Effects of foreign language learning on executive functions in healthy older adults: study protocol for a randomised controlled trial

Abstract

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.

Peer Review reports

Background

The number of people aged 60 years or older will more than double worldwide to around two billion by 2050 [1]. With age, the majority of cognitive functions decline [2]. This not only threatens individual independence but can also enter pathological stages such as mild cognitive impairment and dementia, in its most severe form [3]. Cognitive ageing concerns a wide range of cognitive functions. Among these, executive functions (EF) are most markedly affected [2]. EF are a set of higher-order cognitive abilities that are involved in the control of mental activities and behaviour and are predominantly seated in the prefrontal cortex [4]. However, cognitive decline proceeds not linearly, because it is impacted by numerous variables. These include not only genetic and medical [5], but also psychosocial factors such as education and intelligence [6]. Moreover, cognitive benefits have already been documented for a variety of cognitively stimulating mental activities in older age such as playing the piano [7] or video gaming [8] (see [9] for a review, see also [10]). Mental activity builds up a cognitive reserve, which is a presumed mechanism for coping with age-related brain damage through a more effective and flexible use of cognitive networks [11]. Interest in foreign language learning as a cognitively stimulating mental activity later in life has only recently emerged and could constitute a promising approach to benefit cognitive functioning.

The idea of investigating foreign language learning as a powerful candidate for enhancing cognition in later life originated from research on bilingualism. Bilingualism can be defined as the ability to speak two languages fluently [12]. It has been associated with better cognitive performance compared to monolinguals, particularly in EF [13, 14]. Moreover, bilinguals exhibit slower cognitive ageing [15]. This so-called ‘bilingual advantage’ in EF probably arises from the demands placed on the cognitive control system by handling two languages. For example, although only one language is being used, both are always simultaneously active in the brain. Therefore, interference caused by the irrelevant language must be inhibited (see [16] for a review). Evidently, foreign language learning differs from bilingualism in important aspects, e.g. in the degree of proficiency. Nevertheless, foreign language learning is likely to promote EF in a comparable way, since language learning also engages an extensive cortical and sub-cortical brain network [17, 18]. This network is responsible for the control of both linguistic and non-linguistic information [19], and overlaps with the network affected by cognitive decline [20]. In initial stages of foreign language acquisition, the left inferior frontal gyrus of the prefrontal cortex is likely to play a major role [18]. Especially when it comes to producing the weaker (foreign) language, this gyrus is involved in the regulation of automatic processes that require attentional control. These processes include inhibition, interference or response selection and suppression [17]. Importantly, attentional dysregulation is probably also contributing to age-related deficits in other cognitive domains such as task switching or response competition [2]. For this reason, foreign language learning could enhance cognitive functions that are particularly affected by cognitive decline.

So far, however, research on cognitive outcomes of foreign language learning in older age is still sparse and has produced mixed results. In a small review summarising results of studies involving a foreign language training intervention [21], five papers [22,23,24,25,26] investigated cognitive outcomes before and after a language course intervention. After adding three more recently published studies to this overview [27,28,29], no clear cognitive advantage of foreign language learning became evident. Half of the studies detected benefits in one or more cognitive domains, including attentional switching [26], inhibition [24], working memory [29], and global cognition [27, 29]. In contrast, others found no effect on spatial and verbal intelligence [22], working memory [22], task switching [23], and global cognition [25, 28]. This inconsistent picture could be due to several reasons. Overall, there was little overlap between cognitive domains and tasks applied among studies. Interestingly, studies focusing on EF tasks that required high amounts of attentional control were among those showing significant improvements in cognition after foreign language learning [24, 26]. Studies also differed considerably in their effectiveness depending on the design of the intervention. For example, studies with shorter (e.g. 1 week [26]) but higher intensity interventions (at least 5 h of training per week, spread over several days a week) [24, 26] were more consistently associated with cognitive improvements than studies with longer but less intensive interventions [25, 28]. Thus, studies with a higher-intensity foreign language training might be more likely to affect cognition. It is also important to note that some previous studies exhibited limitations, e.g. lack of a control group [24, 25], no randomised group allocation [23, 26], lack of follow-up periods [22,23,24,25, 27, 28] and missing control of cognitive impairment [24,25,26]. These should be considered in future studies. We therefore decided to conduct a randomised controlled trial with high-intensity training and comprehensive control of cognitive impairment to determine whether foreign language learning can improve EF in older adults.

Methods/design

Aims

The objective of the present study is to assess the effects of short and intensive foreign language learning on EF in healthy older adults. We hypothesise that, compared to a passive control group, foreign language learning improves EF (hypothesis 1), and that these effects persist in the long-term over 3 months after the intervention (hypothesis 2). To test our hypotheses, we will focus primarily on two tasks affording a high degree of attentional control, since foreign language learning is likely to address this fundamental process of EF. However, as this field still is largely unexplored, we will additionally consider a wider range of EF, including inhibition, shifting, and updating, as the most commonly accepted EF [30]. Moreover, we will evaluate domains that can broadly be classified as EF, but which equally cover linguistic functions (verbal fluency) and non-executive components of attention.

To further explore our results, we will also assess the role of cognitive reserve, as different levels of cognitive reserve have been shown to influence training-related changes in global cognition [31]. This might also apply for previous foreign language knowledge and usage. Therefore, we assume that both the degree of cognitive reserve (hypothesis 3) and prior foreign language knowledge and usage (hypothesis 4) can predict changes in cognitive scores.

Study design and setting

The present study is a randomised controlled superiority trial with two parallel groups which investigates the effects of a three-week-long foreign language course on EF in healthy older adults. Sixty community-dwelling older adults will be randomised in a 1:1 ratio to one of two study arms: a language learning group (LLG) and a waiting list control group (WLCG). Data will be collected at the Network Aging Research (NAR), Heidelberg University, Germany and the SRH University Heidelberg, Germany. This study protocol follows the Consolidated Standard of Reporting Trials (CONSORT) statement [32] and is presented according to the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) guidelines [33].

Recruitment

Participants will be recruited from the general public in Heidelberg, Germany, and the surrounding regions through advertisements in local newspapers, advertising in trains, at public lectures, and on the NAR homepage. We will also inform individuals who agreed to be notified about ongoing studies via an e-mailing list of the NAR. Additionally, we will distribute flyers and posters in senior and sports centres, language schools, medical practices, and pharmacies.

Eligibility criteria

Eligibility criteria for participation are listed in Table 1.

Table 1 Eligibility criteria for participation

Interventions

This study comprises two trial arms: a LLG and a WLCG.

Language learning group (LLG)

The LLG will study Spanish in a three-week course for beginners. Daily lessons of 90 min will be scheduled in the morning from Monday until Friday. In sum, participants will receive 7.5 h of teaching per week, resulting in a total course duration of 22.5 h. The idea of a relatively short but high-intensity training stems from a study by Bak et al. [26], who found a positive effect of foreign language learning on attentional switching after only 1 week of 14 h of foreign language instruction.

A qualified teacher will give the lessons face-to-face at a language school in the centre of Heidelberg, which is easily accessible by car and public transportation. Beyond attending regular classes, participants may do homework and will be allowed to practice at home to consolidate the newly learned content. Following the example of previous studies [23, 38], we will limit the group size to a maximum of ten participants per group, to enable the teacher to address all participants and to give them sufficient opportunity to participate in class. A commonly used work book in adult education [39] will serve as teaching material. By the end of the course, approximately three chapters will have been completed. Participants will learn accent and pronunciation as well as grammatical rules of the Spanish language and will acquire elementary communication skills in various topics (e.g. introducing themselves, asking for directions).

Waiting list control group (WLCG)

The WLCG will not receive any treatment during the intervention phase but will take part in a three-week waiting period during which subjects will follow their usual daily routine. To reduce barriers to participation due to possible group preferences [40], the WLCG will attend a control group programme after their study completion. The programme consists of the same language course intervention as the LLG and an additional voluntary examination after the end of the course. This appointment is not included in the main study design as the scope for participation should differ as little as possible between groups.

Outcomes

Baseline variables, as well as primary, secondary, and language course outcome measures are presented in Fig. 1. Unless otherwise stated, primary and secondary outcome measures are valid and reliable tests from the Vienna Test System (VTS) [34]. The VTS is a computerised test system for the assessment of neuropsychological functions and has become a well-established tool in clinical practice. Each cognitive outcome will begin with an instruction phase, followed by a practice phase, in which participants will receive immediate feedback on their errors. If necessary, the practice phase can be repeated to ensure a sufficient understanding of the task.

Fig. 1
figure1

SPIRIT figure for the schedule of enrolment, interventions, and assessments. P primary outcome measure, S secondary outcome measure, −t2 telephone screening, −t1 face-to-face screening, t1 pre-assessment, t2 language course/waiting period, t3 post-assessment, t4 3-month follow-up assessment, t5 language course, t6 4-month follow-up assessment (waiting list control group only). Abbreviations: CFD Cognitive Functions Dementia, CRIq Cognitive Reserve Index questionnaire, DSB Digit Span Backwards, DSF Digit Span Forwards, FLANDERS Flinders Handedness Survey, INHIB Response Inhibition, LLG Language learning group, LSBQ The Language and Social Background Questionnaire, NBV N-Back Verbal, STROOP Stroop Interference Test, SWITCH Task Switching, TMT-A/−B Trail-Making Test – Langensteinbach Version part A/part B, WAFA Perception and Attention Function Battery – Alertness, WAFG Perception and Attention Function Battery – Divided Attention, WIWO Vienna Verbal Fluency Test, WLCG Waiting list control group

Baseline variables

Baseline variables include socio-demographic variables such as date of birth, gender, marital and occupational status, as well as an assessment of global cognitive functions. Additionally, cognitive reserve, foreign language knowledge and usage, and handedness will be examined.

Cognitive reserve

We will evaluate cognitive reserve using the Cognitive Reserve Index questionnaire (CRIq) [41]. The CRIq is a valid and reliable half-structured interview, which quantifies cognitive reserve over an individual’s lifetime using three established measures of cognitive reserve: education (CRI-Education), occupation (CRI-WorkingActivity), and engagement in cognitively stimulating activities (CRI-LeisureTime) [42]. The three sub-scores can be combined into an overall score (CRI-Index). All measures are age-adjusted to allow for comparisons between different age groups.

Foreign language knowledge and usage

Foreign language knowledge and usage will be determined using the Language and Social Background Questionnaire (LSBQ) [43]. The LSBQ is a validated and reliable questionnaire for self-assessment of foreign language skills and usage in various contexts. A composite factor score quantifies the degree of bilingualism on a continuum from clearly monolingual to highly bilingual.

Global cognitive functions

We will assess global cognitive functioning using the Cognitive Functions Dementia test set (CFD, test form: S1 [touchscreen operation]) [34, 35] to exclude participants with suspected cognitive decline according to Petersen’s criteria (no subtest z ≤ − 1.5) [36].

The CFD is a comprehensive computer-based assessment from the VTS and takes about 60 min to perform. Previous studies in this field of research only used brief screening measures such as the Mini-Mental State Examination (MMSE) [44] or the Montreal Cognitive Assessment (MoCA) [45]. Both instruments can distinguish pathological cognitive decline from healthy ageing. However, they are less accurate than comprehensive multidimensional neuropsychological inventories [46]. In the CFD, cognitive performance is measured by eleven tasks falling into five cognitive domains: attention, verbal long-term memory, EF, expressive speech, and perceptual motor functions.

Handedness

The Flinders Handedness survey (FLANDERS) [47] is a short standardised questionnaire to measure hand preference. It contains ten items describing ten different activities (e.g. writing). Participants are asked to indicate whether they prefer the left, the right or either hand for each activity.

Primary outcomes

The Stroop Interference Test (STROOP, test form: S7) [48] and the Divided Attention, a subtest of the Perception and Attention Function Battery (WAFG, test form: S3) [49], are the two primary outcome measures.

Stroop Interference Test (STROOP)

The STROOP is a sensory-motor speed test that determines interference — a measure of inhibitory control. In a small pilot study older adults performed significantly better in this task after having participated in a foreign language training [24]. The task consists of two baseline and two interference conditions (see Fig. 2a). In the (i) reading baseline condition, participants read one of four German colour words (blue, green, red, yellow) printed in black one after the other on a computer screen. Similarly, in the (ii) naming baseline condition, subjects see coloured bars (blue, green, red, yellow). The task is to select the corresponding colour on the response panel as quickly as possible. In the two interference conditions, participants see German colour words printed in a different colour (e.g. the written word ‘yellow’ printed in red). In the (iii) reading interference condition, participants must read the word and ignore the colouring. Conversely, in the (iv) naming interference condition, participants must respond to the colouring and ignore the meaning of the word. Reactions in the two interference conditions are usually slower since the processing of the two simultaneously presented stimuli (the written word and the colour in which it is printed) requires attention. This leads to delayed processing and thus to longer reaction times. Each test part consists of 128 stimuli, which are presented until a response is given. Immediately afterwards, the next stimulus appears. The total test duration is approximately 15 min. The ‘naming interference tendency’ is the primary outcome variable. It is calculated from the difference between ‘median of reaction times – naming interference condition’ and ‘median of reaction times – naming baseline’. Using the median reaction time ensures that asymmetries caused by circumstances, such as ‘getting stuck’ on certain items, do not distort results. The reliability of the naming interference tendency measure is α = .97.

Fig. 2
figure2

Illustration of primary outcomes, a) the Stroop Interference Test (STROOP) and b) the Divided Attention (WAFG). White speakers represent the high-pitched sound. Black speakers depict the low-pitched sound. Squares or speakers outlined in red indicate the targets of the visual and the auditory channels. These targets are either two squares or two high-pitched sounds which immediately follow each other

Divided Attention (WAFG)

The WAFG is a measure of cross-modal (visual/auditory) divided attention. In the WAFG, subjects are simultaneously confronted with a visual and an auditory channel (see Fig. 2b). On the former one, either a triangle or a square appears on a computer screen. On the auditory one, either a low- or a high-pitched tone is emitted. The task is to press a key on the response panel as quickly as possible when either two squares or two high-pitched tones immediately follow each other. The total number of items is 85, of which 21 are relevant. Stimuli are presented until a response is given or after a maximum of 1500 ms followed by an inter-stimulus interval of 1000 ms. If no reaction has occurred within the presentation period, an omission error is counted. Reaction times below 100 ms will not be considered, as physiological responses below 100 ms are not possible [50]. The total test duration is 9 min. The outcome variable is the logarithmic mean reaction time, which accounts for the expected skewness in the distribution of reaction times. The WAFG, test form S3, obtains a reliability score of α = .84.

Secondary outcomes

Secondary outcomes are cognitive measures of EF other than the STROOP and the WAFG. In particular, we will apply tasks from the three core domains of EF: inhibition, shifting, and updating [30]. For comparison reasons, we will also assess verbal fluency and non-executive components of attention. As these predominantly refer to linguistic and attentional functions, they are less likely to load on EF [51, 52]. Details of the respective tasks for each domain of EF and the corresponding dependent variables are presented in Table 2. Every domain is measured by at least two tasks to better capture each construct [60].

Table 2 Overview of secondary outcomes

Inhibition

Inhibition is the ability to suppress unwanted reactions. It will be assessed using the Response Inhibition (INHIB) [53] and the ‘reading interference tendency’, which is another outcome measure of the STROOP, as already described in the Primary outcomes section.

Shifting

Shifting refers to the ability to switch flexibly between tasks or mental sets. We will measure shifting using the SWITCH [54] and the Trail-Making Test – Langensteinbach Version part B minus part A (TMT-B – TMT-A) [55].

Updating

Updating (as a core working memory process) reflects the ability to maintain and continuously update information. It will be evaluated using the Digit Span Backwards (DSB) from the Wechsler Adult Intelligence Scale – Fourth Edition (WAIS-IV) [56] and the N-Back Verbal (NBV) [57].

Verbal fluency

Verbal fluency is defined as a person’s ability to find words of a specific characteristic in the mental lexicon [51]. To assess verbal fluency, we will conduct the Vienna Verbal Fluency Test (WIWO) [58]. The test distinguishes between two dimensions: semantic and lexical verbal fluency.

Attention

Attention will be represented by a measure of alertness, a basal process of short-term attention activation. It will be measured using the Alertness, a subtest of the Perception and Attention Function Battery (WAFA) [59]. Attention span and information processing speed will be assessed using the Digit Span Forwards (DSF) from the WAIS-IV [56] and the TMT-A [55], respectively.

Language course outcomes

We will collect the following language course outcomes to evaluate the intervention:

Adherence

Adherence to the language course will be documented daily by the Spanish language teacher. The teacher will inform the study team if a participant does not show up for class without giving prior notice.

Homework and learning time

We will collect information about the time spent on additional learning activities in Spanish at home. In a table, participants will indicate in minutes, how much time they invested each day, including at weekends, in doing homework and voluntary learning activities in Spanish. Records will start from the beginning of the course and will end on the last day of the course. The outcome is the total time spent on additional learning activities at home.

Course evaluation

A questionnaire will be completed anonymously on the last day of the course to evaluate the perceived quality and acceptability of the intervention. On a four-point Likert scale from ‘fully agree’ to ‘fully disagree’ or ‘cannot judge’, participants will give their opinions on the lessons, the teacher, the textbook, their degree of motivation, and their general satisfaction with the course. Additionally, three open format questions allow participants to provide more specific feedback on aspects they appreciated, disliked, or would recommend for improvement.

Vocabulary test

To assess the degree of acquired Spanish language skills, participants will take a vocabulary test on the last day of the course. Following the example of Berggren et al. [22], the vocabulary test will include 108 out of around 577 words learnt during class. Two points will be awarded if the word translated from German into Spanish is translated and spelt correctly. One point will be granted if it has the correct meaning but is misspelt, ignoring punctuation. If the translation is wrong or no answer is given, zero points will be assigned. Thus, a maximum of 216 points can be achieved.

Participant timeline

Figure 3 illustrates the flow of participants through the trial. Eligibility for participation will be ascertained via a telephone and a subsequent face-to-face screening. In the telephone screening, initial inclusion and exclusion criteria regarding demographic, medical and health-related aspects (see Table 1) as well as availability to participate in the intervention and assessments will be clarified. Moreover, self-reported foreign language skills and usage will be surveyed. Participants who claim to possess few previous skills in Spanish and have not yet attained level A1.1, or who have attended less than one regular course (< 18 h of classes), will be asked a list of questions to determine their Spanish skills. The questions are derived from units 1–5 of the course book [39]. An appointment for the face-to-face screening will be scheduled if they meet all eligibility criteria clarified by telephone.

Fig. 3
figure3

CONSORT flow diagram of participants

The face-to-face screening will take around 2 h and will evaluate the remaining exclusion criteria. The CFD will be applied to exclude participants with suspected cognitive decline and the whispered voice test [37] will be used to ascertain sufficient hearing. Participants who indicated in the telephone screening to already have slight experiences in Spanish will take a placement test [61] to ensure that their previous skills are low enough (< level A1.1) for a Spanish course for beginners. Additionally, further baseline data will be collected (see section ‘Baseline variables’).

Subjects that meet eligibility criteria after the face-to-face screening will be randomly assigned to either the LLG or the WLCG. Within 2 weeks before the start of the language course or the three-week waiting period, both groups will participate in a pre-assessment. Both post- and 3-month follow-up assessments will be carried out within 2 weeks immediately (post) and 3 months (3-month follow-up) after the end of the intervention or the waiting period. After this, the LLG will have completed study participation while the WLCG will attend the control group programme consisting of the language course and a voluntary 4-month follow-up assessment.

Pre-, post-, and follow-up assessments will last around 2 h each and will be scheduled at the same time of day, either in the morning or in the afternoon, to control for day-dependent variability in cognitive performance. Assessments will include both the primary and secondary outcome measures listed in Fig. 1. The test order will be randomised by a computer for each individual. However, the WAFA, as the most straightforward task, will always be applied first to allow participants to become familiar with the computerised test system.

To enhance participant retention, we will arrange appointments for pre-, post-, and follow-up assessments with each participant individually before the start of the study. A confirmation document with the scheduled dates and times will be sent to participants. Additionally, participants will receive reminder phone calls 1 week before each assessment. There will be no financial compensation apart from the language course, which will be offered for free. However, participants may obtain information about their results and the conclusion of the study after having completed participation.

Sample size

Sample size calculation was based on the main (first) research question for the two primary outcomes, the STROOP and the WAFG, and was conducted using G*Power (version 3.1.9.2). The alpha level was set to α = .05 with the power to detect significant differences of 0.8. A total of N = 42 participants will be needed to detect a medium effect size of d = 0.25 [24, 26, 62] between pre- and post-assessment, assuming a correlation between repeated measures of r = .5. We will adjust for multiple comparisons using the Bonferroni correction. A total sample size of N = 60, with n = 30 individuals per group, will be required to account for a 30% drop-out rate [24].

Allocation and blinding

Participants who provide written informed consent and pass all screening procedures will be randomly assigned at a 1:1 ratio to one of the two trial arms. A researcher (MGD), who is not involved in the implementation of the current trial, will generate the randomisation sequence using a web-based randomisation system [63]. To avoid predictability of group allocation, the system will build permuted blocks of random sizes, namely two, four, six, and eight, with a list length of 20 [33]. The randomisation sequence and the block sizes will not be disclosed to trial implementers. To ensure concealment, MGD will prepare and store sequentially numbered, sealed, opaque envelopes containing information on group allocation for each participant. She will not open the envelope assigned to a participant until he or she has been included in the trial by JAG. JAG will also inform participants by telephone about their group assignment.

Due to the nature of our study design, participants cannot be blinded to treatment allocation. There can also be no blinding of assessors and teachers. However, assessments will be predominantly computer-based and standardised to reduce test leader effects.

Data collection and management

JAG and trained research assistants will conduct the assessments. To limit the impact of the test leader on results, we aim to ensure that for each participant at least pre- and post-assessments will be conducted by the same assessor. For every assessor, the number of assessments will be balanced between groups.

Data will be saved and stored according to the DSGVO. At the start of the study, every participant will be allotted a unique identification number. Only persons involved in study conduct will have access to the connection code and the data. As assessments will be mainly conducted via computer, most data will be generated and saved automatically. Data from paper documents will be continuously entered into the database throughout the study period and will be kept in a locked cabin. All electronic data will be stored on a secure server and password-protected computers of the NAR. Additional password protection for electronic documents with identifying participant information will be provided. To promote data quality, we will check data randomly throughout study conduct. Missing data will be addressed as quickly as possible. Before the start of the analysis, we will recheck all data for completeness and correctness. We will fully anonymise data upon completion of data collection, at the latest by 31 March 2021.

Monitoring

Adverse events will be assessed as part of routine monitoring. No formal data monitoring committee will be established, as this study will involve mostly standardised cognitive assessments. Also, foreign language training poses only a minimal risk of adverse events and will be of short duration. The principal author (JAG) is responsible for trial conduct. She will continuously discuss with the immediate trial team all aspects concerning participant safety, study design, and data management. Participants will be informed that they can contact the study team at any time if they have questions or concerns about the study. Any adverse event related or potentially related to study participation will be instantaneously reported to the immediate trial team, the sponsor, and the local ethics committee.

Statistical analysis

Statistical analysis will be conducted using IBM SPSS Statistics 26 (IBM Corporation: Armonk, NY, USA). We will use the intention-to-treat dataset, considering all participants as randomised who have completed at least pre-assessment and regardless of adherence to protocol. Hypotheses will be tested two-sided on an alpha level of α ≤ .05, which will be adjusted for multiplicity for primary outcomes by applying the Bonferroni correction. Multiple imputation techniques will be applied to account for missing data assuming that data are missing at random (MAR). Additionally, we will report reasons for withdrawal and analyse them qualitatively.

Primary and secondary outcomes will be analysed using 2 (group) × 3 (time) repeated measures analysis of variance (ANOVAs) with group as between-subjects factor and time-point of assessment (pre-, post-, 3-month follow-up) as within-subjects factor. Bonferroni’s post hoc test will be conducted to test hypotheses. We predict a significant group x time interaction, in which the LLG will outperform the WLCG at post- compared to pre-assessment (hypothesis 1) and at 3-month follow-up compared to pre-assessment (hypothesis 2). Partial eta square (ηp2) will be used as an indicator of effect size.

For the LLG, exploratory subgroup analyses will be performed to evaluate whether effects of foreign language learning on cognitive outcomes are dependent on different levels of cognitive reserve (hypothesis 3) and foreign language knowledge and usage (hypothesis 4). Therefore, we will conduct multiple and simple regression analyses, respectively. The difference in primary outcome measures between pre- and post-assessment will be defined as the dependent variable. Age and indicators of cognitive reserve (CRI-Education, CRI-WorkingActivity, CRI-LeisureTime, and CRI-Index) (hypothesis 3) and the LSBQ-score (hypothesis 4) will be considered as independent variables.

Additionally, we will investigate whether short-term effects of foreign language learning on cognitive measures also apply to the WLCG after completing the control group programme. For this purpose, the WLCG will serve as its control. Using t-tests for dependent means, we predict a significant difference between the difference scores from 3- to 4-month follow-up compared to the difference scores from pre- to post-assessment.

To assess the robustness of results, we will perform sensitivity analyses for the following:

  • We will examine the influence of protocol non-adherence by comparing the intention-to-treat to the per-protocol dataset. Participants will be included in the per-protocol dataset if they have completed at least pre- and post-assessment and a minimum of 14 h of formal language instruction (> 62% of the total course duration) referring to Bak et al. [26].

  • Effects of missing values will be assessed by comparing results from the complete case (only including subjects without any missing values) to the imputed dataset.

Dissemination

Results will be disseminated regardless of the magnitude or direction of effects. They will be communicated to the scientific community through journal publications and congress presentations. We will also inform participants and interested individuals, groups, and institutions about trial results.

Discussion

In this randomised controlled trial, we will investigate whether foreign language learning can improve EF in healthy older adults. The very few studies that have addressed this question to date yielded highly contradictory results. Consequently, well-controlled randomised trials are urgently needed in this field. In our study, we will compare changes in EF in healthy older adults after having attended an intensive three-week, face-to-face, group-based Spanish course for beginners (LLG) with a passive control group (WLCG). As primary outcomes, we will focus on two tasks requiring effortful attentional control, the STROOP, a measure of interference, and the WAFG, an assessment of divided attention. Our secondary outcomes will include tasks from the most widely accepted domains of EF – inhibition, shifting, and updating [30]. To extend the spectrum of EF covered and also to highlight the specificity of our results, we will include two additional domains that largely relate to linguistic [51] and attentional functions [52]. We will also investigate the longevity of any cognitive improvement after foreign language learning. Additionally, we will explore whether different levels of cognitive reserve and previous foreign language skills and usage influence our results.

Our study will have several strengths and limitations. One limitation is that the comparator is only a passive control condition. It is included to monitor improvements in cognitive performance through repeated measurements. The use of a passive control as the only comparison group has already been subject of extensive debate. Some authors argue that clinical trials should ideally include an active control of similar duration and intensity to control for effects attributable to specific treatment modalities, e.g. social activity [21, 64]. However, the inclusion of an active comparator depends on the research question. To date, foreign language learning has not provided clear evidence of maintaining or improving cognitive performance in older adults [21]. Thus, from an economic perspective, it is necessary to examine its effectiveness against a passive control before controlling for other influences or demonstrating its superiority over other activities [65]. Therefore, we decided not to include an active comparator. To still be able to differentiate effects of the intervention from more general effects, we included some secondary outcomes which should not benefit from foreign language learning. This can be presumed because verbal fluency and non-executive components of attention largely relate to cognitive functions which might be less affected by foreign language learning. Furthermore, a significant regression of previous foreign language skills and usage on our results could also be informative. Different levels of cognitive reserve have already been associated with changes in cognition after cognitive training [31]. Thus, assuming previous foreign language skills and usage are part of cognitive reserve, varying results depending on prior skills could indicate a direct effect of language training.

To our knowledge, we are conducting the first randomised controlled trial of its kind with a short and intensive foreign language training. We opted for this approach, as more intensive and short foreign language learning programmes were more likely to be associated with cognitive improvements than less intense trainings with longer durations [24,25,26, 28]. Furthermore, this short intervention period increases our chances of achieving the targeted sample size, since older adults, although retired, often lead an active lifestyle, and thus have limited time resources.

Our work might also contribute to the current debate on the bilingual advantage hypothesis. This hypothesis suggests that bilinguals perform better in cognitive domains involved in language control, particularly in EF, and suffer less cognitive decline compared to monolinguals [66]. However, accumulating evidence challenges this advantage. For example, a recent large-scale meta-analysis of 152 studies could not find any support for a bilingual advantage across all domains of EF after controlling for publication bias [67]. Although intensive foreign language training and bilingualism differ in important aspects (e.g. short-term learning vs. long-term use), we still might learn more about cognitive processes that underlie foreign language learning. This is of considerable importance as the bilingual advantage might only occur under certain circumstances, which are not yet fully understood [68]. Nevertheless, we would like to emphasise that this study was not intended to address the debate on the bilingual advantage. Our study concerns a well-defined pattern of foreign language usage and a low level of language skills. Thus, no general conclusion can be drawn about the bilingual advantage hypothesis, and any comparison with bilingualism should be taken with caution.

Preserving and enhancing cognitive health in older age is highly relevant, given our ageing world population [1]. As Bak [12] has already noted, if foreign language learning turns out to enhance EF in older adults, it might have clear-cut advantages over drugs or other provisions against cognitive decline. Foreign language learning is inexpensive, already widely available and easily combinable with other activities such as music or travelling. Therefore, foreign language learning could constitute an attractive and enjoyable opportunity to promote cognitive reserve, and thus healthy cognitive ageing.

Trial status

This study is still ongoing. Recruitment began on 1 March 2019 and is expected to continue until 1 July 2020. By the time of submission of this manuscript (31 March 2020), n = 54 participants were already enrolled in the trial.

Availability of data and materials

This document is the full protocol. No public access to the anonymised dataset and the statistical code will be provided. However, both will be available from the corresponding author upon legitimate request.

Abbreviations

ANOVA:

Analysis of variance

CFD:

Cognitive Functions Dementia

CONSORT:

Consolidated Standard of Reporting Trials

CRIq:

Cognitive Reserve Index questionnaire

DSB:

Digit Span Backwards

DSF:

Digit Span Forwards

EF:

Executive functions

FLANDERS:

Flinders Handedness Survey

INHIB:

Response Inhibition

LLG:

Language learning group

LSBQ:

The Language and Social Background Questionnaire

MAR:

Missing at random

MMSE:

Mini-Mental State Examination

MoCA:

Montreal Cognitive Assessment

NAR:

Network Aging Research

NBV:

N-Back Verbal

SPIRIT:

Standard Protocol Items: Recommendations for Interventional Trials

STROOP:

Stroop Interference Test

SWITCH:

Task Switching

TMT-A:

Trail-Making Test – Langensteinbach Version Part A

TMT-B:

Trail-Making Test – Langensteinbach Version Part B

VTS:

Vienna Test System

WAFA:

Perception and Attention Function Battery – Alertness

WAFG:

Perception and Attention Function Battery – Divided Attention

WAIS-IV:

Wechsler Adult Intelligence Scale – Fourth Edition

WIWO:

Vienna Verbal Fluency Test

WLCG:

Waiting list control group

References

  1. 1.

    World Health Organisation. Fact file. 2020. https://www.who.int/features/factfiles/ageing/ageing_facts/en. Accessed 5 Dec 2020.

  2. 2.

    Park DC, Reuter-Lorenz P. The adaptive brain: aging and neurocognitive scaffolding. Annu Rev Psychol. 2009;60:173–96.

    PubMed  PubMed Central  Article  Google Scholar 

  3. 3.

    Sperling RA, Aisen PS, Beckett LA, Bennett DA, Craft S, Fagan AM, et al. Toward defining the preclinical stages of Alzheimer's disease: recommendations from the National Institute on Aging-Alzheimer's Association workgroups on diagnostic guidelines for Alzheimer's disease. Alzheimers Dement. 2011;7(3):280–92.

    PubMed  PubMed Central  Article  Google Scholar 

  4. 4.

    Miyake A, Friedman NP. The nature and organization of individual differences in executive functions: four general conclusions. Curr Dir Psychol Sci. 2012;21(1):8–14.

    PubMed  PubMed Central  Article  Google Scholar 

  5. 5.

    Casanova R, Saldana S, Lutz MW, Plassman BL, Kuchibhatla M, Hayden KM. Investigating predictors of cognitive decline using machine learning. J Gerontol B Psychol Sci Soc Sci. 2020;75(4):733–42.

    PubMed  Article  Google Scholar 

  6. 6.

    Drag LL, Bieliauskas LA. Contemporary review 2009: cognitive aging. J Geriatr Psychiatry Neurol. 2010;23(2):75–93.

    PubMed  Article  PubMed Central  Google Scholar 

  7. 7.

    Bugos JA, Perlstein WM, McCrae CS, Brophy TS, Bedenbaugh PH. Individualized piano instruction enhances executive functioning and working memory in older adults. Aging Ment Health. 2007;11(4):464–71.

    CAS  PubMed  Article  Google Scholar 

  8. 8.

    Basak C, Boot WR, Voss MW, Kramer AF. Can training in a real-time strategy video game attenuate cognitive decline in older adults? Psychol Aging. 2008;23(4):765–77.

    PubMed  PubMed Central  Article  Google Scholar 

  9. 9.

    Strout KA, David DJ, Dyer EJ, Gray RC, Robnett RH, Howard EP. Behavioral interventions in six dimensions of wellness that protect the cognitive health of community-dwelling older adults: a systematic review. J Am Geriatr Soc. 2016;64(5):944–58.

    PubMed  Article  Google Scholar 

  10. 10.

    Sprague BN, Freed SA, Webb CE, Phillips CB, Hyun J, Ross LA. The impact of behavioral interventions on cognitive function in healthy older adults: a systematic review. Ageing Res Rev. 2019;52:32–52.

    PubMed  Article  PubMed Central  Google Scholar 

  11. 11.

    Stern Y. What is cognitive reserve?: theory and research application of the reserve concept. J Int Neuropsychol Soc. 2002;8(3):448–60.

    PubMed  Article  PubMed Central  Google Scholar 

  12. 12.

    Bak TH. Language lessons to help protect against dementia. BMJ. 2016;354:i5039.

    PubMed  Article  PubMed Central  Google Scholar 

  13. 13.

    Bialystok E. The bilingual adaptation: how minds accommodate experience. Psychol Bull. 2017;143(3):233–62.

    PubMed  PubMed Central  Article  Google Scholar 

  14. 14.

    Grundy JG, Timmer K. Bilingualism and working memory capacity: a comprehensive meta-analysis. Second Lang Res. 2016;33(3):325–40.

    Article  Google Scholar 

  15. 15.

    Bak TH, Nissan JJ, Allerhand MM, Deary IJ. Does bilingualism influence cognitive aging? Ann Neurol. 2014;75(6):959–63.

    PubMed  PubMed Central  Article  Google Scholar 

  16. 16.

    Bialystok E, Craik FIM, Green DW, Gollan TH. Bilingual minds. Psychol Sci Public Interest. 2009;10(3):89–129.

    PubMed  Article  PubMed Central  Google Scholar 

  17. 17.

    Abutalebi J, Green DW. Neuroimaging of language control in bilinguals: neural adaptation and reserve. Bilingualism. 2016;19(4):689–98.

    Article  Google Scholar 

  18. 18.

    Rodríguez-Fornells A, Cunillera T, Mestres-Missé A, de Diego-Balaguer R. Neurophysiological mechanisms involved in language learning in adults. Philos Trans R Soc B. 2009;364(1536):3711–35.

    Article  Google Scholar 

  19. 19.

    Antoniou M. The advantages of bilingualism debate. Annu Rev Linguist. 2019;5(1):395–415.

    Article  Google Scholar 

  20. 20.

    Raz N, Rodrigue KM. Differential aging of the brain: patterns, cognitive correlates and modifiers. Neurosci Biobehav Rev. 2006;30(6):730–48.

    PubMed  PubMed Central  Article  Google Scholar 

  21. 21.

    Pot A, Porkert J, Keijzer M. The bidirectional in bilingual: cognitive, social and linguistic effects of and on third-age language learning. Behav Sci. 2019;9(9):98.

    Article  Google Scholar 

  22. 22.

    Berggren R, Nilsson J, Brehmer Y, Schmiedek F, Lövdén M. Foreign language learning in older age does not improve memory or intelligence: evidence from a randomized controlled study. Psychol Aging. 2020;35(2):212–9.

    PubMed  Article  PubMed Central  Google Scholar 

  23. 23.

    Ramos S, Fernández García Y, Antón E, Casaponsa A, Duñabeitia JA. Does learning a language in the elderly enhance switching ability? J Neurolinguistics. 2017;43:39–48.

    Article  Google Scholar 

  24. 24.

    Pfenninger SE, Polz S. Foreign language learning in the third age: a pilot feasibility study on cognitive, socio-affective and linguistic drivers and benefits in relation to previous bilingualism of the learner. JESLA. 2018;2(1):1.

    Article  Google Scholar 

  25. 25.

    Ware C, Damnee S, Djabelkhir L, Cristancho V, Wu Y-H, Benovici J, et al. Maintaining cognitive functioning in healthy seniors with a technology-based foreign language program: a pilot feasibility study. Front Aging Neurosci. 2017;9:42.

    PubMed  PubMed Central  Article  Google Scholar 

  26. 26.

    Bak TH, Long MR, Vega-Mendoza M, Sorace A. Novelty, challenge, and practice: the impact of intensive language learning on attentional functions. PLoS One. 2016;11(4):e0153485.

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  27. 27.

    Bubbico G, Chiacchiaretta P, Parenti M, Di Marco M, Panara V, Sepede G, et al. Effects of second language learning on the plastic aging brain: functional connectivity, cognitive decline, and reorganization. Front Neurosci. 2019;13:423.

    PubMed  PubMed Central  Article  Google Scholar 

  28. 28.

    Valis M, Slaninova G, Prazak P, Poulova P, Kacetl J, Klimova B. Impact of learning a foreign language on the enhancement of cognitive functions among healthy older population. J Psycholinguist Res. 2019;48(6):1311–8.

    PubMed  Article  PubMed Central  Google Scholar 

  29. 29.

    Wong PCM, Ou J, Pang CWY, Zhang L, Tse CS, Lam LCW, Antoniou M. Language training leads to global cognitive improvement in older adults: a preliminary study. J Speech Lang Hear Res. 2019;62(7):2411–24.

    PubMed  Article  PubMed Central  Google Scholar 

  30. 30.

    Miyake A, Friedman NP, Emerson MJ, Witzki AH, Howerter A, Wager TD. The unity and diversity of executive functions and their contributions to complex "frontal lobe" tasks: a latent variable analysis. Cogn Psychol. 2000;41(1):49–100.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  31. 31.

    Mondini S, Madella I, Zangrossi A, Bigolin A, Tomasi C, Michieletto M, et al. Cognitive reserve in dementia: implications for cognitive training. Front Aging Neurosci. 2016;8:84.

    PubMed  PubMed Central  Article  Google Scholar 

  32. 32.

    Schulz KF, Altman DG, Moher D. CONSORT 2010 statement: updated guidelines for reporting parallel group randomised trials. BMJ. 2010;340:c332.

    PubMed  PubMed Central  Article  Google Scholar 

  33. 33.

    Chan A-W, Tetzlaff JM, Gøtzsche PC, Altman DG, Mann H, Berlin JA, et al. SPIRIT 2013 explanation and elaboration: guidance for protocols of clinical trials. BMJ. 2013;346:e7586.

    PubMed  PubMed Central  Article  Google Scholar 

  34. 34.

    Schuhfried G. Vienna Test System. Moedling. Austria: SCHUHFRIED GmbH.

  35. 35.

    Jahn T, Heßler JB. Cognitive functions dementia. Moedling, Austria: SCHUHFRIED GmbH; 2017.

    Google Scholar 

  36. 36.

    Petersen RC, Smith GE, Waring SC, Ivnik RJ, Tangalos EG, Kokmen E. Mild cognitive impairment: clinical characterization and outcome. Arch Neurol. 1999;56(6):760.

    Article  Google Scholar 

  37. 37.

    Swan IR, Browning GG. The whispered voice as a screening test for hearing impairment. J R Coll Gen Pract. 1985;35(273):197.

    CAS  PubMed  PubMed Central  Google Scholar 

  38. 38.

    Kliesch M, Giroud N, Pfenninger SE, Meyer M. Research on second language acquisition in old adulthood: what we have and what we need. In: Gabryś-barker D, editor. Third age learners of foreign languages. Bristol, Blue Ridge Summit: Multilingual Matters; 2018.

    Google Scholar 

  39. 39.

    Goerrissen M. Caminos hoy A1: Kurs- und Übungsbuch mit MP3-CD und DVD. 1st ed. Stuttgart: Ernst Klett Sprachen; 2016.

    Google Scholar 

  40. 40.

    Mills EJ, Seely D, Rachlis B, Griffith L, Wu P, Wilson K, et al. Barriers to participation in clinical trials of cancer: a meta-analysis and systematic review of patient-reported factors. Lancet Oncol. 2006;7(2):141–8.

    PubMed  Article  PubMed Central  Google Scholar 

  41. 41.

    Nucci M, Mapelli D, Mondini S. Cognitive reserve index questionnaire (CRIq): a new instrument for measuring cognitive reserve. Aging Clin Exp Res. 2012;24(3):218–26.

    PubMed  PubMed Central  Google Scholar 

  42. 42.

    Opdebeeck C, Martyr A, Clare L. Cognitive reserve and cognitive function in healthy older people: a meta-analysis. Aging Neuropsychol Cogn. 2016;23(1):40–60.

    Article  Google Scholar 

  43. 43.

    Anderson JAE, Mak L, Keyvani Chahi A, Bialystok E. The language and social background questionnaire: assessing degree of bilingualism in a diverse population. Behav Res Methods. 2018;50(1):250–63.

    PubMed  PubMed Central  Article  Google Scholar 

  44. 44.

    Folstein MF, Folstein SE, McHugh PR. “Mini-mental state”: a practical method for grading the cognitive state of patients for the clinician. J Psychiat Res. 1975;12(3):189–98.

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  45. 45.

    Nasreddine ZS, Phillips NA, Bédirian V, Charbonneau S, Whitehead V, Collin I, et al. The Montreal cognitive assessment, MoCA: a brief screening tool for mild cognitive impairment. J Am Geriatr Soc. 2005;53(4):695–9.

    PubMed  Article  PubMed Central  Google Scholar 

  46. 46.

    Roalf DR, Moberg PJ, Xie SX, Wolk DA, Moelter ST, Arnold SE. Comparative accuracies of two common screening instruments for classification of Alzheimer's disease, mild cognitive impairment, and healthy aging. Alzheimers Dement. 2013;9(5):529–37.

    PubMed  Article  Google Scholar 

  47. 47.

    Nicholls MER, Thomas NA, Loetscher T, Grimshaw GM. The Flinders handedness survey (FLANDERS): a brief measure of skilled hand preference. Cortex. 2013;49(10):2914–26.

    PubMed  Article  Google Scholar 

  48. 48.

    Schuhfried G. Manual Stroop interference test. Moedling, Austria: SCHUHFRIED GmbH; 1999.

    Google Scholar 

  49. 49.

    Sturm W, Manual WAF. Perception and attention function battery - divided attention. Moedling, Austria: SCHUHFRIED GmbH; 2006.

    Google Scholar 

  50. 50.

    Di Martino A, Ghaffari M, Curchack J, Reiss P, Hyde C, Vannucci M, et al. Decomposing intra-subject variability in children with attention-deficit/hyperactivity disorder. Biol Psychiatry. 2008;64(7):607–14.

    PubMed  PubMed Central  Article  Google Scholar 

  51. 51.

    Shao Z, Janse E, Visser K, Meyer AS. What do verbal fluency tasks measure? Predictors of verbal fluency performance in older adults. Front Psychol. 2014;5:772.

    PubMed  PubMed Central  Article  Google Scholar 

  52. 52.

    Suchy Y. Executive functioning: overview, assessment, and research issues for non-neuropsychologists. Ann Behav Med. 2009;37(2):106–16.

    PubMed  Article  PubMed Central  Google Scholar 

  53. 53.

    Kaiser S, Aschenbrenner S, Pfueller U, Roesch-Ely D, Weisbrod M. Manual response inhibition. Moedling, Austria: SCHUHFRIED GmbH; 2010.

    Google Scholar 

  54. 54.

    Gmehlin D, Stelzel C, Weisbrod M, Kaiser S, Aschenbrenner S. Manual task switching. Moedling, Austria: SCHUHFRIED GmbH; 2012.

    Google Scholar 

  55. 55.

    Rodewald K, Weisbrod M, Aschenbrenner S. Manual Trail-Making Test - Langensteinbach Version. Moedling, Austria: SCHUHFRIED GmbH; 2012.

    Google Scholar 

  56. 56.

    Petermann F. WAIS-IV: Wechsler adult intelligence scale - fourth edition - German adaptation after David Wechsler. Frankfurt: Pearson; 2012.

    Google Scholar 

  57. 57.

    Schelling D, Schuri U. Manual N-Back Verbal. Moedling, Austria: SCHUHFRIED GmbH; 2009.

    Google Scholar 

  58. 58.

    Jahn T. Manual Vienna verbal fluency test. Moedling, Austria: SCHUHFRIED GmbH; 2016.

    Google Scholar 

  59. 59.

    Sturm W, Manual WAF. Perception and attention function battery - alertness. Moedling, Austria: SCHUHFRIED GmbH; 2006.

    Google Scholar 

  60. 60.

    Schmiedek F, Lövdén M, Lindenberger U. A task is a task is a task: putting complex span, n-back, and other working memory indicators in psychometric context. Front Psychol. 2014;5:1475.

    PubMed  PubMed Central  Article  Google Scholar 

  61. 61.

    Ernst Klett Verlag. Placement test Spanish A1. 2004. https://tests.online-platform.net/test_es.php. Accessed 4 Jan 2019.

  62. 62.

    Cohen J. Statistical power analysis for the behavioral sciences. 2nd ed. Hillsdale, NY: Erlbaum; 1988.

    Google Scholar 

  63. 63.

    Sealed Envelope. Simple Randomiser. 2020. https://www.sealedenvelope.com/simple-randomiser/v1/lists. Accessed 9 Dec 2020.

  64. 64.

    Kelly ME, Duff H, Kelly S, McHugh Power JE, Brennan S, Lawlor BA, Loughrey DG. The impact of social activities, social networks, social support and social relationships on the cognitive functioning of healthy older adults: a systematic review. Syst Rev. 2017;6(1):259.

    PubMed  PubMed Central  Article  Google Scholar 

  65. 65.

    Puhan MA, Vollenweider D, Steurer J, Bossuyt PM, Ter Riet G. Where is the supporting evidence for treating mild to moderate chronic obstructive pulmonary disease exacerbations with antibiotics? a systematic review. BMC Med. 2008;6:28.

    PubMed  PubMed Central  Article  Google Scholar 

  66. 66.

    Bialystok E, Craik FIM, Luk G. Bilingualism: consequences for mind and brain. Trends Cogn Sci. 2012;16(4):240–50.

    PubMed  PubMed Central  Article  Google Scholar 

  67. 67.

    Lehtonen M, Soveri A, Laine A, Järvenpää J, de Bruin A, Antfolk J. Is bilingualism associated with enhanced executive functioning in adults? A meta-analytic review. Psychol Bull. 2018;144(4):394–425.

    PubMed  Article  PubMed Central  Google Scholar 

  68. 68.

    Paap KR, Johnson HA, Sawi O. Bilingual advantages in executive functioning either do not exist or are restricted to very specific and undetermined circumstances. Cortex. 2015;69:265–78.

    PubMed  Article  PubMed Central  Google Scholar 

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Acknowledgements

We would like to thank all colleagues who help in conducting the trial. Finally, we would like to thank SCHUHFRIED GmbH, Moedling, for supporting the study with non-monetary means.

Funding

This work is funded by a scholarship from the Klaus Tschira Foundation gGmbH to JAD. The SRH Clinic Karlsbad-Langensteinbach and the F + U Academy of Languages will provide funding for the language courses. We also acknowledge financial support by the German Research Foundation within the funding programme Open Access Publishing, by the Baden-Wuerttemberg Ministry of Science, Research and the Arts, and by the Ruprecht Karl University of Heidelberg. No funding source had a role in the study concept, design, or publication of this protocol or will have in study implementation, analysis, interpretation, or dissemination of results. Open Access funding enabled and organized by Projekt DEAL.

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Authors

Contributions

JAG, PM, and BT conceived the study and designed the trial protocol. SA, MGD, and VMK contributed to the design of the study. JAG and VMK drafted the manuscript. SA, MGD, PM, and BT critically reviewed the manuscript for relevant intellectual content. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Judith Alina Grossmann.

Ethics declarations

Ethics approval and consent to participate

This study is conducted according to the Declaration of Helsinki and obtained ethical approval from the Ethics Committee of the Faculty of Behavioural and Empirical Cultural Studies of the Ruprecht Karl University of Heidelberg, reference number 2018/1–2, on 10 January 2019. The Ethics Committee is advised of and will evaluate any substantive modifications to the protocol. The consent form will be sent to participants prior to enrolment in the trial. It will be signed at the first appointment at the study site. Additionally, a trained researcher will provide information about central aspects of the trial, including the course of the intervention, accompanying assessments, and data management. We will ensure that participants will accept their allocation to one of the two study groups regardless of any personal preference. There are no criteria for discontinuing or altering allocated interventions. Participants may end their participation at any time during the trial without incurring any disadvantages.

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Not applicable.

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The authors declare that they have no competing interests.

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Grossmann, J.A., Koelsch, V.M., Degirmenci, M.G. et al. Effects of foreign language learning on executive functions in healthy older adults: study protocol for a randomised controlled trial. BMC Geriatr 21, 122 (2021). https://doi.org/10.1186/s12877-021-02051-x

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Keywords

  • Foreign language training
  • Cognitive reserve
  • Cognition
  • Attentional control
  • Inhibition
  • Updating
  • Shifting
  • Verbal fluency