Chronic fatigue syndrome: an update focusing on phenomenology and pathophysiology

Comparison of Fatigue Level, Musculoskeletal Disorders and Physical Activity Level in Aircraft Engineers Working in the Morning Shift and Night Shift

Background Shift work is a system in which different groups of workers work at different times of the day and night. It may affect the physiological health of an individual and hence fatigue, musculoskeletal disorder and changes in physical activity may arise.

Objective To compare the fatigue level, musculoskeletal disorders (MSDs) and physical activity level in aircraft engineers working in morning shift and night shift.

Method The study consisted of 100 aircraft engineers working at Indira Gandhi International Airport, Terminal 1. 50 aircraft engineers working in morning shift and 50 aircraft engineers working in night shift participated in the study. Self-administered questionnaire i. e., Chalder Fatigue Scale, Nordic Musculoskeletal Questionnaire and International Physical Activity Questionnaire were used to access the fatigue level, the number of MSDs, and physical activity level, respectively.

Results The results showed significant difference in fatigue level, and the level of physical activity morning shift versus night shift workers (p<0.001). The mean value of fatigue level in morning shift was 4.9 and in night shift was 14.6. The average mean value of physical activity level in morning shift was 1972.61 MET min a week and in night shift was 1277.83 MET min a week. MSDs were more common in night shift workers as compared to morning shift workers.

Conclusion The findings of the study suggested an increased in the level of fatigue and decrease in the physical activity level among aircraft engineers working night shift compared to those working morning shift. There are more MSDs in aircraft engineers working night shift as compared to those working morning shift.

Effect of Coelogyne cristata Lindley in alleviation of chronic fatigue syndrome in aged Wistar rats

BACKGROUND

Swarna Jibanti scientifically known as Coelogyne cristata Lindley (Orchidaceae), an orchid mentioned in Ayurvedic medicine is used to promote healthy life span.

OBJECTIVE(S)

The present work was planned to study the efficacy of hydro-alcoholic extract of pseudobulbs of C. cristata (CCE) to assess its role on chronic fatigue syndrome (CFS) induced behavioural and biochemical changes in aged Wistar rats compared to Panax ginseng (PG), a prototype anti-stress agent.

MATERIALS AND METHODS

CFS was induced by forced swimming for consecutive 21 days for fixed duration (15 min sessions). The criteria of CFS due to fatigue were counted using locomotor activity, depression and anxiety through automated photactometer, immobility time and plus maze activity respectively. Acute toxicity study of CCE (upto 2 g/kg, Limit test) was also performed. For CFS, animals were divided into five groups, naive control, control, CCE treated (25 mg/kg b.w., 250 mg/kg b.w.) and standard PG treated (100 mg/kg b.w.) groups. All drugs were given orally for consecutive 21 days along with CFS. After assessing behavioural parameters, all animals were sacrificed at day 21 and in vivo antioxidant potential of CCE was determined by lipid peroxides, nitrite, catalase (CAT) and superoxide dismutase (SOD) in brain tissue.

RESULTS

CCE was found to be non-toxic. CCE treated aged rats significantly improved (p < 0.001) the spontaneous locomotor movement with respect to control rats, while, decreased the mobility period or depression score. In CFS, CCE also enhanced the time spent (p < 0.001) in open arms while reducing the time spent in closed arm as compared to CFS control, indicating lowering anxiety score. Moreover, marked diminution in lipid peroxidation, nitrite and SOD level was exhibited after CCE treatment and significantly enhanced catalase level significantly (p < 0.01) with respect to CFS control. PG also showed similar actions.

CONCLUSION

The results confirmed the potential therapeutic actions of CCE against experimentally induced CFS in aged rats that might be due to its CNS mediatory antioxidant properties.

The association between borderline personality disorder, fibromyalgia and chronic fatigue syndrome: systematic review

BACKGROUND

Overlap of aetiological factors and demographic characteristics with clinical observations of comorbidity has been documented in fibromyalgia syndrome, chronic fatigue syndrome (CFS) and borderline personality disorder (BPD).

AIMS

The purpose of this study was to assess the association of BPD with fibromyalgia syndrome and CFS. The authors reviewed literature on the prevalence of BPD in patients with fibromyalgia or CFS and vice versa.

METHODS

A search of five databases yielded six eligible studies. A hand search and contact with experts yielded two additional studies. We extracted information pertaining to study setting and design, demographic information, diagnostic criteria and prevalence.

RESULTS

We did not identify any studies that specifically assessed the prevalence of fibromyalgia or CFS in patients with BPD. Three studies assessed the prevalence of BPD in fibromyalgia patients and reported prevalence of 1.0, 5.25 and 16.7%. Five studies assessed BPD in CFS patients and reported prevalence of 3.03, 1.8, 2.0, 6.5 and 17%.

CONCLUSIONS

More research is required to clarify possible associations between BPD, fibromyalgia and CFS.

DECLARATION OF INTEREST

None.

COPYRIGHT AND USAGE

© The Royal College of Psychiatrists 2016. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) license.

The impact of chronic fatigue syndrome on cognitive functioning in adolescents

Chronic fatigue syndrome (CFS) is characterized by persistent fatigue and severe disability. Most adolescent patients report attention and concentration problems, with subsequent poor performance at school. This study investigated the impact of CFS on intellectual capacity by (1) assessing discrepancies between current intelligence quotient (IQ) and school level and (2) exploring differences in current IQ and pre-CFS school performance, compared with healthy individuals. Current data was cross-sectionally gathered and compared with retrospective pre-CFS school performance data. Fifty-nine CFS adolescents and 40 controls were evaluated on performance on age-appropriate intelligence tests and school level. Current IQ scores of CFS adolescents were lower than expected on the basis of their school level. Furthermore, there was a difference in intelligence performance across time when current IQ scores were compared with pre-CFS cognitive achievement. Healthy controls did not show any discrepancies.

CONCLUSION

According to their pre-CFS intelligence assessments, CFS patients started with appropriate secondary school levels at the age of 12. Our data suggest that CFS may be accompanied by a decline in general cognitive functioning. Given the critical age for intellectual development, we recommend a timely diagnosis followed by appropriate treatment of CFS in adolescents.

WHAT IS KNOWN

Adolescent chronic fatigue syndrome (CFS) is a debilitating condition with major impact on social and intellectual development. Most patients report concentration problems, with subsequent poor performance at school. Little is known about the influence of CFS on intellectual performances.

WHAT IS NEW

IQ scores of CFS adolescents are lower than the IQ scores of healthy peers with an equivalent school level. There is a decrease in intelligence performance across time when current IQ scores are compared with pre-CFS cognitive achievement. Healthy controls do not show any discrepancies between their current IQ, school level and previous cognitive functioning. This suggest that adolescent CFS may be accompanied by a decline in general cognitive functioning.

Distinct plasma immune signatures in ME/CFS are present early in the course of illness

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is an unexplained incapacitating illness that may affect up to 4 million people in the United States alone. There are no validated laboratory tests for diagnosis or management despite global efforts to find biomarkers of disease. We considered the possibility that inability to identify such biomarkers reflected variations in diagnostic criteria and laboratory methods as well as the timing of sample collection during the course of the illness. Accordingly, we leveraged two large, multicenter cohort studies of ME/CFS to assess the relationship of immune signatures with diagnosis, illness duration, and other clinical variables. Controls were frequency-matched on key variables known to affect immune status, including season of sampling and geographic site, in addition to age and sex. We report here distinct alterations in plasma immune signatures early in the course of ME/CFS (n = 52) relative to healthy controls (n = 348) that are not present in subjects with longer duration of illness (n = 246). Analyses based on disease duration revealed that early ME/CFS cases had a prominent activation of both pro- and anti-inflammatory cytokines as well as dissociation of intercytokine regulatory networks. We found a stronger correlation of cytokine alterations with illness duration than with measures of illness severity, suggesting that the immunopathology of ME/CFS is not static. These findings have critical implications for discovery of interventional strategies and early diagnosis of ME/CFS.

Myalgic Encephalomyelitis: Symptoms and Biomarkers

Myalgic Encephalomyelitis (ME) continues to cause significant morbidity worldwide with an estimated one million cases in the United States. Hurdles to establishing consensus to achieve accurate evaluation of patients with ME continue, fueled by poor agreement about case definitions, slow progress in development of standardized diagnostic approaches, and issues surrounding research priorities. Because there are other medical problems, such as early MS and Parkinson's Disease, which have some similar clinical presentations, it is critical to accurately diagnose ME to make a differential diagnosis. In this article, we explore and summarize advances in the physiological and neurological approaches to understanding, diagnosing, and treating ME. We identify key areas and approaches to elucidate the core and secondary symptom clusters in ME so as to provide some practical suggestions in evaluation of ME for clinicians and researchers. This review, therefore, represents a synthesis of key discussions in the literature, and has important implications for a better understanding of ME, its biological markers, and diagnostic criteria. There is a clear need for more longitudinal studies in this area with larger data sets, which correct for multiple testing.

Childhood stressors in the development of fatigue syndromes: a review of the past 20 years of research

BACKGROUND

Chronic fatigue syndrome (CFS) and fibromyalgia (FM) are both highly prevalent conditions associated with extreme disability and with the development of co-morbid psychiatric disorders, such as depression and anxiety. Childhood stressors have been shown to induce persistent changes in the function of biological systems potentially relevant to the pathogenesis of both CFS and FM, such as the inflammatory system and the hypothalamic-pituitary-adrenal (HPA) axis. In this review, we examined whether multiple forms of childhood stressors are contributing factors to the development of these disorders, and of the associated psychiatric symptoms.

METHOD

Using PubMed, we identified 31 papers relevant to this narrative review. We included cohort studies and case-control studies, without any exclusion in terms of age and gender. No study characteristics or publication date restrictions were imposed.

RESULTS

Most studies across the literature consistently show that there is a strong association between experiences of childhood stressors and the presence of CFS and FM, with rates of CFS/FM being two- to three-fold higher in exposed than in unexposed subjects. We also found evidence for an increased risk for the development of additional symptoms, such as depression, anxiety and pain, in individuals with CFS and FM with a previous history of childhood stressors, compared with individuals with CFS/FM and no such history.

CONCLUSIONS

Our review confirms that exposure to childhood stressors is associated with the subsequent development of fatigue syndromes such as CFS and FM, and related symptoms. Further studies are needed to identify the mechanisms underlying these associations.

Construct validity and temporal stability of the abridged 31-item Illness Behaviour Questionnaire

OBJECTIVE

Key psychometric information was sought for three newly derived dimensions from an abridged Illness Behaviour Questionnaire (IBQ-31): Affirmation of Illness (AI), Concern for Health (CH) and General Affective State (GAS). The construct validity of these scales was examined along with their test-retest reliability and long-term stability.

DESIGN

A longitudinal, observational study was conducted with 675 participants (general community members and those with either asthma, diabetes and chronic pain or chronic fatigue syndrome) providing self-report questionnaire data at baseline, with additional information sought at three (n = 483; 71.6%) and 12 months (n = 517, 76.6%).

MAIN OUTCOME MEASURES

Construct validity of the IBQ-31 was explored using well-validated psychological measures of Symptom Attributions and Symptom Experience, Cognitive Distortion of Somatic Information and Illness Likelihood.

RESULTS

In general, AI, CH and GAS shared predictable empirical overlap with related psychological indices across the five samples. Adequate three-month test-retest reliability was evident, with greater score variability over 12 months.

CONCLUSION

The IBQ-31 comprises three theoretically relevant dimensions which demonstrate relative short- and long-term stability for individuals with diverse illness experiences. Future investigations should explore the predictive validity of AI, CH and GAS, along with the potential value of 'cut-off' scores for clinical use.

Construction and evaluation of a self rating scale for stress-induced exhaustion disorder, the Karolinska Exhaustion Disorder Scale

Prolonged stress (≥ six months) may cause a condition which has been named exhaustion disorder (ED) with ICD-10 code F43.8. ED is characterised by exhaustion, cognitive problems, poor sleep and reduced tolerance to further stress. ED can cause long term disability and depressive symptoms may develop. The aim was to construct and evaluate a self-rating scale, the Karolinska Exhaustion Disorder Scale (KEDS), for the assessment of ED symptoms. A second aim was to examine the relationship between self-rated symptoms of ED, depression, and anxiety using KEDS and the Hospital Anxiety and Depression Scale (HAD). Items were selected based on their correspondence to criteria for ED as formulated by the Swedish National Board of Health and Welfare (NBHW), with seven response alternatives in a Likert-format. Self-ratings performed by 317 clinically assessed participants were used to analyse the scale’s psychometric properties. KEDS consists of nine items with a scale range of 0–54. Receiver operating characteristics analysis demonstrated that a cut-off score of 19 was accompanied by high sensitivity and specificity (each above 95%) in the discrimination between healthy subjects and patients with ED. Reliability was satisfactory and confirmatory factor analysis revealed that ED, depression and anxiety are best regarded as different phenomena. KEDS may be a useful tool in the assessment of symptoms of Exhaustion Disorder in clinical as well as research settings. There is evidence that the symptom clusters of ED, anxiety and depression, respectively, reflect three different underlying dimensions.

Association of fibromyalgia with altered skeletal muscle characteristics which may contribute to postexertional fatigue in postmenopausal women

OBJECTIVE

To identify muscle physiologic properties that may contribute to postexertional fatigue and malaise in women with fibromyalgia (FM).

METHODS

Healthy postmenopausal women with (n = 11) and without (n = 11) FM, ages 51-70 years, participated in this study. Physical characteristics and responses to self-reported questionnaires were evaluated. Strength loss and tissue oxygenation in response to a fatiguing exercise protocol were used to quantify fatigability and the local muscle hemodynamic profile. Muscle biopsies were performed to assess between-group differences in baseline muscle properties using histochemical, immunohistochemical, and electron microscopic analyses.

RESULTS

There was no significant difference between healthy controls and FM patients in muscle fatigue in response to exercise. However, self-reported fatigue and pain were correlated with prolonged loss of strength following 12 minutes of recovery in patients with FM. Although there was no difference in percent succinate dehydrogenase (SDH)-positive (type I) and SDH-negative (type II) fibers or in mean fiber cross-sectional area between groups, FM patients exhibited greater variability in fiber size and altered fiber size distribution. In healthy controls only, fatigue resistance was strongly correlated with the size of SDH-positive fibers and hemoglobin oxygenation. In contrast, FM patients with the highest percentage of SDH-positive fibers recovered strength most effectively, and this was correlated with capillary density. However, overall, capillary density was lower in the FM group.

CONCLUSION

Peripheral mechanisms, i.e., altered muscle fiber size distribution and decreased capillary density, may contribute to postexertional fatigue in FM. Understanding of these defects in fibromyalgic muscle may provide valuable insight with regard to treatment.

Relationship between autonomic cardiovascular control, case definition, clinical symptoms, and functional disability in adolescent chronic fatigue syndrome: an exploratory study

Chronic Fatigue Syndrome (CFS) is characterized by severe impairment and multiple symptoms. Autonomic dysregulation has been demonstrated in several studies. We aimed at exploring the relationship between indices of autonomic cardiovascular control, the case definition from Centers for Disease Control and Prevention (CDC criteria), important clinical symptoms, and disability in adolescent chronic fatigue syndrome. 38 CFS patients aged 12–18 years were recruited according to a wide case definition (ie. not requiring accompanying symptoms) and subjected to head-up tilt test (HUT) and a questionnaire. The relationships between variables were explored with multiple linear regression analyses. In the final models, disability was positively associated with symptoms of cognitive impairments (p<0.001), hypersensitivity (p<0.001), fatigue (p=0.003) and age (p=0.007). Symptoms of cognitive impairments were associated with age (p=0.002), heart rate (HR) at baseline (p=0.01), and HR response during HUT (p=0.02). Hypersensitivity was associated with HR response during HUT (p=0.001), high-frequency variability of heart rate (HF-RRI) at baseline (p=0.05), and adherence to the CDC criteria (p=0.005). Fatigue was associated with gender (p=0.007) and adherence to the CDC criteria (p=0.04). In conclusion, a) The disability of CFS patients is not only related to fatigue but to other symptoms as well; b) Altered cardiovascular autonomic control is associated with certain symptoms; c) The CDC criteria are poorly associated with disability, symptoms, and indices of altered autonomic nervous activity.

Somatic symptom disorders and illness behaviour: current perspectives

The behavioural aspects of somatic symptom disorders have received minimal research attention to date. The first section of this paper identifies key theoretical perspectives relevant to behavioural responses to illness. Specifically, the sociological concept of illness behaviour is offered as a general framework in which to consider the range of psychosocial factors associated with responses to perceived illness. Further, the potential relevance of the construct of abnormal illness behaviour and the cognitive behavioural conceptualization of health anxiety is explored. The second part of the paper describes various approaches to the operationalization of illness behaviour, with particular emphasis on the Illness Behaviour Questionnaire, an instrument with a rich history of application. Additional insight is provided into two contemporary instruments which aim to measure overt behavioural aspects of illness more specifically. The third and final section of the paper makes recommendations for how future research may advance the understanding of state- versus trait-based characteristics of illness behaviour. Suggestions are made for how adaptive forms of behaviour (e.g. self-management, appropriate coping) may reduce the risk of developing a somatic symptom disorder or alternatively, minimizing the potentially negative psychosocial implications of such a presentation.

Chronic fatigue syndrome

Chronic fatigue syndrome (CFS) is an illness characterized by disabling fatigue of at least 6 months. The aetiology of the condition has been hotly debated. In this chapter the evidence for CFS as a post viral condition and/or a neurological condition is reviewed. Although there is evidence that CFS is triggered by certain viruses in some patients and that neurobiological changes such as hypocortisolism are associated with the syndrome, neither mechanism is sufficient to explain the extent of the symptoms or disability experienced by patients. It is unlikely that CFS can be understood through one aetiological mechanisms. Rather it is a complex illness which is best explained in terms of a multifactorial cognitive behavioural model. This model proposes that CFS is precipitated by life events and/or viral illness in vulnerable individuals, such as those who are genetically predisposed, prone to distress, high achievement, and over or under activity. A self perpetuating cycle where physiological changes, illness beliefs, reduced and inconsistent activity, sleep disturbance, medical uncertainty and lack of guidance interact to maintain symptoms. Treatments based on this model including cognitive behavioural therapy and graded exercise therapy are effective at significantly reducing fatigue and disability in CFS. This chapter provides a description of these approaches and details of the trials conducted in the area.

Inflammatory fatigue and sickness behaviour - lessons for the diagnosis and management of chronic fatigue syndrome

Persistent and severe fatigue is a common part of the presentation of a diverse range of disease processes. There is a growing body of evidence indicating a common inflammatory pathophysiology underlying many conditions where fatigue is a primary patient concern, including chronic fatigue syndrome. This review explores current models of how inflammatory mediators act on the central nervous system to produce fatigue and sickness behaviour, and the commonality of these processes in conditions as diverse as surgical trauma, infection, various cancers, inflammatory bowel disease, connective tissue diseases and autoimmune diseases. We also discuss evidence indicating chronic fatigue syndrome may have important pathophysiological similarities with cytokine mediated sickness behaviour, and what lessons can be applied from sickness behaviour to chronic fatigue syndrome with regards to the diagnosis and management.

[Etiopathogenetic aspects of somatoform disorders]

The etiopathology of somatoform disorders can only be understood against the background of an integrated biopsychosocial model. Cultural and historical influences must be taken into account as well as contemporary settings of scientific or medical priorities. In this context the emphasis on neurobiological findings can be interpreted as the non-accidental struggle for legitimacy of both patients and physicians. Altogether the available data on factors influencing the formation and maintenance of somatoform symptoms has to be described as both diverse and unspecific and thus points to a challenging research program in the coming years.

A systematic review of chronic fatigue syndrome: don't assume it's depression

OBJECTIVE

Chronic fatigue syndrome (CFS) is characterized by profound, debilitating fatigue and a combination of several other symptoms resulting in substantial reduction in occupational, personal, social, and educational status. CFS is often misdiagnosed as depression. The objective of this study was to evaluate and discuss different etiologies, approaches, and management strategies of CFS and to present ways to differentiate it from the fatigue symptom of depression.

DATA SOURCES

A MEDLINE search was conducted to identify existing information about CFS and depression using the headings chronic fatigue syndrome AND depression. The alternative terms major depressive disorder and mood disorder were also searched in conjunction with the term chronic fatigue syndrome. Additionally, MEDLINE was searched using the term chronic fatigue. All searches were limited to articles published within the last 10 years, in English. A total of 302 articles were identified by these searches. Also, the term chronic fatigue syndrome was searched by itself. This search was limited to articles published within the last 5 years, in English, and resulted in an additional 460 articles. Additional publications were identified by manually searching the reference lists of the articles from both searches.

STUDY SELECTION AND DATA EXTRACTION

CFS definitions, etiologies, differential diagnoses (especially depression) and management strategies were extracted, reviewed, and summarized to meet the objectives of this article.

DATA SYNTHESIS

CFS is underdiagnosed in more than 80% of the people who have it; at the same time, it is often misdiagnosed as depression. Genetic, immunologic, infectious, metabolic, and neurologic etiologies were suggested to explain CFS. A biopsychosocial model was suggested for evaluating, managing, and differentiating CFS from depression.

CONCLUSIONS

Evaluating and managing chronic fatigue is a challenging situation for physicians, as it is a challenging and difficult condition for patients. A biopsychosocial approach in the evaluation and management is recommended. More studies about CFS manifestations, evaluation, and management are needed.

Clonidine in the treatment of adolescent chronic fatigue syndrome: a pilot study for the NorCAPITAL trial

BACKGROUND

This pilot study (ClinicalTrials.gov ID: NCT01507701) assessed the feasibility and safety of clonidine in adolescent chronic fatigue syndrome (CFS). Specifically, we assessed clonidine dosage in relation to a) plasma concentration levels, b) orthostatic cardiovascular responses, and c) possible adverse effects.

FINDINGS

Five adolescent CFS patients (14-19 years old) received 50 μg clonidine twice per day during 14 days in an open, uncontrolled design. Plasma concentration of clonidine was assayed by standard laboratory methods. Changes in orthostatic cardiovascular responses were assessed by a 20o head-up tilt-test (HUT). Adverse effects were mapped by a questionnaire.After 14 days, C0 median (range) of clonidine was 0.21 (0.18-0.36) μg/L, and Cmax median (range) of clonidine was 0.41 (0.38-0.56) μg/L. Also, supine blood pressures and heart rate were lower during clonidine treatment, and the HUT response was closer to the normal response. No serious adverse effects were registered.

CONCLUSION

Clonidine 50 μg BID seems to be safe enough to proceed from a pilot study to a controlled trial in a select group of adolescents with CFS (ClinicalTrials.gov ID: NCT01040429).

Adolescent chronic fatigue syndrome; a follow-up study displays concurrent improvement of circulatory abnormalities and clinical symptoms

BACKGROUND

The pathophysiology of chronic fatigue syndrome (CFS) in adolescents is unknown, and the clinical course and prognosis is still questioned. Recent research indicates that abnormalities of autonomic cardiovascular control may play an important role. The aim of this research project was to perform a follow-up study of adolescents with chronic fatigue syndrome, focusing on clinical symptoms and autonomic cardiovascular control.

METHODS

47 adolescents (12-18 years old) with CFS were recruited from the outpatient clinic at the Department of Pediatrics, Oslo University Hospital. In a primary visit and a follow-up visit (3-17 months later), we evaluated: a) a wide range of complaints and symptoms and b) cardiovascular variables at baseline and during a 20° head-up tilt-test (HUT).

RESULTS

At the second visit, patients reported significant improvement regarding functional impairments, fatigue severity, muscular pain, concentration problems, post-exertional malaise and the problem of non-relieving rest. Also, at the second visit, baseline heart rate (HR), blood pressure, total peripheral resistance index (TPRI) and LF/HF (low-frequency:high-frequency heart rate variability ratio, an index of sinus node sympathovagal balance derived from spectral analyses of heart rate) were significant lower, and the increases in HR, mean blood pressure (MBP), diastolic blood pressure (DBP) and TPRI during tilt were significantly less pronounced as compared to the first visit. There was a significant correlation between changes in autonomic symptom score, fatigue severity score and functional impairment score from the first to the second visit.

CONCLUSIONS

The majority of adolescents with CFS experienced an improvement over time in functional impairment, self-reported fatigue and additional symptoms, and a concurrent improvement of autonomic cardiovascular control. A possible connection between clinical symptoms and abnormal autonomic control in CFS might represent a focus for further research.

Chronic fatigue syndrome after Giardia enteritis: clinical characteristics, disability and long-term sickness absence

Background

A waterborne outbreak of Giardia lamblia gastroenteritis led to a high prevalance of long-lasting fatigue and abdominal symptoms. The aim was to describe the clinical characteristics, disability and employmentloss in a case series of patients with Chronic Fatigue Syndrome (CFS) after the infection.

Methods

Patients who reported persistent fatigue, lowered functional capacity and sickness leave or delayed education after a large community outbreak of giardiasis enteritis in the city of Bergen, Norway were evaluated with the established Centers for Disease Control and Prevention criteria for CFS. Fatigue was self-rated by the Fatigue Severity Scale (FSS). Physical and mental health status and functional impairment was measured by the Medical Outcome Severity Scale-short Form-36 (SF-36). The Hospital Anxiety and Depression Scale (HADS) was used to measure co-morbid anxiety and depression. Inability to work or study because of fatigue was determined by sickness absence certified by a doctor.

Results

A total of 58 (60%) out of 96 patients with long-lasting post-infectious fatigue after laboratory confirmed giardiasis were diagnosed with CFS. In all, 1262 patients had laboratory confirmed giardiasis. At the time of referral (mean illness duration 2.7 years) 16% reported improvement, 28% reported no change, and 57% reported progressive course with gradual worsening. Mean FSS score was 6.6. A distinctive pattern of impairment was documented with the SF-36. The physical functioning, vitality (energy/fatigue) and social functioning were especially reduced. Long-term sickness absence from studies and work was noted in all patients.

Conclusion

After giardiasis enteritis at least 5% developed clinical characteristics and functional impairment comparable to previously described post-infectious fatigue syndrome.

Hypothalamic-pituitary-adrenal axis dysfunction in chronic fatigue syndrome

The weight of current evidence supports the presence of the following factors related to hypothalamic-pituitary-adrenal (HPA) axis dysfunction in patients with chronic fatigue syndrome (CFS): mild hypocortisolism; attenuated diurnal variation of cortisol; enhanced negative feedback to the HPA axis; and blunted HPA axis responsiveness. Furthermore, HPA axis changes seem clinically relevant, as they are associated with worse symptoms and/or disability and with poorer outcomes to standard treatments for CFS. Regarding etiology, women with CFS are more likely to have reduced cortisol levels. Studies published in the past 8 years provide further support for a multifactorial model in which several factors interact to moderate HPA axis changes. In particular, low activity levels, depression and early-life stress appear to reduce cortisol levels, whereas the use of psychotropic medication can increase cortisol. Addressing these factors-for example, with cognitive behavioral therapy-can increase cortisol levels and is probably the first-line approach for correcting HPA axis dysfunction at present, as steroid replacement is not recommended. Given what is now a fairly consistent pattern of findings for the type of HPA axis changes found in CFS, we recommend that future work focuses on improving our understanding of the cause and relevance of these observed changes.

The common immunogenic etiology of chronic fatigue syndrome: from infections to vaccines via adjuvants to the ASIA syndrome

Chronic fatigue syndrome (CFS) is characterized by unexplained fatigue that lasts for at least 6 months with a constellation of other symptoms. Most cases start suddenly, and are usually accompanied by a flu-like illness. It is a symptom-based diagnosis of exclusion, the pathogenesis of which is unknown. Studies have examined and hypothesized about the possible biomedical and epidemiologic characteristics of the disease, including genetic predisposition, infections, endocrine abnormalities, and immune dysfunction and psychological and psychosocial factors. Recently, the AISA (autoimmune/inflammatory syndrome induced by adjuvants) syndrome was recognized, indicating the possible contribution of adjuvants and vaccines to the development of autoimmunity.

Fatigue, depressive symptoms, and anxiety from adolescence up to young adulthood: a longitudinal study

Fatigue is a common complaint among adolescents. We investigated the course of fatigue in females during the transition from adolescence to young adulthood and examined psychological, immunological, and life style risk factors for development of fatigue and chronic fatigue syndrome (CFS)-related symptoms. Six hundred and thirty-three healthy females (age 14.63±1.37 years) filled out questionnaires measuring fatigue severity, depressive symptoms, anxiety, chronic fatigue syndrome (CFS)-related symptoms, sleep features, and life style characteristics at baseline and 4½ years thereafter. Of 64 participants LPS- and CD2CD28-induced cytokine data at baseline were available. The best predictor of fatigue in young adulthood was previous fatigue severity. In participants who were non-fatigued during adolescence and who experienced a notable increase in fatigue, fatigue development was preceded by emotional problems and CFS-related complaints during adolescence. Increases as well as decreases in fatigue severity were accompanied by respectively increase and decrease in depressive symptoms and anxiety, suggesting that these symptoms cluster and co-vary over time. Higher interferon (IFN)-γ, higher IFN-γ/interleukin (IL)-4 ratio, lower tumor necrosis factor-α and lower IL-10 at baseline were related to fatigue severity at follow up. The rise in total number of CFS-related symptoms at follow up was predicted by anxiety and decreased physical activity during adolescence. Sleep and substance use were associated with fatigue severity and anxiety and depression. In conclusion, vulnerability to develop fatigue and associated symptoms in young adulthood can to a certain extent be identified already years before the manifestation of complaints.

Chronic fatigue syndrome

Chronic fatigue syndrome (CFS) is defined by a profound, debilitating fatigue, lasting for at least 6 months and resulting in a substantial reduction of occupational, personal, social and educational status. CFS is a relatively poorly recognized clinical entity, although everyday experience shows that there are many patients with CFS symptoms. The incidence and prevalence of CFS remain unknown in most countries; however, the working population is most affected with predominantly female patients in generative period. Although, CFS was first mentioned four centuries ago, mysterious aethiopathogensis of CFS still intrigues scientists as hundreds of studies are still published every year on the subject. About 80 different aetiological CFS factors are mentioned, which can be classified into five basic groups: genetics, immunology, infectious diseases, endocrinology and neuropsychiatry-psychology. Even today the condition is passed established based on the diagnosis by exclusion of organic and psychiatric disorders, which demands a multidisciplinary approach. As the syndrome is often misdiagnosed and mistreated, self-medication is not uncommon in CFS patients'. In addition, such patients usually suffer for years tolerating severe fatigue. Thus, at the moment there are three priorities regarding CFS; understanding pathogenesis, development of diagnostic tests and creating efficient treatment program.

Serum cytokine and glucose levels as predictors of poststroke fatigue in acute ischemic stroke patients

Fatigue is a common but often overlooked symptom after stroke. This study investigated whether stroke type, infarct volume, and laterality, as well as the levels of various cytokines and other blood components in the acute phase of acute ischemic stroke (AIS), can predict the level of fatigue at 6, 12, and 18 months after its onset. In 45 patients with acute stroke, serum levels of C-reactive protein, hemoglobin, glucose, and 13 cytokines were measured within 72 h of stroke onset. The cytokine measurements were performed using BioPlex XMap technology (Luminex). The acute serum levels of interleukin (IL)-1β and glucose were positively correlated with the score on the Fatigue Severity Scale (FSS) at 6 months after the stroke (r = 0.37, p = 0.015, and r = 0.37, p = 0.017, respectively). The acute serum levels of IL-ra and IL-9 were negatively correlated with FSS score at 12 months after the stroke (r = −0.38, p = 0.013, and r = −0.36, p = 0.019, respectively). The FSS score at 12 months after stroke was significantly lower in patients with radiologically confirmed infarction than in those without such confirmation (p = 0.048). The FSS score at 18 months was not correlated with any of the measured variables. High acute serum levels of glucose and IL-1β, and low IL1-ra and IL-9 may predict fatigue after AIS, indicating that the development of poststroke fatigue can be accounted for by the proinflammatory response associated with AIS. These novel findings support a new cytokine theory of fatigue after stroke. However, more research is needed to validate the results of this study.

Polymorphisms of adrenergic cardiovascular control genes are associated with adolescent chronic fatigue syndrome

AIM

To explore the frequency of polymorphisms in adrenergic cardiovascular control genes in adolescent with chronic fatigue syndrome (CFS) and the relation of such polymorphisms to cardiovascular variables.

METHODS

DNA from 53 patients with CFS, 12-18 years old, was analysed for five single nucleotide polymorphisms (SNPs) in the genes catechol-O-methyltransferase (COMT), the β₂ -adrenergic receptor (two SNPs), the β₁ -adrenergic receptor and the α₂(a) -adrenergic receptor. Frequencies were compared to a reference population constructed from the National Center for Biotechnology Information (NCBI) database, and associations between frequencies and autonomic cardiovascular responses during a 20° head-up tilt-test were explored.

RESULTS

For the COMT SNP Rs4680, patients with CFS had a higher frequency of the AA genotype and a lower frequency of the G containing genotypes (AG and GG), when compared to the reference sample (p = 0.046). Also, the AA genotype was associated with a smaller increase in LF/HF ratio (low-frequency:high-frequency heart rate variability ratio, an index of cardiac sympathovagal balance) during head-up tilt when compared to the AG/GG genotypes. For the β₂ -adrenergic receptor SNP Rs1042714, patients with CFS had a lower frequency of the GG genotype and a higher frequency of the genotypes containing C (CG and CC) (p = 0.044).

CONCLUSIONS

CFS might be related to polymorphisms of COMT and the β₂ -adrenergic receptor. More details of the molecular mechanisms remain to be investigated.

Elevated nocturnal blood pressure and heart rate in adolescent chronic fatigue syndrome

AIM

To compare ambulatory recordings of heart rate (HR) and blood pressure in adolescents with chronic fatigue syndrome (CFS) and healthy controls. We hypothesized both HR and blood pressure to be elevated among CFS patients.

METHODS

Forty-four CFS patients aged 12-18 years were recruited from our paediatric outpatient clinic. The controls were 52 healthy adolescents having similar distribution of age and gender. 24-h ambulatory blood pressure and HR were recorded using a validated, portable oscillometric device.

RESULTS

At night (sleep), HR, mean arterial blood pressure and diastolic blood pressure were significantly higher in CFS patients as compared with controls (p < 0.01). During daytime, HR was significantly higher among CFS patients (p < 0.05), whereas blood pressures were equal among the two groups.

CONCLUSIONS

The findings support previous experimental evidence of sympathetic predominance of cardiovascular control in adolescent CFS patients. Also, the findings prompt increased focus on cardiovascular risk assessment and suggest a possible target for therapeutic intervention.

No differences in cardiovascular autonomic responses to mental stress in chronic fatigue syndrome adolescents as compared to healthy controls

Chronic fatigue syndrome (CFS) is a disabling disease with unknown etiology. There is accumulating evidence of altered cardiovascular autonomic responses to different somatic stressors, in particular orthostatic stress, whereas autonomic responses to mental stress remain to be investigated. In this study, we explored cardiovascular autonomic responses to a simple mental stress test in CFS patients and healthy controls.A consecutive sample of 13 patients with CFS, aged 12 to 18 years, and a volunteer sample of 53 healthy control subjects of equal age and gender distribution were included. Blood pressure, heart rate and acral skin blood flow were continuously recorded during an arithmetic exercise.At baseline, heart rate was significantly higher among CFS patients than controls (p = 0.02). During the arithmetic exercise, however, there were no significant differences in the responses between the two groups.In conclusion, CFS patients have unaltered autonomic responses to simple mental stress as compared to healthy control subjects.

Blood pressure variability and closed-loop baroreflex assessment in adolescent chronic fatigue syndrome during supine rest and orthostatic stress

Hemodynamic abnormalities have been documented in the chronic fatigue syndrome (CFS), indicating functional disturbances of the autonomic nervous system responsible for cardiovascular regulation. The aim of this study was to explore blood pressure variability and closed-loop baroreflex function at rest and during mild orthostatic stress in adolescents with CFS. We included a consecutive sample of 14 adolescents 12–18 years old with CFS diagnosed according to a thorough and standardized set of investigations and 56 healthy control subjects of equal sex and age distribution. Heart rate and blood pressure were recorded continuously and non-invasively during supine rest and during lower body negative pressure (LBNP) of –20 mmHg to simulate mild orthostatic stress. Indices of blood pressure variability and baroreflex function (α-gain) were computed from monovariate and bivariate spectra in the low-frequency (LF) band (0.04–0.15 Hz) and the high–frequency (HF) band (0.15–0.50 Hz), using an autoregressive algorithm. Variability of systolic blood pressure in the HF range was lower among CFS patients as compared to controls both at rest and during LBNP. During LBNP, compared to controls, α-gain HF decreased more, and α-gain LF and the ratio of α-gain LF/α-gain HF increased more in CFS patients, all suggesting greater shift from parasympathetic to sympathetic baroreflex control. CFS in adolescents is characterized by reduced systolic blood pressure variability and a sympathetic predominance of baroreflex heart rate control during orthostatic stress. These findings may have implications for the pathophysiology of CFS in adolescents.

Hormonal alterations in adolescent chronic fatigue syndrome

AIM

The chronic fatigue syndrome is associated with alterations in the hypothalamus-pituitary-adrenal axis and cardiovascular autonomic nervous activity, suggesting a central dysregulation. This study explored differences among adolescent chronic fatigue syndrome patients and healthy controls regarding antidiuretic hormone, the renin-angiotensin-aldosterone-system, sex hormones and cardiac peptides.

METHODS

We included a consecutive sample of 67 adolescents aged 12-18 years with chronic fatigue syndrome diagnosed according to a thorough and standardized set of investigations, and a volunteer sample of 55 healthy control subjects of equal gender and age distribution. Hormones were assayed with standard laboratory methods.

RESULTS

Among patients, plasma antidiuretic hormone was significantly decreased and serum osmolality and plasma renin activity were significantly increased (p < or = 0.001). Serum concentration of aldosterone, cortisol, NT-proBNP and sex hormones were not significantly different in the two groups.

CONCLUSION

Chronic fatigue syndrome in adolescents is associated with alterations in hormonal systems controlling osmolality and blood volume, possibly supporting a theory of central dysregulation.

A tale of two comorbidities: Understanding the neurobiology of depression and pain

The comorbidity of chronic pain and depression has been consistently associated with a poor prognosis and greater disability in patients as compared to those suffering from each illness alone. This further has implications on significant financial costs to the patients and to our society. The biological underpinnings of major depression and chronic pain have considerable overlap in the areas of genetic, structural, functional, neuroendocrine and neurotransmitter functionality. Although the field has evolved in the past decade, more efforts should now focus on understanding the biological underpinnings of this shared comorbidity, while shedding light on treatment implications for these two devastating conditions.

Prevalence of xenotropic murine leukaemia virus-related virus in patients with chronic fatigue syndrome in the Netherlands: retrospective analysis of samples from an established cohort

OBJECTIVE

The presence of the retrovirus xenotropic murine leukaemia virus-related virus (XMRV) has been reported in peripheral blood mononuclear cells of patients with chronic fatigue syndrome. Considering the potentially great medical and social relevance of such a discovery, we investigated whether this finding could be confirmed in an independent European cohort of patients with chronic fatigue syndrome.

DESIGN

Analysis of a well defined cohort of patients and matched neighbourhood controls by polymerase chain reaction.

SETTING

Certified (ISO 15189) laboratory of clinical virology in a university hospital in the Netherlands. Population Between December 1991 and April 1992, peripheral blood mononuclear cells were isolated from 76 patients and 69 matched neighbourhood controls. In this study we tested cells from 32 patients and 43 controls from whom original cryopreserved phials were still available.

MAIN OUTCOME MEASURES

Detection of XMRV in peripheral blood mononuclear cells by real time polymerase chain reaction assay targeting the XMRV integrase gene and/or a nested polymerase chain reaction assay targeting the XMRV gag gene.

RESULTS

We detected no XMRV sequences in any of the patients or controls in either of the assays, in which relevant positive and negative isolation controls and polymerase chain reaction controls were included. Spiking experiments showed that we were able to detect at least 10 copies of XMRV sequences per 10(5) peripheral blood mononuclear cells by real time as well as by nested polymerase chain reaction, demonstrating high sensitivity of both assays.

CONCLUSIONS

This study failed to show the presence of XMRV in peripheral blood mononuclear cells of patients with chronic fatigue syndrome from a Dutch cohort. These data cast doubt on the claim that XMRV is associated with chronic fatigue syndrome in the majority of patients.

Gene expression in peripheral blood leukocytes in monozygotic twins discordant for chronic fatigue: no evidence of a biomarker

BACKGROUND

Chronic fatiguing illness remains a poorly understood syndrome of unknown pathogenesis. We attempted to identify biomarkers for chronic fatiguing illness using microarrays to query the transcriptome in peripheral blood leukocytes.

METHODS

Cases were 44 individuals who were clinically evaluated and found to meet standard international criteria for chronic fatigue syndrome or idiopathic chronic fatigue, and controls were their monozygotic co-twins who were clinically evaluated and never had even one month of impairing fatigue. Biological sampling conditions were standardized and RNA stabilizing media were used. These methodological features provide rigorous control for bias resulting from case-control mismatched ancestry and experimental error. Individual gene expression profiles were assessed using Affymetrix Human Genome U133 Plus 2.0 arrays.

FINDINGS

There were no significant differences in gene expression for any transcript.

CONCLUSIONS

Contrary to our expectations, we were unable to identify a biomarker for chronic fatiguing illness in the transcriptome of peripheral blood leukocytes suggesting that positive findings in prior studies may have resulted from experimental bias.

The role of antioxidant properties of Nardostachys jatamansi in alleviation of the symptoms of the chronic fatigue syndrome

An experimental model of chronic fatigue syndrome (CFS) is utilized for evaluation of antidepressant, anti-stress effects, wherein the rat is forced to swim in water for 15 min/day on 21 consecutive days. Rats were divided into stressed control, stressed plus standard drug (Panax ginseng) and stressed plus 200 and 500 mg/kg of test drug, i.e., Nardostachys jatamansi extract (NJE) given orally. The immobility during each 5 min periods of 0-5, 5-10 and 10-15 min of stress were noted. Similarly the climbing (struggling) behaviour was noted in the above four groups of rats in intervals of 5 min. The locomotor activity and also the anxiety state in animals were evaluated in an elevated plus maze after CFS in all the four groups. There was a significant increase in despair behaviour and anxiety in stressed control animals on successive days of CFS. Locomotor activity gradually decreased in stressed control group. Treatment with NJE (200 and 500 mg/kg) significantly reversed both paradigms. Biochemical analysis showed that CFS significantly increased lipid peroxidation, nitrite and superoxide dismutase levels and decreased catalase level in rat brain. Administration of NJE (200 and 500 mg/kg) tended to normalize both augmented lipid peroxidation, nitrite, superoxide dismutase activities and catalase level significantly. NJE per se has an antioxidant effect. The results indicate that CFS may lead to oxidative stress, which is mitigated by NJE and so its antioxidant property may be responsible for anti-stress effect of NJE.

Association of peripheral inflammatory markers with chronic fatigue in a population-based sample

Alterations in the innate immune response may contribute to the pathogenesis of chronic fatigue syndrome (CFS). However, studies have been limited by small sample sizes, use of patients from tertiary care settings, inappropriate selection of controls, and failure to control for confounding demographic, medical and behavioral factors independently associated with immune activity. It is also not known whether specific symptoms account for observed associations between CFS and the innate immune response. To address these limitations, the current study examined plasma concentrations of high-sensitivity c-reactive protein (hs-CRP), white blood cell count (WBC) and a combined inflammation factor in a large population-based sample. Log-transformed mean plasma concentrations of hs-CRP were increased in subjects with CFS (n=102) and in subjects with unwellness symptoms that did not meet diagnostic criteria for CFS (defined as "insufficient fatigue" [ISF]) (n=240) when compared to subjects who were well (n=115). Log transformed WBC was increased in ISF and was increased at a trend level in CFS. The combined inflammation factor was increased in both CFS and ISF. Subjects with CFS and ISF did not differ on any of the inflammation measures. In the entire subject population, the physical component summary score (PCS), but not the mental component summary score (MCS), from the Medical Outcomes Study Short Form-36 (SF-36) was negatively associated with each of the inflammation measures. Depressive symptoms were also associated with increased log hs-CRP. After adjustment for age, sex, race, location of residence, BMI, depressive status and immune-modulating medications, subjects classified as ISF continued to demonstrate increased log hs-CRP, WBC and elevations on the inflammation factor when compared to well controls; however, associations between CFS and log hs-CRP and the inflammation factor were no longer statistically significant. After adjustment, PCS score also remained independently associated with each of the inflammation measures. These findings support a role for innate immune activation in unexplained fatigue and unwellness, but do not suggest that immune activation is specific to CFS.

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.

Does hypothalamic-pituitary-adrenal axis hypofunction in chronic fatigue syndrome reflect a 'crash' in the stress system?

The etiopathogenesis of chronic fatigue syndrome (CFS) remains poorly understood. Although neuroendocrine disturbances - and hypothalamic-pituitary-adrenal (HPA) axis hypofunction in particular - have been found in a large proportion of CFS patients, it is not clear whether these disturbances are cause or consequence of the illness. After a review of the available evidence we hypothesize that that HPA axis hypofunction in CFS, conceptualized within a system-biological perspective, primarily reflects a fundamental and persistent dysregulation of the neurobiological stress system. As a result, a disturbed balance between glucocorticoid and inflammatory signaling pathways may give rise to a pathological cytokine-induced sickness response that may be the final common pathway underlying central CFS symptoms, i.e. effort/stress intolerance and pain hypersensitivity. This comprehensive hypothesis on HPA axis hypofunction in CFS may stimulate diagnostic refinement of the illness, inform treatment approaches and suggest directions for future research, particularly focusing on the neuroendocrine-immune interface and possible links between CFS, early and recent life stress, and depression.

Enhanced vagal withdrawal during mild orthostatic stress in adolescents with chronic fatigue

BACKGROUND

Hemodynamic abnormalities have been documented in the chronic fatigue syndrome (CFS), indicating functional disturbances of the autonomic nervous system responsible for cardiovascular regulation. The aim of this study was to investigate autonomic heart rate control during mild orthostatic stress in adolescents with CFS.

METHODS

A total of 14 CFS patients and 56 healthy controls having equal distribution of age and gender underwent lower body negative pressure (LBNP) of horizontal line 20 mmHg. The RR interval (RRI) was recorded continuously, and spectral power densities were computed in the low-frequency (LF) band (0.04-0.15 Hz) and the high-frequency (HF) band (0.15-0.50 Hz) from segments of 120-second length, using an autoregressive algorithm. In addition, the time-domain indices SDNN, pNN50, and r-MSSD were computed.

RESULTS

At rest, CFS had lower RRI than controls (P < 0.05), but indices of variability were similar in the two groups. During LBNP, compared to controls, CFS patients had lower normalized and absolute HF power and r-MSSD (P < 0.05), and higher RRI (P < 0.001), normalized LF power and LF/HF (P < 0.05).

CONCLUSIONS

During mild orthostatic stress, adolescents with CFS appear to have enhanced vagal withdrawal, leading to a sympathetic predominance of heart rate control compared to controls. Possible underlying mechanisms include hypovolemia and abnormalities of reflex mechanisms.

Radiopharmaceuticals: molecular imaging using positron emission tomography

We describe the use of molecules labeled with short-lived emitting radionuclides for molecular imaging in combination with the positron emission tomography technique. How to use molecular probes to visualize and quantitatively determine rates of specific biochemical events such as synaptic transmission, enzymatic processes and binding to specific receptor proteins is highlighted. The sensitivity of the PET technique and the ability to measure and validate relationships between molecular events and biological functions is a key factor for the successful application of PET in biomedical research. In specific applications, the opportunity of using molecules labeled in specific positions may be critical. Molecular imaging using PET is also gaining increasing interest as a tool in drug development, especially when applied to early proof of concept studies in man. In this chapter, the concept of molecular imaging is exemplified and the use of position-specific labeling of tracer molecules as a tool to gain understanding of complex biological processes will be discussed.

Sympathetic cardiovascular control during orthostatic stress and isometric exercise in adolescent chronic fatigue syndrome

The chronic fatigue syndrome (CFS) has been shown to be associated with orthostatic intolerance and cardiovascular dysregulation. We investigated the cardiovascular responses to combined orthostatic stress and isometric exercise in adolescents with CFS. We included a consecutive sample of 15 adolescents 12-18 years old with CFS diagnosed according to a thorough and standardized set of investigations, and a volunteer sample of 56 healthy control subjects of equal sex and age distribution. Heart rate, systolic, mean and diastolic blood pressure, stroke index, and total peripheral resistance index were non-invasively recorded during lower body negative pressure (LBNP) combined with two consecutive periods of handgrip. In addition, we measured baseline plasma catecholamines, and recorded symptoms. At rest, CFS patients had higher heart rate, diastolic blood pressure, plasma norepinephrine (P < 0.01), mean blood pressure and plasma epinephrine (P < 0.05) than controls. During LBNP, CFS patients had a greater increase in heart rate, diastolic blood pressure, mean blood pressure (P < 0.05) and total peripheral resistance index (n.s.) than controls. During handgrip, CFS patients had a smaller increase in heart rate, diastolic blood pressure (P < 0.05), mean blood pressure and total peripheral resistance index (n.s.) than controls. Our results indicate that adolescents with CFS have increased sympathetic activity at rest with exaggerated cardiovascular response to orthostatic stress, but attenuated cardiovascular response when performing isometric exercise during orthostatic stress. This suggests that CFS might be causally related to sympathetic dysfunction.

Sympathetic cardiovascular control during orthostatic stress and isometric exercise in adolescent chronic fatigue syndrome

The chronic fatigue syndrome (CFS) has been shown to be associated with orthostatic intolerance and cardiovascular dysregulation. We investigated the cardiovascular responses to combined orthostatic stress and isometric exercise in adolescents with CFS. We included a consecutive sample of 15 adolescents 12-18 years old with CFS diagnosed according to a thorough and standardized set of investigations, and a volunteer sample of 56 healthy control subjects of equal sex and age distribution. Heart rate, systolic, mean and diastolic blood pressure, stroke index, and total peripheral resistance index were non-invasively recorded during lower body negative pressure (LBNP) combined with two consecutive periods of handgrip. In addition, we measured baseline plasma catecholamines, and recorded symptoms. At rest, CFS patients had higher heart rate, diastolic blood pressure, plasma norepinephrine (P < 0.01), mean blood pressure and plasma epinephrine (P < 0.05) than controls. During LBNP, CFS patients had a greater increase in heart rate, diastolic blood pressure, mean blood pressure (P < 0.05) and total peripheral resistance index (n.s.) than controls. During handgrip, CFS patients had a smaller increase in heart rate, diastolic blood pressure (P < 0.05), mean blood pressure and total peripheral resistance index (n.s.) than controls. Our results indicate that adolescents with CFS have increased sympathetic activity at rest with exaggerated cardiovascular response to orthostatic stress, but attenuated cardiovascular response when performing isometric exercise during orthostatic stress. This suggests that CFS might be causally related to sympathetic dysfunction.

Rehabilitation of decreased motor performance in patients with chronic fatigue syndrome: should we treat low effort capacity or reduced effort tolerance?

Aim: The aetiology, pathophysiology, diagnostic delineation and treatment of chronic fatigue syndrome (CFS) remain a matter of debate. Here some aspects of the debate are elucidated, with a particular focus on the patients' decreased motor performance.

Hypothesis: The pathophysiological basis of decreased motor performance in CFS may, theoretically, involve three components: (1) a peripheral energetic deficit (impaired oxidative metabolism and/or physical deconditioning); (2) a central perceptual disturbance (higher effort sense or increased `interoception'); and (3) a fundamental failure of the neurobiological stress system, leading to an abnormal `sickness response'. It is proposed that the first two components may lead to low effort capacity, while the third component may lead to reduced effort tolerance. Although there is evidence for low effort capacity influencing symptoms and functional limitations in CFS, it is assumed that reduced effort tolerance might be the primary disturbance in CFS.

Diagnostic implications: Distinguishing low effort capacity and reduced effort tolerance may contribute to a refinement of current diagnostic criteria of CFS and the identification of subgroups.

Therapeutic implications: The above-mentioned distinction may make it possible to formulate a rationale for an effective implementation and adequate outcome evaluation of rehabilitation strategies in CFS.

Research implications: This new heuristic framework may inform future research aimed at disentangling the complex determination of impaired motor performance in CFS, as well as studies aimed at customizing treatment to different subtypes of patients.