Cognitive fatigue during a test requiring sustained attention: a pilot study

A systematic literature review of the measurement of patient-reported fatigue in studies of disease modifying therapies for multiple sclerosis

BACKGROUND

Fatigue is the most commonly experienced symptom among people with multiple sclerosis (MS) and has the greatest impact in reducing quality of life. It is important to measure change in MS-related fatigue (MS-fatigue) in response to treatment, particularly the more recent disease modifying therapies (DMTs). To date there has been no systematic literature review of the patient reported outcome (PRO) tools used to measure MS- fatigue specifically in the context of DMTs.

METHODS

MEDLINE, Embase and Clinicaltrials.gov were searched from 01 January 2000 to 13 April 2021 to identify published studies of the treatment of MS with DMTs. Studies where MS-fatigue was measured as an outcome using a PRO tool were included in the review. Further literature searches were undertaken to provide information about the development and validation of each PRO tool.

RESULTS

739 abstracts and 96 clinical trials were manually screened resulting in 68 articles for full text screening. 48 studies were identified for the review; 10 of these were RCTs that considered MS-fatigue as a secondary outcome (4 were Phase 3 trials). The PRO instruments used in the 10 RCTs were the Fatigue Scale for Motor and Cognitive Functions, Fatigue Impact Scale, Modified Fatigue Impact Scale, Fatigue Severity Scale, and Fatigue Symptoms and Impacts Questionnaire - Relapsing Multiple Sclerosis. The other 38 studies were all open-label, longitudinal, non-randomized studies and used the following PRO instruments in addition to those listed above: the Visual Analogue Scale for Fatigue, the Fatigue Descriptive Scale, Modified Fatigue Impact Scale (5 items) and the Würzburger Fatigue Inventory for MS. All these PRO tools were specifically developed for MS-fatigue. Of these 9 PRO tools, 7 were of good methodological quality according to the existing validation studies using the Consensus-based standards for the selection of health measurement instruments (COSMIN) check list and were used in the majority of the MS DMT studies (44/48, 92%). The median follow-up time from baseline to PRO measurement was 12 months (range 1-36 months). Most studies reported on MS fatigue in terms of its change from baseline and whether the change was statistically significant. 5 studies also reported what they considered to be a clinically meaningful difference.

CONCLUSIONS

Although fatigue has the greatest impact on quality of life in people with MS, few studies have rigorously investigated the impact of DMTs on fatigue. Comparisons between study outcomes using different PRO tools is challenging due to the variety of psychometric constructs addressed by the questionnaires and differences in the recall period for fatigue symptoms and the measurement scale. Furthermore most of the PRO tools used to quantify MS-fatigue in studies of DMTs are descended from PRO tools developed during the 1990s before DMTs emerged and before widespread patient involvement in PRO development. New PRO tools should involve patients in their development as recommended by the US Food and Drug Administration and the validation process should consider the sensitivity of the PRO tool to change in fatigue over time or between groups.

Fatigue and cognitive fatigability in patients with chronic pain

OBJECTIVES

Fatigue is common in patients with chronic pain. Still, there is a lack of studies examining objectively measurable cognitive aspects of fatigue: cognitive fatigability (CF). We aimed to investigate the presence of CF in patients with chronic pain and its relation to self-rated fatigue, attention, pain characteristics, sleep disturbance, depression, and anxiety.

METHODS

Two hundred patients with chronic pain and a reference group of 36 healthy subjects underwent a comprehensive neuropsychological test battery, including measurement of CF with the Wechsler Adult Intelligence Scale-III Coding subtest, and self-assessment of trait and state fatigue.

RESULTS

The patients with chronic pain did not show more CF as compared to the reference group. There was an association between CF and processing speed on a test of sustained and selective attention in the chronic pain group, while self-rated fatigue measures and pain characteristics were not associated with CF. Self-rated fatigue measures were highly correlated with self-rated pain intensity, spreading of pain, depression, anxiety, and sleep disturbance.

CONCLUSIONS

The findings highlight the distinction between objective and subjective aspects of fatigue in chronic pain, and that the underlying causes of these different aspects of fatigue need to be studied further.

Cognitive and mental fatigue in chronic pain: cognitive functions, emotional aspects, biomarkers and neuronal correlates-protocol for a descriptive cross-sectional study

INTRODUCTION

Chronic pain (CP) is one of the most frequently presenting conditions in health care and many patients with CP report mental fatigue and a decline in cognitive functioning. However, the underlying mechanisms are still unknown.

METHODS AND ANALYSIS

This study protocol describes a cross-sectional study aimed at investigating the presence of self-rated mental fatigue, objectively measured cognitive fatigability and executive functions and their relation to other cognitive functions, inflammatory biomarkers and brain connectivity in patients with CP. We will control for pain-related factors such as pain intensity and secondary factors such as sleep disturbances and psychological well-being. Two hundred patients 18-50 years with CP will be recruited for a neuropsychological investigation at two outpatient study centres in Sweden. The patients are compared with 36 healthy controls. Of these, 36 patients and 36 controls will undergo blood sampling for inflammatory markers, and of these, 24 female patients and 22 female controls, between 18 and 45 years, will undergo an functional MRI investigation. Primary outcomes are cognitive fatigability, executive inhibition, imaging and inflammatory markers. Secondary outcomes include self-rated fatigue, verbal fluency and working memory. The study provides an approach to study fatigue and cognitive functions in CP with objective measurements and may demonstrate new models of fatigue and cognition in CP.

ETHICS AND DISSEMINATION

The study has been approved by the Swedish Ethics Review Board (Dnr 2018/424-31; 2018/1235-32; 2018/2395-32; 2019-66148; 2022-02838-02). All patients gave written informed consent to participate in the study. The study findings will be disseminated through publications in journals within the fields of pain, neuropsychology and rehabilitation. Results will be spread at relevant national and international conferences, meetings and expert forums. The results will be shared with user organisations and their members as well as relevant policymakers.

TRIAL REGISTRATION NUMBER

NCT05452915.

Slowing processing speed is associated with cognitive fatigue in newly diagnosed multiple sclerosis patients

OBJECTIVE

To further investigate objective measures of cognitive fatigue (CF), defined as the inability to sustain performance over time, in newly diagnosed multiple sclerosis (MS) patients, by conducting a performance analysis on the Paced Auditory Serial Addition Test (PASAT) based on the type of errors (omissions vs. incorrect responses) committed.

METHOD

Sixty-two newly diagnosed patients with MS (pwMS) and 41 healthy controls (HC) completed the PASAT. Analysis of the change in performance during the test was performed by comparing the number of correct responses, incorrect responses, and omissions in the 1^st versus the 3^rd tertile of the PASAT.

RESULTS

A significant decline in accuracy over time was observed to be related to an increment in the number of omissions, significantly more pronounced in pwMS than in HC. No change in the number of incorrect responses throughout the PASAT was observed for either group.

CONCLUSIONS

CF can be detected even in newly diagnosed pwMS and might objectively manifest as a progressive increase in omissions during a sustained highly demanding task (i.e., PASAT). This pattern may reflect slowed processing speed and increased fatigue in pwMS. Focusing on omissions on the PASAT instead of correct responses only may improve its specificity as an objective measure of CF.

Fatigue and Human Performance: An Updated Framework

Fatigue has been defined differently in the literature depending on the field of research. The inconsistent use of the term fatigue complicated scientific communication, thereby limiting progress towards a more in-depth understanding of the phenomenon. Therefore, Enoka and Duchateau (Med Sci Sports Exerc 48:2228-38, 2016, [3]) proposed a fatigue framework that distinguishes between trait fatigue (i.e., fatigue experienced by an individual over a longer period of time) and motor or cognitive task-induced state fatigue (i.e., self-reported disabling symptom derived from the two interdependent attributes performance fatigability and perceived fatigability). Thereby, performance fatigability describes a decrease in an objective performance measure, while perceived fatigability refers to the sensations that regulate the integrity of the performer. Although this framework served as a good starting point to unravel the psychophysiology of fatigue, several important aspects were not included and the interdependence of the mechanisms driving performance fatigability and perceived fatigability were not comprehensively discussed. Therefore, the present narrative review aimed to (1) update the fatigue framework suggested by Enoka and Duchateau (Med Sci Sports Exerc 48:2228-38, 2016, [3]) pertaining the taxonomy (i.e., cognitive performance fatigue and perceived cognitive fatigue were added) and important determinants that were not considered previously (e.g., effort perception, affective valence, self-regulation), (2) discuss the mechanisms underlying performance fatigue and perceived fatigue in response to motor and cognitive tasks as well as their interdependence, and (3) provide recommendations for future research on these interactions. We propose to define motor or cognitive task-induced state fatigue as a psychophysiological condition characterized by a decrease in motor or cognitive performance (i.e., motor or cognitive performance fatigue, respectively) and/or an increased perception of fatigue (i.e., perceived motor or cognitive fatigue). These dimensions are interdependent, hinge on different determinants, and depend on body homeostasis (e.g., wakefulness, core temperature) as well as several modulating factors (e.g., age, sex, diseases, characteristics of the motor or cognitive task). Consequently, there is no single factor primarily determining performance fatigue and perceived fatigue in response to motor or cognitive tasks. Instead, the relative weight of each determinant and their interaction are modulated by several factors.

Impact of the self-directed learning approach and attitude on online learning ineffectiveness: The mediating roles of internet cognitive fatigue and flow state

Online learning has become an important learning approach in universities. However, since many students may have been exposed to online learning for the first time during this period of the COVID-19 pandemic, the quality factors of online learning and psychological distress of students need to be considered in the research on their learning. This paper discusses factors that influence the learning effect of university students in the online learning environment. A total of 377 university students participated in the survey. Structural equation modeling was used to verify the research hypotheses. The results show that the self-directed learning (SDL) approach and attitude can negatively predict students' Internet cognitive fatigue (ICF) and positively predict their Flow, whereas perceived learning ineffectiveness can be predicted by Internet cognitive fatigue positively and by Flow state negatively. The results can be a reference for online teachers to enhance students' online SDL attitude, and to discipline their SDL approach so as to promote online learning effectiveness.

Conscientiousness protects visual search performance from the impact of fatigue

Visual search-looking for targets among distractors-underlies many critical professions (e.g., radiology, aviation security) that demand optimal performance. As such, it is important to identify, understand, and ameliorate negative factors such as fatigue-mental and/or physical tiredness that leads to diminished function. One way to reduce the detrimental effects is to minimize fatigue itself (e.g., scheduled breaks, adjusting pre-shift behaviors), but this is not always possible or sufficient. The current study explored whether some individuals are less susceptible to the impact of fatigue than others; specifically, if conscientiousness, the ability to control impulses and plan, moderates fatigue's impact. Participants (N = 374) self-reported their energy (i.e., the inverse of fatigue) and conscientiousness levels and completed a search task. Self-report measures were gathered prior to completing the search task as part of a large set of surveys so that participants could not anticipate any particular research question. Preregistered linear mixed-effect analyses revealed main effects of energy level (lower state energy related to lower accuracy) and conscientiousness (more trait conscientiousness related to higher accuracy), and, critically, a significant interaction between energy level and conscientiousness. A follow-up analysis, that was designed to illustrate the nature of the primary result, divided participants into above- vs. below-median conscientiousness groups and revealed a significant negative relationship between energy level and accuracy for the below median, but not above-median, group. The results raise intriguing operational possibilities for visual search professions, with the most direct implication being the incorporation of conscientiousness measures to personnel selection processes.

Assessment of Saccades and Gaze Stability in the Diagnosis of Pediatric Concussion

OBJECTIVE

To evaluate the discriminatory ability of different repetition increments of saccades and gaze stability testing for diagnosing concussion in adolescents.

DESIGN

Cross-sectional.

SETTING

Suburban high school and academic pediatric tertiary care center.

PARTICIPANTS

Sixty-nine adolescent athletes within 28 days of a sports- or recreation-related concussion and 69 adolescent athletes without recent concussion.

ASSESSMENT OF INDEPENDENT VARIABLES

Symptom provocation with horizontal and vertical saccades and gaze stability testing performed up to 30 repetitions.

MAIN OUTCOME MEASURES

Sensitivity and specificity at 10-repetition increments (≤10, ≤20, ≤30) and area under the receiver operating characteristic curves (AUC) of a visio-vestibular examination (VVE) subscore, scored 0 to 4 based on the number of assessments with symptom provocation, at each repetition increment.

RESULTS

Sensitivity improved when increasing from ≤10 to ≤20 to ≤30 repetitions for horizontal (25% to 50% to 69%) and vertical (32% to 52% to 74%) saccades and horizontal (19% to 45% to 71%) and vertical (23% to 45% to 72%) gaze stability. Specificity was comparable at ≤10 and ≤20 repetitions, but decreased at ≤30 repetitions across assessments. For a VVE subscore (0-4) based on the number of symptomatic assessments, the discriminatory ability of the test was highest at ≤20 repetitions (AUC of 0.79) with an optimal subscore of one (sensitivity 59%, specificity 96%).

CONCLUSIONS

A VVE including a higher threshold level of repetitions for saccades and gaze stability has improved discriminatory ability for concussion, with an optimized AUC of 0.79 at ≤20 repetitions.

CLINICAL RELEVANCE

The findings in this study suggest that a higher threshold level of repetitions of 2 commonly used visio-vestibular assessments enables clinicians to more accurately diagnose youth concussion.

Experienced fatigue in people with rare disorders: a scoping review on characteristics of existing research

BACKGROUND

Experienced fatigue is an under-recognized and under-researched feature in persons with many different rare diseases. A better overview of the characteristics of existing research on experienced fatigue in children and adults with rare diseases is needed. The purpose of this review was to map and describe characteristics of existing research on experienced fatigue in a selection of rare diseases in rare developmental defects or anomalies during embryogenesis and rare genetic diseases. Furthermore, to identify research gaps and point to research agendas.

METHODS

We applied a scoping review methodology, and performed a systematic search in March 2020 in bibliographic databases. References were sorted and evaluated for inclusion using EndNote and Rayyan. Data were extracted on the main research questions concerning characteristics of research on experienced fatigue (definition and focus on fatigue, study populations, research questions investigated and methods used).

RESULTS

This review included 215 articles on ten different rare developmental defects/anomalies during embryogenesis and 35 rare genetic diseases. Of the 215 articles, 82 had investigation of experienced fatigue as primary aim or outcome. Included were 9 secondary research articles (reviews) and 206 primary research articles. A minority of articles included children. There were large differences in the number of studies in different diseases. Only 29 of 215 articles gave a description of how they defined the concept of experienced fatigue. The most common research-question reported on was prevalence and/ -or associations to fatigue. The least common was diagnostics (development or validation of fatigue assessment methods for a specific patient group). A large variety of methods were used to investigate experienced fatigue, impeding comparisons both within and across diagnoses.

CONCLUSION

This scoping review on the characteristics of fatigue research in rare diseases found a large variety of research on experienced fatigue. However, the minority of studies had investigation of experienced fatigue as a primary aim. There was large variation in how experienced fatigue was defined and also in how it was measured, both within and across diagnoses. More research on experienced fatigue is needed, both in children and adults with rare diseases. This review offers a basis for further research.

Cognitive fatigability assessment test (cFAST): Development of a new instrument to assess cognitive fatigability and pilot study on its association to perceived fatigue in multiple sclerosis

Background

Fatigue is a common symptom of many diseases, including multiple sclerosis. It manifests as a cognitive or physical condition. Fatigue is poorly understood, and effective therapies are missing. Furthermore, there is a lack of methods to measure fatigue objectively. Fatigability, the measurable decline in performance during a task, has been suggested as a complementary method to quantify fatigue.

Objective

To develop a new and objective measurement of cognitive fatigability and investigate its association with perceived fatigue.

Methods

We introduced the cognitive fatigability assessment test (cFAST), a novel smartphone-based test to quantify cognitive fatigability. Forty-two people with multiple sclerosis (23 fatigued and 19 non-fatigued, defined by the Fatigue Scale for Motor and Cognitive Functions) took part in our validation study. Patients completed cFAST twice. We used t-tests, Monte Carlo sampling, and area under the receiver operating characteristic curves to evaluate our approach using two sets of proposed metrics.

Results

When classifying fatigue, our fatigability metric Δresponse time has a mean area under the receiver operating characteristic curve of 0.74 (95% CI 0.64–0.84), making it the best performing metric for this task. Furthermore, Δresponse time shows a statistically significant difference between the fatigued and non-fatigued groups (t = 2.27, P = .03). Particularly, cognitively-fatigued patients decline in performance, while non-fatigued patients do not.

Conclusions

We introduce cFAST, a new instrument to quantify cognitive fatigability. Our pilot study provides evidence that cognitive fatigability assessment test produces a quantifiable drop in cognitive performance in a short period. Furthermore, our results indicate that cFAST may have the potential to serve as a surrogate for subjective cognitive fatigue. cFAST is significantly shorter than the existing fatigability assessments and does not require specialized equipment. Thus, it could enable frequent and remote monitoring, which could substantially aid clinicians in better understanding and treating fatigue.

Predictors of cognitive fatigue and fatigability in multiple sclerosis

BACKGROUND

Persons with multiple sclerosis (PwMS) commonly experience cognitive fatigue (CF), defined as a decrease in cognitive performance with sustained activity, yet CF remains understudied. Further, the relationship between subjective CF and objective CF, or cognitive fatiguability, has not been fully elucidated in previous studies. Understanding the predictors of cognitive fatigue may scaffold the development of interventions that target this symptom. The objective of this prospective study was to evaluate the extent to which depression, anxiety, information processing speed, and sleep quality predict subjective and objective CF.

METHODS

PwMS were recruited from one academic MS clinic in London (ON) Canada. Objective CF was measured by the Paced Auditory Serial Addition Test (PASAT), where performance on the last third of the PASAT is compared to performance on the 1st third, a validated measurement of objective CF. Subjective CF was measured by the cognitive component of the Modified Fatigue Impact Scale (MFIS). Additionally, depression, anxiety, information processing speed, and sleep quality data was collected. All assessments took place on the same day. Pearson's r was calculated to examine the relationship among all continuous outcome measures while linear regression analyses were used to examine predictors of subjective and objective CF.

RESULTS

The sample consisted of 53 subjects who were mostly female (37; 69.8%) with a mean age of 44.2 years; the majority (47; 88.7%) had relapsing MS. Objective CF and subjective CF were not significantly related (r = - 0.16). Further, there was no statistically significant predictors of objective CF noted. In contrast, subjective CF demonstrated a statistically significant relationship with the Symbol Digit Modalities Test (SDMT; r = - 0.29, p = .05), Hospital Anxiety and Depression Scale (HADS), depression subscale (r = 0.61, p < .001), HADS anxiety subscale (r = 0.54, p < .001), and sleep quality (r = 0.33, p = .02). Additionally, all variables predicted subjective CF, R²_adj = 0.384 [F (6, 40) = 5.783, p = .0002]. In particular, anxiety significantly predicted subjective CF when controlling for depression, information speed, and sleep quality.

CONCLUSION

This study demonstrated that subjective CF is significantly predicted by anxiety, and strongly influenced by information processing impairment and depression. Addressing underlying affective factors, such as anxiety or depression, may help alleviate perceived or subjective CF among PwMS, thus improving their function and quality of life. Further studies with a larger sample size or longitudinal follow up may help define predictors of objective CF.

Cognitive Fatigue Predicts Cognitive Failure in Multiple Sclerosis Patients and Healthy Controls: A Case-Control Study

OBJECTIVE

Fatigue and cognitive deficits are frequent symptoms of multiple sclerosis (MS). However, the exact nature of their co-occurrence is not fully understood. We sought to determine the impact of cognitive and physical fatigue on subjective cognitive deficits in MS patients and healthy controls.

METHODS

Self-reports of fatigue (FSMC), depression (CES-D), cognitive deficits (CFQ), and personality traits (NEO-FFI, ANPS) among 30 MS inpatients and 30 healthy controls were analyzed using hierarchical regression models. The frequency of cognitive mistakes was used as the dependent variable and the extent of cognitive and physical fatigue as the independent variable.

RESULTS

Cognitive fatigue was the only unique and significant predictor of cognitive mistakes in both groups, explaining 13.3% of additional variance in the MS group after correcting for age, mood, and physical fatigue. Physical fatigue had no significant impact on cognitive mistakes. While age had an impact on cognitive mistakes and depression in healthy controls, this association was not significant in MS patients. Depression was significantly correlated with cognitive mistakes and cognitive fatigue in MS patients.

CONCLUSIONS

The interplay of cognitive fatigue and subjective cognitive impairment can be generalized, with the exception of the variables of age and depression, which were shown to have differing impacts on cognitive mistakes in MS patients and healthy controls, respectively. Cognitive fatigue was linked to cognitive mistakes even after correcting for overlapping items in MS patients only. Future research should further investigate the link between cognitive fatigue and attention lapses in daily life by using various objective assessments.

Cognitive fatigue interventions for people with multiple sclerosis: A scoping review

BACKGROUND

Fatigue is a common symptom experienced by people with multiple sclerosis (MS) and can be categorized as physical or cognitive fatigue. The existing body of literature mostly focuses on physical fatigue in MS and there is limited research on cognitive fatigue and interventions to effectively manage cognitive fatigue in this cohort. Therefore, the aim of this scoping review is to identify and summarize available research literature about different types of interventions to manage cognitive fatigue to provide a comprehensive perspective on treatment options.

METHODS

The PRISMA Extension for Scoping Reviews methodology was used. Searches were conducted in May 2021 in the following databases: CINAHL Plus with Full Text, MEDLINE via Ovid, PsycINFO, Embase via Ovid, and ProQuest Dissertations and Theses Global. The inclusion criteria were: peer-reviewed journal articles written in English or French that included an intervention to manage MS cognitive fatigue. Search keywords included multiple sclerosis, cognitive fatigue, and intervention. All retrieved citations' titles and abstracts were screened, and eligible articles were fully reviewed by two reviewers. The included studies were categorized based on the type of intervention, and effect size were calculated to estimate the effectiveness of the interventions.

RESULTS

Of 653 retrieved citations, 34 were retained for this review. Participants of the included studies were mostly middle-aged adults with relapsing-remitting MS, without severe mobility issues, who were living with MS for about 10 years on average. The majority of studies were randomized controlled trials (n = 17), followed by pilot and feasibility trials (n = 4), case-control (n = 2), and other experimental designs (n = 11). The interventions were categorized as educational programs (such as self-management programs, diet, and counselling) (n = 18), medical and pharmacological (such as monoaminergic stabilizers, natalizumab, and dalfampridine) (n = 6), and exercise and physical interventions (such as resistance training, aquatic exercise, and walking) (n = 10). Of the included interventions, fatigue self-management interventions that incorporate educational materials and involve trained facilitators seem to be optimal for reducing the negative effects of cognitive fatigue.

CONCLUSION

This review identified a variety of interventions for MS cognitive fatigue management. However, there is not sufficient evidence leading to a clear recommendation about appropriate and effective approaches for cognitive fatigue management. More research in this field is needed.

Usability and Effectiveness of Immersive Virtual Grocery Shopping for Assessing Cognitive Fatigue in Healthy Controls: Protocol for a Randomized Controlled Trial

BACKGROUND

Cognitive fatigue (CF) is a human response to stimulation and stress and is a common comorbidity in many medical conditions that can result in serious consequences; however, studying CF under controlled conditions is difficult. Immersive virtual reality provides an experimental environment that enables the precise measurement of the response of an individual to complex stimuli in a controlled environment.

OBJECTIVE

We aim to examine the development of an immersive virtual shopping experience to measure subjective and objective indicators of CF induced by instrumental activities of daily living.

METHODS

We will recruit 84 healthy participants (aged 18-75 years) for a 2-phase study. Phase 1 is a user experience study for testing the software functionality, user interface, and realism of the virtual shopping environment. Phase 2 uses a 3-arm randomized controlled trial to determine the effect that the immersive environment has on fatigue. Participants will be randomized into 1 of 3 conditions exploring fatigue response during a typical human activity (grocery shopping). The level of cognitive and emotional challenges will change during each activity. The primary outcome of phase 1 is the experience of user interface difficulties. The primary outcome of phase 2 is self-reported CF. The core secondary phase 2 outcomes include subjective cognitive load, change in task performance behavior, and eye tracking. Phase 2 uses within-subject repeated measures analysis of variance to compare pre- and postfatigue measures under 3 conditions (control, cognitive challenge, and emotional challenge).

RESULTS

This study was approved by the scientific review committee of the National Institute of Nursing Research and was identified as an exempt study by the institutional review board of the National Institutes of Health. Data collection will begin in spring 2021.

CONCLUSIONS

Immersive virtual reality may be a useful research platform for simulating the induction of CF associated with the cognitive and emotional challenges of instrumental activities of daily living.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04883359; http://clinicaltrials.gov/ct2/show/NCT04883359.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/28073.

Does Intensive Training of Attention Influence Cognitive Fatigability in Patients With Acquired Brain Injury?

Research Objectives

Impairments in attention and the speed of information processing are central to the experience of cognitive fatigue in patients with acquired brain injury (ABI). Attention may be improved through intensive training in a rehabilitation setting. The aim of the study was to investigate the feasibility of reducing cognitive fatigability (CF) using attention training and to explore the effect of two different approaches to attention training.

Design

Randomised controlled study in a rehabilitation setting.

Participants

59 patients (age 19-59 years) with mild to moderate stroke or traumatic brain injury in the early (<4 month) phase.

Interventions

Patients were randomly assigned to intensive specific training with Attention Process Training (APT) or Activity-Based Attention Training (ABAT) for 3-5 days per week for a period of 5-6 weeks with a total of 20 h, in addition to traditional interdisciplinary rehabilitation.

Main Outcome Measure

CF was conceptualised as performance decline in terms of an increased number of incorrect responses between the first and the last quintiles of the Paced Auditory Serial Addition Test (PASAT). A negative result was defined as fatigability. The evaluator of fatigability was blinded to treatment.

Results

At baseline, there were no differences between the groups in age, education, reasoning, anxiety or depression. After training, a significant treatment effect was found (p = 0.020), as the APT-group, but not the ABAT-group, had improved. However, after controlling for baseline differences regarding CF on the PASAT-f, the difference was no longer significant.

Conclusion

The results indicate that cognitive training might be a feasible method for reducing CF through attention training and that patients with high levels of CF benefit most from attention training. The type of intervention provided, whether specific or activity-based attention training, appears to be of less importance, as there was no treatment effect after controlling for the baseline level of CF. Future studies are required to confirm the validity of the findings.

Biomarker-Informed Machine Learning Model of Cognitive Fatigue from a Heart Rate Response Perspective

Cognitive fatigue is a psychological state characterised by feelings of tiredness and impaired cognitive functioning arising from high cognitive demands. This paper examines the recent research progress on the assessment of cognitive fatigue and provides informed recommendations for future research. Traditionally, cognitive fatigue is introspectively assessed through self-report or objectively inferred from a decline in behavioural performance. However, more recently, researchers have attempted to explore the biological underpinnings of cognitive fatigue to understand and measure this phenomenon. In particular, there is evidence indicating that the imbalance between sympathetic and parasympathetic nervous activity appears to be a physiological correlate of cognitive fatigue. This imbalance has been indexed through various heart rate variability indices that have also been proposed as putative biomarkers of cognitive fatigue. Moreover, in contrast to traditional inferential methods, there is also a growing research interest in using data-driven approaches to assessing cognitive fatigue. The ubiquity of wearables with the capability to collect large amounts of physiological data appears to be a major facilitator in the growth of data-driven research in this area. Preliminary findings indicate that such large datasets can be used to accurately predict cognitive fatigue through various machine learning approaches. Overall, the potential of combining domain-specific knowledge gained from biomarker research with machine learning approaches should be further explored to build more robust predictive models of cognitive fatigue.

Early neuropsychological markers of cognitive involvement in multiple sclerosis

BACKGROUND

Cognitive impairment due to multiple sclerosis (MS) is common and often limits occupational functioning, contributes to disability, and reduces quality of life. Early detection of cognitive involvement in MS is critical for treatment planning and intervention, and frequent, regular cognitive monitoring may provide insight into subtle changes in disease progression.

OBJECTIVE

To compare the sensitivity and specificity of clinical, computer-based and experimental measures to early cognitive involvement in MS.

METHODS

Cognitive functioning was compared in MS participants early in the disease course to matched healthy controls using conventional, computer-based and functional assessments: the Brief International Cognitive Assessment in MS (BICAMS); the computer-based Cogstate Brief Battery (CBB); the Attention Network Test-Interaction (ANT-I), including intra-individual variability; and the Test of Everyday Cognitive Ability (TECA), a functional measure of instrumental activities of daily living.

RESULTS

MS participants (n = 25, mean disease duration= 5.82 ± 3.65 years) and demographically matched healthy controls (n = 29) completed the cognitive assessments. The Cogstate measure of choice reaction time (AUC = 0.73, p = .004), intra-individual variability on the ANT-I (AUC = 0.79, p = .001), and TECA (AUC = 0.78, p = .001) scores were the most sensitive and specific markers of cognitive involvement in MS.

CONCLUSIONS

Brief, repeatable, computer-based measures of reaction time and variability detect early MS associated cognitive involvement.

Cognitive Fatigability is Independent of Subjective Cognitive Fatigue and Mood in Multiple Sclerosis

BACKGROUND

Sustained cognitive testing is used to detect cognitive fatigability and is often considered a substitute for subjective cognitive fatigue (CF). However, the relationship between cognitive fatigability and subjective CF in people with multiple sclerosis (PwMS) remains undetermined.

OBJECTIVE

To explore potential associations between fatigability induced by sustained cognitive testing and subjective CF in PwMS.

METHODS

We gave 120 PwMS and 60 demographically matched, healthy individuals the Beck Depression Inventory-FastScreen (BDI-FS) to measure mood and the Modified Fatigue Impact Scale to measure CF. In addition, we used the Quotient ADHD Test, a sustained attention test, to measure cognitive fatigability. We also explored potential correlations between the individuals' performance on the sustained attention test and thalamic volume using recent MRI scans.

RESULTS

Forty-one (34.2%) of the PwMS exhibited cognitive fatigability. These 41 were found to be significantly older (P=0.006), had been diagnosed with the disease for longer (P=0.03), had higher scores (P<0.001) on the Expanded Disability Status Scale, and had reduced thalamic volume (P=0.04) compared with the 79 (65.8%) PwMS not exhibiting cognitive fatigability. The PwMS exhibiting cognitive fatigability scored similarly on the BDI-FS (P=0.21) and self-reported similar rates of CF (P=0.62) as the PwMS not exhibiting cognitive fatigability.

CONCLUSION

Cognitive fatigability induced by sustained cognitive testing is not an accurate clinical alternative to subjective CF. This study provides evidence to support cognitive fatigability and CF in PwMS as two distinct concepts.

Walking and cognitive performance in adults with multiple sclerosis: Do age and fatigability matter?

BACKGROUND

Co-occurring walking and cognitive performance deficits are debilitating consequences of multiple sclerosis (MS) that worsen with age. However, it is unknown if fatigability influences such age-related worsening of walking and cognitive performance.

OBJECTIVE

This cross-sectional study examined possible age-related differences in walking-related motor fatigability (incremental six-minute-walk (6MW) performance) and cognitive fatigability (incremental Symbol Digit Modalities Test (SDMT) performance) in adults with MS.

METHODS

196 adults with MS were categorized into age-groups: younger (20-39 years; n = 53), middle-aged (40-59 years; n = 89), and older (60-79 years; n = 54), and completed the 6MW and SDMT. Age-group differences in incremental 6MW and SDMT performance, controlling for disability status, were examined using separate, mixed-factor ANCOVAs.

RESULTS

There were no statistically significant age-group-by-time interactions on walking-related motor or cognitive fatigability when controlling for disability. However, there were significant main effects of time on incremental 6MW (p = 0.01) and SDMT (p < 0.01) performance indicating the presence of walking-related motor and cognitive fatigability, respectively, collapsed across age-groups.

CONCLUSION

Fatigability does not exert a primary influence on age-related worsening of walking and cognitive neuroperformance outcomes among adults with MS. This suggests that walking-related motor fatigability and cognitive fatigability may not be optimal targets for mitigating age-related declines in ambulation and cognition among adults with MS.

Cognitive Fatigability Interventions in Neurological Conditions: A Systematic Review

INTRODUCTION

Although fatigue is a well-studied concept in neurological disease, cognitive fatigability (CF) is less understood. While most studies measure fatigue using subjective self-report, fewer have measured CF objectively. Given the negative impact of CF on quality-of-life, there is a need for targeted interventions. The objective of this review was to determine which procedural, behavioural and pharmacological treatments for objectively measured CF are available to people living with neurological conditions.

METHODS

In accordance with the PRISMA guidelines, systematic searches for randomized control trials (RCTs), case-controlled studies and case reports/series were conducted across the Ovid Medline, PsycInfo, EMBASE and Cochrane Library databases. English-language articles published between 1980 and February 2019 were considered for eligibility. Included were those that objectively measured CF in individuals with neurological disease/disorder/dysfunction between the ages of 18 and 65 years. Studies were reviewed using a modified Cochrane Data Extraction Template. Risk of bias was assessed using the Cochrane Risk of Bias tool. The review process was facilitated using Covidence software (www.covidence.org). Two authors reviewed articles independently, with a third resolving conflicts regarding article inclusion.

RESULTS

The search identified 450 records. After duplicates were removed and remaining titles/abstracts were screened for eligibility, 28 full-text articles were assessed, and two studies were included in the qualitative synthesis. Studies were a priori divided into those with pharmacological, procedural or behavioural interventions. Two studies met eligibility criteria; both of these included participants with multiple sclerosis. One study utilized a procedural intervention (i.e. transcranial direct current stimulation), while the other utilized a pharmacological intervention (i.e. fampridine-SR). Studies were evaluated for risk of bias, and evidence from both eligible studies was discussed.

CONCLUSION

Despite the positive results of the procedural intervention, the paucity of eligible studies and the nascent nature of the field suggests that more studies are required before firm conclusions can be drawn regarding the amenability of CF to treatment.

TRIAL REGISTRATION

The review was registered with PROSPERO (CRD42019118706).

Cognitive fatigability is a quantifiable distinct phenomenon in multiple sclerosis

Cognitive fatigability in multiple sclerosis represents the decrease in cognitive performance over time. It is a frequent symptom that negatively affects quality of life and ability to work. There are no objective measures of cognitive fatigability. This study aimed at quantifying cognitive fatigability despite the learning effect and to clarify whether cognitive fatigability represents a free-standing phenomenon rather than an aspect of cognitive impairment. We measured information processing speed with the Symbol Digit Modalities Test, and the number of right answers was recorded every 30 s for 180 s. We approximated the number of right answers as function of time with two logarithmic models, one including a first-order term alone and the other adding also a second-order term. The coefficient of the latter (B) may quantify performance deflection and may represent cognitive fatigability. We tested 173 patients with multiple sclerosis, including 119 cognitively impaired and 54 cognitively preserved patients, and 35 healthy subjects. The performance of cognitively preserved patients showed a deflection at the end of task that was detected neither in controls nor in cognitively impaired patients and needed a second-order term to be approximated (p < .03, F = 14.02). B was explained neither by depression nor fatigue. We proposed for the first time a method to quantify cognitive fatigue via a second-order least square fit model, easily usable in the clinical practice. By using this novel approach, cognitive fatigability results to be a free-standing phenomenon that is more evident in cognitively preserved than in cognitive impaired patients.

The SwAD-Task – An Innovative Paradigm for Measuring Costs of Switching Between Different Attentional Demands

Task switching paradigms are frequently used to identify costs of switching between modalities, spatiality, attributes, rules, etc., but switching between different attentional demands has been somehow neglected. The present study introduces an innovative paradigm, that allows to test single attentional demands (such as selective and divided attention), and more importantly the process of switching between these demands. We examined the feasibility of the paradigm by focusing on the demands of selective and divided attention with a sample of 94 people (age: M = 21.44 years, SD = 2.68; 76 women). In addition, we tested correlations between the implemented single attentional demands and commonly used measures of selective and divided attention. Results show no general difference between individual assessments under single demand conditions. Reaction times under divided attention are significantly higher compared to selective attention. In the switching condition, reaction times in both demands increase with increased switching. Furthermore, switching costs significantly increase in selective but not in divided attention. Means of selective and divided attention in single and switching conditions significantly correlate with a commonly used measure of selective attention. Means of divided attention under single demand significantly correlate with performance in a commonly used dual-task paradigm. Summarizing the present findings, it can be stated that the introduced paradigm comprises a feasible way for quantifying the process of switching attention between different demands.

An observational study of trait and state fatigue, and their relation to cognitive fatigability and saccade performance

Aim:

Different fatigue measurements and their relation to saccadic functions were investigated in 15 patients with a mild traumatic brain injury (mTBI) and 15 orthopedic controls.

Materials & methods:

State fatigue was measured with the Fatigue Severity Scale and trait fatigue with the question on fatigue in the Rivermead Post Concussion Questionnaire and fatigability as decreased performance over time on a neuropsychological measure.

Results:

Patients with an mTBI scored significantly higher in state fatigue and showed more fatigability compared with the orthopedic controls. Among patients with mTBI, state fatigue correlated with prosaccade latency and cognitive fatigability, while trait fatigue correlated with anxiety and antisaccade latency and variability.

Conclusion:

This pilot study indicates that saccade measurements might, in the future, be useful in the understanding of fatigue and in the search for prognostic factors after mTBI.

Motivation in multiple sclerosis cognitive fatigue: An experimental approach

Introduction: Cognitive fatigue is a common symptom in multiple sclerosis (MS). Recent research has implicated dopaminergic pathways originating in the basal ganglia as neurological correlates of cognitive fatigue in MS. This same system has long been associated with goal-directed behavior and reward-based motivation. While researchers have demonstrated that reward has a reliable impact on performance in tasks of sustained attention in healthy individuals, the effect of reward on fatigue is less clear, as prior research has not adequately controlled for desensitization to reward in a sustained attention task. The primary aims of this study were to examine the effect of reward on attention in MS patients, and to examine the effect of reward on objective cognitive fatigue. Method: The study employed a 3 × 3 repeated measures design to evaluate performance of N = 64 patients with definite MS on a measure of cognitive fatigue across several reward conditions. The study utilized a novel delayed-reward paradigm to better control the measured effect of reward on fatigue. Results: Reward (main effect) displayed a significant effect on overall performance (F = 3.050, p < .05). Reward was also shown to affect fatigue trajectory (Reward × Interval, F = 2.433, p < .05). However, this effect was dependent on the method of reward administration. Conclusions: Study findings support the role of motivation in MS cognitive performance, particularly in objective cognitive fatigue, a behavioral finding that is consistent with current neuropsychological theory. Study findings support the delayed-reward paradigm as an effective method for measuring reward effect on tasks of sustained attention.

Negative Binomial Models for Visual Fixation Counts on Test Items

With the development of technology-enhanced learning platforms, eye-tracking biometric indicators can be recorded simultaneously with students item responses. In the current study, visual fixation, an essential eye-tracking indicator, is modeled to reflect the degree of test engagement when a test taker solves a set of test questions. Three negative binomial regression models are proposed for modeling visual fixation counts of test takers solving a set of items. These models follow a similar structure to the lognormal response time model and the two-parameter logistic item response model. The proposed modeling structures include individualized latent person parameters reflecting the level of engagement of each test taker and two item parameters indicating the visual attention intensity and discriminating power of each test item. A Markov chain Monte Carlo estimation method is implemented for parameter estimation. Real data are fitted to the three proposed models, and the results are discussed.

Cognitive Fatigue in Multiple Sclerosis: An Objective Approach to Diagnosis and Treatment by Transcranial Electrical Stimulation

Cognitive fatigue is one of the most frequent symptoms in multiple sclerosis (MS), associated with significant impairment in daily functioning and quality of life. Despite its clinical significance, progress in understanding and treating fatigue is still limited. This limitation is already caused by an inconsistent and heterogeneous terminology and assessment of fatigue. In this review, we integrate previous literature on fatigue and propose a unified schema aiming to clarify the fatigue taxonomy. With special focus on cognitive fatigue, we survey the significance of objective behavioral and electrophysiological fatigue parameters and discuss the controversial literature on the relationship between subjective and objective fatigue assessment. As MS-related cognitive fatigue drastically affects quality of life, the development of efficient therapeutic approaches for overcoming cognitive fatigue is of high clinical relevance. In this regard, the reliable and valid assessment of the individual fatigue level by objective parameters is essential for systematic treatment evaluation and optimization. Transcranial electrical stimulation (tES) may offer a unique opportunity to manipulate maladaptive neural activity underlying MS fatigue. Therefore, we discuss evidence for the therapeutic potential of tES on cognitive fatigue in people with MS.

Neural Indicators of Fatigue in Chronic Diseases: A Systematic Review of MRI Studies

While fatigue is prevalent in chronic diseases, the neural mechanisms underlying this symptom remain unknown. Magnetic resonance imaging (MRI) has the potential to enable us to characterize this symptom. The aim of this review was to gather and appraise the current literature on MRI studies of fatigue in chronic diseases. We systematically searched the following databases: MedLine, PsycInfo, Embase and Scopus (inception to April 2016). We selected studies according to a predefined inclusion and exclusion criteria. We assessed the quality of the studies and conducted descriptive statistical analyses. We identified 26 studies of varying design and quality. Structural and functional MRI, alongside diffusion tensor imaging (DTI) and functional connectivity (FC) studies, identified significant brain indicators of fatigue. The most common regions were the frontal lobe, parietal lobe, limbic system and basal ganglia. Longitudinal studies offered more precise and reliable analysis. Brain structures found to be related to fatigue were highly heterogeneous, not only between diseases, but also for different studies of the same disease. Given the different designs, methodologies and variable results, we conclude that there are currently no well-defined brain indicators of fatigue in chronic diseases.

A Longitudinal Evaluation of Cognitive Fatigue on a Task of Sustained Attention in Early Relapsing-Remitting Multiple Sclerosis

Background

Cognitive fatigue can be objectively measured on tasks of sustained attention and can be defined as decreased performance as a result of sustained cognitive effort. Individuals with multiple sclerosis (MS) early in their disease are vulnerable to cognitive fatigue, although this has yet to be evaluated longitudinally. We aimed to evaluate cognitive fatigue over a 3-year interval in individuals with early-phase relapsing-remitting MS (RRMS). The sensitivity of the Paced Auditory Serial Addition Test (PASAT) at detecting cognitive fatigue was evaluated, as was the impact of scoring method.

Methods

32 people with MS and 32 controls completed the 3- and 2-second PASAT (PASAT-3″ and -2″) as a measure of sustained attention at baseline and 3-year follow-up.

Results

Performance on the PASAT remained stable across time, with improvement noted on the PASAT-2″ likely due to practice and the small sample size. Cognitive fatigue was noted at both times, although sensitivity varied based on scoring method. No evidence of worsening cognitive fatigue was noted over time. The MS group performed worse only when cognitive fatigue was the outcome variable.

Conclusions

Although individuals with MS continue to be vulnerable to cognitive fatigue at follow-up, severity does not seem to increase with time. Cognitive fatigue may be a more sensitive marker of cognitive impairment than overall task performance in those with early-phase RRMS, which has important implications given that clinically only task performance is typically assessed.

Fatigue and Cognitive Fatigability in Mild Traumatic Brain Injury are Correlated with Altered Neural Activity during Vigilance Test Performance

Introduction

Fatigue is the most frequently reported persistent symptom following a mild traumatic brain injury (mTBI), but the explanations for the persisting fatigue symptoms in mTBI remain controversial. In this study, we investigated the change of cerebral blood flow during the performance of a psychomotor vigilance task (PVT) by using pseudo-continuous arterial spin labeling (PCASL) MRI technique to better understand the relationship between fatigability and brain activity in mTBI.

Material and methods

Ten patients (mean age: 37.5 ± 11.2 years) with persistent complaints of fatigue after mTBI and 10 healthy controls (mean age 36.9 ± 11.0 years) were studied. Both groups completed a 20-min long PVT inside a clinical MRI scanner during simultaneous measurements of reaction time and regional cerebral blood flow (rCBF) with PCASL technique. Cognitive fatigability and neural activity during PVT were analyzed by dividing the performance and rCBF data into quintiles in addition to the assessment of self-rated fatigue before and after the PVT.

Results

The patients showed significant fatigability during the PVT while the controls had a stable performance. The variability in performance was also significantly higher among the patients, indicating monitoring difficulty. A three-way ANOVA, modeling of the rCBF data demonstrated that there was a significant interaction effect between the subject group and performance time during PVT in a mainly frontal/thalamic network, indicating that the pattern of rCBF change for the mTBI patients differed significantly from that of healthy controls. In the mTBI patients, fatigability at the end of the PVT was related to increased rCBF in the right middle frontal gyrus, while self-rated fatigue was related to increased rCBF in left medial frontal and anterior cingulate gyri and decreases of rCBF in a frontal/thalamic network during this period.

Discussion

This study demonstrates that PCASL is a useful technique to investigate neural correlates of fatigability and fatigue in mTBI patients. Patients suffering from fatigue after mTBI used different brain networks compared to healthy controls during a vigilance task and in mTBI, there was a distinction between rCBF changes related to fatigability vs. perceived fatigue. Whether networks for fatigability and self-rated fatigue are different, needs to be investigated in future studies.

The impact of subjective cognitive fatigue and depression on cognitive function in patients with multiple sclerosis

BACKGROUND

The association between subjective cognitive fatigue and objective cognitive dysfunction in patients with multiple sclerosis (PwMS) has been studied, with conflicting results.

OBJECTIVE

To explore the impact of fatigue on cognitive function, while controlling for the influence of depression, disability, comorbidities, and psychotropic medications.

METHODS

PwMS completed a computerized cognitive testing battery with age- and education-adjusted cognitive domain scores. Disability (Expanded Disability Status Scale (EDSS)), cognitive fatigue, and depression were concurrently evaluated.

RESULTS

In all, 699 PwMS were included. Both cognitive fatigue and depression were significantly and negatively correlated with the same cognitive domains: information processing speed, executive function, attention, motor function, and memory (-0.15 ⩽ r ⩽ -0.14 for cognitive fatigue; -0.24 ⩽ r ⩽ -0.19 for depression). Multivariate analysis revealed significant but small independent correlations only between depression and neuropsychological test results, while cognitive fatigue had no independent correlation with objective cognitive function except for a trend toward impaired motor function in highly fatigued PwMS. Depression and cognitive fatigue accounted for no more than 6% of the variance in objective cognitive domain scores.

CONCLUSION

Cognitive fatigue is not independently related to objective cognitive impairment. Depression may influence cognitive function of PwMS primarily when it is severe. Cognitive impairment in PwMS should not be ascribed to fatigue or mild depression.

Operationalising cognitive fatigability in multiple sclerosis: A Gordian knot that can be cut?

BACKGROUND

Researchers have attempted to operationalise objective measures of cognitive fatigability in multiple sclerosis (MS) to overcome the perceived subjectivity of patient-reported outcomes of fatigue (PROs). Measures of cognitive fatigability examine decrements in performance during sustained neurocognitive tasks.

OBJECTIVE

This personal viewpoint briefly summarises available evidence for measures of cognitive fatigability in MS and considers their overall utility.

RESULTS

Studies suggest there may be a construct that is distinct from self-reported fatigue, reflecting a new potential intervention target. However, assessments vary and findings across and within measures are inconsistent. Few measures have been guided by a coherent theory, and those identified are likely to be influenced by other confounds, such as cognitive impairment caused more directly by disease processes, depression and assessment biases.

CONCLUSION

Future research may benefit from (a) developing a guiding theory of cognitive fatigability, (b) examining ecological and construct validity of existing assessments and (c) exploring whether the more promising cognitive fatigability measures are correlated with impaired functioning after accounting for possible confounds. Given the issues raised, we caution that our purposes as researchers may be better served by continuing our search for a more objective cognitive fatigability construct that runs in parallel with improving, rather than devaluing, current PROs.

The effect of Fampridine-SR on cognitive fatigue in a randomized double-blind crossover trial in patients with MS

BACKGROUND

Cognitive fatigue (CF) is a common complaint in persons with MS (PwMS). Fampridine-SR improves ambulation, fatigue and endurance, due to enhancing action potential formation by blocking potassium channels in demyelinated axons. Thus, through this same mechanism, it is hypothesized that Fampridine-SR could improve CF.

OBJECTIVE

To determine if Fampridine-SR objectively improves CF in PwMS.

METHODS

Sixty PwMS of any type with CF, defined as 3 or less correct responses when comparing the last third to the first third on the Paced Auditory Serial Addition Test (PASAT), were recruited from a tertiary care MS clinic in London (ON) Canada. Subjects also had to be between 18 and 64 years of age, inclusive, not had a relapse in the last 60 days or corticosteroids in the last 30 days, EDSS 0.0-7.0, and no other diagnosis that could cause cognitive impairment. A randomized double blind crossover design was used: subjects were randomized to either placebo or Fampridine-SR for 4 weeks, then after at least a one week washout, received the opposite treatment. Subjects were assessed before and after each treatment block. The primary outcome was the PASAT CF score after treatment with Fampridine-SR compared to placebo. T-tests and chi-square were used to compare demographics between the two groups (placebo-Fampridine-SR vs. Fampridine SR-placebo). Treatment effects were assessed using factorial ANOVA, with treatment (Fampridine-SR vs. placebo) and time (before and after treatment) as within-subject variables.

RESULTS

Of the 60 subjects randomized, 48 completed the study; three were removed due to an adverse event while in the treatment arm (one due to relapse while on placebo, one due to urinary retention and one due to dizziness and headache while on Fampridine-SR). The subjects had a mean age of 46.5±10.0 years, education of 13.6±1.9 years, and were diagnosed with MS 10.6±9.6 years ago. The majority were female (46, 76.7%), had relapsing remitting MS (41, 68.3%) with median EDSS of 3.5 (range 1.0-7.0). There were no significant demographic differences between the two groups. The treatment x time interaction within the factorial ANOVA on PASAT CF scores was statistically significant, F(1, 45)=8.28, p=0.006, suggesting there is a difference between the treatments (placebo vs. Fampridine-SR), over the course of the study. An evaluation of the mean scores suggests, however, that subjects saw a greater improvement when they were given the placebo, than when they were given the active medication. Similarly, individuals showed a greater increase in their information processing speed (as measured by the PASAT) over the course of treatment when they were given the placebo, as compared with the active medication F(1,45)=4.17, p=0.047.

CONCLUSION

Although this small pilot study does not suggest that Fampridine-SR results in a statistically significant improvement of CF in MS patients, as compared to placebo, individuals demonstrated an improvement in both information processing speed and CF, suggesting further studies are warranted.

Rasagiline for the symptomatic treatment of fatigue in Parkinson's disease

BACKGROUND

Fatigue affects 40% to 50% of all PD patients and is a leading cause of disability, with no clearly established or efficacious established treatments.

METHODS

In this double-blinded, placebo-controlled, pilot trial, we investigated whether rasagiline improved fatigue among PD patients. Subjects were randomized to 1 mg daily of rasagiline or placebo for 12 weeks. The primary endpoint was a change in the Modified Fatigue Impact Scale from baseline to week 12.

RESULTS

Thirty PD subjects (16 men), with Modified Fatigue Impact Scale baseline score of 67 ± 15, were randomized (16 to rasagiline vs. 14 to placebo). Significant improvement was noted in the mean Modified Fatigue Impact Scale score of the rasagiline group (12 points) as compared to placebo (8.5 points) from baseline to week 12 (P = 0.003).

CONCLUSION

In this pilot study, rasagiline at a dose of 1 mg per day improved fatigue. Larger randomized studies are needed to confirm this finding.

Counteracting Fatigue in Multiple Sclerosis with Right Parietal Anodal Transcranial Direct Current Stimulation

Background

Fatigue in multiple sclerosis (MS) patients appears to correlate with vigilance decrement as reflected in an increase in reaction time (RT) and errors with prolonged time-on-task.

Objectives

The aim of this study was to investigate whether anodal transcranial direct current stimulation (tDCS) over the right parietal or frontal cortex counteracts fatigue-associated vigilance decrement and subjective fatigue.

Methods

In study I, a randomized double-blind placebo-controlled study, anodal tDCS (1.5 mA) was delivered to the right parietal cortex or the right frontal cortex of 52 healthy participants during the first 20 min of a 40-min lasting visual vigilance task. Study II, also a randomized double-blind placebo-controlled study, investigated the effect of anodal tDCS (1.5 mA) over the right parietal cortex in 46 MS patients experiencing cognitive fatigue. tDCS was delivered for 20 min before patients performed a 20-min lasting visual vigilance task.

Results

Study I showed that right parietal stimulation, but not right frontal stimulation, counteracts the increase in RT associated with vigilance decrement. Hence, only right parietal stimulation was applied to the MS patients in study II. Stimulation had a significant effect on vigilance decrement in mildly to moderately cognitively fatigued MS patients. Vigilance testing significantly increased the feeling of fatigue independent of stimulation.

Conclusion

Anodal tDCS over the right parietal cortex can counteract the increase in RTs during vigilance performance, but not the increase in subjective fatigue. This finding is compatible with our model of fatigue in MS, suggesting a dissociation between the feeling and the behavioral characteristics of fatigue.

What you get from what you see: Parametric assessment of visual processing capacity in multiple sclerosis and its relation to cognitive fatigue

Multiple sclerosis (MS(1)) is a diffusely disseminated inflammatory disease affecting widespread cerebral networks. Major cognitive impairments are a reduction of processing capacity and mental fatigue, i.e., an "abnormal sense of tiredness or lack of energy". Here, the present study provides the first assessment of the distinct components of visual processing capacity based on a 'theory of visual attention' (TVA(2)) in MS patients and relates it to measures of subjective as well as (more) objective fatigue. The performance of 36 relapsing-remitting MS patients in a whole report task of brief letter arrays was compared to healthy control subjects matched for gender, age and education. Additionally, the sustained attention test PASAT-3(3) served as a measure of objective fatigue, and the self-report questionnaire MFIS(4) as a measure of subjective fatigue. Results indicate generally diminished processing speed as well as iconic memory buffers, and increased perceptual thresholds in MS patients compared to healthy controls. Block-wise analysis of attentional parameters shows that the processing speed performance of MS patients declines in the second half of the TVA-based test compared to healthy controls and in particular for patients with high versus low objective fatigue. These findings describe which aspects of processing capacity are impaired in MS, and show that fatigue mainly affects speed of processing. Thus, TVA-based assessment provides a novel approach in the determination of cognitive impairments and fatigue in MS. However, further research is required to elucidate the complex relations of processing capacity and cognitive functions in MS.

The PASAT performance among patients with multiple sclerosis: analyses of responding patterns using different scoring methods

The Paced Auditory Serial Addition Test (PASAT) is widely used in the evaluation of multiple sclerosis (MS) patients’ cognitive performance, and also used as the sole measure of cognition in a recently developed assessment tool for MS clinical trials, the Multiple Sclerosis Functional Composite (MSFC). We analysed if MS patients and healthy controls have different patterns of responding in the PASAT, and whether different scoring methods influence the PASAT’s sensitivity and specificity in detecting disease-associated cognitive impairment. Forty-five relapsing-remitting MS patients and 48 healthy controls were evaluated using the PASAT and a comprehensive neuropsychological examination. Cognitively deteriorated MS patients compensated for their difficulties in PASAT by omitting rather than guessing answers. They skipped items intermittently, which reduces the difficulty of the task. Furthermore, towards the end of the PASAT’s 60-item series MS patients’ performance had a trend to fade whereas controls’ performance was more even throughout the task. The dyad score or the percent dyad score did not essentially improve the sensitivity or the specificity, but the accuracy improved when the answers at the end of the PASAT series were specifically emphasized. Using the combined score, 73% of the patients were correctly classified as cognitively impaired or unimpaired.

Validation of the PASAT in Argentina

The Paced Auditory Serial Addition Test (PASAT) is one of the most used neuropsychological tests to assess information processing speed and working memory in brain injured patients. This study was carried out with the purpose of obtaining normative data for the PASAT-3″ in a healthy Argentinean population, which would result in a reference control population. The PASAT-3″ was administered in a sample of 296 healthy voluntary subjects, born and living in Argentina. The age range went from 20 to 70 years-old. The level of education was 0 to 13 or more years of schooling. The sample obtained a mean of 44.60 (SD = 10.72) in the PASAT-3″. It was found that the score obtained in the PASAT-3″ was related to the age and the level of instruction of the participants. Their performance diminished as age increased and, conversely, it increased as the level of instruction was higher. Normative data was obtained for a Latin American population from Argentina. Percentile distributions obtained by decades of age and different levels of education should be considered as useful reference values for clinicians and investigators when applying the PASAT-3″ to assess cognitive function in different pathologies.

Dissociation between mental fatigue and motivational state during prolonged mental activity

Mental fatigue (MF) is commonly observed following prolonged cognitive activity and can have major repercussions on the daily life of patients as well as healthy individuals. Despite its important impact, the cognitive processes involved in MF remain largely unknown. An influential hypothesis states that MF does not arise from a disruption of overused neural processes but, rather, is caused by a progressive decrease in motivation-related task engagement. Here, to test this hypothesis, we measured various neural, autonomic, psychometric and behavioral signatures of MF and motivation (EEG, ECG, pupil size, eye blinks, Skin conductance responses (SCRs), questionnaires and performance in a working memory (WM) task) in healthy volunteers, while MF was induced by Sudoku tasks performed for 120 min. Moreover extrinsic motivation was manipulated by using different levels of monetary reward. We found that, during the course of the experiment, the participants’ subjective feeling of fatigue increased and their performance worsened while their blink rate and heart rate variability (HRV) increased. Conversely, reward-induced EEG, pupillometric and skin conductance signal changes, regarded as indicators of task engagement, remained constant during the experiment, and failed to correlate with the indices of MF. In addition, MF did not affect a simple reaction time task, despite the strong influence of extrinsic motivation on this task. Finally, alterations of the motivational state through monetary incentives failed to compensate the effects of MF. These findings indicate that MF in healthy subjects is not caused by an alteration of task engagement but is likely to be the consequence of a decrease in the efficiency, or availability, of cognitive resources.

An investigation of attention, executive, and psychomotor aspects of cognitive fatigability

OBJECTIVE

Self-perceived mental fatigue is a common presenting symptom in many neurological diseases. Discriminating objective fatigability from self-perceived mental fatigue might facilitate neuropsychological diagnosis and treatment programs. However clinically valid neuropsychological instruments suitable for assessment of fatigability are still lacking. The prime aim of the study was to investigate aspects of cognitive fatigability and to identify properties of neuropsychological tests suitable to assess fatigability in patients with persistent cognitive complaints after mild brain injury. Another aim was to investigate whether cognitive fatigability captured by neuropsychological measures is influenced by depression or sleep disturbances.

METHOD

Twenty-four patients with persistent cognitive symptoms after mild traumatic brain injury (mTBI), (aged 18-51 years) and 31 healthy controls (aged 20-49 years) underwent neuropsychological testing measuring three cognitive fatigability domains: Attention fatigability was assessed using the Ruff 2 & 7 Selective Attention Test, executive fatigability using the Color Word Test (Stroop), and psychomotor fatigability using the Digit Symbol Substitution Test from the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III). Subjective fatigue was measured using the Fatigue Severity Scale and a questionnaire of everyday consequences of fatigue. Depression was screened using the Hospital Anxiety and Depression Scale and sleep disturbances using the Pittsburgh Sleep Quality Index.

RESULTS

The patients reported significantly more mental fatigue and performed worse on tests of psychomotor and executive fatigability than the healthy controls. Furthermore, the cognitive fatigability measures were not influenced by depression or sleep disturbances, as was the case in self-reported fatigue.

CONCLUSION

Tests demanding executive or simultaneous processing of several neuropsychological functions seem most sensitive in order to capture cognitive fatigability. Clinical tests that can capture fatigability enable a deeper understanding of how fatigability might contribute to cognitive complaints and problems in maintaining daily activities.

Cognitive fatigue in individuals with multiple sclerosis undergoing immunoablative therapy and hematopoietic stem cell transplantation

BACKGROUND

Fatigue presents as a significant problem in multiple sclerosis (MS). Cognitive fatigue (CF) can be defined as a decrease in, or inability to maintain task performance throughout the duration of a continuous cognitive task. CF was evaluated using the Paced Auditory Serial Addition Test (PASAT) both pre- and post-immunoablation and hematopoietic stem cell transplantation (IA-HSCT) over a 3-year follow-up period. The magnitude of CF was examined and the impact of scoring methodology was evaluated.

METHODS

Twenty-three individuals with rapidly progressive MS and poor prognosis underwent high dose immunosuppression and subsequent HSCT. Individuals completed the 3″ and 2″ PASAT at baseline and every 6 months thereafter over a period of 36 months. As scoring methodology can impact its sensitivity to CF, the PASAT was scored according to three scoring methods.

RESULTS

CF was noted across all three scoring methods at baseline and at the majority of time points post-IA-HSCT on both the 3″ and 2″ PASAT. The magnitude of CF remained consistent both pre-and post-IA-HSCT.

CONCLUSIONS

While results suggest that the procedure itself does not ameliorate an individual's susceptibility to CF; neither does it seem to negatively impact levels of CF. As such, results support the notion that the IA-HSCT procedure, despite its aggressive nature, does not exacerbate CF in this particular sample.

Effect of estrogen and testosterone replacement therapy on cognitive fatigue

Both estrogen and testosterone insufficiency has been associated with reduced psychological well-being including fatigue. However, hormonal replacement studies on fatigue are rare. Therefore, we wanted to study the effect of testosterone and estrogen replacement therapy on cognitive fatigue and the relation between sex hormone levels and cognitive fatigue in oophorectomized women. Fifty women with surgically induced menopause (mean age: 54.0 ± 2.9 years) were randomly assigned to treatment with estradiol valerate in combination with testosterone undecanoate or placebo for 24 weeks in a double-blind cross-over study. Neuropsychological tests and questionnaires were used to assess cognitive fatigue and psychological well-being. Cognitive fatigue was significantly associated to poor self-rated health and higher body mass index but not to general psychological well-being or sex hormone levels. Treatment with testosterone + estrogen had no significant effect on cognitive fatigue but the results indicated a curvilinear relation for hormonal levels. The estrogen/testosterone ratio was more related to functions rather than high or low hormone levels per se. We found that cognitive fatigue is frequent in oophorectomized women and negatively associated to self-perceived health and positively associated to BMI. A well-balanced ratio between estrogen and testosterone levels may be important for cognitive fatigue.