How bilingualism can hold back a flood of Alzheimer's symptoms

A long line of research projects have found a range of benefits of bilingualism when it comes to the brain, from shortening recovery times from stroke to staving off the cognitive decline associated with dementia and Alzheimer’s. Scientists looking into the latter have uncovered some interesting new insights, finding that while knowing a second language can delay the onset of the disease, it can also significantly accelerate the deterioration into severe Alzheimer’s thereafter.

The research was carried out at Canada’s York University, where scientists in the Department of Psychology set out to investigate how bilingualism can boost what is known as our cognitive reserve, and what that means for Alzheimer’s. This refers to the brain’s resilience to neurological damage, with previous studies finding that a greater cognitive reserve can, at least temporarily, mitigate the impacts of Alzheimer’s in our later years.

The team conducted a five-year study involving 158 patients who had been diagnosed with mild cognitive impairment. These subjects were matched on age, education and cognitive levels, and then categorized as either bilingual with a high cognitive reserve, or monolingual with a low cognitive reserve. The team believes this is the first study to compare conversion times for Alzheimer’s between monolingual and bilingual patients.

Across the five years, the subjects’ cognitive levels were assessed at six-month intervals as a way of tracking the progression from mild cognitive impairment to Alzheimer’s disease. The team found that the time it took for the monolingual group to make this transition was 2.6 years, while the bilingual group progressed in just 1.8 years.

This adds further weight to the theory that bilinguals and a greater cognitive reserve can stave off the symptoms of Alzheimer’s and neurodegeneration, but only for so long. The team believes that while both groups presented with the same level of cognitive function at the outset of the study, the Alzheimer’s pathology was already building up in the bilingual group in greater amounts behind the scenes.

“Imagine sandbags holding back the floodgates of a river,” says lead investigator Ellen Bialystok. "At some point the river is going to win. “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.”

While this rapid decline into Alzheimer’s might seem like bad news, the upside is that the greater cognitive reserve enables bilingual individuals to live without symptoms of the disease for longer, until that vital threshold is crossed.

“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,” says Bialystok. “That’s huge.”

The research was published in the journal Alzheimer Disease and Associated Disorders.

Source: York University