Researchers say speaking multiple languages may protect against cognitive impairment after stroke.
Each year, more than 795,000 people in the US have a stroke, which occurs when a blood vessel in the brain bursts (hemorrhagic stroke) or a clot blocks blood supply to the brain (ischemic stroke).
The effects of stroke depend on its location in the brain and how much brain tissue has been damaged; some stroke survivors may experience paralysis, speech and language problems, changes in behavior and cognitive impairment, such as memory loss.
But according to Subhash Kaul, senior investigator of the new study and developer of the stroke registry at Nizam's Institute of Medical Sciences (NIMS) in India, bilingualism - the ability to speak multiple languages - may protect against cognitive impairment from stroke.
To reach their findings, the team reviewed 2006-13 data from 608 stroke patients from Hyderabad, India, who were part of the NIMS stroke registry.
Around half of the patients were bilingual - defined by the researchers as speaking two or more languages - and the team analyzed the effects stroke had on each patient.
Bilingual stroke patients more likely to have normal cognitive function
The researchers found that bilingual patients were twice as likely as single-language patients to have normal cognitive function after stroke; around 40% of bilingual stroke patients had normal cognitive functioning, compared with only 20% of single-language stroke patients.
- Stroke kills almost 130,000 people in the US every year
- Around 87% of all strokes are ischemic strokes
- Stroke costs the US around $34 billion annually.
Patients who were bilingual also produced better scores on tests of attention and memory following stroke than single-language patients, according to the team.
The researchers were surprised to find there were no differences in likelihood of aphasia after stroke - a communication disorder characterized by difficulties reading, writing and speaking - between bilingual and single-language patients.
Lead study author Suvarna Alladi, a neurology professor at NIMS, believes this may be down to the ability of bilingual patients to rapidly switch from one language to another. "So while they inhibit one language, they have to activate another to communicate," he explains.
On the other hand, study coauthor Dr. Thomas Bak, of the UK's University of Edinburgh, notes that because bilingual individuals have a mixed vocabulary, it can make it harder for them to identify certain words. "This may explain what appears to be a surprising result," he adds.
Overall, Kaul says the findings do not necessarily suggest people who speak one language should begin learning another; any mentally challenging task could offer benefits:
"Our study suggests that intellectually stimulating activities pursued over time, from a young age or even starting in mid-life, can protect you from the damage brought on by a stroke."
The team notes a key limitation to the study; the findings may not be applicable to all people who speak more than one language.
"Constantly switching languages is a daily reality for many residents of Hyderabad," notes Alladi, who says people in Hyderabad often speak Telugu, Urdu, Hindi and English. "The cognitive benefit may not be seen in places where the need to function in two or more languages isn't as extensive."
This study follows another conducted by Dr. Bak and colleagues last year, which suggested speaking at least two languages may prevent later-life cognitive decline.