Bilingualism and multilingualism in dementia research: a systematic review of empirical studies

The increasing prevalence of dementia in Western societies, combined with factors such as migration, multilingualism, and demographic change, poses a multifaceted societal and scientific challenge. Understanding the interplay between multilingualism, aging, and cognitive decline is, therefore, important to address this development effectively. This systematic review provides an overview of empirical research on the intersection of bi- and multilingualism and dementia. An initial database search yielded 5,648 records, of which 29 studies were included for systematic evaluation. Among the empirical studies reviewed, four thematic areas were identified: (i) effects of cognitive decline on languages, (ii) diagnostic assessments, (iii) linguistic changes on specific levels (e.g. morphosyntactic, lexical or discourse-level), and (iv) care interactions. Findings reveal an unevenly developed field, with advanced research on cognitive decline and diagnostics but limited studies on linguistic structures and interaction. Notable imbalances include overrepresentation of the English-Spanish language set, early-stage dementia, and balanced bilingualism. This systematic review, therefore, lays open both the questions that have been explored and those that remain unanswered, calling for integrative, context-sensitive research on multilingualism and dementia.