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Behavioural Neurology
Volume 2014, Article ID 808137, 8 pages
http://dx.doi.org/10.1155/2014/808137
Research Article

Delaying Onset of Dementia: Are Two Languages Enough?

1Department of Medicine, Division of Neurology, Baycrest, Toronto, ON, Canada M6A 2E1
2Department of Medicine, Division of Neurology, Mt. Sinai Hospital, Toronto, ON, Canada M5G 1X5
3Rotman Research Institute, Baycrest, 3560 Bathurst Street, Toronto, ON, Canada M6A 2E1
4Department of Medicine (Neurology), University of Toronto, Toronto, Canada M5G 2C4
5Department of Neurology, Nizam’s Institute of Medical Sciences, Punjagutta, Hyderabad 500 082, India
6Bloomfield Centre for Research in Aging, Lady Davis Institute for Medical Research and Jewish General Hospital/McGill University Memory Clinic, Jewish General Hospital, 3744 Chemin de la Côte-Sainte-Catherine, Montreal, QC, Canada H3T 1E2
7Division of Geriatric Medicine, Department of Medicine, McGill University, Canada H3T 1E2
8Department of Clinical Neurosciences, Sir Mortimer B. Davis—Jewish General Hospital, Canada H3T 1E2
9Department of Psychology, York University, 4700 Keele Street, Toronto, ON, Canada M3J IP3
10Department of Psychology, University of Toronto, Toronto, ON, Canada M5S 3G3
11Department of Psychology/Centre for Research in Human Development, Concordia University, 7141 Sherbrooke Street West, Montreal, QC, Canada H4B 1R6
12Centre for Research on Brain, Language, and Music, McGill University, Montreal, Canada H3G 2A8
13Department of Linguistics, University College of Arts & Social Sciences, Osmania University, Hyderabad 500 007, India
14Centre for Neural and Cognitive Sciences, University of Hyderabad, Gachibowli, Hyderabad 500 046, India
15Human Cognitive Neuroscience and Centre for Cognitive Aging and Cognitive Epidemiology School of Philosophy, Psychology and Language Sciences, University of Edinburgh, 7 George Square, Edinburgh EH8 9JZ, UK
16Centere for Clinical Brain Sciences, University of Edinburgh, 49 Little France Crescent, Edinburgh EH16 4SB, UK

Received 18 March 2013; Revised 10 April 2014; Accepted 28 April 2014; Published 18 May 2014

Academic Editor: Luigi J. Ferini-Strambi

Copyright © 2014 Morris Freedman et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

There is an emerging literature suggesting that speaking two or more languages may significantly delay the onset of dementia. Although the mechanisms are unknown, it has been suggested that these may involve cognitive reserve, a concept that has been associated with factors such as higher levels of education, occupational status, social networks, and physical exercise. In the case of bilingualism, cognitive reserve may involve reorganization and strengthening of neural networks that enhance executive control. We review evidence for protective effects of bilingualism from a multicultural perspective involving studies in Toronto and Montreal, Canada, and Hyderabad, India. Reports from Toronto and Hyderabad showed a significant effect of speaking two or more languages in delaying onset of Alzheimer’s disease by up to 5 years, whereas the Montreal study showed a significant protective effect of speaking at least four languages and a protective effect of speaking at least two languages in immigrants. Although there were differences in results across studies, a common theme was the significant effect of language use history as one of the factors in determining the onset of Alzheimer’s disease. Moreover, the Hyderabad study extended the findings to frontotemporal dementia and vascular dementia.