Bilingualism Can Delay Early Dementia Symptoms, But May Mean Faster Decline After Diagnosis
A new study provides new evidence that bilingualism can delay early symptoms of dementia.
However, researchers at York University in Canada also found that once diagnosed, the decline to full-blown Alzheimer’s disease is much faster in bilingual people than in monolingual people because the disease is actually more severe.
According to researchers, of all activities with neuroplastic benefits, language is the most sustained, consuming the largest proportion of time within a day. It also activates regions across the entire brain.
That led Ellen Bialystok, Distinguished Research Professor in York’s Department of Psychology, Faculty of Health, and her research team to test the theory that bilingualism can increase cognitive reserve, delaying the age of onset of Alzheimer’s disease symptoms in elderly patients.
The researchers say their study is the first to investigate conversion times from mild cognitive impairment to Alzheimer’s disease in monolingual and bilingual patients.
And while they found that bilingualism does delays the onset of symptoms, once diagnosed, the disease is actually more severe in people who are bilingual.
“Imagine sandbags holding back the floodgates of a river. At some point the river is going to win,” said 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.”
In the five-year study, researchers followed 158 patients who had been diagnosed with mild cognitive impairment. 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 a hospital memory 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, according to the study’s findings.
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, the researchers explain.
These results contribute to the growing body of evidence showing that bilinguals are more resilient in dealing with neurodegeneration than monolinguals, the researchers noted.
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 said.
The study also adds new evidence 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,” she said. “That’s huge.”
The study was published in Alzheimer Disease and Associated Disorders.
Source: York University
Wood, J. (2020). Bilingualism Can Delay Early Dementia Symptoms, But May Mean Faster Decline After Diagnosis. Psych Central. Retrieved on July 15, 2020, from https://psychcentral.com/news/2020/02/19/bilingualism-can-delay-early-dementia-symptoms-but-may-mean-faster-decline-after-diagnosis/154224.html