A team of Canadian researchers, including a York University professor, has uncovered further evidence that bilingualism can delay the onset of Alzheimer’s by up to five years.
The study, published today in the journal Neurology, follows up on a 2007 study led by York University, which found that lifelong use of two or more languages keeps symptoms of Alzheimer’s and other forms of dementia at bay (see YFile, Jan. 15, 2007).
Led by the Rotman Research Institute, the current study examined the clinical records of more than 200 patients diagnosed with probable Alzheimer’s disease in the Sam & Ida Ross Memory Clinic at Toronto’s Baycrest Research Centre for Aging and the Brain.
"All the patients in the study had been diagnosed with Alzheimer’s, so clearly bilingualism does not prevent the onset of dementia," says study co-author Ellen Bialystok (right), Distinguished Research Professor of psychology in York’s Faculty of Health and associate scientist at the Rotman Research Institute, which is part of Baycrest.
"Instead, our results show that people who have been lifelong bilinguals have built up a cognitive reserve that allows them to cope with the disease for a longer period of time before showing symptoms," she says.
While the brains of bilingual patients did show deterioration, researchers believe that the use of more than one language equips them with compensatory skills that keep symptoms like memory loss and confusion in check.
The research team included Fergus Craik, senior scientist at the Rotman Research Institute, and Dr. Morris Freedman, professor in the University of Toronto’s Faculty of Medicine (Neurology), and scientist at the Rotman Research Institute. They found that bilingual patients were diagnosed with Alzheimer’s 4.3 years later and had reported the onset of symptoms five years later than those who spoke only one language. The groups were equivalent on measures of cognitive and occupational level; there was no apparent effect of immigration status, and there were no differences between genders.
The Neurology paper replicates findings from the team’s 2007 study led by Bialystok and published in Neuropsychologia. That study examined the clinical records of 184 patients diagnosed with probable Alzheimer’s and other forms of dementia. It found that bilingual patients delayed the onset of their symptoms by four years compared to monolingual patients.
"Overall, bilingualism should be seen as an important tool for healthy aging, along with exercise, diet, and other lifestyle choices," Bialystok says. "It’s also another reason to encourage people in multicultural societies like ours to keep speaking their native tongue and pass it along to their children," she says.
The study was funded in part by grants from the Canadian Institutes for Health Research (CIHR) and the Alzheimer’s Society of Canada to York University and the Rotman Research Institute.