People born in May have an increased risk of developing multiple sclerosis, according to a new study.
In multiple sclerosis (MS), the lining of the sheaths enclosing the nerves become eroded, leading to a range of disabling neurological symptoms. The cause is unknown. However, according to researchers at the University of Oxford, England, the month of birth seems to be a risk factor.

They looked at a group of 17,874 Canadian patients and 11,502 British patients with MS, and compared them with unaffected brothers and sisters and with the general population. In Canada, fewer people with MS were born in November, compared to controls. In Britain, fewer people with MS were born in November and more were born in May. Altogether, this means that those born in May have a 13 per cent increase in risk of MS compared to those born in November. It is not clear why this seasonal link occurs - but perhaps it has some link with the mother's sun exposure during pregnancy which might affect the brain development of the baby.

Source
British Medical Journal Online First 6th December 2004

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