Perception of cognitive performance in patients with chronic fatigue syndrome

Two-month period of 500 mg lecithin-based delivery form of quercetin daily dietary supplementation counterbalances chronic fatigue symptoms: A double-blind placebo controlled clinical trial

BACKGROUND

Chronic fatigue (CF) is a complex phenomenon without clear etiology that may require long-term treatment, but to date, no specific therapy has been identified for it. Some botanicals might be helpful in the management of CF. Among these botanicals, quercetin demonstrates its capacity to modulate multiple biological pathways and acknowledged major properties in CF: antioxidant, anti-inflammatory, immunomodulating, improving exercise endurance, enhancing mitochondrial biogenesis, repairing mitochondrial dysfunction.

PURPOSE

Given this background, the aim of this study was to evaluate if a 2-month period of daily Quercetin Phytosome™ 500 mg supplementation is of benefit for the relief of CF.

METHODS

The primary end point has been the evaluation of fatigue, by Fatigue Impact Scale (FIS-40). The secondary end points have been the assessment of sleep, by Pittsburgh Sleep Quality Index (PSQI), evaluation of muscle performance, by short physical performance battery and by wearable armband-shaped sensor in order to evaluate the number of steps, body composition, by DXA and quality of life by Short-Form 12-Item Health Survey (SF-12).

RESULTS

Seventy-eight subjects (42 F; 36 M) (mean age 56 ± 9) reporting CF symptoms, completed the study (placebo/supplement 38/40). The FIS-40 mean difference changes between groups (supplement minus placebo) was - 10.583 points (CI95% -11.985; -9.182) (p < 0.001). Also, statistically significant changes between groups have been recorded in Pittsburgh Sleep Quality Index - 2.040 points (CI95%: -2.770; -1.309), p < 0.01), number of steps 1443.152 (CI95%: 1199.556; 1686.749), and SPPB (score) 0.248 (CI95%: 0.105; 0.391) (p < 0.001).

CONCLUSION

The quercetin supplementation counterbalances CF symptoms.

Evaluation of Speech and Pause Alterations in Patients With Acute and Chronic Heart Failure

Background

Acute heart failure is the most frequent cause of unplanned hospital admission in elderly patients. Various biomarkers have been evaluated to better assess the status of these patients and prevent decompensation. Recently, voice has been suggested as a cost‐effective and noninvasive way to monitor disease progression. This study evaluates speech and pause alterations in patients with acute decompensated and stable heart failure. Specifically, we aim to identify a vocal biomarker that could be used to monitor patients with heart failure and to prevent decompensation.

Methods and Results

Speech and pause patterns were evaluated in 68 patients with acute and 36 patients with stable heart failure. Voice recordings were performed using a web‐browser based application that consisted of 5 tasks. Speech and pause patterns were automatically extracted and compared between acute and stable patients and with clinical markers. Compared with stable patients, pause ratio was up to 14.9% increased in patients with acute heart failure. This increase was largely independent of sex, age, and ejection fraction and persisted in patients with lower degrees of edema or dyspnea. Furthermore, pause ratio was positively correlated with NT‐proBNP (N‐terminal pro‐B‐type natriuretic peptide) after controlling for acute versus stable heart failure. Collectively, our findings indicate that the pause ratio could be useful in identifying acute heart failure, particularly in patients who do not display traditional indicators of decompensation.

Conclusions

Speech and pause patterns are altered in patients with acute heart failure. Particularly, we identified pause ratio as an easily interpretable vocal biomarker to support the monitoring of heart failure decompensation.

Systematic review and meta-analysis of cognitive impairment in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is commonly associated with cognitive complaints. To bring out the neuropsychological symptomatology inherent to ME/CFS, we conducted a systematic review according to PRISMA and MOOSE guidelines of the literature through the analysis of 764 studies published between 1988 and 2019 by using PubMed Central website and Clarivate analytics platform. We performed a meta-analysis to delineate an idea of the neuropsychological profile inherent in ME/CFS. The clinical picture typically affects visuo-spatial immediate memory (g = - 0.55, p = 0.007), reading speed (g = - 0.82, p = 0.0001) and graphics gesture (g = - 0.59, p = 0.0001). Analysis also revealed difficulties in several processes inherent in episodic verbal memory (storage, retrieval, recognition) and visual memory (recovery) and a low efficiency in attentional abilities. Executive functions seemed to be little or not affected and instrumental functions appeared constantly preserved. With regard to the complexity and heterogeneity of the cognitive phenotype, it turns out that determining a sound clinical picture of ME/CFS cognitive profile must go through a neuropsychological examination allowing a complete evaluation integrating the notion of agreement between the choice and the number of tests and the complexity intrinsic to the pathology.

Patterns of daytime physical activity in patients with chronic fatigue syndrome

OBJECTIVES

To classify patients with chronic fatigue syndrome (CFS) by pattern of physical activity and determine the clinical associations of each type.

METHODS

579 out of 641 participants with CFS from the PACE (Pacing, graded Activity, Cognitive behavioural therapy: a randomised Evaluation) trial wore an Actiwatch (accelerometer) for between 3 and 7 days before any trial treatments, which provided a measure of physical activity. Participants' activity was categorised into one of four patterns (pervasively inactive, pervasively active, boom and bust, or indeterminate) primarily using a priori definitions of activity. Clinical associations were sought with each group using an exploratory logistic regression with the indeterminate activity group being the reference group.

RESULTS

124 (21%) of the participants were classified as pervasively inactive, 65 (11%) as pervasively active, 172 (30%) showed a 'boom and bust' pattern of activity, and 218 (38%) had an indeterminate pattern. Pervasively inactive patients were more physically disabled, those in the pervasively active group were more anxious, and those in the boom and bust group had more sleep disturbance.

CONCLUSION

We were able to classify patients with CFS into groups by their daytime activity pattern. The different patterns of activity were associated with important clinical variables, suggesting that they might be helpful in determining prognosis and targeting treatments. These associations need replication.

A unifying theory for cognitive abnormalities in functional neurological disorders, fibromyalgia and chronic fatigue syndrome: systematic review

BACKGROUND

Functional cognitive disorder (FCD) describes cognitive dysfunction in the absence of an organic cause. It is increasingly prevalent in healthcare settings yet its key neuropsychological features have not been reported in large patient cohorts. We hypothesised that cognitive profiles in fibromyalgia (FM), chronic fatigue syndrome (CFS) and functional neurological disorders (FNDs) would provide a template for characterising FCD.

METHODS

We conducted a systematic review of studies with cognition-related outcomes in FM, CFS and FND.

RESULTS

We selected 52 studies on FM, 95 on CFS and 39 on FND. We found a general discordance between high rates of subjective cognitive symptoms, including forgetfulness, distractibility and word-finding difficulties, and inconsistent objective neuropsychological deficits. Objective deficits were reported, including poor selective and divided attention, slow information processing and vulnerability to distraction. In some studies, cognitive performance was inversely correlated with pain, exertion and fatigue. Performance validity testing demonstrated poor effort in only a minority of subjects, and patients with CFS showed a heightened perception of effort.

DISCUSSION

The cognitive profiles of FM, CFS and non-cognitive FND are similar to the proposed features of FCD, suggesting common mechanistic underpinnings. Similar findings have been reported in patients with mild traumatic brain injury and whiplash. We hypothesise that pain, fatigue and excessive interoceptive monitoring produce a decrease in externally directed attention. This increases susceptibility to distraction and slows information processing, interfering with cognitive function, in particular multitasking. Routine cognitive processes are experienced as unduly effortful. This may reflect a switch from an automatic to a less efficient controlled or explicit cognitive mode, a mechanism that has also been proposed for impaired motor control in FND. These experiences might then be overinterpreted due to memory perfectionism and heightened self-monitoring of cognitive performance.

Beyond depression: Predictors of self-reported cognitive function in adults living with MS

OBJECTIVE

To investigate the association between self-reported cognition and demographic/psychosocial variables in individuals with a self-reported diagnosis of multiple sclerosis (MS).

DESIGN

Secondary longitudinal analysis of mailed self-report surveys over a period of 2 years.

SETTING

Community.

PARTICIPANTS

407 community-dwelling individuals from the Pacific Northwest with a self-reported diagnosis of MS.

MAIN OUTCOME MEASURES

Subjective general cognitive concerns and subjective executive difficulties as measured by the Neuro-QOL Applied Cognition-Executive Function-Short Form (SF) and the Applied Cognition-General Concerns-SF.

RESULTS

Univariate and multiple linear regression analyses were used to identify statistically significant longitudinal predictors of perceived cognitive difficulties 2 years later. Fatigue and anxiety were statistically significant predictors of general cognitive concerns. Fatigue and perceived stress were statistically significant predictors of perceived executive difficulties. Fatigue was the strongest predictor in both models.

CONCLUSIONS

In MS, perceived cognitive impairment is frequently linked to depression without consideration of other possible contributors. This study suggests that in people with MS, fatigue is a stronger predictor of self-reported cognitive function 2 years later than depression.

Cognitive functioning in chronic fatigue syndrome: a meta-analysis

BACKGROUND

Cognitive problems are commonly reported in persons with chronic fatigue syndrome (CFS) and are one of the most disabling symptoms of this condition. A number of cognitive deficits have been identified, although the findings are inconsistent and hindered by methodological differences. The current study therefore conducted a meta-analysis of research examining cognitive functioning in persons with CFS in order to identify the pattern and magnitude of any deficits that are associated with this condition.

METHOD

A comprehensive search of the PubMed and PsycINFO databases for studies that examined cognitive functioning in CFS between 1988 and 2008 identified 50 eligible studies. Weighted Cohen's d effect sizes, 95% confidence intervals and fail-safe Ns were calculated for each cognitive score.

RESULTS

Evidence of cognitive deficits in persons with CFS was found primarily in the domains of attention, memory and reaction time. Deficits were not apparent on tests of fine motor speed, vocabulary, reasoning and global functioning.

CONCLUSIONS

Persons with CFS demonstrate moderate to large impairments in simple and complex information processing speed and in tasks requiring working memory over a sustained period of time.

The central role of cognitive processes in the perpetuation of chronic fatigue syndrome

OBJECTIVE

Chronic fatigue syndrome (CFS) is considered to be one of the functional somatic syndromes (FSS). Cognitions and behavior are thought to perpetuate the symptoms of CFS. Behavioral interventions based on the existing models of perpetuating factors are quite successful in reducing fatigue and disabilities. The evidence is reviewed that cognitive processes, particularly those that determine the perception of fatigue and its effect on behavior, play a central role in the maintenance of symptoms.

METHOD

Narrative review.

RESULTS

Findings from treatment studies suggest that cognitive factors mediate the positive effect of behavioral interventions on fatigue. Increased fitness or increased physical activity does not seem to mediate the treatment response. Additional evidence for the role of cognitive processes is found in studies comparing the subjective beliefs patients have of their functioning with their actual performance and in neurobiological research.

CONCLUSION

Three different cognitive processes may play a role in the perpetuation of CFS symptoms. The first is a general cognitive representation in which fatigue is perceived as something negative and aversive and CFS is seen as an illness that is difficult to influence. The second process involved is the focusing on fatigue. The third element is formed by specific dysfunctional beliefs about activity and fatigue.

An assessment of prospective memory retrieval in women with chronic fatigue syndrome using a virtual-reality environment: an initial study

People with chronic fatigue syndrome (CFS) have increased rates of depression, anxiety, and illness intrusiveness; they may also suffer from cognitive problems such as retrospective memory (RM) deficits and concentration difficulties that can stem from diminished information-processing capability. We predicted that this diminished capacity may also lead to deficits in other cognitive functions, such as prospective memory (ProM). Event-, time-, and activity-based ProM was assessed in 11 women with CFS and 12 healthy women using a computer-generated virtual environment (VE). RM was assessed using a free-recall test, and subjective assessment of both ProM and RM was assessed by questionnaire. Groups were equivalent in age and measures of IQ. People with CFS performed slightly worse than healthy controls on both the event- and time-based ProM measures, although these were not statistically significant. However, the CFS group performed significantly worse than the healthy controls on both the free recall-task and on subjective assessment of both RM and ProM. Women with CFS do have some subtle decrements in memory, particularly RM. However, it is possible that the decrements found in the present sample would be greater in real life. Further studies utilizing both healthy controls and illness controls are now needed to ascertain how sensitive the VE measure is and to inform the development of tasks in the VE that place progressively increasing demands on working memory capacity.

An investigation into the cognitive deficits associated with chronic fatigue syndrome

This study addresses, among other things, the debate as to whether cognitive deficits do occur with a diagnosis of Chronic Fatigue Syndrome (CFS). Previous studies have indicated a potential mismatch between subjective patient ratings of impairment and clinical assessment. In an attempt to tackle some of the methodological problems faced by previous research in this field, this study recruited a large sample of CFS patients where adequate diagnosis had been made and administered an extensive battery of measures. In doing so this study was able to replicate previous published evidence of clear cognitive impairment in this group and demonstrate also that these deficits occurred independent of psychopathology. The conclusion drawn is that cognitive impairments can be identified if appropriate measures are used. Furthermore, the authors have shown that performance changes in these measures have been used to assess both efficacy of a treatment regime and rates of recovery.

Can sustained arousal explain the Chronic Fatigue Syndrome?

We present an integrative model of disease mechanisms in the Chronic Fatigue Syndrome (CFS), unifying empirical findings from different research traditions. Based upon the Cognitive activation theory of stress (CATS), we argue that new data on cardiovascular and thermoregulatory regulation indicate a state of permanent arousal responses - sustained arousal - in this condition. We suggest that sustained arousal can originate from different precipitating factors (infections, psychosocial challenges) interacting with predisposing factors (genetic traits, personality) and learned expectancies (classical and operant conditioning). Furthermore, sustained arousal may explain documented alterations by establishing vicious circles within immunology (Th2 (humoral) vs Th1 (cellular) predominance), endocrinology (attenuated HPA axis), skeletal muscle function (attenuated cortical activation, increased oxidative stress) and cognition (impaired memory and information processing). Finally, we propose a causal link between sustained arousal and the experience of fatigue. The model of sustained arousal embraces all main findings concerning CFS disease mechanisms within one theoretical framework.

Cognitive Functioning and Aging in Women

Deficits in cognitive function may impact one's ability to attend to stimuli, think clearly, reason, and remember. Impaired cognitive function is a common complaint among older women presenting for treatment in both mental health and medical care settings, and differential diagnosis of type and extent of cognitive impairment is important for appropriate treatment planning and prognosis. Although overall gender differences in prevalence of cognitive dysfunction are minimal, it is important when treating older women to take into account unique challenges they face in the aging process that impact the cause, type and extent of cognitive complaints with which they present in clinical settings. The current paper provides an overview to guide accurate diagnosis, particularly in women, of different types of cognitive impairment under the broad category of dementias, including Alzheimer's, Lewy Body Disease, Vascular Dementia, and due to general medical conditions such as coronary artery bypass surgery, head injury, menopause, hypothyroidism, breast cancer treatment, Fibromyalgia, and chronic fatigue. In addition, emotional factors such as depression in older female patients complicate differential diagnosis of cognitive impairment and must be addressed. Given the multiplicity of causes of cognitive difficulties for women across the life span, careful assessment is crucial; the current paper reviews assessment strategies to prepare an integrated, biopsychosocial strategy for identifying particular cognitive deficits and related psychological and medical problems. In addition, prognostic indicators and treatment planning are discussed to help the practitioner organize an empathic, reasoned and multifaceted treatment approach to maximize recovery, minimize deterioration, and manage symptoms for older women in the context of their social support system and living environment.

Personality and chronic fatigue syndrome: Methodological and conceptual issues

Among clinical psychologists, consulting physicians, scientific researchers and society in general an image has emerged of patients with chronic fatigue syndrome (CFS) as perfectionist, conscientious, hardworking, somewhat neurotic and introverted individuals with high personal standards, a great desire to be socially accepted and with a history of continuously pushing themselves past their limits. The aim of this article is to (a) give a concise review of the main recent studies on personality and CFS, (b) address the major methodological problems in the study of personality in CFS and (c) discuss some of the conceptual assumptions that seem to limit the research on personality and CFS. The results of the reviewed studies range from no evidence of major differences between the personalities of patients with CFS and controls, to evidence of severe psychopathology and personality disorder in patients with CFS. Although personality seems to play a role in CFS, it is difficult to draw general conclusions on the relation between personality and CFS. It is argued that this is partially due to the diversity and heterogeneity in study methods, patient populations, control groups and CFS case definitions. Personality should be regarded as an important factor to be studied in CFS. However, additional studies are needed, not focusing exclusively on personality disorder, or personality considered on a general trait level. In recent developments in personality research, the continually evolving life narrative that makes sense of, and gives direction to, an individual's life is also regarded as an important aspect of personality. New insights into personality and CFS might be gained by systematically studying the self-narratives of patients with the syndrome.

The chronic fatigue syndrome--an update

BACKGROUND

In this article, current scientific knowledge on the chronic fatigue syndrome (CFS) is reviewed. The US case definition of CFS (the CDC-definition) is most widespread in research and clinical practice. Estimates of prevalence vary from 0.2% to above 2%. The female-male ratio is approximately 3:1.

CLINICAL FEATURES

Severe fatigue is the dominating complaint; it is worsened from exertions and not substantially relieved by rest. In addition, the patients might have a varying combination of accompanying symptoms. Clinical evaluation should be based upon standardized guidelines, including an assessment of functional impairments.

PATHOPHYSIOLOGY

The pathophysiology should be interpreted within a biopsychosocial framework. Present knowledge suggests that certain genetic polymorphisms and personality traits might be regarded as predisposing factors, some infections and severe psychosocial stress constitute precipitating factors, whereas disturbances of immunity, skeletal muscle, cognitive abilities, endocrine control and cardiovascular homeostasis are possible perpetuating factors.

TREATMENT

Cognitive behavioural therapy and graded exercise therapy are of proven value in randomized controlled trials. Several pharmaceutical measures have been explored and found to have no beneficial effect. Most patients might expect long-term improvement, but full recovery is rare; however, the prognosis is better among adolescents.

The effect of cognitive behaviour therapy for chronic fatigue syndrome on self-reported cognitive impairments and neuropsychological test performance

BACKGROUND

Patients with chronic fatigue syndrome (CFS) often have concentration and memory problems. Neuropsychological test performance is impaired in at least a subgroup of patients with CFS. Cognitive behavioural therapy (CBT) for CFS leads to a reduction in fatigue and disabilities.

AIM

To test the hypothesis that CBT results in a reduction of self-reported cognitive impairment and in an improved neuropsychological test performance.

METHODS

Data of two previous randomised controlled trials were used. One study compared CBT for adult patients with CFS, with two control conditions. The second study compared CBT for adolescent patients with a waiting list condition. Self-reported cognitive impairment was assessed with questionnaires. Information speed was measured with simple and choice reaction time tasks. Adults also completed the symbol digit-modalities task, a measure of complex attentional function.

RESULTS

In both studies, the level of self-reported cognitive impairment decreased significantly more after CBT than in the control conditions. Neuropsychological test performance did not improve.

CONCLUSIONS

CBT leads to a reduction in self-reported cognitive impairment, but not to improved neuropsychological test performance. The findings of this study support the idea that the distorted perception of cognitive processes is more central to CFS than actual cognitive performance.

A case control study of premorbid and currently reported physical activity levels in chronic fatigue syndrome

BACKGROUND

Patients with chronic fatigue syndrome typically report high levels of physical activity before becoming ill. Few studies have examined premorbid and current activity levels in chronically fatigued patients.

METHODS

In a case-control study, 33 patients with chronic, unexplained, disabling fatigue attending a university-based clinic specializing in fatigue were compared to 33 healthy, age- and sex-matched controls. Patients rated their activity levels before their illness and currently, using scales designed for this purpose. Controls reported their level of activity of 2 years previously and currently. Chi-square analyses, Student's t tests, and Wilcoxon signed rank tests were used in pair matched analyses.

RESULTS

Compared to healthy controls, patients with chronic, unexplained fatigue rated themselves as more active before their illness (p < or = 0.001) and less active currently (p < or = 0.001). The patients also reported they currently stood or walked less than the controls (median [inter-quartile range] = 4 2345 versus 9 [7.5-12] hours, p < or = 0.001), and spent more time reclining (median [inter-quartile range] = 12 10111213141516 versus 8 [8-9.5] hours, p < or = 0.001). These differences remained significant for the subset of patients who met strict criteria for chronic fatigue syndrome or fibromyalgia.

CONCLUSION

Patients with chronic, unexplained, disabling fatigue reported being more active before becoming ill than healthy controls. This finding could be explained by greater premorbid activity levels that could predispose to illness, or by an overestimation of previous activity. Either possibility could influence patients' perceptions of their current activity levels and their judgments of recovery. Perceived activity should be addressed as part of management of the illness.

Chronic fatigue syndrome

During the past two decades, there has been heated debate about chronic fatigue syndrome (CFS) among researchers, practitioners, and patients. Few illnesses have been discussed so extensively. The existence of the disorder has been questioned, its underlying pathophysiology debated, and an effective treatment opposed; patients' organisations have participated in scientific discussions. In this review, we look back on several controversies over CFS with respect to its definition, diagnosis, pathophysiology, and treatment. We review issues of epidemiology and clinical manifestations, focusing on the scientific status of CFS. Modern neuroscience and genetics research offer interesting findings for new hypotheses on the aetiology and pathogenesis of the illness. We also discuss promising future issues, such as psychopathophysiology and mechanisms of improvement, and suggest multidisciplinary prospective studies of CFS and fatigue in the general population. These studies should pay particular attention to similarities to and differences from functional somatic syndromes and other fatiguing conditions.

Chronic treatment with modafinil may not be beneficial in patients with chronic fatigue syndrome

Fourteen patients (7 male, 7 female, 22-63 years), classified as having chronic fatigue syndrome (CFS), but without concurrent major depression, significant sleepiness or use of psychoactive medication, completed a double-blind, placebo-controlled, crossover study of the effects of the selective wakefulness-promoting agent, modafinil (200 and 400mg/day). The treatment periods were each 20 days, with washout periods of 2 weeks. The primary aim was to determine effects on cognition and the secondary aim was to determine effects on self-ratings of fatigue, quality of life and mood. Modafinil had mixed effects in two cognitive tasks. In a test of sustained attention, treatment with 200mg reduced the latency to correctly detect sequences, but 400mg increased the number of missed targets. In a test of spatial planning, the 200mg dose resulted in a slower initial thinking time for the easiest part of the task, whereas 400mg reduced the initial thinking time for the hardest part of the test. Lastly, in a test of mental flexibility and one of motor speed, patients performed worse whilst on modafinil (400mg), compared with the placebo period. No effects were observed on the performance of other psychometric tests or on self-ratings of fatigue, quality of life or mood, but this may have been due to insufficient statistical power. It is discussed whether the limited and mixed cognitive effects that we observed could have occurred by chance, or whether a subgroup of CFS patients with daytime sleepiness would have shown greater benefits.

Subjective quality of life in patients with chronic fatigue syndrome

The aim of this study was to (1) assess Subjective Quality of Life (SQOL) of patients with Chronic Fatigue Syndrome (CFS) using a generic concept and to compare the findings with those in groups with mental disorders and healthy subjects, and (2) investigate whether and, if so, to what extent socio-demographic and clinical variables predict SQOL in CFS patients. Seventy-three patients diagnosed with CFS were randomly selected and interviewed from two specialised clinics. CFS was diagnosed using the Oxford Criteria. SQOL was assessed on the Manchester Short Assessment of Quality of Life (MANSA) and Health-Related Quality of Life (HRQOL) on the Medical Outcome Study Short-Form 36 (MOS) SF-36. A battery of mood and symptom questionnaires, including the Symptom Checklist Questionnaire (SCL-90-R), was administered to assess various aspects of symptomatology as potential predictor variables. Multiple regression analyses were conducted to identify predictors of SQOL. Overall, SQOL was low in CFS patients and less favourable than in groups with mental disorders and healthy subjects. Satisfaction was particularly low with life as a whole, leisure activities and financial situation. Whilst SQOL was only moderately correlated with HRQOL, the SCL-90-R score, especially SCL-90-R Depression scale score, was the best predictor of SQOL explaining 35% of the variance. HRQOL and generic SQOL appear distinct despite some overlap. The findings underline that SQOL is significantly disrupted in CFS patients. Depressive symptoms are statistically the strongest 'predictor' of SQOL, although the direction of the relationship is not established. These data suggest that treatment of depression associated with CFS, regardless of causation, could help to improve SQOL in CFS patients.

The cognitive performance of patients with multiple sclerosis during periods of high and low fatigue

The objective of this study was to examine whether multiple sclerosis (MS)-related fatigue affects patients' cognitive performance. Thirty patients who had substantial fatigue in conjunction with MS and who reported marked diurnal variability in the severity of their fatigue were tested on two occasions: during a period of high fatigue and during a period of relatively low fatigue. The order of these sessions was counterbalanced across patients. During both sessions, patients completed a questionnaire concerning their present state of fatigue and a battery of neuropsychological tests of planning, selective attention, and paired associate learning. Although patients confirmed greater fatigue during the period of high fatigue and felt they had performed more poorly during this period, there were no differences in cognitive performance that could be attributed to fatigue. Instead, all subjects showed improvement from the first to the second session regardless of whether the latter entailed a period of high or low fatigue. In contrast to studies reporting fatigue-related declines in MS patients' cognitive performance, no differences in performance were found when MS patients were tested during periods of high versus low fatigue. These contrasting results, stemming from differences in experimental design, are discussed in terms of their implications for assessing cognitive function in patients with MS.