Number of siblings can predict brain tumor risk

Reported by Susan Aldridge, PhD, medical journalist

Family size is a factor in the risk of developing a brain tumor, suggesting that infection may play a role.
The factors affecting the risk of developing a brain tumor are not well understood. Now a team at the German Cancer Research Center reveals that childhood infection may play a role, through exposure to siblings.

They carried out a study, the largest of its kind, which showed that people with four or more siblings were more than twice as likely to develop a brain tumor as people with no siblings. They also learned that there was a two to fourfold increase in brain tumor rates among children younger than 15 who had three or more younger brothers or sisters, compared to only children of the same age.

There was no link between the number of older siblings and brain tumors. To the researchers, this suggests that exposure to infections - from their younger siblings - in late childhood may sensitize the brain toward developing a brain tumor. The fact that there is no link with the presence of older siblings suggests that exposure to infection in infancy is not a factor. The next stage in this research should be to identify which infectious agents might be responsible for increasing the risk of brain tumors. Infection has been shown to play a role in other cancers - for instance, human papillomavirus is strongly linked to cervical cancer.

Source
Neurology 12th December 2006

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