Multiple Sclerosis Society of Canada

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‘Month of birth’ effect in MS

Summary
Researchers from Queen Mary University of London, UK, analyzed datasets from previously published studies of month of birth and subsequent MS risk. They observed a significant increase of MS risk in people living in northern hemisphere countries who were born in April and a reduction in risk for those born in November and December. [Dobson R, Giovannoni G, Ramagopalan S.J Neurol Neurosurg Psychiatry. 2012 Nov 14. [Epub ahead of print]]


The Study:
Researchers examined the ‘month of birth’ effect — where people born in the winter have a reduced risk of developing MS and those born in the spring have an increased risk — by analyzing previously published data on month of birth from 151, 978 people with MS and compared them to expected birth rates. They observed a significant increase of MS risk in people living in northern hemisphere countries who were born in April, and a reduction in risk for those who were born in November and December. This could be due to ultraviolet light exposure and maternal vitamin D levels, as demonstrated by the correlation between risk and latitude.

One of the noted study limitations was a lack of data from southern hemisphere studies. Additional southern hemisphere data is required to confirm whether reversal of the ‘month of birth’ effect occurs in other countries. The findings from this study also emphasize the need for early intervention studies in preventing the development of MS through vitamin D supplement.