Role of bilingualism in neurodegenerative disease II. Beyond Alzheimer's.

Abstract

Over the past decades, bilingualism has emerged as a potential factor having a significant impact on cognition and brain structure. Such research typically examines the effects of bilingualism in healthy children and adults. Conversely, the body of literature examining bilingualism effects in ageing populations remains comparatively small. This holds especially true with regards to effects of bilingualism in clinical ageing populations. Current evidence suggests that bilingualism might contribute to delaying the expression and/or progression of the symptoms of Alzheimer’s dementia for as much as 5 years. To the extent bilingualism plays an ameliorative role at all, it seems reasonable to expect that it would have similar effects for other neurodegenerative disorders. Nevertheless, relevant studies examining disorders other than Alzheimer’s Disease or Mild Cognitive Impairment are extremely limited. Despite compelling reasons to the contrary, the few relevant studies that do exist are not properly linked, nor appreciated as a meaningful cohort in their own right. Making links across neurodegenerative disorders and bilingualism, to the extent possible, serves both practical health-related and theoretical-oriented needs. This chapter considers whether the currently available evidence is sufficient to allow for claims of bilingualism conveying more general protective effects in clinical ageing while identifying gaps in our knowledge and recommending future work to better understand these proposed links.