Comparing the impact of lifelong multilingualism and later-life language learning on cognitive and brain reserve in older adults with cognitive decline due to Alzheimer’s disease: A systematic review

Abstract

The neurocognitive adaptations associated with language engagement have received particular attention in research on dementia prevention. Studies suggest that by placing great demands on executive functions, (lifelong) multilingualism (LM) and later-life language learning (LLLL) cause changes in the neural substrate, enhancing reserve and sustaining cognitive functioning (Antoniou & Wright, 2017; Bialystok, 2021). However, current research has not yet directly investigated the ways and degree to which LM and LLLL differ in their impact on neurocognition. This systematic review addresses this gap by comparing the scope of LM and LLLL impact on brain structure, function, and cognition in older adults across different stages of Alzheimer’s disease. A systematic search was conducted on PubMed, Web of Science, Scopus, and PsycINFO. Eighteen empirical studies were included and reviewed in connection with current theoretical models on the role of bilingualism as a reserve-enhancing factor. Findings show that LM contributes to the development of brain and cognitive reserve by engaging cognitive control and inducing neurocognitive adaptations from earlier to most severe stages of Alzheimer’s disease, while protective effects of LLLL were mainly observed on memory. Nevertheless, a general lack of studies and variability in study design and terminology highlighted the need for further research.