BBC News: Being bilingual 'protects the brain'
"Being fluent in two languages may help to keep the brain sharper for longer, a study suggests.
Researchers from York University in Canada carried out tests on 104 people between the ages of 30 and 88.
They found that those who were fluent in two languages rather than just one were sharper mentally."
Of course, they don't mention anything about you doing your head in trying to learn the language in the first place...