Bilinguals show evidence of brain maintenance in Alzheimer’s disease

Abstract

We examined brain and cognitive reserve related to bilingualism in older adults with, or at-risk for, Alzheimer’s disease (AD) from the Canadian Consortium on Neurodegeneration in Aging and the Quebec Consortium for the Early Identification of Alzheimer’s Disease. We used surface-based morphometry methods to measure cortical thickness and volume of language-related and AD-related brain regions. We did not observe evidence of brain reserve in language-related regions. However, reduced hippocampal volume was observed for monolingual, but not bilingual, older adults with AD. Thus, bilingualism is hypothesized to contribute to reserve in the form of brain maintenance in the context of AD.

Plain Language Summary

Certain life experiences might be protective against Alzheimer’s disease. Some research suggests that bilingualism (knowing two languages) may act as one such protective factor. For example, some studies show that bilingual people have more brain matter in areas that are involved in controlling their two (or more) languages. Some research suggests that bilinguals may be less affected by brain damage associated with Alzheimer’s disease compared to monolinguals (people who know only one language). However, more research with individuals with Alzheimer’s disease, and those at risk, is needed to better understand the potential protective effect of speaking more than one language. To this end, we examined brain structure of monolingual and bilingual people with Alzheimer’s disease, or at risk for it. In contrast to previous research with healthy people, we did not find a difference between monolingual and bilingual participants in the brain structure of areas involved in bilingual language control. When we looked at people with Alzheimer’s disease, bilinguals had less brain damage in regions typically affected by Alzheimer’s disease compared to monolinguals. This suggests that speaking more than one language throughout one’s life may lead to better maintained brain structure in Alzheimer’s disease. Future studies should explore how this protective effect of bilingualism on brain structure relates to brain function and the progression of Alzheimer’s disease.