Redefining bilingualism as a spectrum of experiences that differentially affects brain structure and function

DeLuca, Vincent; Rothman, Jason; Bialystok, Ellen; Pliatsikas, Christos

doi:10.1073/pnas.1811513116

Cited by 271 publications

(295 citation statements)

References 63 publications

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“…Researchers can apply objective measures for bilingualism (Clare et al, 2016;Estanga et al, 2017), rather than asking participants or family members to self-report language status (Alladi et al, 2013;Chertkow et al, 2010). Formal assessments of second language proficiency while treating the degree of bilingualism as a continuous variable (DeLuca, Rothman, Bialystok, & Pliatsikas, 2019;Laine & Lehtonen, 2018;Luk & Bialystok, 2013) should be applied. Authors have recently developed questionnaires to quantify participants' language profiles on a continuum (Anderson et al, 2018) and to measure language proficiency, dominance, as well as immersion (Li et al, 2019).…”

Section: Suggestions For Future Researchmentioning

confidence: 99%

Bilingualism Is Associated with a Delayed Onset of Dementia but Not with a Lower Risk of Developing it: a Systematic Review with Meta-Analyses

et al. 2020

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Some studies have linked bilingualism with a later onset of dementia, Alzheimer's disease (AD), and mild cognitive impairment (MCI). Not all studies have observed such relationships, however. Differences in study outcomes may be due to methodological limitations and the presence of confounding factors within studies such as immigration status and level of education. We conducted the first systematic review with meta-analysis combining cross-sectional studies to explore if bilingualism might delay symptom onset and diagnosis of dementia, AD, and MCI. Primary outcomes included the age of symptom onset, the age at diagnosis of MCI or dementia, and the risk of developing MCI or dementia. A secondary outcome included the degree of disease severity at dementia diagnosis. There was no difference in the age of MCI diagnosis between monolinguals and bilinguals [mean difference: 3.2; 95% confidence intervals (CI): −3.4, 9.7]. Bilinguals vs. monolinguals reported experiencing AD symptoms 4.7 years (95% CI: 3.3, 6.1) later. Bilinguals vs. monolinguals were diagnosed with dementia 3.3 years (95% CI: 1.7, 4.9) later. Here, 95% prediction intervals showed a large dispersion of effect sizes (−1.9 to 8.5). We investigated this dispersion with a subgroup meta-analysis comparing studies that had recruited participants with dementia to studies that had recruited participants with AD on the age of dementia and AD diagnosis between mono-and bilinguals. Results showed that bilinguals vs. monolinguals were 1.9 years (95% CI: −0.9, 4.7) and 4.2 (95% CI: 2.0, 6.4) older than monolinguals at the time of dementia and AD diagnosis, respectively. The mean difference between the two subgroups was not significant. There was no significant risk reduction (odds ratio: 0.89; 95% CI: 0.68-1.16) in developing dementia among bilinguals vs. monolinguals. Also, there was no significant difference (Hedges' g = 0.05; 95% CI: −0.13, 0.24) in disease severity at dementia diagnosis between bilinguals and monolinguals, despite bilinguals being significantly older. The majority of studies had adjusted for level of education suggesting that education might not have played a role in the observed delay in dementia among bilinguals vs. monolinguals. Although findings indicated that bilingualism was on average related to a delayed onset of dementia, the magnitude of this relationship varied across different settings. This variation may be due to unexplained heterogeneity and different sources of bias in the included studies. Registration: PROSPERO CRD42015019100.

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Section: Suggestions For Future Researchmentioning

confidence: 99%

Bilingualism Is Associated with a Delayed Onset of Dementia but Not with a Lower Risk of Developing it: a Systematic Review with Meta-Analyses

et al. 2020

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“…In this study, the probable AD patients showed a "bilingual advantage" in the expression of Alzheimer's clinical syndrome. Bilingualism could increase cognitive reserve through the constant management of two simultaneously active and competing languages [13,40,[45][46][47][48][49][50][51][52][53][54][55][56][57]. Better reserve, with better compensation or masking of worsening cognition, could explain the worse dementia severity as per MMSE scores on presentation for bilinguals.…”

Section: Discussionmentioning

confidence: 99%

Bilingualism Delays Expression of Alzheimer’s Clinical Syndrome

Mendez¹,

Chavez²,

Akhlaghipour³

2019

Dement Geriatr Cogn Disord

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Objective: To evaluate the effects of bilingualism on the emergence of Alzheimer's clinical syndrome. Background: Studies have proposed an increase in cognitive and neural reserve from the management and control of two languages, with a consequent delayed expression of dementia. Methods: In a clinic with a large immigrant population, we identified 253 patients with probable Alzheimer's disease (AD) with intermediate or high evidence of AD pathophysiological process. These patients were reviewed for demographic variables, native language (L1) other than English, ages of onset and presentation, Mini-Mental State Examination (MMSE), digit spans, word fluencies, naming, and memory. Results: Among these patients, 74 (29.2%) were bilinguals with various L1s (Farsi, Spanish, Chinese, Tagalog, Arabic, others). When compared to the 179 monolingual AD patients, those who were bilingual had significant delays in ages of onset and presentation of approximately 4 years (p = 0.003). These delays persisted despite bilinguals having worse MMSE scores on presentation. There were no significant group differences on other variables except for worse naming in English among bilinguals versus monolinguals. Caregiver/informants reported that 66 (89.2%) of the 74 bilingual AD patients had gradually regressed to the predominant use of their L1. Conclusions: In line with published reports worldwide, we found that bilingualism delays the expression of Alzheimer's clinical syndrome. We also found frequent reversion to the first learned language. These findings suggest that, among bilinguals, the availability of an L1 "back-up" either facilitates compensation or masks emergence of the early symptoms of dementia.

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“…DeLuca et al. () tested longer‐term neuroanatomical effects of language use in already immersed bilinguals. They reported volumetric increases in the cerebellum, which were positively correlated with the amount of prior immersion, accompanied by subcortical restructuring and increases in diffusivity in the forceps minor (an anterior extension of the corpus callosum connecting it to the frontal lobes).…”

Section: Moving Forward: Examining the (Long‐term) Effects Of Individmentioning

confidence: 99%

The Many Shades of Bilingualism: Language Experiences Modulate Adaptations in Brain Structure

2019

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Recent years have seen an expansion in the research related to structural brain adaptations related to the acquisition and processing of additional languages. However, the accumulating evidence remains to a great extent inconsistent, with a large variety of cortical, subcortical, and cerebellar effects reported in various studies. Here we propose that the variability in the data can be explained by the differences in the language background and experiences of the tested samples. We also propose that the field should move away from monolithic bilingual versus monolingual comparisons; instead, it should focus on the experiences of the bilingual groups as predictors of structural changes in the brain, and also employ longitudinal designs to test the dynamic effects of active bilingualism. The implications of the proposed approaches for the suggested benefits of bilingualism on ageing and patient populations are also discussed.

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Redefining bilingualism as a spectrum of experiences that differentially affects brain structure and function

Cited by 271 publications

References 63 publications

Bilingualism Is Associated with a Delayed Onset of Dementia but Not with a Lower Risk of Developing it: a Systematic Review with Meta-Analyses

Bilingualism Is Associated with a Delayed Onset of Dementia but Not with a Lower Risk of Developing it: a Systematic Review with Meta-Analyses

Bilingualism Delays Expression of Alzheimer’s Clinical Syndrome

The Many Shades of Bilingualism: Language Experiences Modulate Adaptations in Brain Structure

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