Background
Chronic fatigue syndrome (CFS) is characterised by persistent, medically unexplained fatigue, as well as symptoms such as musculoskeletal pain, sleep disturbance, headaches and impaired concentration and short-term memory. CFS presents as a common, debilitating and serious health problem. Treatment may include physical interventions, such as exercise therapy, which was last reviewed in 2004.

Objectives
The objective of this review was to determine the effects of exercise therapy (ET) for patients with CFS as compared with any other intervention or control.

• Exercise therapy versus 'passive control' (e.g. treatment as usual, waiting-list control, relaxation, flexibility).

• Exercise therapy versus other active treatment (e.g. cognitive-behavioural therapy (CBT), cognitive treatment, supportive therapy, pacing, pharmacological therapy such as antidepressants).

• Exercise therapy in combination with other specified treatment strategies versus other specified treatment strategies (e.g. exercise combined with pharmacological treatment vs pharmacological treatment alone).

Search methods
We searched The Cochrane Collaboration Depression, Anxiety and Neurosis Controlled Trials Register (CCDANCTR), the Cochrane Central Register of Controlled Trials (CENTRAL) and SPORTDiscus up to May 2014 using a comprehensive list of free-text terms for CFS and exercise. We located unpublished or ongoing trials through the World Health Organization (WHO) International Clinical Trials Registry Platform (to May 2014). We screened reference lists of retrieved articles and contacted experts in the field for additional studies

Selection criteria
Randomised controlled trials involving adults with a primary diagnosis of CFS who were able to participate in exercise therapy. Studies had to compare exercise therapy with passive control, psychological therapies, adaptive pacing therapy or pharmacological therapy.

Data collection and analysis
Two review authors independently performed study selection, risk of bias assessments and data extraction. We combined continuous measures of outcomes using mean differences (MDs) and standardised mean differences (SMDs). We combined serious adverse reactions and drop-outs using risk ratios (RRs). We calculated an overall effect size with 95% confidence intervals (CIs) for each outcome.

Main results
We have included eight randomised controlled studies and have reported data from 1518 participants in this review. Three studies diagnosed individuals with CFS using the 1994 criteria of the Centers for Disease Control and Prevention (CDC); five used the Oxford criteria. Exercise therapy lasted from 12 to 26 weeks. Seven studies used variations of aerobic exercise therapy such as walking, swimming, cycling or dancing provided at mixed levels in terms of intensity of the aerobic exercise from very low to quite rigorous, whilst one study used anaerobic exercise. Control groups consisted of passive control (eight studies; e.g. treatment as usual, relaxation, flexibility) or CBT (two studies), cognitive therapy (one study), supportive listening (one study), pacing (one study), pharmacological treatment (one study) and combination treatment (one study). Risk of bias varied across studies, but within each study, little variation was found in the risk of bias across our primary and secondary outcome measures.

Investigators compared exercise therapy with 'passive' control in eight trials, which enrolled 971 participants. Seven studies consistently showed a reduction in fatigue following exercise therapy at end of treatment, even though the fatigue scales used different scoring systems: an 11-item scale with a scoring system of 0 to 11 points (MD -6.06, 95% CI -6.95 to -5.17; one study, 148 participants; low-quality evidence); the same 11-item scale with a scoring system of 0 to 33 points (MD -2.82, 95% CI -4.07 to -1.57; three studies, 540 participants; moderate-quality evidence); and a 14-item scale with a scoring system of 0 to 42 points (MD -6.80, 95% CI -10.31 to -3.28; three studies, 152 participants; moderate-quality evidence). Serious adverse reactions were rare in both groups (RR 0.99, 95% CI 0.14 to 6.97; one study, 319 participants; moderate-quality evidence), but sparse data made it impossible for review authors to draw conclusions. Study authors reported a positive effect of exercise therapy at end of treatment with respect to sleep (MD -1.49, 95% CI -2.95 to -0.02; two studies, 323 participants), physical functioning (MD 13.10, 95% CI 1.98 to 24.22; five studies, 725 participants) and self-perceived changes in overall health (RR 1.83, 95% CI 1.39 to 2.40; four studies, 489 participants). It was not possible for review authors to draw conclusions regarding the remaining outcomes.

Investigators compared exercise therapy with CBT in two trials (351 participants). One trial (298 participants) reported little or no difference in fatigue at end of treatment between the two groups using an 11-item scale with a scoring system of 0 to 33 points (MD 0.20, 95% CI -1.49 to 1.89). Both studies measured differences in fatigue at follow-up, but neither found differences between the two groups using an 11-item fatigue scale with a scoring system of 0 to 33 points (MD 0.30, 95% CI -1.45 to 2.05) and a nine-item Fatigue Severity Scale with a scoring system of 1 to 7 points (MD 0.40, 95% CI -0.34 to 1.14). Serious adverse reactions were rare in both groups (RR 0.67, 95% CI 0.11 to 3.96). We observed little or no difference in physical functioning, depression, anxiety and sleep, and we were not able to draw any conclusions with regard to pain, self-perceived changes in overall health, use of health service resources and drop-out rate.

With regard to other comparisons, one study (320 participants) suggested a general benefit of exercise over adaptive pacing, and another study (183 participants) a benefit of exercise over supportive listening. The available evidence was too sparse to draw conclusions about the effect of pharmaceutical interventions.

Authors' conclusions
Patients with CFS may generally benefit and feel less fatigued following exercise therapy, and no evidence suggests that exercise therapy may worsen outcomes. A positive effect with respect to sleep, physical function and self-perceived general health has been observed, but no conclusions for the outcomes of pain, quality of life, anxiety, depression, drop-out rate and health service resources were possible. The effectiveness of exercise therapy seems greater than that of pacing but similar to that of CBT. Randomised trials with low risk of bias are needed to investigate the type, duration and intensity of the most beneficial exercise intervention.

/pdf/exercise-therapy-for-chronic-fatigue-syndrome-1wr6399vh0.pdf

Exercise therapy for chronic fatigue syndrome

The novel virus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a pandemic of coronavirus disease 2019 (COVID-19). Across the globe, a subset of patients who sustain an acute SARS-CoV-2 infection are developing a wide range of persistent symptoms that do not resolve over the course of many months. These patients are being given the diagnosis Long COVID or Post-acute sequelae of COVID-19 (PASC). It is likely that individual patients with a PASC diagnosis have different underlying biological factors driving their symptoms, none of which are mutually exclusive. This paper details mechanisms by which RNA viruses beyond just SARS-CoV-2 have be connected to long-term health consequences. It also reviews literature on acute COVID-19 and other virus-initiated chronic syndromes such as post-Ebola syndrome or myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) to discuss different scenarios for PASC symptom development. Potential contributors to PASC symptoms include consequences from acute SARS-CoV-2 injury to one or multiple organs, persistent reservoirs of SARS-CoV-2 in certain tissues, re-activation of neurotrophic pathogens such as herpesviruses under conditions of COVID-19 immune dysregulation, SARS-CoV-2 interactions with host microbiome/virome communities, clotting/coagulation issues, dysfunctional brainstem/vagus nerve signaling, ongoing activity of primed immune cells, and autoimmunity due to molecular mimicry between pathogen and host proteins. The individualized nature of PASC symptoms suggests that different therapeutic approaches may be required to best manage care for specific patients with the diagnosis.

/pdf/long-covid-or-post-acute-sequelae-of-covid-19-pasc-an-4ke9c5zwcr.pdf

Long COVID or Post-acute Sequelae of COVID-19 (PASC): An Overview of Biological Factors That May Contribute to Persistent Symptoms

Although some signs of inflammation have been reported previously in patients with myalgic encephalomyelitis or chronic fatigue syndrome (ME/CFS), the data are limited and contradictory. High-throughput methods now allow us to interrogate the human immune system for multiple markers of inflammation at a scale that was not previously possible. To determine whether a signature of serum cytokines could be associated with ME/CFS and correlated with disease severity and fatigue duration, cytokines of 192 ME/CFS patients and 392 healthy controls were measured using a 51-multiplex array on a Luminex system. Each cytokine’s preprocessed data were regressed on ME/CFS severity plus covariates for age, sex, race, and an assay property of newly discovered importance: nonspecific binding. On average, TGF-β was elevated (P = 0.0052) and resistin was lower (P = 0.0052) in patients compared with controls. Seventeen cytokines had a statistically significant upward linear trend that correlated with ME/CFS severity: CCL11 (Eotaxin-1), CXCL1 (GROα), CXCL10 (IP-10), IFN-γ, IL-4, IL-5, IL-7, IL-12p70, IL-13, IL-17F, leptin, G-CSF, GM-CSF, LIF, NGF, SCF, and TGF-α. Of the 17 cytokines that correlated with severity, 13 are proinflammatory, likely contributing to many of the symptoms experienced by patients and establishing a strong immune system component of the disease. Only CXCL9 (MIG) inversely correlated with fatigue duration.

https://www.pnas.org/content/pnas/114/34/E7150.full.pdf

Cytokine signature associated with disease severity in chronic fatigue syndrome patients

Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is a disease characterized by chronic, profound, disabling, and unexplained fatigue. Although it is hypothesized that brain inflammation is involved in the pathophysiology of CFS/ME, there is no direct evidence of neuroinflammation in patients with CFS/ME. Activation of microglia or astrocytes is related to neuroinflammation. 11C-(R)-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinoline-carboxamide (11C-(R)-PK11195) is a ligand of PET for a translocator protein that is expressed by activated microglia or astrocytes. We used 11C-(R)-PK11195 and PET to investigate the existence of neuroinflammation in CFS/ME patients. Methods: Nine CFS/ME patients and 10 healthy controls underwent 11C-(R)-PK11195 PET and completed questionnaires about fatigue, fatigue sensation, cognitive impairments, pain, and depression. To measure the density of translocator protein, nondisplaceable binding potential (BPND) values were determined using linear graphical analysis with the cerebellum as a reference region. Results: The BPND values of 11C-(R)-PK11195 in the cingulate cortex, hippocampus, amygdala, thalamus, midbrain, and pons were 45%–199% higher in CFS/ME patients than in healthy controls. In CFS/ME patients, the BPND values of 11C-(R)-PK11195 in the amygdala, thalamus, and midbrain positively correlated with cognitive impairment score, the BPND values in the cingulate cortex and thalamus positively correlated with pain score, and the BPND value in the hippocampus positively correlated with depression score. Conclusion: Neuroinflammation is present in widespread brain areas in CFS/ME patients and was associated with the severity of neuropsychologic symptoms. Evaluation of neuroinflammation in CFS/ME patients may be essential for understanding the core pathophysiology and for developing objective diagnostic criteria and effective medical treatments.

https://jnm.snmjournals.org/content/jnumed/55/6/945.full.pdf

Neuroinflammation in Patients with Chronic Fatigue Syndrome/Myalgic Encephalomyelitis: An ¹¹C-(R)-PK11195 PET Study.

Objective To identify case definitions for chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME), and explore how the validity of case definitions can be evaluated in the absence of a reference standard. Design Systematic review. Setting International. Participants A literature search, updated as of November 2013, led to the identification of 20 case definitions and inclusion of 38 validation studies. Primary and secondary outcome measure Validation studies were assessed for risk of bias and categorised according to three validation models: (1) independent application of several case definitions on the same population, (2) sequential application of different case definitions on patients diagnosed with CFS/ME with one set of diagnostic criteria or (3) comparison of prevalence estimates from different case definitions applied on different populations. Results A total of 38 studies contributed data of sufficient quality and consistency for evaluation of validity, with CDC-1994/Fukuda as the most frequently applied case definition. No study rigorously assessed the reproducibility or feasibility of case definitions. Validation studies were small with methodological weaknesses and inconsistent results. No empirical data indicated that any case definition specifically identified patients with a neuroimmunological condition. Conclusions Classification of patients according to severity and symptom patterns, aiming to predict prognosis or effectiveness of therapy, seems useful. Development of further case definitions of CFS/ME should be given a low priority. Consistency in research can be achieved by applying diagnostic criteria that have been subjected to systematic evaluation.

https://bmjopen.bmj.com/content/bmjopen/4/2/e003973.full.pdf

Case definitions for chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME): a systematic review.

12 FatigueConsultationClinic,SaltLake RegionalMedicalCenter; 13 InternalMedicine,FamilyPractice,UniversityofUtah,SaltLakeCity,UT,USA; 14 ME ⁄CFSCenter,OsloUniversity HospitalHF,Norway; 15 DepartmentofPaediatrics,StateUniversityofNewYork,Buffalo,NY,USA; 16 Independent,Pavia,Italy; 17 Harbor-UCLA MedicalCenter,UniversityofCalifornia,LosAngeles,CA; 18 EVMedResearch,Lomita,CA,USA; 19 UniversityofLimerick,Limerick,Ireland; 20 Pain Clinic,KonyangUniversityHospital,Daejeon,Korea; 21 DonvaleSpecialistMedicalCentre,Donvale,Victoria,Australia; 22 Departmentsof Anesthesiology,NeurobiologyandAnatomy,UniversityofUtah,SaltLakeCity,UT,USA; 23 DepartmentofMedicinaNuclear,ClinicaLasCondes, Santiago,Chile; 24 WhittemorePetersonInstitute,UniversityofNevada,Reno,NV,USA; 25 MiwaNaikaClinic,Toyama,Japan; 26 A.Kirchenstein InstituteofMicrobiologyandVirology,RigaStradinsUniversity,Riga,Latvia; 27 DepartmentofBiochemistryBand 28 DepartmentofSportsSciences,UniversityofthePacific,Stockton,CAUSA

/pdf/myalgic-encephalomyelitis-international-consensus-criteria-p4byo9u7n7.pdf

M. L. Pall

Papers

Myalgic encephalomyelitis: International Consensus Criteria