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This article was published 14/10/2011 (3629 days ago), so information in it may no longer be current.
TORONTO -- A small study has found that people who speak more than one language have twice as much brain damage as those who are unilingual before they begin exhibiting symptoms of Alzheimer's disease.
The finding suggests that being bilingual somehow conserves cognitive function for some time, despite areas of brain cells being destroyed by the disease.
The study by a team of Toronto researchers, which analyzed brain scans of patients with probable Alzheimer's disease, is being called the first to provide physical evidence confirming observational studies suggesting speaking more than one language is beneficial for the brain.
To conduct the study, the researchers studied the CT scans of 40 patients whose cognitive skills -- including attention, memory, planning and organizational abilities -- were found on testing to be similar. Half the patients were fluently bilingual while the other half spoke only one language.
Tom Schweizer, a neuroscientist at St. Michael's Hospital who led the study, published in the journal Cortex, said researchers analyzed how much damage had occurred in a certain area of the brain linked to Alzheimer's disease in each of the patients.
"And to our surprise, the bilingual patients had twice as much atrophy in that area, despite the fact that they were maintaining their function and cognitive levels just as well as the monolingual patient," he said Thursday.
"So that was quite striking. That was extremely counterintuitive to most people, because if you have more disease burden and your brain looks more damaged, you should be performing worse.
"So there's something afforded by this bilingualism and we think it's mapped onto this idea of cognitive reserve."
Previous observational studies have found bilingualism delays the onset of Alzheimer's symptoms by up to five years, and this research adds the physical proof, Schweizer added.
Individuals who speak more than one language are constantly using their brain and keeping it active, which may contribute to overall brain health, he said. That's why many physicians encourage older people to do crossword or Sudoku puzzles.
Although the exact mechanism isn't known, scientists suspect giving the brain a constant workout juggling languages may allow a person to create enhanced neural networks that get around damaged areas in the brain.
Schweizer stressed that bilingualism does not prevent someone from developing Alzheimer's. Once symptoms start to appear in bilingual people, it is not clear whether the disease progresses at an accelerated rate.
He said the next step would be to repeat the study in a larger sample of patients, followed over time and using more sophisticated MRI analysis.
-- The Canadian Press