Memory deficits associated with chronic fatigue immune dysfunction syndrome

ME/CFS and Long COVID share similar symptoms and biological abnormalities: road map to the literature

Some patients remain unwell for months after "recovering" from acute COVID-19. They develop persistent fatigue, cognitive problems, headaches, disrupted sleep, myalgias and arthralgias, post-exertional malaise, orthostatic intolerance and other symptoms that greatly interfere with their ability to function and that can leave some people housebound and disabled. The illness (Long COVID) is similar to myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) as well as to persisting illnesses that can follow a wide variety of other infectious agents and following major traumatic injury. Together, these illnesses are projected to cost the U.S. trillions of dollars. In this review, we first compare the symptoms of ME/CFS and Long COVID, noting the considerable similarities and the few differences. We then compare in extensive detail the underlying pathophysiology of these two conditions, focusing on abnormalities of the central and autonomic nervous system, lungs, heart, vasculature, immune system, gut microbiome, energy metabolism and redox balance. This comparison highlights how strong the evidence is for each abnormality, in each illness, and helps to set priorities for future investigation. The review provides a current road map to the extensive literature on the underlying biology of both illnesses.

[Diagnosis and treatment of early forms of cognitive impairment: possibilities of influencing neuronal energy metabolism. Resolution of the Council of Experts]

Diagnosis and treatment of early forms of cognitive impairment: possibilities of influencing neuronal energy metabolism. Resolution of the Council of Experts.

Quality of Life Is Independently Associated With Neurocognitive Function in Patients With Brain Tumors: Analysis of a Prospective Clinical Trial

PURPOSE

We conducted the first prospective longitudinal study examining the independent association between patient-reported health-related quality of life (hrQoL) (physical, social/family, emotional, functional, and brain cancer-specific) and neurocognitive function (NCF), while controlling for mood symptoms in patients with primary brain tumors.

METHODS AND MATERIALS

Patients with primary brain tumors (n = 59) receiving brain radiation therapy underwent hrQOL (Functional Assessment of Cancer Therapy-Brain), mood (Beck Depression and Anxiety Inventories), and neurocognitive evaluation at baseline and 3, 6, and 12 months postradiation therapy in a prospective clinical trial. Neurocognitive assessments measured attention/processing speed, memory, and executive function, including the Delis-Kaplan Executive Function System Verbal Fluency, Hopkins Verbal Learning Test Revised (HVLT-R), and Brief Visuospatial Memory Test. Subjects underwent neurocognitive, mood, and hrQoL assessments in the same testing session. Multivariable linear mixed-effects models assessed associations between hrQOL and NCF over time, controlling for patient, tumor, and treatment characteristics as well as timepoint-specific patient-reported mood (ie, anxiety and depression symptoms). P values were adjusted for multiple comparisons.

RESULTS

Higher physical hrQoL was associated with better verbal memory (HVLT-R Total Recall, P = .047), and higher functional hrQoL was associated with better executive function (Delis-Kaplan Executive Function System Verbal Fluency Switching Total, P = .009) and verbal memory (HVLT-R Delayed Recall, P = .006). Higher brain tumor-specific hrQoL was associated with better verbal and nonverbal memory (HVLT-R Total, P = .004 and Delayed Recall, P = .030; Brief Visuospatial Memory Test Total, P = .049 and Delayed Recall, P = .049). There was no association between social/family or emotional hrQoL and NCF after controlling for mood.

CONCLUSIONS

Higher physical, functional, and brain tumor-specific hrQoL were associated with better executive function and memory among patients with primary brain tumors. Physical and functional impairments are correlated with cognitive performance. Interventions to maximize quality of life after treatment may influence neurocognition and vice versa.

Neuropsychiatric Status of Patients with Chronic Fatigue Syndrome: An Overview

Chronic fatigue syndrome (CFS) is an illness that results in debilitating fatigue as well as rheumatological, infectious, and neuropsychiatric symptoms. The present paper is a brief overview of the neuropsychological and psychiatric research on CFS. Studies from our laboratory contrasting CFS with patients with multiple sclerosis, depression, and healthy controls are detailed. Our hypothesis of the neuropsychological impairments in CFS is discussed.

White Paper: Neuropsychiatric Aspects of Sensitivity to Low-Level Chemicals: A Neural Sensitization Model

The present paper summarizes the proposed time-dependent sensitization (TDS) and partial limbic kindling model for illness from low-level chemicals; reviews and critiques prior studies on CNS aspects of multiple chemical sensitivity (MCS); and outlines possible experimental approaches to future studies. TDS is the progressive and persistent amplification of behavioral, neurochemical, endocrine, and/or immunological responses to repeated intermittent stimuli over time. Partial limbic kindling is a progressive and persistent lowering of the threshold for eliciting electrical afterdischarges, but not motor seizures, in certain brain structures such as amygdala and hippocampus; behavioral consequences include increased avoidant behaviors.

The focus of the paper is the controversial claim of altered sense of smell and illness from low levels of environmental chemicals (i. e., cacosmia), levels that should not have any biologically harmful effects by the rules of classical neurotoxicology. A major perspective of this paper is that the phenomenology of MCS is similar to that of time-dependent sensitization (reverse tolerance) and tolerance as studied in the substance abuse literature.

The TDS model for MCS proposes that neurobiological amplification underlies the symptoms and phenomenology of these patients, including their behavioral features of heightened affective and somatic distress. It is hypothesized that MCS patients, who are mostly women, may be individuals who sensitize to substances rapidly and to the extreme, to the point of aversive symptomatology with less complete capacity for development of tolerance. Possible parallels between MCS and TDS include: (a) initiation by single or multiple intermittent

Objective cognitive performance and subjective complaints in patients with chronic Q fever or Q fever fatigue syndrome

Background

Primary aim of this study was to compare cognitive performance of patients with chronic Q fever or Q fever fatigue syndrome (QFS) to matched controls from the general population, while taking performance validity into account. Second, we investigated whether objective cognitive performance was related to subjective cognitive complaints or psychological wellbeing.

Methods

Cognitive functioning was assessed with a neuropsychological test battery measuring the domains of processing speed, episodic memory, working memory and executive functioning. Tests for performance validity and premorbid intelligence were also included. Validated questionnaires were administered to assess self-reported fatigue, depressive symptoms and cognitive complaints.

Results

In total, 30 patients with chronic Q fever, 32 with QFS and 35 controls were included. A high percentage of chronic Q fever patients showed poor performance validity (38%) compared to controls (14%, p = 0.066). After exclusion of participants showing poor performance validity, no significant differences between patients and controls were found in the cognitive domains. QFS patients reported a high level of cognitive complaints compared to controls (41.2 vs 30.4, p = 0.023). Cognitive complaints were not significantly related to cognitive performance in any of the domains for this patient group.

Conclusions

The high level of self-reported cognitive complaints in QFS patients does not indicate cognitive impairment. A large proportion of the chronic Q fever patients showed suboptimal mental effort during neuropsychological assessment. More research into the underlying explanations is needed. Our findings stress the importance of assessing cognitive functioning by neuropsychological examination including performance validity, rather than only measuring subjective cognitive complaints.

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.

Cortical hypoactivation during resting EEG suggests central nervous system pathology in patients with chronic fatigue syndrome

We investigated central fatigue in 50 patients with chronic fatigue syndrome (CFS) and 50 matched healthy controls (HC). Resting state EEG was collected from 19 scalp locations during a 3 min, eyes-closed condition. Current densities were localized using exact low-resolution electromagnetic tomography (eLORETA). The Multidimensional Fatigue Inventory (MFI-20) and the Fatigue Severity Scale (FSS) were administered to all participants. Independent t-tests and linear regression analyses were used to evaluate group differences in current densities, followed by statistical non-parametric mapping (SnPM) correction procedures. Significant differences were found in the delta (1-3 Hz) and beta-2 (19-21 Hz) frequency bands. Delta sources were found predominately in the frontal lobe, while beta-2 sources were found in the medial and superior parietal lobe. Left-lateralized, frontal delta sources were associated with a clinical reduction in motivation. The implications of abnormal cortical sources in patients with CFS are discussed.

Intrinsic Functional Hypoconnectivity in Core Neurocognitive Networks Suggests Central Nervous System Pathology in Patients with Myalgic Encephalomyelitis: A Pilot Study

Exact low resolution electromagnetic tomography (eLORETA) was recorded from nineteen EEG channels in nine patients with myalgic encephalomyelitis (ME) and 9 healthy controls to assess current source density and functional connectivity, a physiological measure of similarity between pairs of distributed regions of interest, between groups. Current source density and functional connectivity were measured using eLORETA software. We found significantly decreased eLORETA source analysis oscillations in the occipital, parietal, posterior cingulate, and posterior temporal lobes in Alpha and Alpha-2. For connectivity analysis, we assessed functional connectivity within Menon triple network model of neuropathology. We found support for all three networks of the triple network model, namely the central executive network (CEN), salience network (SN), and the default mode network (DMN) indicating hypo-connectivity in the Delta, Alpha, and Alpha-2 frequency bands in patients with ME compared to controls. In addition to the current source density resting state dysfunction in the occipital, parietal, posterior temporal and posterior cingulate, the disrupted connectivity of the CEN, SN, and DMN appears to be involved in cognitive impairment for patients with ME. This research suggests that disruptions in these regions and networks could be a neurobiological feature of the disorder, representing underlying neural dysfunction.

Psychosocial factors involved in memory and cognitive failures in people with myalgic encephalomyelitis/chronic fatigue syndrome

BACKGROUND

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is characterized by persistent emotional, mental, and physical fatigue accompanied by a range of neurological, autonomic, neuroendocrine, immune, and sleep problems. Research has shown that psychosocial factors such as anxiety and depression as well as the symptoms of the illness, have a significant impact on the quality of life of people with ME/CFS. In addition, individuals may suffer from deficits in memory and concentration. This study set out to explore the relationships between variables which have been found to contribute to cognitive performance, as measured by prospective and retrospective memory, and cognitive failures.

METHODS

Eighty-seven people with ME/CFS answered questionnaires measuring fatigue, depression, anxiety, social support, and general self-efficacy. These were used in a correlational design (multiple regression) to predict cognitive function (self-ratings on prospective and retrospective memory), and cognitive failures.

RESULTS

Our study found that fatigue, depression, and general self-efficacy were directly associated with cognitive failures and retrospective (but not prospective) memory.

CONCLUSION

Although it was not possible in this study to determine the cause of the deficits, the literature in this area leads us to suggest that although the pathophysiological mechanisms of ME/CFS are unclear, abnormalities in the immune system, including proinflammatory cytokines, can lead to significant impairments in cognition. We suggest that fatigue and depression may be a result of the neurobiological effects of ME/CFS and in addition, that the neurobiological effects of the illness may give rise to both fatigue and cognitive deficits independently.

Cognitive deficits in patients with chronic fatigue syndrome compared to those with major depressive disorder and healthy controls

OBJECT

Chronic fatigue syndrome (CFS) patients report usually cognitive complaints. They also have frequently comorbid depression that can be considered a possible explanation for their cognitive dysfunction. We evaluated the cognitive performance of patients with CFS in comparison with a control group of healthy volunteers and a group of patients with MDD.

PATIENTS AND METHODS

Twenty-five patients with CFS, 25 patients with major depressive disorder (MDD), and 25 healthy control subjects were given standardized tests of attention, working memory, and verbal and visual episodic memory, and were also tested for effects related to lack of effort/simulation, suggestibility, and fatigue.

RESULTS

Patients with CFS had slower phasic alertness, and also had impaired working, visual and verbal episodic memory compared to controls. They were, however, no more sensitive than the other groups to suggestibility or to fatigue induced during the cognitive session. Cognitive impairments in MDD patients were strongly associated with depression and subjective fatigue; in patients with CFS, there was a weaker correlation between cognition and depression (and no correlation with fatigue).

CONCLUSIONS

This study confirms the presence of an objective impairment in attention and memory in patients with CFS but with good mobilization of effort and without exaggerated suggestibility.

Neuropsychological functioning, illness perception, mood and quality of life in chronic fatigue syndrome, autoimmune thyroid disease and healthy participants

BACKGROUND

This study attempted to longitudinally investigate neuropsychological function, illness representations, self-esteem, mood and quality of life (QoL) in individuals with chronic fatigue syndrome (CFS) and compared them with both healthy participants and a clinical comparison group of individuals with autoimmune thyroid disease (AITD).

METHOD

Neuropsychological evaluation was administered at two time points, five weeks apart. Twenty-one individuals with CFS, 20 individuals with AITD and 21 healthy participants were matched for age, pre-morbid intelligence, education level and socio-economic status (SES). All groups also completed measures of illness perceptions, mood, self-esteem and QoL at both time points.

RESULTS

The CFS group showed significantly greater impairment on measures of immediate and delayed memory, attention and visuo-constructional ability, and reported significantly higher levels of anxiety and depression. After controlling for the effects of mood, the CFS group still demonstrated significant impairment in attention. The CFS group also reported significantly lower self-reported QoL than the AITD and healthy participants. In terms of illness perceptions, the AITD group believed that their condition would last longer, that they had more treatment control over their condition, and reported less concern than the CFS group.

CONCLUSIONS

These results suggest that the primary cognitive impairment in CFS is attention and that this is not secondary to affective status. The lower treatment control perceptions and greater illness concerns that CFS patients report may be causally related to their affective status.

Is human herpesvirus-6 a trigger for chronic fatigue syndrome?

Chronic fatigue syndrome (CFS) is an illness currently defined entirely by a combination of non-specific symptoms. Despite this subjective definition, CFS is associated with objective underlying biological abnormalities, particularly involving the nervous system and immune system. Most studies have found that active infection with human herpesvirus-6 (HHV-6)--a neurotropic, gliotropic and immunotropic virus--is present more often in patients with CFS than in healthy control and disease comparison subjects, yet it is not found in all patients at the time of testing. Moreover, HHV-6 has been associated with many of the neurological and immunological findings in patients with CFS. Finally, CFS, multiple sclerosis and seizure disorders share some clinical and laboratory features and, like CFS, the latter two disorders also are being associated increasingly with active HHV-6 infection. Therefore, it is plausible that active infection with HHV-6 may trigger and perpetuate CFS in a subset of patients.

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.

Cognitive Complaints Are Associated With Depression, Fatigue, Female Sex, and Pain Catastrophizing in Patients With Chronic Pain

OBJECTIVE

To examine the relation between demographic, pain-related, psychosocial, affective, and treatment factors and complaints of cognitive dysfunction among patients with chronic pain.

DESIGN

Cross-sectional survey.

SETTING

A university hospital outpatient multidisciplinary chronic pain program.

PARTICIPANTS

Chronic pain patients (N=222; 135 women, 87 men) completed a battery of psychometric questionnaires as part of an initial evaluation on referral to the program.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Cognitive impairment was assessed with items from the Brief Symptom Inventory; measures of depressive symptoms, pain intensity, posttraumatic stress disorder (PTSD), and pain catastrophizing were obtained from the Beck Depression Inventory (negative affect, negative self, somatic/physical function), McGill Pain Questionnaire, Modified Posttraumatic Chronic Pain Test, and Coping Strategies Questionnaire, respectively; and measures of subjective sleep disturbance, fatigue, opiate use, compensation/litigation status, pain location, and relevant demographic data were obtained from an open-ended questionnaire.

RESULTS

Correlational analysis indicated that female sex, pain intensity, PTSD symptoms, depressive symptoms, catastrophizing, pain location (neck), and fatigue were all positively related to cognitive complaints. Simultaneous regression analysis showed that all factors combined accounted for 52% of the variance in self-report of cognitive difficulties and that 6 variables had a significant unique contribution to the report of cognitive complaints in the following order of importance: depression-negative affect (beta=.28, P <.05), fatigue (beta=.17, P <.05), depression-somatic/physical function (beta=.16, P <.05), depression-negative self (beta=.14, P =.05), pain catastrophizing (beta=.12, P =.08), and female sex (beta=.12, P <.05).

CONCLUSIONS

Complaints of cognitive impairment among chronic pain patients appear to be associated with multiple factors, with particular attention to depressive symptoms, fatigue, and catastrophizing. Our results also suggest that women with chronic pain are particularly vulnerable to cognitive dysfunction.

Chronic Fatigue: A Survey, Outcome Study and Proposals

BACKGROUND

  Sample sizes in studies of childhood chronic fatigue remain small and there is a need to integrate research findings and establish common criteria.

METHOD

  This is a detailed report of 20 children with medically unexplained fatigue, referred to as Chronic Fatigue Syndrome (CFS). It includes an uncontrolled outcome study of treatment based on a pragmatic cognitive-behavioural model adapted for children at Great Ormond Street Hospital for Children.

RESULTS

  The data revealed psychological distress at 30 times the prevalence found in the normal child population, with specific high-ranking symptoms, including headache, social withdrawal and decreased appetite. Onset tended to occur at 11 years of age with some earlier problems at school age, suggesting it might be possible to identify those most at risk. Follow-up demonstrated improvement in 87% of the sample (parental report), a significant increase in school attendance and a significant decrease in symptom severity. Factors associated with good outcome were short duration of fatigue (less than a year) and behaviours that tended to combat the cycle of avoidance, such as carefully planned home-tuition.

CONCLUSIONS

  Recording a comprehensive range of symptoms and factors facilitates comparisons within and between child studies. It is proposed that symptom severity is a particularly relevant measure for Chronic Fatigue Syndrome which is characterised by persisting symptoms.

Electrodermal dissociation of chronic fatigue and depression: evidence for distinct physiological mechanisms

Chronic fatigue syndrome (CFS) has an estimated prevalence between 0.5% and 3%, yet its diagnosis remains contentious. CFS is characterized by subjective symptoms that can be difficult to verify; moreover, depression is a commonly reported CFS complaint, whereas fatigue is a common symptom of depression. Our primary goal was dissociation of these disorders using psychophysiological methods. As previous research has implicated the autonomic nervous system in CFS, we conducted what we believe to be the first analysis of bilateral electrodermal and skin temperature responses of dextral females in a cross-modal orienting task, to investigate differences between these two patient groups and controls. A multivariate analysis of variance (MANOVA) examining three measures of electrodermal activity revealed prestimulus tonic skin conductance levels (SCLs) were markedly lower for the CFS group, with no difference between controls and depressives. Concurrent skin temperature levels were higher for the CFS group than the other two groups. These findings indicate that, despite overtly similar cognitive and symptom profiles, depression and CFS patients can be differentiated with psychophysiological measures. This study adds to the growing body of evidence demonstrating that CFS and depression have distinct neurobiological profiles, consistent with unique aetiologies.

Neuropsychological deficits in patients with chronic fatigue syndrome

The degree of neuropsychological dysfunction across multiple domains was examined in individuals suffering from chronic fatigue syndrome (CFS). In this descriptive study, a similar series of neuropsychological tests was administered to a group of CFS patients and healthy participants. More specifically, CFS patients (n = 141) who met the 1994 Case Definition criteria were compared to 76 healthy control participants on tests of memory, attention (concentration), speed of information processing, motor speed, and executive functioning. On the 18 measures administered, CFS patients scored 1 standard deviation below the healthy mean on nine measures and scored 2 standard deviations below the healthy mean on four of the measures. Moreover, results indicated that CFS patients were more likely than healthy controls to fail (1.6 SD below the healthy mean) at least one test in each of the following domains: attention, speed of information processing, and motor speed, but not on measures of memory and executive functioning. Finally, CFS patients demonstrated a greater total number of tests failed across domains.

Cognitive Processing in Monozygotic Twins Discordant for Chronic Fatigue Syndrome

Twenty-one pairs of monozygotic twins discordant for chronic fatigue syndrome (CFS) and 21 matched healthy control (HC) subjects were assessed with 5 untimed tests and 5 timed tests from the computer-based NeuroCognitive Assessment Battery (R. K. Mahurin, 1993). Random effects regression showed no difference between CFS and healthy twins on any of the cognitive tests. Further, the twin groups did not differ from the HC group on any content-dependent measure. In contrast, both sets of twins performed worse than the HC group on all speed-dependent tests except Finger Tapping. Self-rated fatigue and dysphoric mood were only weakly correlated with cognitive performance. These data point toward a shared genetic trait related to information processing that is manifest in the CFS context. The findings have implications for differentiating genetic and acquired vulnerability in the symptomatic expression of the disorder. ((c) 2004 APA, all rights reserved)

Examining the influence of biological and psychological factors on cognitive performance in chronic fatigue syndrome: a randomized, double-blind, placebo-controlled, crossover study

The pathophysiology of chronic fatigue syndrome (CFS) remains unclear; however, both biological and psychological factors have been implicated in establishing or maintaining this condition. People with CFS report significant and disabling cognitive difficulties such as impaired concentration that in some cases are exacerbated by exposure to chemical triggers. The aim of this study was to determine if neuropsychological deficits in CFS are triggered by exposure to chemicals, or perceptions about the properties of these substances. Participants were 36 people with a primary diagnosis of CFS, defined according to Centers for Disease Control (CDC) criteria. A randomized, double-blind, placebo-controlled, crossover design was used, with objective assessment of neuropsychological function and participant rating of substance type, before and after exposure to placebo or chemical trigger. Results showed decrements in neuropsychological tests scores on three out of four outcome measures when participants rated the substance they had been exposed to as "chemical." No change in performance was found based on actual substance type. These results suggest that cognitive attributions about exposure substances in people with CFS may be associated with worse performance on neuropsychological tasks. In addition, these findings suggest that psychological interventions aimed at modifying substance-related cognitions may reduce some symptoms of CFS.

Immunological variables mediate cognitive dysfunction in gulf war veterans but not civilians with chronic fatigue syndrome

We explored the relationship between a set of immunological variables and a set of cognitive and functional status measures and a diagnosis of chronic fatigue syndrome (CFS) in civilians and veterans using various regression and factor analytic methods. Our approach emphasized the extraction of a few distinct factors in order to limit statistical problems associated with doing large numbers of multiple comparisons. This approach led to our finding cytokine data grouping into type 1 and type 2 clusters. A type 2 cluster plus a T and B cell factor predicted CFS caseness for Gulf War veterans but not for civilians with CFS. When a cognitive variable, reaction time, was added into the model, both immunological factors lost statistical significance; this indicates that the cognitive variable reaction time moderated the effects of the immunological factors in predicting patient status. We did a similar analysis on the roles of the immunological and cognitive variables in functional status using SF-36 data. Higher levels of these same two immunological factors predicted poorer general health as well as poorer physical and social functioning in Gulf War veterans but not in civilians with CFS. When the reaction time factor was added, only the lymphocyte factor remained significant. This implies that lymphocytes are directly related to functional status in Gulf War veterans with CFS, but the Th2 factor produces its effect on functional status via changes in cognitive abilities.

Psychological correlates of functional status in chronic fatigue syndrome

BACKGROUND

The present study was designed to test a cognitive model of impairment in chronic fatigue syndrome (CFS) in which disability is a function of severity of fatigue and depressive symptoms, generalized somatic symptom attributions and generalized illness worry.

METHODS

We compared 45 CFS and 40 multiple sclerosis (MS) outpatients on measures of functional ability, fatigue severity, depressive symptoms, somatic symptom attribution and illness worry.

RESULTS

The results confirmed previous findings of lower levels of functional status and greater fatigue among CFS patients compared to a group of patients with MS. Fatigue severity was found to be a significant predictor of physical functioning but not of psychosocial functioning in both groups. In CFS, when level of fatigue was controlled, making more somatic attributions was associated with worse physical functioning, and both illness worry and depressive symptoms were associated with worse psychosocial functioning.

CONCLUSIONS

Our findings support the role of depression and illness cognitions in disability in CFS sufferers. Different cognitive factors account for physical and psychosocial disability in CFS and MS. The SF-36 may be sensitive to symptom attributions, suggesting caution in its interpretation when used with patients with ill-defined medical conditions.

Neuropsychological function in patients with chronic fatigue syndrome, multiple sclerosis, and depression

Patients with chronic fatigue syndrome (CFS), multiple sclerosis (MS), and major depression were compared with controls and with each other on a neuropsychological battery that included standard neuropsychological tests and a computerized set of tasks that spanned the same areas of ability. A total of 101 participants were examined, including 29 participants with CFS, 24 with MS, 23 with major depressive disorder, and 25 healthy controls. There were significant differences among the groups in 3 out of 5 cognitive domains: memory, language, and spatial ability. Assessment of psychiatric symptoms indicated that all 3 patient groups had a higher prevalence of depression than the controls. A total measure of psychiatric symptomatology also differentiated the patients from the controls. After covarying the cognitive test scores by a measure of depression, the patient groups continued to differ from controls primarily in the area of memory. The findings support the view that the cognitive deficits found in CFS cannot be attributed solely to the presence of depressive symptomatology in the patients.

Sleep and pain

Noxious stimuli and painful disorders interfere with sleep, but disturbances in sleep also contribute to the experience of pain.Chronic paroxysmal hemicrania and possibly cluster headaches are related to REM sleep. Whereas headache is associated with snoring and sleep apnea, morning headaches are not specific for any primary sleep disorder. Nevertheless, the management of the sleep disorder ameliorates both morning headache and migraine.Noxious stimuli administered into muscles during slow-wave sleep (SWS) result in decreases in delta and sigma but an increase in alpha and beta EEG frequencies during sleep. Noise stimuli that disrupt SWS result in unrefreshing sleep, diffuse musculoskeletal pain, tenderness, and fatigue in normal healthy subjects. Such symptoms accompany alpha EEG sleep patterns that often occur in patients with fibromyalgia. The alpha EEG patterns include phasic and tonic alpha EEG sleep as well as periodic K alpha EEG sleep or frequent periodic cyclical alternating pattern. Moreover, alpha EEG sleep, as well as sleep-related breathing disorder and periodic limb movement disorder, occur in some patients with fibromyalgia, rheumatoid arthritis and osteoarthritis. Depression and not alpha EEG sleep are features of somatoform pain disorder. Disturbances in sleep, pain behaviour and psychological distress influence return to work in workers who have suffered a soft tissue injury, e.g. low back pain. Patients with irritable bowel disorder have disturbed sleep and have increased REM sleep. In conclusion, there is a reciprocal relationship between sleep quality and pain. The recognition of disturbed or unrefreshing sleep influences the management of painful medical disorders.

Coping and illness cognitions: chronic fatigue syndrome

The chronic fatigue syndrome (CFS) is described, and research on coping with this illness reviewed and analysed. CFS is a severely disabling illness of unknown etiology, which has occurred in epidemic forms all over the world. However, the number of sufferers has dramatically increased over previous years. The heterogeneous symptomatology of CFS was reviewed, and diagnostic criteria were discussed. The difficulty in establishing causality was emphasized. An interaction of factors appears most likely to be associated with illness onset and maintenance. As the mediating factor could be sufferers' coping behavior, the existing coping literature was reviewed. There might be an association between coping and physical and psychological well-being. Finally, recommendations are made for longitudinal research on coping and coping effectiveness, and for the development of therapeutic interventions.

Neuropsychological functioning in chronic fatigue syndrome: a review

OBJECTIVE

In this paper we review critically the current status of neurocognitive studies in patients with chronic fatigue syndrome (CFS).

METHOD

CFS literature was monitored as part of a large research project which involved several neuropsychological and psychopathological studies. The literature survey was the result of several consecutive searches on Medline and PsycInfo databases.

RESULTS

The neurocognitive studies are reviewed in terms of scientificaly accepted aspects of attention and memory. In addition, we review possible explanations for cognitive dysfunction in CFS. This is preceded with a discussion of the methodological limitations that are considered to explain inconcistencies across neuropsychological studies in CFS.

CONCLUSION

The current research shows that slowed processing speed, impaired working memory and poor learning of information are the most prominent features of cognitive dysfunctioning in patients with CFS. Furthermore, to this date no specific pattern of cerebral abnormalities has been found that uniquely characterizes CFS patients. There is no overwhelming evidence that fatigue is related to cognitive performance in CFS, and researchers agree that their performance on neuropsychological tasks is unlikely to be accounted solely by the severity of the depression and anxiety.

Multiple chemical sensitivity: a review of the theoretical and research literature

Multiple chemical sensitivity (MCS) is a term used to describe a disorder characterized by a vast array of somatic, cognitive, and affective symptoms, the cause of which is attributed to exposure to extremely low levels of a variety of chemicals. Upon examination of the patient with a diagnosis of MCS, objective physical findings and consistent laboratory abnormalities are typically nonexistent. The concept of MCS has ignited considerable controversy in the fields of toxicology, immunology, allergy, psychology, and neuropsychology. Central to the controversy is the disagreement over the extent to which the manifestation of MCS is mediated by psychological factors. Because of the large number of neuropsychological symptoms associated with a diagnosis of MCS, neuropsychologists are increasingly receiving referrats for the assessment of these patients. It is important, therefore, that neuropsychologists become aware of the variety of clinical issues that must be taken into account when assessing an individual with a diagnosis of MCS. The theoretical and research literature on individuals with a diagnosis of MCS is reviewed here.

Chronic fatigue syndrome: reviewing the research findings

This article reviews the current state of research in chronic fatigue syndrome (CFS). The evolving definition, prevalence, and prognosis of this controversial illness are presented. We review studies examining psychiatric, personality, and psychosocial etiology for CFS. The evidence for pathophysiology in CFS is also presented, and studies investigating viral, immune, neuroimaging, neuroendocrine, and central and autonomic nervous system abnormalities in CFS are assessed. Current evidence indicates that CFS is multi-determined and heterogeneous and that subgrouping patients according to factors such as psychiatric state and symptom onset may be fruitful. The current state of treatment for CFS is reviewed, and the challenges for research aimed at resolving this prototypical mind/body problem are discussed.

Chronic fatigue syndrome: an update

Among the many patients who seek medical care for the complaint of fatigue, a small number suffer from chronic fatigue syndrome (CFS). CFS is a poorly understood condition characterized by debilitating fatigue and associated symptoms lasting at least six months. Studies indicate that the illness is not simply a manifestation of an underlying psychiatric disorder, but rather is an illness characterized by activation of the immune system, various abnormalities of several hypothalamic-pituitary axes, and reactivation of certain infectious agents.

Cognitive deficits in patients suffering from chronic fatigue syndrome, acute infective illness or depression

BACKGROUND

Patients with chronic fatigue syndrome (CFS) report neuro-psychological symptoms as a characteristic feature. We sought to assess cognitive performance in patients with CFS, and compare cognitive performance and subjective workload experience of these patients with that of two disease comparison groups (non-melancholic depression and acute infection) and healthy controls.

METHOD

A computerized performance battery employed to assess cognitive functioning included tests of continuous attention, response speed, performance accuracy and memory. Severity of mood disturbance and subjective fatigue were assessed by questionnaire.

RESULTS

All patient groups demonstrated increased errors and slower reaction times, and gave higher workload ratings than healthy controls. Patients with CFS and non-melancholic depression had more severe deficits than patients with acute infection. All patient groups reported more severe mood disturbance and fatigue than healthy controls, but patients with CFS and those with acute infection reported less severe mood disturbance than patients with depression.

CONCLUSIONS

As all patients demonstrated similar deficits in attention and response speed, it is possible that common pathophysiological processes are involved. The differences in severity of mood disturbance, however, suggest that the pathophysiological processes in patients with CFS and acute infection are not simply secondary to depressed mood.

The Effects of Fatigue on Neuropsychological Performance in Patients With Chronic Fatigue Syndrome, Multiple Sclerosis, and Depression

The effects of fatigue on neuropsychological performance were examined in patients with fatiguing illnesses. Repeated testing with the Paced Auditory Serial Addition Test (PASAT; Gronwall, 1977) was employed over the course of a demanding neuropsychological testing session. It was hypothesized that if fatigue affects performance, one would expect to observe "blunting" of the PASAT practice effect. Fifteen of the study participants live with chronic fatigue syndrome (CFS), 15 with multiple sclerosis (MS), 14 with depression (DEP), and 15 are healthy, sedentary controls. Overall PASAT performance was significantly reduced for CFS and DEP participants compared to controls, whereas mean performance did not differ across the three fatiguing illness groups. Degree of improvement across trials (i.e., practice effect) for the groups did not differ from controls'. Neither subjective fatigue or DEP were significantly related to PASAT performance. These findings suggest that fatigue does not universally impair performance during neuropsychological assessment even in groups in which fatigue is a prominent symptom.

Neuropsychology of chronic fatigue syndrome: a critical review

This article provides a comprehensive and critical review of the neuropsychological and related literature on chronic fatigue syndrome (CFS). Despite the methodological limitations observed in several studies, some consistent findings are noted. The most consistently documented neuropsychological impairments are in the areas of complex information processing speed and efficiency. General intellectual abilities and higher order cognitive skills are intact. Emotional factors influence subjective report of cognitive difficulty, whereas their effect on objective performance remains uncertain. Although the neuropathological processes underlying cognitive dysfunction in CFS are not yet known, preliminary evidence suggests the involvement of cerebral white matter. Directions for future research are outlined.

Memory functioning in patients with primary fibromyalgia and major depression and healthy controls

Memory functioning was assessed in 25 primary fibromyalgia (FM) patients by comparing them with 22 major depressed patients and 18 healthy controls. A broad range of short- and long-term memory tasks were included. Both major depressed and FM patients were significantly impaired on long-term memory tasks requiring effortful processing, compared to healthy controls. When the depressive status of the fibromyalgia patients was accounted for, only the subsample with a lifetime major depressive disorder showed memory impairment as compared with the healthy controls.

Cognitive functioning is impaired in patients with chronic fatigue syndrome devoid of psychiatric disease

OBJECTIVE

To examine the effect of the presence or absence of psychiatric disease on cognitive functioning in chronic fatigue syndrome.

METHODS

Thirty six patients with chronic fatigue syndrome and 31 healthy controls who did not exercise regularly were studied. Subgroups within the chronic fatigue syndrome sample were formed based on the presence or absence of comorbid axis I psychiatric disorders. Patients with psychiatric disorders preceding the onset chronic fatigue syndrome were excluded. Subjects were administered a battery of standardised neuropsychological tests as well as a structured psychiatric interview.

RESULTS

Patients with chronic fatigue syndrome without psychiatric comorbidity were impaired relative to controls and patients with chronic fatigue syndrome with concurrent psychiatric disease on tests of memory, attention, and information processing.

CONCLUSION

Impaired cognition in chronic fatigue syndrome cannot be explained solely by the presence of a psychiatric condition.

Cognitive slowing and working memory difficulties in chronic fatigue syndrome

OBJECTIVE

Patients with chronic fatigue syndrome (CFS) commonly report problems with attention, memory, learning, and speed of cognitive processing. This study attempted to evaluate these complaints using objective test criteria.

METHOD

A test battery composed of six tests assessing these cognitive functions was given on two consecutive days. Twenty CFS patients were compared with 20 healthy control subjects and 14 patients with a history of major depression or dysthymia matched by age, intelligence, education level, and sex.

RESULTS

Compared with control subjects, CFS patients consistently scored lower on tests in which motor and cognitive processing speeds were a critical factor, eg, reaction-time tasks. They also had more difficulty on working-memory tests in which rapid cognitive processing speed is also an important factor. The effort made on the first day of testing did not result in a decline in cognitive function on the following day. CFS patients did not qualify as having affective disorder by several different diagnostic criteria. Nonetheless, CFS patients' test performances did not differ from patients with a history of major depression or dysthymia.

CONCLUSIONS

It is concluded that, although CFS and major depression and dysthymia have distinct clinical features, these disorders have slowed motor and cognitive processing speed in common.

Sudden vs gradual onset of chronic fatigue syndrome differentiates individuals on cognitive and psychiatric measures

To examine the influence of mode of illness onset on psychiatric status and neuropsychological performance, 36 patients with CFS were divided into two groups: sudden vs gradual onset of symptoms. These two CFS subgroups were compared to each other and to sedentary healthy controls on standardized neuropsychological tests of attention/concentration, information processing efficiency, memory, and higher cortical functions. In addition, the distribution of comorbid Axis I psychiatric disease between the two CFS groups was examined. The rate of concurrent psychiatric disease was significantly greater in the CFS-gradual group relative to the CFS-sudden group. While both CFS groups showed a significant reduction in information processing ability relative to controls, impairment in memory was more severe in the CFS-sudden group. Because of the significant heterogeneity of the CFS population, the need for subgroup analysis is discussed.

Fatigue in the chronic fatigue syndrome: a cognitive phenomenon?

What is the source of the perception of excessive fatigue in the chronic fatigue syndrome (CFS)? Studies of physiological response to aerobic activity, of muscle pathology and muscle function in CFS, are reviewed, and suggest that the subjective report of fatigue is not due to any peripheral impairment. In addition, current technological methods such as electroencephalography have failed to uncover the nature of any abnormality in the central motor unit. A physiological model which proposes that patients with CFS possess a reduced threshold for sensory fatigue signals is rejected, because it fails to account for recent findings. Instead, it is suggested that the perception of fatigue in CFS is enhanced by idiosyncrasies in cognitive processing. The implications of this view to our understanding of the perpetuation of CFS as a whole are explored.

Cognitive functioning in patients with chronic fatigue syndrome

A comprehensive battery of neuropsychological tests was administered to 35 outpatients suffering from Chronic Fatigue Syndrome (CFS). They were compared to 33 normal controls matched for age, gender, intelligence, and education. The patients displayed psychomotor slowing and impaired attention. The learning rate of verbal and visual material for patients with CFS was slower, and delayed recall of verbal and visual information was impaired. Because there was a high variability in cognitive impairment within the CFS group, it would be inappropriate to generalize results to the entire CFS population. Two neuropsychological variables indicating aspects of psychomotor performance and verbal memory were found to discriminate best between patients and controls.

Cognitive deficits in patients with chronic fatigue syndrome

Twenty-nine subjects with chronic fatigue syndrome (CFS) and 25 healthy control subjects were administered a lengthy neuropsychological battery that included standard neuropsychological tests and a computerized set of tasks that spanned the same areas of ability. The primary significant differences between patients and controls were found on tests of learning and memory. These differences remained when the degree of psychiatric symptomatology in the subjects was covaried. Patients on and off psychoactive medications did not differ in their performance on these tasks. These results suggest that at least a subset of CFS patients may experience significant impairments in learning and memory.

Research on cognitive complaints and cognitive functioning in patients with chronic fatigue syndrome (CFS): What conclusions can we draw?

People with chronic fatigue syndrome (CFS) complain of difficulties with concentration and memory yet studies suggest that they do not suffer gross deficits in cognitive functioning. Depressed patients make similar cognitive complaints, and there is symptomatic overlap between CFS and depression. Cognitive complaints and depressed mood are positively correlated in CFS patients but, except on tasks which are particularly sensitive to depression, cognitive performance and depression are not. The inconsistency between cognitive complaints and results of tests of cognitive functioning resembles that found in other subject groups and may be due in part to the inappropriate use of laboratory memory tests for assessing "everyday" cognitive functioning. Even when cognitive capacity is intact, cognitive performance may be affected by factors such as arousal, mood, and strategy. In CFS patients, everyday cognitive tasks may require excessive processing resources leaving patients with diminished spare attentional capacity or flexibility.

Selective impairment of auditory processing in chronic fatigue syndrome: a comparison with multiple sclerosis and healthy controls

The most consistent deficit observed in individuals with Chronic Fatigue Syndrome has been in efficiency of information processing. To examine the possibility of a modality-specific impairment, the present study examined subjects with Chronic Fatigue Syndrome, multiple sclerosis, and healthy controls on an auditory-versus visual-paced serial-addition test. 20 subjects with Chronic Fatigue Syndrome, 20 subjects with clinically definite Multiple Sclerosis, and 20 sedentary healthy controls were compared. One-half of the subjects in each group were administered the Paced Auditory Serial Addition Test and the other half were administered the Paced Visual Serial Addition Test. The group with Chronic Fatigue Syndrome was differentially impaired on the auditory relative to the visual processing task. The group with Multiple Sclerosis was equally impaired on both versions of the task. The results are discussed within the framework of Baddeley's model of working memory.

Memory, attention, and executive function in chronic fatigue syndrome

OBJECTIVES

To examine cognitive function in chronic fatigue syndrome.

METHODS

Twenty patients with chronic fatigue syndrome recruited from primary care and 20 matched normal controls were given CANTAB computerised tests of visuospatial memory, attention, and executive function, and verbal tests of letter and category fluency and word association learning.

RESULTS

Patients with chronic fatigue syndrome were impaired, predominantly in the domain of memory but their pattern of performance was unlike that of patients with amnesic syndrome or dementia. They were normal on tests of spatial pattern recognition memory, simultaneous and delayed matching to sample, and pattern-location association learning. They were impaired on tests of spatial span, spatial working memory, and a selective reminding condition of the pattern-location association learning test. An executive test of planning was normal. In an attentional test, eight subjects with chronic fatigue syndrome were unable to learn a response set; the remainder exhibited no impairment in the executive set shifting phase of the test. Patients with chronic fatigue syndrome were also impaired on verbal tests of unrelated word association learning and letter fluency.

CONCLUSION

Patients with chronic fatigue syndrome have reduced attentional capacity resulting in impaired performance on effortful tasks requiring planned or self ordered generation of responses from memory.