Being proficient in two (or more) languages improves brain function and slows down its ageing, delaying the development of neurodegenerative diseases such as dementia, Alzheimer's and Parkinson's, new research reveals.
Worldwide, some 47.5 million people are living with dementia, including 32.7 million Alzheimer's patients, according to the World Health Organisation (WHO). In Belgium and the Netherlands, this concerns hundreds of thousands of patients.
But bilingualism can slow down and reduce the rate of age-related decline in the human brain, a new study from Russia's HSE University and Britain's Northumbria University and published in the scientific journal Frontiers in Psychology shows.
"The language centres are constantly at work in our minds. This experiment highlights how high levels of language proficiency reduce the influence of other components of cognitive decline," said Federico Gallo from HSE University. "This suggests that the benefits of bilingualism on cognitive reserve are stronger than other factors."
The human brain generally performs worse with age, a process that is called "cognitive ageing". This is when the mental ability to process information decreases and short-term memory deteriorates. Language skills also fade and visual-spatial functions decline.
However, the rate of ageing varies and depends on a person's cognitive reserve: the brain's ability to hold back the effects of age-related brain damage and maintain optimal performance.
This reserve is built up over a person's lifetime, as the brain strengthens neural networks in response to various external triggers. The more complex the neural networks are, the greater the person's cognitive reserve and their neurological decline is limited.
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Physical activity, diet, career, leisure habits, education and socioeconomic status are all factors in cognitive reserve.
Now, the researchers also examined 63 adults aged 60 or older to look into the effect of bilingualism on brain function in the elderly. The participants were all healthy and had no history of psychiatric or neurodegenerative disorders.
They did, however, have at least a partial knowledge of a second language. Before the experiment, all participants completed a questionnaire that examined their cognitive reserve. They also had to indicate how long they had spoken a second language, how often and where they used it, and how fluently they spoke it.
The cognitive test showed that bilingualism has a positive effect on the task: the longer participants had studied a second language and the more fluent they were in it, the better they performed in the experiment.
How good the subjects' language skills were appeared to play a greater role than how long they had known a second language. According to the researchers, this is because bilingual speakers have to make constant choices in everyday life and have to switch between two language systems.
"Unlike other factors that shape cognitive reserve, bilingualism is unique in that it is constantly present in our lives. We can intensify or give up physical activity, go on a diet or change jobs, but language always stays with us," said Gallo.
No drug to prevent brain ageing
Proficiency in two or more languages improves brain function, not only in healthy people but also in people with various neurodegenerative diseases (dementia, Alzheimer's, Parkinson's, stroke).
In another article in Frontiers in Human Neuroscience, Gallo and his colleagues show that active bilinguals are diagnosed with neurodegenerative diseases five to seven years later than monolingual speakers, based on existing research on bilingualism and ageing.
"There are no really effective drugs to prevent or delay brain ageing. Huge financial resources are needed to develop pharmaceutical treatments," Gallo said. "Therefore, research into alternative, non-medicinal ways of slowing down cognitive ageing should be a priority."