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Joan Stephenson, PhD

JAMA. 2005;294:1331.

	Since this article does not have an abstract, we have provided the first 150 words of the full text and any section headings.

Older siblings in a family are not more likely than younger siblings to develop multiple sclerosis (MS), a finding that contradicts earlier reports that suggested a link between early birth-order position and a heightened risk of developing the disease. The new finding does not support the prediction of the "hygiene hypothesis" which postulates that children who are exposed to infections introduced by older siblings are at a reduced risk of developing MS.

The report of the study’s findings, published online on August 22, will appear in print in the October issue of Lancet Neurology.

In the study, researchers from Canada and England analyzed data from nearly 11 000 individuals with MS and more than 26 000 healthy siblings. Overall, they found no link with MS and birth-order position.

"The data presented here cast no doubt on the importance of environmental factors to MS risk, and suggest that environmental . . . [Full Text of this Article]

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