Younger siblings up the odds of brain cancer

From Nature:

Brain_25 Younger brothers and sisters are usually considered pests for their whining and fighting. Now it seems they could also be a factor in whether older siblings grow a brain tumour. The cause of brain tumours is a long-standing and impenetrable mystery, because they are very rare and it is difficult to collect together enough cases to find a common cause. But one idea is that viral infections are involved, as they are in causing cervical and other cancers.

To explore this, a team led by Andrea Altieri of the German Cancer Research Centre in Heidelberg, studied the number of brothers and sisters a person has as a surrogate measure for the number of infections they suffered. The idea, used by epidemiologists before, is that a greater number of snotty siblings generally exposes a child to more viruses. The team found that people with four or more siblings (either younger or older) were twice as likely to have developed certain types of brain and nervous-system tumours than those with no siblings.

Sibling count is “one of the highest risk factors we know for nervous-system cancers,” Altieri says.

More here.