According to findings from a Danish study, having brothers and sisters does not appear to raise the risk of MS in younger siblings.

Some researchers have suggested that developing an infection at a certain age during childhood may increase the risk of developing MS, the authors explained. To evaluate this theory, investigators studied whether having an older sibling, who may expose a younger sibling to an infection, would raise the risk of MS in the younger sibling.

The researchers obtained data on family characteristics and vital status from the Danish Civil Registration System to create a group of subjects whose mothers were born since 1935. Individuals who received a diagnosis of MS between 1968 and 1998 were identified from the Danish Multiple Sclerosis Register.

Of the 1.9 million Danes who were identified, 1,036 subjects developed MS.

The results showed no association between the number of older siblings, the number of younger siblings, or the total number of siblings and the risk of MS later in life. In addition, the risk of MS was not related to the age distance from the nearest younger sibling or exposure to younger siblings under 2 years of age.

Furthermore, no association between MS risk later in life and singleton birth or multiple birth (twins, etc.) was detected. The age of the mother or father at birth also did not increase the risk of later MS.

"These results do not lend support to the hypothesis that number of older siblings or any of the other sibship characteristics studied is associated with risk of MS," the investigators wrote.

This study was published May 4 online, ahead of print by the American Journal of Epidemiology.

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