Bilingualism and cognitive control in middle adulthood: a systematic review protocol

Background Recent global demographic shifts toward increasingly older populations have heightened the importance of identifying modifiable lifestyle factors that may positively influence cognitive trajectories associated with healthy aging. Bilingualism has been proposed as one such factor, with the demands of managing multiple languages thought to enhance cognitive control and contribute to cognitive reserve. However, findings regarding bilingual effects on cognitive control in adults remain mixed. To date, previous reviews have excluded studies conducted exclusively within bilingual populations, leaving the relationship between bilingual language experience and cognitive control in middle-aged adults unclear. Methods This systematic review will synthesize published and unpublished research investigating the relationship between bilingual language experience and cognitive control in middle-aged adults (40–60 years). Searches will be conducted in Web of Science, Scopus, and ProQuest. Eligible studies will include monolingual-bilingual comparisons, bilingual-bilingual comparisons, and studies examining associations between dimensions of bilingual language experience and cognitive control within bilingual samples. Screening, selection, extraction, and risk of bias assessment will be completed by two independent reviewers. Tabular, narrative, and quantitative syntheses will be conducted depending on the characteristics of included studies. Where appropriate, quantitative synthesis will be conducted using direction of evidence analyses with Bayesian inference. When quantitative synthesis is not appropriate, findings will be summarized narratively. Discussion This review will provide the first synthesis of bilingual effects on cognitive control in middle-aged adults across both between-group and within-bilingual research designs. Findings are expected to clarify the current state of evidence regarding bilingualism as a potential contributor to cognitive reserve and healthy cognitive aging during middle adulthood. Systematic review registration This protocol was registered on Open Science Framework ( https://osf.io/576hm/ ).