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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: 2.69). 04/2010; 24(2):118-25. DOI: 10.1097/WAD.0b013e3181ca1221
Source: PubMed

ABSTRACT 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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    • "The first studies used retrospective reports of patients at memory clinics and showed that bilingualism delayed the onset of symptoms or diagnosis by several years. Some of these studies confounded bilingualism with immigrant status (Bialystok, Craik, & Freedman, 2007) while another found bilingual benefits within immigrant samples, but not between native samples (Chertkow et al., 2010). Immigrant status is important because it is associated with higher intelligence that, in turn, is associated with delays in dementia onset (Fuller-Thomson, & Kuh 2014). "
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    • "In contrast, a study in Montreal, Canada, found that nonimmigrant monolinguals showed a later decline than nonimmigrant bilinguals; only nonimmigrants who were at least tetralingual showed a protective effect (Chertkow et al., 2010; see Appendix 2 for details). For immigrants the findings were different. "
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    ABSTRACT: The relation between bilingualism and cognition is informative about the connection between language and mind. From the perspective of language, the question is how bilingualism might help or hinder cognition – narrowly interpreted here as executive function. From the perspective of higher cognition, the question is what kinds of experiences improve executive function. Reported cognitive benefits from bilingualism range from none to substantial as a function of age, type of bilingualism (e.g., life-long balanced vs later-onset or infrequent use of the other language), syntactic relation between the two languages, socio-economic and immigrant status, task, and laboratory. To understand the variability and inconsistencies in results with bilingualism, I analyze concepts of executive function and cognitive reserve and examine the range of factors (such as active video game playing, education, musical training, and aerobic exercise) that are known to correlate with or to improve executive function. I suggest that a) “executive function” is a complex set of cognitive processes, the components of which are sometimes minimally correlated with each other, depending on the task; b) bilingualism is inconsistently correlated with superior executive function and delayed onset of dementia; c) all speakers (mono- or bilingual) have non-linguistic ways of improving executive function; and d) benefits from bilingualism – and all cognitively challenging activities – are inconsistent because individuals vary in the number and kinds of experiences they have that promote superior executive function.
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    • "The degree of bilingualism may be important in promoting cognitive reserve [26], and the nature of the particular languages may affect the nature of the interaction with neuropsychological function and bilingualism [27]. One study has shown an advantage for multilingualism [28] but not for bilingualism on age of AD diagnosis, whereas other studies have not shown the effect of language at all [22] [29]. Bilingualism has been shown to enhance cognitive control, conferring an advantage in EF [30]. "
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    ABSTRACT: Objective. Bilingualism has been shown to benefit executive function (EF) and delay the onset of Alzheimer’s disease. This study aims at examining whether a bilingual advantage applies to EF in Parkinson’s disease (PD). Method. In a cross-sectional outpatient cohort of monolingual English () and bilingual Welsh/English () speakers with PD we evaluated the effects of bilingualism compared with monolingualism on performance on EF tasks. In bilinguals we also assessed the effects of the degree of daily usage of each language and the degree of bilingualism. Results. Monolinguals showed an advantage in performance of language tests. There were no differences in performance of EF tests in monolinguals and bilinguals. Those who used Welsh less in daily life had better performance on one test of English vocabulary. The degree of bilingualism correlated with one test of nonverbal reasoning and one of working memory but with no other tests of EF. Discussion. The reasons why the expected benefit in EF in Welsh-English bilinguals with PD was not found require further study. Future studies in PD should include other language pairs, analysis of the effects of the degree of bilingualism, and longitudinal analysis of cognitive decline or dementia together with structural or functional neuroimaging.
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