These results contribute to the growing body of evidence showing that bilinguals are more resilient in dealing with neurodegeneration than monolinguals.
A new study published in Alzheimer Disease and Associated Disorders provides new evidence that bilingualism can delay symptoms of dementia, including Alzheimer’s disease. Led by famed researcher of the effects of bilingualism, Ellen Bialystok, with other psychology researchers from Canada’s York University, distinguished research professor in York’s Department of Psychology, Faculty of Health, the study is believed to be the first to investigate conversion times from mild cognitive impairment to Alzheimer’s disease in monolingual and bilingual patients. Although bilingualism delays the onset of symptoms, Bialystok says, once diagnosed, the decline to full-blown Alzheimer’s disease is much faster in bilingual people than in monolingual people because the disease is probably more developed even through the symptoms are less apparent.
“Imagine sandbags holding back the floodgates of a river. At some point the
river is going to win,” says Bialystok. “The cognitive reserve is holding back
the flood and at the point that they were when they were diagnosed with mild
cognitive impairment they already had substantial pathology but there was no
evidence of it because they were able to function because of the cognitive
reserve. When they can no longer do this, the floodgates get completely washed
out, so they crash faster. Yet they had more time to enjoy the dry land.”
Alzheimer’s disease is the most common form of dementia, making up 60-70% of
dementia cases. Of all activities with neuroplastic benefits, language use
is the most sustained, consuming the largest proportion of time within a day.
It also activates regions across the entire brain. and her team tested the
theory that bilingualism can increase cognitive reserve and thus delay the age
of onset of Alzheimer’s disease symptoms in elderly patients. Bialystok’s team
collaborated with researchers at Baycrest Health Sciences’ Rotman
Research Institute, where Bialystok is an associate scientist.
In the five-year study, researchers followed 158 patients from the Sam
and Ida Ross Memory Clinic at Baycrest Health Sciences who had been
diagnosed with mild cognitive impairment. The patients had been diagnosed after
extensive testing and evaluation conducted by the clinic.
For the study, researchers classified bilingual people as having high
cognitive reserve and monolingual people as having low cognitive reserve.
Patients were matched on age, education, and cognitive level at the time of
diagnosis of mild cognitive impairment. The researchers followed their
six-month interval appointments at the clinic to see the point at which
diagnoses changed from mild cognitive impairment to Alzheimer’s disease. The
conversion time for bilinguals, 1.8 years after initial diagnosis, was
significantly faster than it was for monolinguals, who took 2.6 years to
convert to Alzheimer’s disease. This difference suggests that bilingual
patients had more neuropathology at the time they were diagnosed with mild
cognitive impairment than the monolinguals, even though they presented with the
same level of cognitive function.
These results contribute to the growing body of evidence showing that
bilinguals are more resilient in dealing with neurodegeneration than
monolinguals. They operate at a higher level of functioning because of
the cognitive reserve, which means that many of these individuals will be
independent longer, Bialystok says. This study adds new evidence by showing
that the decline is more rapid once a clinical threshold has been crossed,
presumably because there is more disease already in the brain.
“Given that there is no effective treatment for Alzheimer’s or dementia, the
very best you can hope for is keeping these people functioning so that they
live independently so that they don’t lose connection with family and friends.
That’s huge,” concludes Bialystok.