Bilingual patients were twice as likely as those who spoke one language to have normal cognitive functions after a stroke, in a study has reported.
Previous research found bilingualism may delay 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 Dr Subhash Kaul, senior investigator and developer of the stroke registry at Nizam’s Institute of Medical Sciences (NIMS) in Hyderabad, India.
In the new study, researchers reviewed the records of 608 patients in the NIMS stroke registry in 2006-13. More than half the patients were bilingual, defined in the study as speaking two or more languages. To ensure results weren’t due to bilinguals having a healthier lifestyle, researchers took into account other factors such as smoking, high blood pressure, diabetes and age.
They found: about 40% of bilingual patients had normal cognitive functions following a stroke, compared to about 20% of single language patients; and bilinguals performed better on post-stroke tests that measured attention, and ability to retrieve and organise information.
Surprisingly, there was no difference between bilinguals and those who spoke one language in the likelihood of experiencing aphasia, a disorder that can cause difficulties in speaking, reading and writing, after a stroke.
“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 Dr Suvarna Alladi, lead author and a neurology professor at NIMS.
“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,” said Dr Thomas Bak, study co-author at the University of Edinburgh, UK.
The study’s results may not be universally applicable to all bilingual people. Hyderabad is a multicultural city in which many languages are commonly spoken, including Telugu, Urdu, Hindi and English. “Constantly switching languages is a daily reality for many residents of Hyderabad,” Alladi said. “The cognitive benefit may not be seen in places where the need to function in two or more languages isn’t as extensive.”
People who speak only one language shouldn’t necessarily begin learning another one, Kaul said. “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.”
Background and Purpose—Bilingualism has been associated with slower cognitive aging and a later onset of dementia. In this study, we aimed to determine whether bilingualism also influences cognitive outcome after stroke.
Methods—We examined 608 patients with ischemic stroke from a large stroke registry and studied the role of bilingualism in predicting poststroke cognitive impairment in the absence of dementia.
Results—A larger proportion of bilinguals had normal cognition compared with monolinguals (40.5% versus 19.6%; P<0.0001), whereas the reverse was noted in patients with cognitive impairment, including vascular dementia and vascular mild cognitive impairment (monolinguals 77.7% versus bilinguals 49.0%; P<0.0009). There were no differences in the frequency of aphasia (monolinguals 11.8% versus bilinguals 10.5%; P=0.354). Bilingualism was found to be an independent predictor of poststroke cognitive impairment.
Conclusions—Our results suggest that bilingualism leads to a better cognitive outcome after stroke, possibly by enhancing cognitive reserve.