #MSResearch

et al. Season of birth as a risk factor for multiple sclerosis in Brazil.
J Neurol Sci. 2013 Apr 15. doi:pii: S0022-510X(13)00107-X. 10.1016/j.jns.2013.03.001. 

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. 

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  • The farther from the equator in the southern hemisphere should have the opposite calendar effect as the northern hemisphere i.e. MS incidence should be greater for people born in November. Does the data support this in Australia,New Zealand, South Africa and Argentina? Obviously the latitude affect and subsequent vitamin D deficiency in the southern hemisphere is not as great as in the north.

  • On countries on the equator the effect, if it is vitamin d, would come from when there is heavy cloud, or for cities when there is heavy smog. Looking at Brazil it does have a rainy season but it seems to vary between cities.

By MouseDoctor



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