Being bilingual could delay onset of dementia

People fluent in two languages may be warding off the cognitive decline associated with dementia for up to six years longer than single-language speakers, according to a study published online Nov. 6 in Neurology.

A team of researchers including Thomas H. Bak, MD, a neuroscientist and lecturer from the department of psychology at the Centre for Cognitive Aging and Cognitive Epidemiology and a research fellow for the Centre for Clinical Brain Sciences at the University of Edinburgh, U.K., assessed the clinical data of 648 patients with dementia, 391 of whom spoke another language. Researchers reviewed case records between June 2006 and October 2012 in a specialist memory clinic at a University Hospital in Hyderabad, India, to find out what impact this skill had on the onset of dementia.

Results of the study showed that speaking two languages had a protective effect on cognition and effectively delayed onset of the cognitive symptoms of dementia. This was not just a factor of education, because a subgroup of illiterate bilingual speakers with zero formal education experienced the longest delay, six years, before they showed signs of developing neurodegenerative disease.

“In India there is a very positive attitude toward multilingualism and this study reinforces that,” Bak told Molecular Imaging in an exclusive interview. “In other countries, possibly the U.S. and the U.K., it might be worth encouraging multilingualism more than ever before. What this study does is prove that knowing two languages not only provides benefits to children early in life, but that it continues across their whole lifetime.”

The advantage may be found in the bilingual subjects’ acute attention and executive functions. They may be selectively activating information leading to compensatory networks in the brain that delay symptoms of cognitive decline despite clear areas of atrophy in structural brain imaging. This preliminary study is the largest of its kind and will likely be followed by additional studies looking at functional imaging of the brain in order to map possible compensatory networks engaged during bilingual speech.

“These are positive results in the debate for cognitive reserve,” added Bak. “This shows that a better or more active intellectual life slows cognitive aging. Bilinguals are effectively undergoing cognitive training, switching between different words and often even different social norms.”

This delayed effect of multilingualism was found to be true in cases of four different dementias, including Alzheimer’s disease, frontotemporal dementia, vascular dementia and dementia with Lewy bodies.

The bilingual advantage was independent of not only education level, but also sex, occupation and whether subjects lived in rural or urban areas. This study group was less confounded by factors to do with immigration than similar Canadian studies. Interestingly, there was no added value in speaking more than two languages.