Being able to speak two languages benefits the aging brain, even if the second language is learned in adulthood, new research indicates.

Previous studies have linked bilingualism with improved cognition in older people. However until now, it was unclear whether cognitive function was improved by learning a new language or whether those with better cognitive abilities were more likely to become bilingual.

"Our study is the first to examine whether learning a second language impacts cognitive performance later in life while controlling for childhood intelligence," said the study's lead author, Dr Thomas Bak, of the University of Edinburgh.

The study focused on 835 people born in Scotland in 1936. All were native speakers of English. Each was given an intelligence test at the age of 11 and again when they were in their 70s. Just over 260 of the participants were able to speak at least one other language by the time they were tested in their 70s - around one in five of these had learned this second language after the age of 18.

The study found that those who could speak at least two languages had much better cognitive abilities, particularly in the areas of reading and general intelligence. These effects were seen irrespective of whether the people had learned the second language early or later in life.

"These findings are of considerable practical relevance. Millions of people around the world acquire their second language later in life. Our study shows that bilingualism, even when acquired in adulthood, may benefit the aging brain," the researchers insisted.

Details of these findings are published in the journal, Annals of Neurology.