Multilingualism (But Not Always Bilingualism) Delays the Onset of Alzheimer Disease: Evidence From a Bilingual Community

Bloomfield Centre for Research in Aging, Lady Davis Institute for Medical Research, and Jewish General Hospital/McGill University Memory Clinic, Jewish General Hospital, McGill University, Montreal, Quebec, Canada.
Alzheimer disease and associated disorders (Impact Factor: 2.44). 04/2010; 24(2):118-25. DOI: 10.1097/WAD.0b013e3181ca1221
Source: PubMed


A recent paper by Bialystok et al in Neuropsychologia (vol. 45, pgs. 459 to 464) suggested that early bilingualism produced a statistically significant 4.1-year delay in onset of memory loss symptoms in older individuals with Alzheimer disease, possibly reflecting an increase in the cognitive reserve of these individuals. That study focused on multilingual elderly patients of whom 90% were immigrants. Our memory clinic, in Montreal Canada, has the advantage of having a large set of individuals who are either multilingual immigrants to Canada, or who are nonimmigrants but raised in both official languages of Canada--French and English. We thus attempted to replicate the above findings using a larger cohort in a different setting. We examined age at diagnosis of Alzheimer disease and age at symptom onset for all unilingual versus multilingual participants, and then for those who were nonimmigrant English/French bilinguals. Overall, we found a small but significant protective effect of more than 2 languages spoken, but we found no significant benefit in bilinguals overall in relation to age at diagnosis or age at symptom onset. However, in the immigrant group, the results mirrored those of Bialystok et al with 2 or more languages delaying the diagnosis of Alzheimer disease by almost 5 years. A trend toward the same effect was also seen in nonimmigrants whose first language was French. In contrast, in nonimmigrants whose first language was English, no such effect was found. These results are discussed in relation to the earlier findings and the theory of cognitive reserve.

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Available from: Natalie A. Phillips
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    • "The view has recently emerged that CR may be enhanced by a specific type of linguistic experience: life-long bilingualism (Kavé et al., 2008; Bak et al., 2014). In line with evidence for a bilingual advantage in executive functioning (see Section Bilingualism: Key Notions and Findings), some studies found that symptoms of dementia (Bialystok et al., 2007, 2014; Chertkow et al., 2010; Craik et al., 2010; Alladi et al., 2013; Woumans et al., 2015) and mild cognitive impairment (MCI; Ossher et al., 2013; Bialystok et al., 2014) have a later onset in bilingual/plurilingual than in monolingual patients. Moreover, Schweizer et al. (2012) reported comparable cognitive performance between bilingual and monolingual AD patients despite greater brain atrophy in the former. "
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    ABSTRACT: The decline of cognitive skills throughout healthy or pathological aging can be slowed down by experiences which foster cognitive reserve (CR). Recently, some studies on Alzheimer's disease have suggested that CR may be enhanced by life-long bilingualism. However, the evidence is inconsistent and largely based on retrospective approaches featuring several methodological weaknesses. Some studies demonstrated at least 4 years of delay in dementia symptoms, while others did not find such an effect. Moreover, various methodological aspects vary from study to study. The present paper addresses contradictory findings, identifies possible lurking variables, and outlines methodological alternatives thereof. First, we characterize possible confounding factors that may have influenced extant results. Our focus is on the criteria to establish bilingualism, differences in sample design, the instruments used to examine cognitive skills, and the role of variables known to modulate life-long cognition. Second, we propose that these limitations could be largely circumvented through experimental approaches. Proficiency in the non-native language can be successfully assessed by combining subjective and objective measures; confounding variables which have been distinctively associated with certain bilingual groups (e.g., alcoholism, sleep disorders) can be targeted through relevant instruments; and cognitive status might be better tapped via robust cognitive screenings and executive batteries. Moreover, future research should incorporate tasks yielding predictable patterns of contrastive performance between bilinguals and monolinguals. Crucially, these include instruments which reveal bilingual disadvantages in vocabulary, null effects in working memory, and advantages in inhibitory control and other executive functions. Finally, paradigms tapping proactive interference (which assess the disruptive effect of long-term memory on newly learned information) could also offer useful data, since this phenomenon seems to be better managed by bilinguals and it becomes conspicuous in early stages of dementia. Such considerations may shed light not just on the relationship between bilingualism and CR, but also on more general mechanisms of cognitive compensation.
    Full-text · Article · Jan 2016 · Frontiers in Aging Neuroscience
    • "Some studies have examined effects of bilingualism in a non-immigrant sample and have found positive effects for healthy adults (e.g., Bak, Nissan, Allerhand, & Deary, 2014; Costa et al., 2008; Woumans, Ceuleers, Van der Linden, Szmalec, & Duyck, 2015) and dementia patients (Alladi et al., 2013; Woumans, Santens et al., 2015). On the other hand, studies with non-immigrant samples did not observe a cognitive effect of bilingualism in children (e.g., Antón et al., 2014), younger adults (e.g., Kousaie & Phillips, 2012a, although some differences were found in the ERP data), healthy older adults (e.g., Kousaie & Phillips, 2012b), and dementia patients (e.g., Chertkow et al., 2010; Lawton, Gasquoine, & Weimer, 2015). "
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    ABSTRACT: Bilinguals have been argued to show a cognitive advantage over monolinguals, although this notion has recently been called into question. In many studies, bilinguals and monolinguals vary on background variables. Moreover, most studies do not distinguish between potential effects of language knowledge and language use. We examined the effects of bilingualism on executive control in older adults by comparing active and inactive bilinguals and monolinguals matched on lifestyle, socio-economic status, education, IQ, gender, and age. In the Simon arrow task, no effect of bilingualism was observed on overall RTs or the Simon effect. In the task-switching paradigm, although there was a difference between active (but not inactive) bilinguals and monolinguals on raw switching costs, the groups did not differ on overall RTs and proportional switching or mixing costs. Thus, our findings do not reveal an overall cognitive advantage of bilingualism on executive control tasks in groups matched on background variables.
    No preview · Article · Nov 2015 · Journal of Memory and Language
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    • "In an earlier discussion forum Fuller-Thomson (2015) suggested that the retrospective studies that begin assessment when patients present themselves at a memory clinic and then estimate the onset of MCI retrospectively on the basis of patient and caretaker reports are open to biases in sampling, measurement, and publication. In addition to these general points, some remarkable anomalies in the retrospective study byChertkow et al. (2010)have induced further skepticism on our part that these methods and procedures yield trustworthy results. Consider these two results: (1) French-speaking Canadian monolinguals were diagnosed with dementia an average of 5.3 years earlier than English-speaking Canadian monolinguals. "

    Full-text · Article · Oct 2015 · Cortex
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