Speak more than one language? Bravo! It seems that being bilingual helps delay the onset of several forms of dementia.
Previous studies of people with Alzheimer's disease in Canada showed that those who are fluent in two languages begin to exhibit symptoms four to five years later than people who are monolingual.
Thomas Bak at the University of Edinburgh, UK, wanted to know whether this was truly down to language, or whether education or immigration status might be driving the delay, since most bilingual people living in Toronto, where the first studies were conducted, tended to come from an immigrant background. He also wondered whether people suffering from other forms of dementia might experience similar benefits.
He teamed up with Suvarna Alladi, a neurologist working on memory disorders at Nizam's Institute of Medical Sciences (NIMSH) in Hyderabad, India. "In India, bilingualism is part of everyday life," says Bak.
The team compared the age that dementia symptoms appeared in some 650 people who visited the NIMSH over six years. About half spoke at least two languages. This group's symptoms started on average four and a half years later than those in people who were monolingual.
Language not education
"Incredibly the number of years in delay of symptom onset they reported in the Indian sample is identical to our findings," says Ellen Bialystok, at Toronto's York University, who conducted the original Canadian studies.
What's more, the same pattern appeared in three different types of dementia: Alzheimer's, frontotemporal and vascular. The results also held true for a group of people who were illiterate, suggesting that the benefits of being bilingual don't depend on education.
A leading theory as to why bilingualism can affect dementia suggests the key may be the constant suppression of one language, and switching between the two. "This permanent switching and suppressing offers you constant brain training," says Bak.
If switching languages is the reason, it could also explain why they saw no additional benefits of speaking more than two languages.
Next, Bak is looking at whether people who learn languages later in life reap the same benefits as those who grow up bilingual. Preliminary results suggest they do, so it is something we could all act on.
"It's much cheaper than a lot of brain training sets, it's socially more enjoyable, and it forces your brain to train permanently," he says.
Journal reference: Neurology, DOI: 10.1212/01.wnl.0000436620.33155.a4