Background With age, most cognitive functions decline. As the number of people aged 60 years and older is expected to rise rapidly within the next decades, identifying interventions that promote healthy cognitive ageing is of utmost importance. Promising research on bilingualism has led to the notion that learning a foreign language could protect against cognitive decline. Foreign language learning likely promotes executive functions, which are higher-order cognitive abilities particularly affected by age-related cognitive decline. However, evidence is still sparse and has produced contradictory results. This study aims to investigate the effects of short and intensive foreign language learning on executive functions in healthy older adults. Methods In a randomised controlled trial, we will assign 60 native German-speaking monolingual healthy older adults, aged 65–80 years, to either a foreign language learning or a waiting list control group. Language learners will attend a face-to-face, group-based Spanish course for beginners for 1.5 h a day, 5 days a week, for a total of 3 weeks. Cognitive performance in executive functions will be assessed before and after the intervention or after a waiting period of 3 weeks (waiting list control group). Participants will be tested again after 3 months to evaluate longitudinal effects of foreign language learning. The waiting list control group will receive Spanish lessons only after the final assessment and will be invited to an additional voluntary evaluation after completion of the course. Discussion To the best of our knowledge, we are conducting the first randomised controlled trial on the effects of short and intensive foreign language learning in older adulthood on executive functions. Enhanced cognitive performance after foreign language learning would indicate that learning a foreign language could enlarge cognitive reserve and thus promote healthy cognitive ageing in older adults. Trial registration German Clinical Trials Register DRKS00016552. Registered on 11 February 2019.

Aims and Objectives: Bilinguals have been claimed to develop superior executive functioning compared to monolinguals due to their continuous experience of controlling two languages. Given the developmental trajectory of executive functions, a bilingual advantage could be more pronounced at an advanced age. To gain a clearer understanding, we reviewed the effect of bilingualism executive functions in healthy older adults. Methodology: The present paper systematically examines the methods and the results of 24 studies from 22 articles comparing healthy older monolinguals and bilinguals in at least one domain of executive functions. Data and Analysis: Data of each study were extracted for sample characteristics, country, language background and measures, controlled confounders and task paradigms. Study quality was also calculated for each study. Findings and Conclusions: In general, nine out of the 24 studies fully supported the notion of a bilingual advantage. Four studies showed a bilingual disadvantage. The rest of the studies challenged the existence of a bilingual advantage, as neither full support for bilingual advantages nor bilingual disadvantages were seen in various domains. The available data did not clearly support the widespread notion that bilingualism is related to a general advantage in executive control. However, when looking at the domains of executive functions separately, bilingualism was reliably associated with an advantage in inhibition, especially in two commonly applied tasks: the Stroop test and the Simon task. Originality: This is the first systematic review aimed at exploring the link between bilingualism and executive functions in healthy older adults. Significance/Implications: Heterogeneity in study characteristics and control of confounding variables may partially explain some of the inconsistencies found between studies. Therefore, well-designed studies that measure all core domains of executive functions and consider confounding variables are urgently needed.