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New study suggests that bilingualism protects against dementia

Researchers studied the brains of monolingual and bilingual elders with cognitive decline and found evidence to suggest that bilingualism protects against dementia over time.

Is learning a second language worth the time and energy it takes to do so?  More and more studies seem to indicate that actively speaking a second language can protect us in our older years from different forms of cognitive decline, or the loss of the ability to use our brains effectively to think, make decisions, and communicate.

With the population of Canada slowly aging, one in seven Canadians is age 65 or older.  The Canadian Study of Health and Aging conducted in 1991 shows that approximately 17% of people aged 65 or older have a mild form of cognitive decline.  With such rates of decline, any information that can help improve the wellbeing of elderly people would be very important.  Diseases such as dementia and Alzheimer’s Disease can also cause cognitive decline, and recent research also shows that some factors may protect against or reduce the speed at which these diseases progress.

Some ways to help seniors keep up their mental health are already well known.  These include lifestyle factors such as eating a proper diet, exercising regularly, and getting enough sleep, in addition to taking on challenging mental tasks such as puzzles and games and keeping as much social contact as possible with other people.  However, research is showing that the challenge of using two or more languages on a regular basis might also help protect against cognitive decline, and previous studies have reported that a bilingual person will show signs of cognitive decline an average of five years later than a person who speaks only one language.

Researchers in Spain wanted to test whether bilingualism protects against dementia.  They hypothesized that speaking two languages would protect against loss of brain capacity, and they set about testing this in two ways.  First, they compared the brains of monolingual and bilingual individuals with similar levels of mild cognitive impairment (MCI) to see if there were noticeable differences.  They then compared the level of decline over time between monolingual and bilingual subjects. 

The researchers studied nearly 100 patients with an average age of 73.9 years and nearly equal amounts of men and women.  Since there are two main languages spoken in Spain — Spanish and Catalan — they compared those who spoke both languages to those who spoke only Spanish.  They also compared other factors, such as background, education, where the patients, lived and socioeconomic status, in order to rule out any other factors.  They then tested the participants with a variety of standardized tests for mental capacity and measured their brain size and levels of deterioration using an MRI analysis.

What they found was that the brains of the bilingual subjects had further deteriorated than the brains of the monolingual subjects who had similar levels of mild cognitive impairment.  This might seem like a bad thing, but what it actually means is that it takes more damage for a bilingual person’s brain to show the same level of cognitive decline as it does for a monolingual person.  So, the bilingual individuals appeared to have more efficient brain function to compensate for the loss.

The researchers also wanted to compare changes in cognitive function over time.  They re-tested 32 individuals roughly seven months after their first cognitive evaluation and found that every single person had experienced a drop in their cognitive abilities.  However, the bilingual participants had lost less of their brain’s abilities than the monolingual group.  This seems to indicate that speaking two languages can slow down the rate at which cognitive decline happens.

There are still some unanswered questions, such as whether the same would be true for individuals with a more severe form of cognitive decline, or even dementia or Alzheimer’s Disease.  Also, the study only looked at a small sample of participants over time to check for changes in mental capacity.  A larger sample would be needed in order to confirm such results are accurate.  Finally, a longer study might better be able to see if there really is a greater protective effect over time for those who are bilingual. 

Written by Nancy Lemieux


1. Bilingualism acts as a cognitive reserve factor against dementia. (2020). Retrieved 8 March 2020, from https://www.eurekalert.org/pub_releases/2020-03/upf–baa030420.php

2. Costumero, V. et al.  (2020). A cross-sectional and longitudinal study on the protective effect of bilingualism against dementia using brain atrophy and cognitive measures. Retrieved 8 March 2020, from https://alzres.biomedcentral.com/articles/10.1186/s13195-020-0581-1

3. Findings. (2020). Retrieved 8 March 2020, from https://www150.statcan.gc.ca/n1/pub/82-003-x/2010004/article/11391/findings-resultats-eng.htm

4. Protecting against cognitive decline – Harvard Health. Retrieved 8 March 2020, from https://www.health.harvard.edu/mind-and-mood/protecting-against-cognitive-decline

Image by Gerd Altmann from Pixabay 


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