Bilingualism may protect against cognitive impairment from stroke

People who speak at least two languages are twice as likely as those who speak one language to have normal cognitive functions following a stroke, a new study finds.

Previous studies have shown that bilingualism may play a part in delaying the onset of Alzheimer’s disease.

"People tend to think of Alzheimer's as the only cause of dementia, but they need to know that stroke is also an important cause," said Subhash Kaul, D.M., senior investigator and developer of the stroke registry at Nizam's Institute of Medical Sciences (NIMS) in Hyderabad, India.

A stroke occurs when blood flow to a part of the brain is cut off. Burst of a blood vessel in the brain causes “hemorrhagic stroke,” and blocking of blood supply to the brain due to blood clot causes “ischemic stroke.” The cells in the brain are deprived of oxygen and glucose they need to survive, which causes the death of brain cells. If not detected early, stroke can cause permanent brain damage or even death. [Read more What Causes Aging? Can The Process Be Slowed?]

Stroke is a leading cause of disability in the US. Around 795,000 people have stroke each year, of them 185,000 are first time strokes. Stroke kills almost 130,000 Americans each year. On average, 1 person dies from stroke every 4 minutes in the US.

In the UK, around 152,000 people suffer a stroke each year. In 2010, stroke was ranked the fourth largest cause of death in the UK after cancer, heart disease and respiratory disease. The same year, stroke claimed the lives of 50,000 people in the country.

In the new study, the researchers reviewed data of 608 stroke patients from Hyderabad, India, who were part of the NIMS stroke registry between 2006-2013.

More than half the patients were bilingual – defined by the researchers as speaking two or more languages. Other factors such smoking, high blood pressure, diabetes and age were also taken into account. [Read more Learning foreign languages may sharpen our minds]

The team found that 40% of bilingual patients had normal cognitive functions following a stroke, compared to about 20% of patients who spoke only one language.

Bilingual patients also produced better scores on post-stroke tests that measured attention and ability to retrieve and organize information.

The team was surprised to discover that there were no differences between bilinguals and single language patients in the likelihood of experiencing aphasia – a combination of a speech and language disorder caused by damage to the brain.

"The advantage of bilingualism is that it makes people switch from one language to another, so while they inhibit one language, they have to activate another to communicate," said Suvarna Alladi, D.M., lead author and a neurology professor at NIMS.

Moreover, Thomas Bak, M.D., study co-author at the University of Edinburgh in United Kingdom said: "The combined vocabulary of bilinguals can make it more difficult for them to find specific words. This may explain what appears to be a surprising result."

The results of the study may not be applicable to bilingual people all over the globe. In a multicultural city like Hyderabad, people commonly speak many languages such as, Telegu, Hindi, Urdu and English. [জেনে নিন গাজরের অসংখ্য না জানা গুণাবলী]

"Constantly switching languages is a daily reality for many residents of Hyderabad," explains Alladi.
"The cognitive benefit may not be seen in places where the need to function in two or more languages isn't as extensive."

According to Kaul, the findings do not necessarily suggest people who speak one language should begin learning another. He believes any mentally challenging task could be helpful.

"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," says Kaul.

The United States is largely monolingual. In fact, only about 15-20 percent of Americans consider themselves bilingual, compared to 56 percent of Europeans surveyed in 2006 by the European Commission.

The study was reported in the American Heart Association journal Stroke.

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