A new study has suggested that being bilingual can help ward off three types of dementia for over four years.
The study, published in US journal Neurology, has also indicated that the protective effects of bilingualism can extend to people who are illiterate.
Researchers Suvarna Alladi and Thomas Bak surveyed 648 people from India with an average age of 66, all of whom had dementia.
The study found that bilingual patients had developed Alzheimer’s disease, frontotemporal dementia and vascular dementia four and a half years later than the monolingual participants.
Interestingly, this difference persisted, regardless of whether or not the person was able to read.
The researchers also pointed out that there was no added benefit in speaking more than two languages.
"Our study is the first to report an advantage of speaking two languages in people who are unable to read," said study co-author Suvarna Alladi, from Nizam's Institute of Medical Sciences in Hyderabad, India.
The delayed onset of dementia was seen regardless of factors such as education, gender, occupation and rural or city residency.
"Speaking more than one language is thought to lead to better development of the areas of the brain that handle executive functions and attention tasks, which may help protect from the onset of dementia," Ms Alladi said.
Their results "offer strong evidence for the protective effect of bilingualism against dementia in a population very different from those studied so far in terms of its ethnicity, culture and patterns of language use," she said.
"Bilingualism can be seen as a successful brain training, contributing to cognitive reserve, which can help delay dementia," said Alladi's co-author Dr. Thomas Bak, a lecturer at the Center for Cognitive Aging and Cognitive Epidemiology at the University of Edinburgh in Scotland.
Cognitive reserve is the ability of the brain to keep functioning normally despite significant disease or injury, explained Stephen Rao, a neuropsychologist at Cleveland Clinic's Lou Ruvo Center for Brain Health. "It has been understood that this capacity is influenced by education, higher occupational status, engagement in higher order cognitive [thinking] activities, and now bilingualism," Mr Rao said.
The higher a person’s cognitive reserve, the later in life they will experience the onset of dementia, as thinking and memory functions are able to continue to operate even with the loss of brain cells.
Because the delay of dementia was noted in literate and non-literate people alike, it is hypothesised that it has little to do with the education of the person in question.
"The fact that bilingual advantage is not caused by any differences in education is confirmed by the fact that it was also found in illiterates, who have never attended any school," Mr Bak said.
He notes that their findings "suggest that bilingualism might have a stronger influence on dementia than any currently available drugs."
Mr Bak said this makes the relationship between cognition and bilingualism a high research priority.
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