Lifelong bilingualism can help delay the onset of dementia symptoms by four years, Canadian researchers have found.
Patients who were fluent in two or more languages and spoke them regularly reported dementia symptoms on average about four years after people who spoke only one language, says principal investigator Ellen Bialystok.
Bialystok, a psychology professor at York University, says researchers are "pretty dazzled" by the results.
Bilingualism may help to stave off cognitive decline because of the mental agility necessary to juggle them in day-to-day life, researchers said.
"In the process of using language and using two languages, you are engaging parts of your brain ... that are active and need that kind of constant exercise and activity and with that experience stays more robust," Bialystok said, appearing on CTV's Canada AM.
The study, conducted by researchers with the Rotman Research Institute at the Baycrest Research Centre for Aging and the Brain in Toronto, is published in the February 2007 issue of Neuropsychologia.
"Our study found that speaking two languages throughout one's life appears to be associated with a delay in the onset of symptoms of dementia by four years compared to those who speak one language," said Bialystok, also an associate scientist at the Rotman Research Institute.
The study followed on the heels of previous reports from Bialystok and colleagues showing bilingualism enhances attention and cognitive control in both children and older adults.
"I've been investigating the cognitive effects of bilingualism in children for a long time and so about five or six years ago, we wondered if we could find these benefits throughout adulthood, and we did," Bialystok said.
"And (we) found that with aging, bilingual adults suffered or experienced a slower decline in the normal slowing down and decline of cognition with aging than comparable monolinguals," she said.
Those results compelled Bialystok and her research team to wonder what this would mean for the onset of dementia.
Researchers examined the diagnostic records of 184 Toronto-area patients who came to Baycrest's Sam and Ida Ross Memory Clinic between 2002 and 2005 with cognitive complaints. Of those patients, 91 were monolingual and 93 were bilingual.
The bilingual speakers spoke a combination of 25 different languages, the most prevalent being Polish, Yiddish, German, Romanian and Hungarian.
Researchers found 132 patients met criteria for probable Alzheimer's while the remaining 52 were diagnosed with other dementias.
The researchers determined that the mean age of onset of dementia symptoms in the monolingual group was 71.4 years, while the bilingual group was 75.5 years. This gap remained even after considering the possible effect of other lifestyle factors such as cultural differences, immigration, formal education, employment and gender.
"There are no pharmacological interventions that are this dramatic" in delaying symptoms, said neurologist Dr. Morris Freedman, who is head of the Division of Neurology, and director of the Memory Clinic at Baycrest.
"The data show a huge protective effect," adds co-investigator and psychologist Fergus Craik, an expert on age-related changes in memory processes.
Craik cautioned that this is a preliminary study but aligned with other recent findings about lifestyle effects on dementia.
The team is working on a follow-up study that will further examine bilingualism and dementia onset.
The study was funded by the Canadian Institutes of Health Research.
