Efficacy of rTMS Combined with Cognitive and Language Training in People Living with Alzheimer’s Disease: A Systematic Review

<jats:p>Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation method that has been suggested as a possible treatment method for cognitive impairment in patients with Alzheimer’s Disease (pwAD), similar to multidomain cognitive training (CT). The effectiveness, however, of combining these techniques for pwAD remains controversial due to the variability in rTMS parameters, differences in CT protocol designs—many of which neglect the language domain—and the inclusion of patients at various stages of Alzheimer’s Disease (AD) and with different types of dementia. The current review aims to evaluate the cognitive benefits of combining rTMS with CT, including language training, for individuals with mild to moderate AD. An extensive literature search was conducted in PubMed, Google Scholar, and the Cochrane Library with relevant terms, resulting in nine studies with a total of 290 participants [190 in the Active Group (AG) and 100 in the Control Group (CG)]. The comprehensive review of the articles revealed that the combined treatment improved global cognitive function, as well as neurocognitive, neuropsychiatric, and quality of life in the AG. Nevertheless, these results should be interpreted cautiously, given the relatively small number of existing studies on this specific combination.</jats:p>

section_content: Alzheimer's disease (AD) is a leading neurodegenerative condition. It is linked to the buildup of abnormal proteins in the brain, including beta-amyloid plaques and tau tangles, which result in the loss of brain cells. AD is a form of dementia leading to cognitive deficits, personality and behavioral changes, and motor impairments [1]. AD is associated with a gradual decline in memory, cognitive abilities, attention, and executive functions, as well as deterioration in thinking and behavioral skills [2, 3]. It also affects language, reasoning, social conduct, verbal and auditory naming, and the capacity to perform basic tasks, all of which are significantly impaired by the underlying neurodegenerative mechanisms [4]. Available medications, such as cholinesterase inhibitors (donepezil, rivastigmine, and galantamine) [5] and the glutamate receptor antagonist memantine [6], are used for symptomatic treatment. These treatments, however, have limited efficacy, do not prevent disease progression, and are not well-tolerated by all patients [7] [8] [9]. 

Brain Sci. 2024, 14, 891 2 of 26 Therefore, it is critically important to expand the range of therapeutic options available for treating AD. One such option is cognitive training (CT) programs, which involve structured tasks/exercises presented either via computer or by paper and pencil. These programs range in difficulty level and target specific cognitive domains. They have shown promising results in AD, with positive effects on global and individual-domain cognitive outcomes [10]. Such interventions seem to be much more effective in a multidomain rather than a single-domain design base [11]. The results are still suboptimal, but they have a limited long-term beneficial impact. It is worth noting that CT programs in AD are often designed primarily to enhance memory, while language and other executive functions are often neglected, sometimes not trained at all, or not properly assessed [12]. Furthermore, despite numerous studies asserting the inclusion of language training in their CT programs, none of them offered detailed information regarding the specific language domains targeted or the content of the language tasks employed [10]. 

Among the non-pharmacological treatment modalities that have emerged in recent years is repetitive transcranial magnetic stimulation (rTMS). This treatment uses rhythmic electromagnetic induction (magnetic pulses) to non-invasively stimulate the brain, modulating cortical excitability and neural activity [13, 14]. These pulses are generated by a coil placed on the scalp and can modulate neural activity in targeted brain regions. rTMS is considered a safe, low-cost, and effective treatment for patients with AD. Additionally, it is a promising alternative for the treatment of certain prevalent non-cognitive symptoms among patients with AD, including depression [15], as well as for the improvement of cognitive and motor functions in otherwise healthy older adults [16]. In addition, the combination of rTMS with neurophysiological techniques such as motor-evoked potential (MEP) allows for the reliable and convenient measurement of cortical plasticity [17]. Recent studies have reported that rTMS may specifically improve global cognitive function, language performance, and memory in patients with AD (pwAD), especially at the mild or early stage of the disease [18]. 

To date, there are four reviews and meta-analyses exploring the beneficial effects of rTMS on cognitive function in AD [19] [20] [21] [22] [23]. These articles, however, vary in terms of rTMS stimulation parameters (i. e., single site, multisite, etc. ) and include both studies utilizing rTMS alone and studies combining rTMS with CT. They lack analytical information about the CT training programs (specific tasks, domains, etc. ), and it appears that the CT programs used did not always include language in the training sessions. Furthermore, these reviews and analyses did not focus on specific clinical groups, as they analyzed studies examining patients with Mild Cognitive Impairment (MCI) as well as those with different stages of AD and other types of dementia. 

Considering the well-established effects of rTMS and CT (with or without language included) on AD [24, 25], we speculated that the combination of rTMS and CT but with language included might produce additional beneficial effects. Therefore, and due to the aforementioned literature gap, we conducted a systematic review carefully designed to summarize evidence from studies that implemented CT but specifically included language in the training, along with multisite rTMS for pwAD exclusively. Furthermore, analytical information regarding their CT programs is provided. In particular, the objectives of the present systematic review are as follows: the present systematic review aimed to (a) explore the effectiveness of combining high-frequency rTMS with CT, including language for patients with mild to moderate AD, and (b) determine which domains benefit most from the intervention.
section_name: Introduction

section_name: Method

section_content: A comprehensive literature search was performed using PubMed, Google Scholar, and the Cochrane Library. The following search terms were employed (entered as free text): (a) "rTMS cognitive and language training" and "Alzheimer"; (b) "Alzheimer" and "language rehabilitation" and "cognitive training" and "rTMS". The final literature search was performed on 30th January 2024. The initial search yielded a total of 1538 studies published up to January 2024. Specifically, 546 studies were retrieved from PubMed, 848 studies from Google Scholar, and 144 studies from Cochrane.
section_name: Search Strategy

section_content: The following eligibility criteria were considered: (1) use of rTMS combined with CT including language, (2) inclusion of participants with AD, (3) availability of pre-and post-intervention cognitive data, and (4) inclusion of at least 8 participants in the rTMS combined with CT (including language) arm. Studies were excluded if they (1) lacked pre-or post-intervention cognitive data, (2) involved different kinds of interventions (e. g., physical training, CT not including language, rTMS without CT including language), (3) included participants with other neurological conditions (e. g., stroke, Parkinson's disease), or (4) were systematic review articles and meta-analyses. Conclusions were based on randomized controlled trials (RCTs). Further information regarding the procedure of the selection for eligible studies is presented in Figure 1 [26].
section_name: Eligibility Criteria

section_content: The following eligibility criteria were considered: (1) use of rTMS combined with CT including language, (2) inclusion of participants with AD, (3) availability of pre-and postintervention cognitive data, and (4) inclusion of at least 8 participants in the rTMS combined with CT (including language) arm. Studies were excluded if they (1) lacked preor post-intervention cognitive data, (2) involved different kinds of interventions (e. g., physical training, CT not including language, rTMS without CT including language), (3) included participants with other neurological conditions (e. g., stroke, Parkinson's disease), or (4) were systematic review articles and meta-analyses. Conclusions were based on randomized controlled trials (RCTs). Further information regarding the procedure of the selection for eligible studies is presented in Figure 1 [26].
section_name: Eligibility Criteria

section_content: The data listed below were exported from the retrieved studies: author, year of publication, number of participants, AD stage, targeted domains for intervention, study design, outcome measures, intervention duration and frequency, and outcomes. The PRISMA guidelines for reporting systematic reviews were followed (Appendix A) [26]. The flow diagram illustrates the progression of information through the different phases of the systematic review, mapping the number of records identified, included, and excluded, as well as the reasons for exclusions [36]. Two independent reviewers (A. N. and N. G. ) conducted the search of the literature, performed the quality evaluation, and independently extracted the data. Any potential discrepancies were resolved by a third author (I. L. ).
section_name: Data Extraction

section_content: Risk of bias was evaluated using the risk of bias (RoB) tool from Cochrane for systematic reviews of interventions (Figure 2 ). Five methodological domains were assessed:

(1) randomization process (including sequence generation, allocation concealment, and baseline differences between groups), (2) deviations from intended interventions (such as blinding of participants and personnel, and appropriateness of analysis), (3) missing outcome data (data availability and reasons for missing data), ( 4 ) measurement of outcomes (methods of measurement for both groups), and (5) selective reporting (prespecified protocols and multiple analyses). Each domain was categorized as "low risk of bias", "high risk of bias", or "some concerns" based on the methodological features and reporting of the reviewed studies.
section_name: Risk of Bias Assessment Tool

section_name: Results

section_content: Study characteristics are included in Table 1. Regarding the study settings, three studies were conducted in Israel [27] [28] [29], one study in both Israel and the USA [30], one study in Italy and the USA [31], one study in North Korea [32], two studies in China [33, 34], and one study in France [35]. Two of them were pilot studies [27, 33], and one was a clinical trial [29]. Three studies were randomized, double-blinded, and placebo-controlled [30] [31] [32] [33]. One was randomized and double-blinded without placebo control [28] ; one was randomized, single-blind, and placebo-controlled [31] ; and, finally, one was a non-randomized open-label study [34]. Six of the studies [28, [30] [31] [32] [33] [34] included both an active group (AG) and a sham group (SG), whereas all participants in the other three studies [27, 29, 35] received active stimulation. In total, 290 participants were included, with 190 in the AG and 100 in the SG. The treatment group received rTMS sessions combined with computer-based CT, including language in all studies except for one [34], which did not specify whether the training was computer-based or paper-pencil.
section_name: Study Characteristics

section_content: Patients' characteristics are presented in Table 2. In total, 290 patients were included. More specifically, the AG consisted of 190 individuals, 100 males and 90 females, while the SG included 100 participants, 52 males and 48 females [27] [28] [29] [30] [31] [32] [33] [34] [35]. The mean age of the participants ranged from 67. 5 to 76. 9 years old; Rabey and Dobronevsky [29] did not provide information about the age of the participants. There were no significant differences in age and gender between the patient groups in the studies of Brem et al. [31], Lee et al. [32], Rabey et al. [28], Sabbagh et al. [30], Zhang et al. [33] and Zhao et al. [34], whereas Rabey and Dobronevsky [29] did not give specific information regarding the comparison in age and gender between groups. The participants in the other two studies [27, 35] were not separated into groups. In terms of disease severity, all nine studies included patients who were classified as having mild to moderate disease [27] [28] [29] [30] [31] [32] [33] [34] [35]. Five studies used the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) criteria [27, 28, 30, 32, 34] to evaluate patients' disease stage, and one study used the 5th edition's criteria (DSM-5) combined with the National Institute on Aging and Alzheimer's Association (NIA-AA) criteria [31]. 

One study fulfilled the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA) criteria [33], and two studies provided no further information about the diagnostic process [29, 35]. Moreover, five of the studies [27] [28] [29] 32, 34] supported the diagnosis with magnetic resonance imaging (MRI), and one study [32] used MRI to exclude cerebrovascular disease. 

As a measure of baseline cognitive function, seven of the studies presented participants' Mini Mental State Examination (MMSE) scores. Specifically, in five studies [27, 28, [30] [31] [32], the MMSE score ranged from 18 to 24; in one study [34], the score ranged from 18 to 26, and one study [29] did not provide the exact score. In addition, five studies used the Clinical Dementia Rate (CDR) scale; in two of these studies [27, 28], the CDR score was 1, and in the other three studies [30, 32, 34], the CDR score was either 1 or 2. Moreover, Rabey and Dobronevsky [29] and Sabbagh et al. [30] used the Alzheimer Disease Assessment Scale-Cognitive (ADAS-Cog). Finally, Zhang et al. [33] conducted a baseline neuropsychological evaluation using CDR, MMSE, activities of daily living (ADL), and the Neuropsychiatric Inventory (NPI). 

Three of the studies did not provide details about the concomitant pharmacological treatment administered to patients [27, 29, 35]. While Rabey et al. [28] noted that patients did not have serious metabolic or cardiac diseases, Zhao et al. [34], both with Lee et al. [32], reported no drug changes two months before and throughout the treatment duration, and Sabbagh et al. [30] and Zhang et al. [33] mentioned that if some patients were medicated for AD, they should have been taking the medication for at least three months at a stable dosage.
section_name: Participants' Characteristics

section_content: In all studies, participants underwent treatment programs with repetitive transcranial magnetic stimulation (rTMS) and CT, including language, which lasted for a period ranging between four weeks and three months, with session frequency varying from once per day to twice per week. Each session lasted from 30 to 60 min. The Neuro AD Neuronix protocol was applied in all studies except for two [33, 34]. 

The majority of the studies stimulated six brain areas. Specifically, in most of the studies [27] [28] [29] [30] [31] [32] 35], the coil was placed on the Broca area (left frontal part of the temporal lobe), the Wernicke area (left posterior part of the temporal lobe), the right and left dorsolateral prefrontal cortex (R-dlPFC and L-dlPFC), and the right and left parietal somatosensory association cortex (R-pSAC + L-pSAC). In one study [34], the coil was placed on the parietal P3/P4 and the posterior temporal T5/T6 areas, and in another study [33], it was placed on the DLPFC and the lateral temporal lobe (LTL). Tasks were designed to train syntax, grammar, lexical meaning, categorization, action naming, object naming, spatial memory, and spatial attention. All tasks were associated with the stimulation of the corresponding brain areas. Analytical information is shown in Table 3.
section_name: Intervention Characteristics

section_content: There was an improvement in the average ADAS-cog score of 3. 76 points after 6 weeks in the treatment group compared to 0. 47 in the placebo group and 3. 52 points after 4. 5 months of treatment, compared to a worsening of 0. 38 in the placebo. There was also an improvement in the average CGIC score of 3. 57 (after 6 weeks) and 3. 67 points (after 4. 5 months), compared to 4. 25 and 4. 29 in the placebo group (mild worsening). NPI improved non-significantly.
section_name: ADAS-cog CGIC NPI

section_content: The targeted domains were language functions, judgment, executive function, long-term memory, spatial and topographical orientation, and praxis in almost all studies [27] [28] [29] [30] [31] [32] 35], except for the studies of Zhao et al. [34], who targeted memory, language and executive function, and Zhang et al. [33], who aimed at the domains of memory, mathematical calculations, language, and logical thinking. 

The comprehensive review of the articles revealed the benefits of rTMS and CT, including language treatment, which are summarized in Table 4. Two studies [29, 30] used only the Alzheimer Disease Assessment Scale-Cognitive (ADAS-cog) to evaluate the outcomes of the therapy sessions; both showed a statistically significant benefit favoring the active group over the sham group. Four studies [27, 28, 31, 32] evaluated the language and cognitive profile before and after treatment with the ADAS-cog and the Mini Mental State Examination (MMSE). Specifically, Rabey and Dobronevsky [29] found statistically significant improvement in both tests after the combination of rTMS CT, including language treatment, whereas patients in the studies of Bentwich et al. [27] and Lee et al. [32] showed significant improvement only in ADAS-cog. In the latter research, however, the MMSE score improved significantly between baseline and six weeks after treatment in the mild AD group. Brem et al. [31] noticed that the group with active stimulation and real CT, including language treatment, showed significant improvement compared to the sham stimulation and sham CT/language group but not compared to the real CT/language and sham stimulation group. 

The other three studies [33] [34] [35] assessed participants' outcomes with additional tests. In particular, Zhao et al. [34] found significantly improved performance in the ADAS-cog; the MMSE; and the World Health Organization University of California-Los Angeles, Auditory Verbal Learning Test (WHO-UCLA AVLT) score for the AG, with notably improved Montreal Cognitive Assessment (MoCA) scores in mild AD patients of the AG. Nguyen et al. [35] used the ADAS-cog, the MMSE, the Stroop color test, and Dubois' five-word testing (5WT), of which only the ADAS-cog indicated a significantly improved score. Finally, Zhang et al. [33] reported improved scores in the ADAS-cog (specifically in the word recall memory subscale), the MMSE, and Addenbrooke's Cognitive Examination III (ACE-III, in the domains of attention, memory, visual-spatial function), with these effects lasting for at least four weeks. Apart from language and cognitive domains, seven studies [27, 28, [30] [31] [32] [33] 35 ] also evaluated non-cognitive factors. Three of these studies [27, 31, 33] assessed the impact of the treatment on patients' quality of life. For this purpose, Bentwich et al. [27] and Brem et al. [31] used the Alzheimer Disease Assessment Scale-Activities of Daily Living (ADAS-ADL) with positive outcomes, and Zhang et al. [33] demonstrated a tendency toward improvement in the Activities of Daily Living (ADL). Depression was measured either with the Hamilton Rating Scale for Depression [27] or with the Geriatric Depression Scale (GDS) [31, 32]. The study by Bentwich et al. [27] showed an improved score but without statistical significance, whereas the study by Lee et al. [32] found that the GDS score did not improve significantly in the treatment group. Brem et al. [31] evaluated depression only at baseline. 

Five of the studies [27, 28, [30] [31] [32] used the Clinical Global Impression of Change scale (CGIC), all of which indicated better results. In addition, three studies assessed the presence and severity of neuropsychiatric symptoms using the Neuropsychiatric Inventory test (NPI); two of them [28, 33] found an improvement after treatment, while the other one [27] noted that the NPI scores did not change after treatment. Moreover, two studies [31, 33] assessed patients using the Clinical Dementia Rating (CDR) at the baseline phase. Lastly, Nguyen et al. [35] utilized the Frontal Assessment Battery (FAB), locomotor, apathy score, Zarit score, and dependence score, showing an improvement in apathy and dependence scores. His section may be divided by subheadings. It should provide a concise and precise description of the experimental results, their interpretation, and the experimental conclusions that can be drawn.
section_name: Cognitive Including Language Outcomes

section_content: To the best of our knowledge, the present review is the first to focus on the impact of combining rTMS with CT, including language, for pwAD, on their overall language and cognitive profile. The critical examination of the retrieved studies revealed that this combinatory treatment led to language and cognitive improvement as assessed with the ADAS-Cog, WHO-UCLAAVLT, MMSE, MoCA, and ACE-III. In contrast, using rTMS or CT, including language alone, did not result in notable improvements. 

Our findings are consistent with those of Cheng et al. [37], who concluded in their meta-analysis that combining rTMS with CT enhances cognitive abilities in Alzheimer's disease more effectively than rTMS alone. It should be noted, however, that their analysis included studies where CT did not necessarily train language along with other cognitive domains. Furthermore, Lin et al. [19], in their review, did not reveal significantly improved results when combining rTMS with CT but observed that the complementary use of CT yielded greater overall enhancement than either treatment alone. Similar findings were observed in the reviews and meta-analyses by Xie et al. [20], Wei et al. [21], and Liu [23]. In contrast to our findings, Yan et al. [38] found in their systematic review and metaanalysis that the additional application of CT did not show significant improvement in the cognitive status of the participants. Their sample, however, included both Mild Cognitive Impairment (MCI) participants and individuals with different stages of pwAD. Specifically, beneficial outcomes were observed for language and overall cognitive profile [28, [31] [32] [33] [34] [35], as well as for memory and overall cognitive profile [27, [32] [33] [34], and for quality of life [27, 31, 33]. Furthermore, outcomes regarding neuropsychiatric symptoms and quality of life were conflicting and lacked statistical significance. Specifically, while quality of life outcomes showed a tendency towards improvement [27, 31, 34], improvements in neuropsychiatric symptoms did not reach significance [27, 28, 35]. It is worth noting that all studies reported beneficial effects for their active groups on overall cognitive profile [27] [28] [29] [30] [31] [32] [33] [34] [35]. 

The studies that provided stronger evidence were primarily those offering outcome data for both language and executive functions [28, [31] [32] [33] [34] [35]. These results, however, should be interpreted cautiously due to several factors. Firstly, participant nationality varied across the studies, leading to potential differences in language tasks. Additionally, sample sizes varied, further influencing the robustness of the findings. Moreover, there remains an insufficient number of studies focusing on pwAD and the impact of combining rTMS with CT, including language intervention, to draw definite conclusions. Another significant limitation is the lack of comprehensive analytical evaluation beyond the language sections of assessment tools such as ADAS-Cog and ACE-III, both before and after interventions, which hampers the ability to assess the specific impact on the language domain distinct from other cognitive and executive functions. 

It has been suggested that combining rTMS with CT merges "exogenous" and "endogenous" stimulation, thus enhancing neuroplasticity. rTMS may pre-activate the neural system, while subsequent CT interacts with the ongoing brain activation to amplify or extend the neural effects [39] [40] [41]. This synergistic interaction may allow CT to modulate the impact of rTMS, potentially explaining why studies involving both rTMS and CT predominantly yield more consistent results than those without cognitive training. Multidomain or holistic CT, including language, would be the optimal approach. This review and the data derived from the aggregation of the results of the included studies demonstrate originality, as it is the first time the effectiveness of rTMS combined with CT and language training has been investigated. Additionally, it contributes to the current literature and holds significant clinical relevance, as the role of language (and its training) in AD seems to be critically important and should always be taken into consideration. 

Furthermore, our review fully supports the relevance of non-pharmacological multidomain interventions for pwAD and provides the groundwork for future studies to build upon. When it comes to the effectiveness of these interventions, there is growing evidence (supported even by the present review) that a multidomain design, which targets a variety of domains and brain regions, seems to be more efficient and effective [11, [42] [43] [44] [45]. Many questions, however, remain to be answered, including how language and other cognitive improvements would translate into improved patients' quality of life and whether neurophysiological measures could act as potential biomarkers for designing interventions in AD. Future research should assess in greater detail the potential that language rehabilitation might play a more important role in the improvement of the overall everyday living profile of patients and their caregivers/families. List and define all outcomes for which data were sought. Specify whether all results that were compatible with each outcome domain in each study were sought (e. g., for all measures, time points, analyses), and if not, the methods used to decide which results to collect.
section_name: Discussion

section_content: List and define all other variables for which data were sought (e. g., participant and intervention characteristics, funding sources). Describe any assumptions made about any missing or unclear information.
section_name: NA 10b

section_content: Specify the methods used to assess the risk of bias in the included studies, including details of the tool(s) used, how many reviewers assessed each study and whether they worked independently, and if applicable, details of automation tools used in the process.
section_name: NA Study risk of bias assessment 11

section_content: Effect measures 12 Specify for each outcome the effect measure(s) (e. g., risk ratio, mean difference) used in the synthesis or presentation of results. NA
section_name: 4, 5

section_name: Section and Topic Item # Checklist Item Location Where Item Is Reported

section_content: Describe the processes used to decide which studies were eligible for each synthesis (e. g., tabulating the study intervention characteristics and comparing against the planned groups for each synthesis (item #5)).
section_name: Synthesis methods 13a

section_content: Describe any methods required to prepare the data for presentation or synthesis, such as handling of missing summary statistics or data conversions.
section_name: 13b

section_content: Describe any methods used to tabulate or visually display the results of individual studies and syntheses. 

13d

Describe any methods used to synthesize results and provide a rationale for the choice(s). If meta-analysis was performed, describe the model(s), method(s) to identify the presence and extent of statistical heterogeneity, and software package(s) used.
section_name: NA 13c

section_content: Describe any methods used to explore possible causes of heterogeneity among study results (e. g., subgroup analysis, meta-regression). NA 13f Describe any sensitivity analyses conducted to assess the robustness of the synthesized results. NA Reporting bias assessment 14 Describe any methods used to assess the risk of bias due to missing results in a synthesis (arising from reporting biases). NA Certainty assessment 15 Describe any methods used to assess certainty (or confidence) in the body of evidence for an outcome. NA
section_name: NA 13e

section_name: RESULTS

section_content: Describe the results of the search and selection process, from the number of records identified in the search to the number of studies included in the review, ideally using a flow diagram.
section_name: Study selection 16a

section_content: Cite studies that might appear to meet the inclusion criteria but which were excluded, and explain why they were excluded. NA
section_name: NA 16b

section_content: Cite each included study and present its characteristics. 9

Risk of bias in studies 18 Present assessments of risk of bias for each included study. NA
section_name: Study characteristics 17

section_content: For all outcomes, present, for each study, (a) summary statistics for each group (where appropriate) and (b) an effect estimate and its precision (e. g., confidence/credible interval), ideally using structured tables or plots.
section_name: Results of individual studies 19

section_name: 17-25

section_content: For each synthesis, briefly summarise the characteristics and risk of bias among contributing studies. NA 20b

Present results of all statistical syntheses conducted. If meta-analysis was performed, present for each the summary estimate and its precision (e. g., confidence/credible interval) and measures of statistical heterogeneity. If comparing groups, describe the direction of the effect.
section_name: Results of syntheses 20a

section_name: NA

section_name: Institutional Review Board Statement: Not applicable.

section_content: Funding: This research received no external funding.

section_content: Informed Consent Statement: Not applicable.
section_name: Institutional Review Board Statement: Not applicable.

section_name: Data Availability Statement:

section_content: No new data were created.
section_name: Data Availability Statement: