Wednesday, 9 January 2013

Month of Birth Effect

Torkildsen O, Grytten N, Aarseth J, Myhr KM, Kampman MT. Month of birth as a risk factor for multiple sclerosis: an update. Acta Neurol Scand Suppl. 2012;(195):58-62. doi: 10.1111/ane.12040.

BACKGROUND: Several studies have indicated month of birth as a risk factor for multiple sclerosis (MS) susceptibility and disease progression.

METHODS: We performed a systematic search on PubMed and Medline up to May 2012 using the search string 'multiple sclerosis' and 'month of birth' or 'season of birth'. In addition, congress abstracts and the reference lists of the publications identified were examined for further citations of relevance.

RESULTS: A total of fifteen published studies and two congress abstracts were found on the effect of month or season of birth on MS risk (sixteen in the northern and one in the southern hemisphere). Most studies in the northern hemisphere detected an excess of MS births in spring and a decrease in autumn. In the southern hemisphere, a reverse pattern was detected, with an excess in November and a decrease in April. Only three studies did not report any month of birth effect, all in low-risk areas for MS. Five studies have analysed a possible effect on disease course by month of birth. Of these, two studies reported an association between month of birth and age at onset of relapsing-remitting MS, with a younger disease onset for those born in the winter months. No consistent findings have been detected on the association between month of birth and disease progression.

DISCUSSION: The month of birth effect is consistently found to influence the risk of MS, and the effect seems to be most prominent in high-risk areas of the disease, especially in areas with low sunlight exposure. There seems to be little or no month of birth effects in areas with high sunlight exposure. These findings indicate a possible role for vitamin D concentrations during pregnancy or early life of the newborn. A possible effect of vitamin D supplementation needs to be further investigated.


Evidence mounts for the Vitamin D hypothesis!

3 comments:

  1. As one anecedote against the weight of 'evidence-based' studies of these type, I (and my mother) am one of the minority: born in May in Southern hemisphere in far south to summer sun worshiper (a teacher who spent up to 6 weeks at the beach baking (hey it was the 70s) each summer incl that summer before I was born).

    So to me it is hard find meaning to my personal situation in these studies.

    Perhaps it may be about mechanisms for effective Vit D uptake rather than quantities...

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    Replies
    1. I wondered about that too.

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    2. You have to remember that these studies are indicative of a vitamin D effect as a contributor to the development of MS, it isn't the whole story. There will always be exceptions to the trend. The risk is also higher for southern states such as Tasmania compared to northern states where UV levels are higher.

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