It may, according to recent research by psychologist Ellen Bialystok, a scientist at York University and the Rotman Research Institute of Baycrest Hospital in Toronto.
Three years ago, Bialystok’s team showed that people who had been bilingual all their lives did better at paying attention and doing the kind of intellectual tasks that the prefrontal cortex of the brain (right behind the forehead) is responsible for: planning, being able to tune out distractions and making judgments. That led Bialystok to wonder whether bilingualism might also protect against Alzheimer’s disease. Bilingualism has been shown to boost the power of the prefrontal cortex because, in order to speak one language, the speaker must activity “inhibit”or tune out the other language.
In a study published in February in the journal Neuropsychologia, she looked at the hospital records of people who had visited Baycrest’s memory clinic, two-thirds of whom had Alzheimer’s and one-third, other kinds of dementia. Roughly half were “perfect bilinguals,” she said, meaning that they had been speaking at least two languages every day for 50 years or more, typically English plus Polish, Russian, or Yiddish.
The rest were monolingual. “What we found is that all else being equal – education, occupational skills, marital status, money, etc.” – the age of onset of dementia was on average 71 for the monolinguals and 75 for the bilinguals, she said. “That difference is huge,” she said. “The neurologist on the team was astonished.”
It doesn’t appear that learning learning a second language in midlife would carry the same benefit. Dr. Charles De Carli [cq], a neurologist and director of the University of California, Davis Alzheimer’s Disease Center, was skeptical. “The brain is most ‘plastic’ during early life,” he said, meaning that it can most easily learn new tasks and use one region to compensate for another if necessary. “It’s not clear what suddenly taking on a second language at age 60 would do.”
Bialystok is studying that now, and so far, is finding “that there is a much diminished effect for later bilinguals.”