Dementia onset is delayed in bilingual people

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It is estimated that over 40 per cent of Indians are bilingual.— PHOTO: M. SATHYAMOORTHY
It is estimated that over 40 per cent of Indians are bilingual.— PHOTO: M. SATHYAMOORTHY

How experience of a person modifies brain structure and function has been an engaging theme of research among neuroscientists. The so called “Mozart effect” is an example. Some researchers claimed that youngsters who listened to classical music by the famous composer Mozart performed some mental tasks better than those who did not. This led to many parents playing Mozart to newborns and growing infants with the hope that it will make the child smarter. Alas, the jury is still out on this issue. Then a group in UK claimed to have found structural changes in the hippocampus region of the brains of London taxi drivers, related to the amount of navigational information that they have stored in their memory. Yet others have claimed that learning juggling, videogames or even architecture affects the brain in a positive manner. Is this effect permanent, or does it alter the brain structure in a lasting fashion are questions that tease neuroscientists.

Put another way, how does learning, or the mind, affect the brain? We check the mind through behavioural aspects of the individual while we check the brain by analysing the molecular, cellular and organ-related changes using histology and pathology. Does learning alter neuro-plasticity, or change the “hardwiring” in the brain? What are the consequences of learning a task affecting the mind and the brain?

A more recent way of addressing this mind-body dialectic is the study of how bilingualism and people who speak two languages fluently and use them in daily life affects their brain health or illness. A remarkable (and easy to download and read) paper has been published online on November 6 in Neurology by Drs. Suvarna Alladi, Thomas Bak, Vasanta Duggirala, Bapiraju Surampudi, Mekala Shailaja, Anuj Kumar Shukla, Jaidip Ray Chaudhuri and Subhash Kaul (from Hyderabad). Titled “Bilingualism delays the age at onset of dementia, independent of education and immigration status,” this study shows that in persons who practice bilingualism dementia or mental cognitive loss (such as Alzheimer’s and related illnesses) occurs a full four years later that those who are monolingual.

Every word in this rather longish title of the above Suvarna et al paper is important because it elaborates and expands on earlier work on the connection between bilingualism and delayed dementia. The proponents of this connection, Drs. Ellen Bialystok and Fergus Craik (both of Toronto, Canada), have been looking at groups who have had to learn to be bilingual because of their family circumstances, place of birth, learning at school as part of curriculum, or immigration history and such-like. On the other hand, the Hyderabad group has the natural advantage of doing the study in India.

What is special about India? First, we are a billion plus, and hence the ‘catchment’ number is far larger. Second, India has an exceptional linguistic diversity and it is estimated that over 40 per cent (if not more) of Indians are bilingual (and many among them tri- or even tetra-lingual). And bilingualism in India is not due to compulsions of immigration, educational levels or even necessarily due to learning in school. Bilingualism is pretty common even among illiterates. It forms part of everyday life negotiations. Dr AK Mohanty of the Central Institute of Indian Languages at Mysore defies bilingual persons as those with ability to meet communication demands of the self and society in their normal functioning. For example, right here in Hyderabad, common people are proficient in Telugu, Dakkhini (a form of Urdu) in the informal, and Hindi and English in formal contexts.

Given this, the researchers zoned in on 648 (largest so far) patients reporting at the Nizam’s Institute of Medical Sciences, Hyderabad, and recorded their age, sex, occupation, education level, lingual status, family history, and relevant medical history and ages of onset of dementia. 391 of them were bilingual (of these over 200 spoke even 3 or 4 tongues) and the rest monolingual. Approvals, consents, registration and study protocols were of standard global status. Each of them was given the Standardized Mini-Mental State Examination (SMMSE, down loadable free for interested readers), following which the results were analysed. The age of onset of monolingual patients was, on an average, 65.4 years while in bilinguals it was 68.6 years. These results compare well with the Toronto ones who found 77.7 for bi- against 73 in mono-linguals there.

By the way, it did not matter what two languages among Telugu, Dakkhini, English and Hindi. Tri- or terta-linguals did not fare any better than bilinguals (one wonders if this offers any other neural benefits). Man or woman does not seem to matter. The two languages need not have a common parent (Chinese and English, or Dakkhini and English or Telugu). When one learns the language might perhaps matter; sorry to report that Canadian data seems to suggest that life-long bilingualism appears to offer better protection, than learning in the 50s or 60s. Finally, CT scans on the brains of dementia patients reveals that bilinguals had more pathology than mono’s, suggesting that they were able to handle the deficit somewhat better. Moral of the story; catch them young, teach then another tongue.

D. Balasubramanian



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