Evidence of altered cardiac autonomic regulation in myalgic encephalomyelitis/chronic fatigue syndrome: A systematic review and meta-analysis

Cardiopulmonary and metabolic responses during a 2-day CPET in myalgic encephalomyelitis/chronic fatigue syndrome: translating reduced oxygen consumption to impairment status to treatment considerations

BACKGROUND

Post-exertional malaise (PEM), the hallmark symptom of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), represents a constellation of abnormal responses to physical, cognitive, and/or emotional exertion including profound fatigue, cognitive dysfunction, and exertion intolerance, among numerous other maladies. Two sequential cardiopulmonary exercise tests (2-d CPET) provide objective evidence of abnormal responses to exertion in ME/CFS but validated only in studies with small sample sizes. Further, translation of results to impairment status and approaches to symptom reduction are lacking.

METHODS

Participants with ME/CFS (Canadian Criteria; n = 84) and sedentary controls (CTL; n = 71) completed two CPETs on a cycle ergometer separated by 24 h. Two-way repeated measures ANOVA compared CPET measures at rest, ventilatory/anaerobic threshold (VAT), and peak effort between phenotypes and CPETs. Intraclass correlations described stability of CPET measures across tests, and relevant objective CPET data indicated impairment status. A subset of case-control pairs (n = 55) matched for aerobic capacity, age, and sex, were also analyzed.

RESULTS

Unlike CTL, ME/CFS failed to reproduce CPET-1 measures during CPET-2 with significant declines at peak exertion in work, exercise time, V ˙ e, V ˙ O2, V ˙ CO2, V ˙ T, HR, O2pulse, DBP, and RPP. Likewise, CPET-2 declines were observed at VAT for V ˙ e/ V ˙ CO2, PetCO2, O2pulse, work, V ˙ O2 and SBP. Perception of effort (RPE) exceeded maximum effort criteria for ME/CFS and CTL on both CPETs. Results were similar in matched pairs. Intraclass correlations revealed greater stability in CPET variables across test days in CTL compared to ME/CFS owing to CPET-2 declines in ME/CFS. Lastly, CPET-2 data signaled more severe impairment status for ME/CFS compared to CPET-1.

CONCLUSIONS

Presently, this is the largest 2-d CPET study of ME/CFS to substantiate impaired recovery in ME/CFS following an exertional stressor. Abnormal post-exertional CPET responses persisted compared to CTL matched for aerobic capacity, indicating that fitness level does not predispose to exertion intolerance in ME/CFS. Moreover, contributions to exertion intolerance in ME/CFS by disrupted cardiac, pulmonary, and metabolic factors implicates autonomic nervous system dysregulation of blood flow and oxygen delivery for energy metabolism. The observable declines in post-exertional energy metabolism translate notably to a worsening of impairment status. Treatment considerations to address tangible reductions in physiological function are proffered.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov, retrospectively registered, ID# NCT04026425, date of registration: 2019-07-17.

Long COVID as a disease of accelerated biological aging: An opportunity to translate geroscience interventions

It has been four years since long COVID-the protracted consequences that survivors of COVID-19 face-was first described. Yet, this entity continues to devastate the quality of life of an increasing number of COVID-19 survivors without any approved therapy and a paucity of clinical trials addressing its biological root causes. Notably, many of the symptoms of long COVID are typically seen with advancing age. Leveraging this similarity, we posit that Geroscience-which aims to target the biological drivers of aging to prevent age-associated conditions as a group-could offer promising therapeutic avenues for long COVID. Bearing this in mind, this review presents a translational framework for studying long COVID as a state of effectively accelerated biological aging, identifying research gaps and offering recommendations for future preclinical and clinical studies.

Faecal microbiota transplantation (FMT) in Norwegian outpatients with mild to severe myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS): protocol for a 12-month randomised double-blind placebo-controlled trial

INTRODUCTION

The observed alteration of the intestinal microbiota in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and the effect of transferring a healthy gut flora from a faecal donor using a faecal microbiota transplantation (FMT) will be explored in this trial.

METHODS AND ANALYSIS

This is a protocol for a randomised, double-blind, placebo-controlled, parallel-group, single-centre trial, with 12 months follow-up. 80 participants will be included and randomised (1:1:2) to either donor FMT (from two different donors) or placebo (autologous FMT). Participants will be included by the International Clinical Criteria for ME/CFS. The clinical measures of ME/CFS and disease activity include Modified DePaul Questionnaire, Fatigue Severity Scale (FSS), Hospital Anxiety and Depression Scale (HADS), 36-Item Short Form Health Survey (SF-36), ROMA IV criteria, Food Frequency Questionnaire, Repeatable Battery for the Assessment of Neuropsychological Status, heart rate variability testing and reports on the use of antibiotics and food supplements, as well as biobanking of blood, urine and faeces.The primary endpoint is proportion with treatment success in FSS score in donor versus autologous FMT group 3 months after treatment. Treatment success is defined as an FSS improvement of more than 1.2 points from baseline at 3 months after treatment. Adverse events will be registered throughout the study.

ETHICS AND DISSEMINATION

The Regional Committee for Medical Research Ethics Northern Norway has approved the study. The study has commenced in May 2019. Findings will be disseminated in international peer-reviewed journal(s), submitted to relevant conferences, and trial participants will be informed via phone calls.

TRIAL REGISTRATION NUMBER

NCT03691987.

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: the biology of a neglected disease

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a chronic, debilitating disease characterised by a wide range of symptoms that severely impact all aspects of life. Despite its significant prevalence, ME/CFS remains one of the most understudied and misunderstood conditions in modern medicine. ME/CFS lacks standardised diagnostic criteria owing to variations in both inclusion and exclusion criteria across different diagnostic guidelines, and furthermore, there are currently no effective treatments available. Moving beyond the traditional fragmented perspectives that have limited our understanding and management of the disease, our analysis of current information on ME/CFS represents a significant paradigm shift by synthesising the disease's multifactorial origins into a cohesive model. We discuss how ME/CFS emerges from an intricate web of genetic vulnerabilities and environmental triggers, notably viral infections, leading to a complex series of pathological responses including immune dysregulation, chronic inflammation, gut dysbiosis, and metabolic disturbances. This comprehensive model not only advances our understanding of ME/CFS's pathophysiology but also opens new avenues for research and potential therapeutic strategies. By integrating these disparate elements, our work emphasises the necessity of a holistic approach to diagnosing, researching, and treating ME/CFS, urging the scientific community to reconsider the disease's complexity and the multifaceted approach required for its study and management.

Herpesvirus Infection of Endothelial Cells as a Systemic Pathological Axis in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Understanding the pathophysiology of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is critical for advancing treatment options. This review explores the novel hypothesis that a herpesvirus infection of endothelial cells (ECs) may underlie ME/CFS symptomatology. We review evidence linking herpesviruses to persistent EC infection and the implications for endothelial dysfunction, encompassing blood flow regulation, coagulation, and cognitive impairment-symptoms consistent with ME/CFS and Long COVID. This paper provides a synthesis of current research on herpesvirus latency and reactivation, detailing the impact on ECs and subsequent systemic complications, including latent modulation and long-term maladaptation. We suggest that the chronicity of ME/CFS symptoms and the multisystemic nature of the disease may be partly attributable to herpesvirus-induced endothelial maladaptation. Our conclusions underscore the necessity for further investigation into the prevalence and load of herpesvirus infection within the ECs of ME/CFS patients. This review offers conceptual advances by proposing an endothelial infection model as a systemic mechanism contributing to ME/CFS, steering future research toward potentially unexplored avenues in understanding and treating this complex syndrome.

Prevalence of orthostatic intolerance in long covid clinic patients and healthy volunteers: A multicenter study

Orthostatic intolerance (OI), including postural orthostatic tachycardia syndrome (PoTS) and orthostatic hypotension (OH), are often reported in long covid, but published studies are small with inconsistent results. We sought to estimate the prevalence of objective OI in patients attending long covid clinics and healthy volunteers and associations with OI symptoms and comorbidities. Participants with a diagnosis of long covid were recruited from eight UK long covid clinics, and healthy volunteers from general population. All undertook standardized National Aeronautics and Space Administration Lean Test (NLT). Participants' history of typical OI symptoms (e.g., dizziness, palpitations) before and during the NLT were recorded. Two hundred seventy-seven long covid patients and 50 frequency-matched healthy volunteers were tested. Healthy volunteers had no history of OI symptoms or symptoms during NLT or PoTS, 10% had asymptomatic OH. One hundred thirty (47%) long covid patients had previous history of OI symptoms and 144 (52%) developed symptoms during the NLT. Forty-one (15%) had an abnormal NLT, 20 (7%) met criteria for PoTS, and 21 (8%) had OH. Of patients with an abnormal NLT, 45% had no prior symptoms of OI. Relaxing the diagnostic thresholds for PoTS from two consecutive abnormal readings to one abnormal reading during the NLT, resulted in 11% of long covid participants (an additional 4%) meeting criteria for PoTS, but not in healthy volunteers. More than half of long covid patients experienced OI symptoms during NLT and more than one in 10 patients met the criteria for either PoTS or OH, half of whom did not report previous typical OI symptoms. We therefore recommend all patients attending long covid clinics are offered an NLT and appropriate management commenced.

Deep phenotyping of post-infectious myalgic encephalomyelitis/chronic fatigue syndrome

Post-infectious myalgic encephalomyelitis/chronic fatigue syndrome (PI-ME/CFS) is a disabling disorder, yet the clinical phenotype is poorly defined, the pathophysiology is unknown, and no disease-modifying treatments are available. We used rigorous criteria to recruit PI-ME/CFS participants with matched controls to conduct deep phenotyping. Among the many physical and cognitive complaints, one defining feature of PI-ME/CFS was an alteration of effort preference, rather than physical or central fatigue, due to dysfunction of integrative brain regions potentially associated with central catechol pathway dysregulation, with consequences on autonomic functioning and physical conditioning. Immune profiling suggested chronic antigenic stimulation with increase in naïve and decrease in switched memory B-cells. Alterations in gene expression profiles of peripheral blood mononuclear cells and metabolic pathways were consistent with cellular phenotypic studies and demonstrated differences according to sex. Together these clinical abnormalities and biomarker differences provide unique insight into the underlying pathophysiology of PI-ME/CFS, which may guide future intervention.

Possible Role of Fibrinaloid Microclots in Postural Orthostatic Tachycardia Syndrome (POTS): Focus on Long COVID

Postural orthostatic tachycardia syndrome (POTS) is a common accompaniment of a variety of chronic, inflammatory diseases, including long COVID, as are small, insoluble, 'fibrinaloid' microclots. We here develop the argument, with accompanying evidence, that fibrinaloid microclots, through their ability to block the flow of blood through microcapillaries and thus cause tissue hypoxia, are not simply correlated with but in fact, by preceding it, may be a chief intermediary cause of POTS, in which tachycardia is simply the body's exaggerated 'physiological' response to hypoxia. Similar reasoning accounts for the symptoms bundled under the term 'fatigue'. Amyloids are known to be membrane disruptors, and when their targets are nerve membranes, this can explain neurotoxicity and hence the autonomic nervous system dysfunction that contributes to POTS. Taken together as a system view, we indicate that fibrinaloid microclots can serve to link POTS and fatigue in long COVID in a manner that is at once both mechanistic and explanatory. This has clear implications for the treatment of such diseases.

Post-exertional malaise in daily life and experimental exercise models in patients with myalgic encephalomyelitis/chronic fatigue syndrome

Post-exertional malaise (PEM) is commonly recognized as a hallmark of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and is often used as one of several criteria for diagnosing ME/CFS. In this perspective paper we want to reflect on how PEM is understood, assessed, and evaluated in scientific literature, and to identify topics to be addressed in future research. Studies show that patients use a wide variety of words and concepts to label their experience of PEM in everyday life, and they report physical or mental exertions as triggers of PEM. They also report that PEM may have an immediate or delayed onset and may last from a few days to several months. When standardized exercise tests are used to trigger PEM experimentally, the exacerbation of symptoms has a more immediate onset but still shows a wide variability in duration. There are indications of altered muscular metabolism and autonomic nervous responses if exercise is repeated on successive days in patients with ME/CFS. The decreased muscular capacity appears to be maintained over several days following such controlled exercise bouts. These responses may correspond to patients' experiences of increased exertion. Based on this background we argue that there is a need to look more closely into the processes occurring in the restitution period following exercise, as PEM reaches the peak in this phase.

A Multi-Center Study Investigating Long COVID-19 in Healthcare Workers from North-Eastern Italy: Prevalence, Risk Factors and the Impact of Pre-Existing Humoral Immunity-ORCHESTRA Project

Introduction: The impact of long-COVID-19 syndrome is rather variable, since it is influenced by several residual confounders. This study aimed to investigate the prevalence of long COVID-19 in healthcare workers (HCWs) from four university hospitals in north-eastern Italy: Trieste, Padua, Verona, and Modena-Reggio Emilia. Methods: During the period June 2022-August 2022, HCWs were surveyed for past COVID-19 infections, medical history, and any acute as well as post-COVID-19 symptoms. The prevalence of long COVID-19 was estimated at 30-60 days or 61+ days since first negative swab following first and second COVID-19 episode. Furthermore, the risk of long COVID-19 was investigated by multivariable logistic regression. Results were expressed as the adjusted odds ratio (aOR) with a 95% confidence interval (95%CI). Results: 5432 HCWs returned a usable questionnaire: 2401 were infected with SARS-CoV-2 at least once, 230 were infected at least twice, and 8 were infected three times. The prevalence of long COVID-19 after a primary COVID-19 infection was 24.0% at 30-60 days versus 16.3% at 61+ days, and 10.5% against 5.5% after the second SARS-CoV-2 event. The most frequent symptoms after a first COVID-19 event were asthenia (30.3%), followed by myalgia (13.7%), cough (12.4%), dyspnea (10.2%), concentration deficit (8.1%), headache (7.3%), and anosmia (6.5%), in decreasing order of prevalence. The risk of long COVID-19 at 30-60 days was significantly higher in HCWs hospitalized for COVID-19 (aOR = 3.34; 95%CI: 1.62; 6.89), those infected with SARS-CoV-2 during the early pandemic waves-namely the Wuhan (aOR = 2.16; 95%CI: 1.14; 4.09) or Alpha (aOR= 2.05; 95%CI: 1.25; 3.38) transmission periods-and progressively increasing with viral shedding time (VST), especially 15+ days (aOR = 3.20; 95%CI: 2.07; 4.94). Further determinants of long COVID-19 at 30-60 days since primary COVID-19 event were female sex (aOR = 1.91; 95%CI: 1.30; 2.80), age >40 years, abnormal BMI, or administrative services (reference category). In contrast, HCWs vaccinated with two doses before their primary infection (aOR = 0.57; 95%CI: 0.34; 0.94), undergraduate students, or postgraduate medical trainees were less likely to experience long COVID-19 at 30-60 days. Apart from pandemic waves, the main determinants of long COVID-19 at 30-60 days were confirmed at 61+ days. Conclusions: The risk of long COVID-19 following primary infection increased with the severity of acute disease and VST, especially during the initial pandemic waves, when more virulent viral strains were circulating, and susceptibility to SARS-CoV-2 was higher since most HCWs had not been infected yet, COVID-19 vaccines were still not available, and/or vaccination coverage was still building up. The risk of long COVID-19 therefore decreased inversely with humoral immunity at the individual level. Nevertheless, the prevalence of long COVID-19 was remarkably lower after SARS-CoV-2 reinfections regardless of vaccination status, suggesting that hybrid humoral immunity did not increase protection against the syndrome compared to immunity mounted by either natural infection or vaccination separately. Since the risk of long COVID-19 is currently low with Omicron and patients who developed the syndrome following SARS-CoV-2 infection in the early pandemic waves tend to return to a state of full health with time, a cost-effective approach to screen post-COVID-19 symptoms during the Omicron time could be restricted to vulnerable individuals developing severe disease and/or with prolonged VST.

Effects of Self-Administered Acupressure on Fatigue Following Traumatic Brain Injury: A Randomized Controlled Trial

BACKGROUND

Fatigue is a common symptom after a traumatic brain injury (TBI) and may persist for weeks or years. However, nonpharmacological management strategies for fatigue alleviations are almost nonexistent; thus, effective fatigue management programs are needed urgently.

PURPOSES

We aimed to evaluate the effects of self-administered acupressure programs on post-TBI fatigue and heart rate variability and identify the possible correlation between the improvements in fatigue symptoms and the changes in heart rate variability.

DESIGN

This randomized controlled trial included 2-point acupressure (TPA; n = 27), 5-point acupressure (FPA; n = 27), and usual care (UC, control; n = 27) groups who underwent several assessments before and after the study intervention. Heart rate variability was evaluated at baseline, weeks 2 and 3, and treatment completion.

METHODS

The TPA and FPA groups self-administered acupressure (3 minutes per acupoint; bilateral), thrice daily for 4 weeks, whereas the UC group received routine treatment without acupressure.

RESULTS

Both the TPA and FPA groups exhibited substantial improvements in fatigue symptoms compared with the baseline findings in the UC group. In addition, the TPA and FPA groups exhibited increased high-frequency power and mean number of times per hour in which the changes in successive normal sinus intervals (RR) gradually exceeded 50 ms (pNN50). Changes in high-frequency power and pNN50 were correlated with improvements in post-TBI fatigue symptoms.

CONCLUSION

Acupressure may alleviate chronic fatigue and enhance parasympathetic activity in TBI survivors. The enhancement of parasympathetic activity may be correlated with improvements in post-TBI fatigue symptoms.

RELEVANCE TO CLINICAL PRACTICE

Healthcare providers should incorporate self-administered acupressure into the care plans for TBI survivors to improve their fatigue symptoms.

Autonomic dysregulation in long-term patients suffering from Post-COVID-19 Syndrome assessed by heart rate variability

Post-COVID-19 Syndrome (PCS) is a condition with multiple symptoms partly related to dysregulation of the autonomic nerve system. Assessment of heart rate variability (HRV) using 24 h Holter-ECG may serve as a surrogate to characterize cardiac autonomic activity. A prospective study including 103 PCS patients (time after infection = 252 days, age = 49.0 ± 11.3 years, 45.7% women) was performed and patients underwent detailed clinical screening, cardiopulmonary exercise testing, and 24 h Holter monitoring. Data of PCS patients was compared to 103 CAD patients and a healthy control group (n = 90). After correction for age and sex, frequency-related variables differed in PCS patients compared to controls including LF/HFpower, LF/HFnu, and LF/HF ratio (24 h; p ≤ 0.001). By contrast, these variables were largely comparable between PCS and CAD patients, while sympathetic activation was highest in PCS patients during the 24 h period. Overall, PCS patients showed disturbed diurnal adjustment of HRV, with impaired parasympathetic activity at night. Patients hospitalized during acute infection showed an even more pronounced overactivation of sympathetic activity compared to patients who underwent ambulant care. Our data demonstrate persistent HRV alterations in PCS patients with long-term symptom duration, suggesting a sustained impairment of sympathovagal balance. Moreover, sympathetic overstimulation and diminished parasympathetic response in long-term PCS patients are comparable to findings in CAD patients. Whether HRV variables have a prognostic value in PCS and/or might serve as biomarkers indicating a successful interventional approach warrants further longitudinal studies.

Cardiovascular and haematological pathology in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS): A role for viruses

ME/CFS is a debilitating chronic condition that often develops after viral or bacterial infection. Insight from the study of Long COVID/Post Acute Sequelae of COVID-19 (PASC), the post-viral syndrome associated with SARS-CoV-2 infection, might prove to be useful for understanding pathophysiological mechanisms of ME/CFS. Disease presentation is similar between the two conditions, and a subset of Long COVID patients meet the diagnostic criteria for ME/CFS. Since Long COVID is characterized by significant vascular pathology - including endothelial dysfunction, coagulopathy, and vascular dysregulation - the question of whether or not the same biological abnormalities are of significance in ME/CFS arises. Cardiac abnormalities have for a while now been documented in ME/CFS cohorts, with recent studies demonstrating major deficits in cerebral blood flow, and hence vascular dysregulation. A growing body of research is demonstrating that ME/CFS is accompanied by platelet hyperactivation, anomalous clotting, a procoagulant phenotype, and endothelial dysfunction. Endothelial damage and dysregulated clotting can impair substance exchange between blood and tissues, and result in hypoperfusion, which may contribute to the manifestation of certain ME/CFS symptoms. Here we review the ME/CFS literature to summarize cardiovascular and haematological findings documented in patients with the condition, and, in this context, briefly discuss the potential role of previously-implicated pathogens. Overall, cardiac and haematological abnormalities are present within ME/CFS cohorts. While atherosclerotic heart disease is not significantly associated with ME/CFS, suboptimal cardiovascular function defined by reduced cardiac output, impaired cerebral blood flow, and vascular dysregulation are, and these abnormalities do not appear to be influenced by deconditioning. Rather, these cardiac abnormalities may result from dysfunction in the (autonomic) nervous system. Plenty of recently published studies are demonstrating significant platelet hyperactivity and endothelial dysfunction in ME/CFS, as well as anomalous clotting processes. It is of particular importance to determine to what extent these cardiovascular and haematological abnormalities contribute to symptom severity, and if these two systems can be targeted for therapeutic purposes. Viral reservoirs of herpesviruses exist in ME/CFS, and most likely contribute to cardiovascular and haematological dysfunction directly or indirectly. This review highlights the potential of studying cardiac functioning, the vasculature, and coagulation system in ME/CFS.

Major Depressive Disorder and Chronic Fatigue Syndrome Show Characteristic Heart Rate Variability Profiles Reflecting Autonomic Dysregulations: Differentiation by Linear Discriminant Analysis

Major depressive disorder (MDD) and chronic fatigue syndrome (CFS) have overlapping symptoms, and differentiation is important to administer the proper treatment. The present study aimed to assess the usefulness of heart rate variability (HRV) indices. Frequency-domain HRV indices, including high-frequency (HF) and low-frequency (LF) components, their sum (LF+HF), and their ratio (LF/HF), were measured in a three-behavioral-state paradigm composed of initial rest (Rest), task load (Task), and post-task rest (After) periods to examine autonomic regulation. It was found that HF was low at Rest in both disorders, but was lower in MDD than in CFS. LF and LF+HF at Rest were low only in MDD. Attenuated responses of LF, HF, LF+HF, and LF/HF to task load and an excessive increase in HF at After were found in both disorders. The results indicate that an overall HRV reduction at Rest may support a diagnosis of MDD. HF reduction was found in CFS, but with a lesser severity. Response disturbances of HRV to Task were observed in both disorders, and would suggest the presence of CFS when the baseline HRV has not been reduced. Linear discriminant analysis using HRV indices was able to differentiate MDD from CFS, with a sensitivity and specificity of 91.8% and 100%, respectively. HRV indices in MDD and CFS show both common and different profiles, and can be useful for the differential diagnosis.

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.

Sex differences in post-exercise fatigue and function in myalgic encephalomyelitis/chronic fatigue syndrome

To assess biobehavioral sex differences in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) utilizing a low burden exercise protocol, 22 females and 15 males with ME/CFS and 14 healthy controls underwent two six-min walk tests. Fifteen daily assessments were scheduled for fatigue and function ratings and heart monitoring. Six-min walk tests were conducted on days 8 and 9. The ME/CFS group showed high self-report fatigue and impaired physical function, whereas healthy controls did not show fatigue or function abnormalities. In patients, no significant post-exercise changes were found for heart rate variability (HRV); however, heart rate decreased in ME/CFS males from Day 14 to Day 15 (p = 0.046). Female patients showed increased fatigue (p = 0.006) after the initial walk test, but a downward slope (p = 0.008) in fatigue following the second walk test. Male patients showed a decrease in self-report work limitation in the days after exercise (p = 0.046). The healthy control group evidenced a decrease in HRV after the walk tests from Day 9-14 (p = 0.038). This pilot study did not confirm hypotheses that females as compared to males would show slower exercise recovery on autonomic or self-report (e.g. fatigue) measures. A more exertion-sensitive test may be required to document prolonged post-exertional abnormalities in ME/CFS.Trial registration: NCT NCT03331419.

Lowered oxygen saturation and increased body temperature in acute COVID-19 largely predict chronic fatigue syndrome and affective symptoms due to Long COVID: A precision nomothetic approach

BACKGROUND

Long coronavirus disease 2019 (LC) is a chronic sequel of acute COVID-19. The exact pathophysiology of the affective, chronic fatigue and physiosomatic symptoms (labelled as "physio-affective phenome") of LC has remained elusive.

OBJECTIVE

The current study aims to delineate the effects of oxygen saturation (SpO2) and body temperature during the acute phase on the physio-affective phenome of LC.

METHOD

We recruited 120 LC patients and 36 controls. For all participants, we assessed the lowest SpO2 and peak body temperature during acute COVID-19, and the Hamilton Depression and Anxiety Rating Scale (HAMD/HAMA) and Fibro Fatigue (FF) scales 3-4 months later.

RESULTS

Lowered SpO2 and increased body temperature during the acute phase and female sex predict 60.7% of the variance in the physio-affective phenome of LC. Using unsupervised learning techniques, we were able to delineate a new endophenotype class, which comprises around 26.7% of the LC patients and is characterised by very low SpO2 and very high body temperature, and depression, anxiety, chronic fatigue, and autonomic and gastro-intestinal symptoms scores. Single latent vectors could be extracted from both biomarkers, depression, anxiety and FF symptoms or from both biomarkers, insomnia, chronic fatigue, gastro-intestinal and autonomic symptoms.

CONCLUSION

The newly constructed endophenotype class and pathway phenotypes indicate that the physio-affective phenome of LC is at least in part the consequence of the pathophysiology of acute COVID-19, namely the combined effects of lowered SpO2, increased body temperature and the associated immune-inflammatory processes and lung lesions.

Pathogenic mechanisms of post-acute sequelae of SARS-CoV-2 infection (PASC)

COVID-19, with persistent and new onset of symptoms such as fatigue, post-exertional malaise, and cognitive dysfunction that last for months and impact everyday functioning, is referred to as Long COVID under the general category of post-acute sequelae of SARS-CoV-2 infection (PASC). PASC is highly heterogenous and may be associated with multisystem tissue damage/dysfunction including acute encephalitis, cardiopulmonary syndromes, fibrosis, hepatobiliary damages, gastrointestinal dysregulation, myocardial infarction, neuromuscular syndromes, neuropsychiatric disorders, pulmonary damage, renal failure, stroke, and vascular endothelial dysregulation. A better understanding of the pathophysiologic mechanisms underlying PASC is essential to guide prevention and treatment. This review addresses potential mechanisms and hypotheses that connect SARS-CoV-2 infection to long-term health consequences. Comparisons between PASC and other virus-initiated chronic syndromes such as myalgic encephalomyelitis/chronic fatigue syndrome and postural orthostatic tachycardia syndrome will be addressed. Aligning symptoms with other chronic syndromes and identifying potentially regulated common underlining pathways may be necessary for understanding the true nature of PASC. The discussed contributors to PASC symptoms include sequelae from acute SARS-CoV-2 injury to one or more organs, persistent reservoirs of the replicating virus or its remnants in several tissues, re-activation of latent pathogens such as Epstein-Barr and herpes viruses in COVID-19 immune-dysregulated tissue environment, SARS-CoV-2 interactions with host microbiome/virome communities, clotting/coagulation dysregulation, dysfunctional brainstem/vagus nerve signaling, dysautonomia or autonomic dysfunction, 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 specific patients.

Skin Temperature Circadian Rhythms and Dysautonomia in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: The Role of Endothelin-1 in the Vascular Tone Dysregulation

There is accumulating evidence of autonomic dysfunction in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS); however, little is known about its association with circadian rhythms and endothelial dysfunction. This study aimed to explore the autonomic responses through an orthostatic test and analysis of the peripheral skin temperature variations and vascular endothelium state in ME/CFS patients. Sixty-seven adult female ME/CFS patients and 48 healthy controls were enrolled. Demographic and clinical characteristics were assessed using validated self-reported outcome measures. Postural changes in blood pressure, heart rate, and wrist temperature were recorded during the orthostatic test. Actigraphy during one week was used to determine the 24-h profile of peripheral temperature and activity. Circulating endothelial biomarkers were measured as indicators of endothelial functioning. Results showed that ME/CFS patients presented higher blood pressure and heart rate values than healthy controls in the supine and standing position (p < 0.05 for both), and also a higher amplitude of the activity rhythm (p < 0.01). Circulating levels of endothelin-1 (ET-1) and vascular cell adhesion molecule-1 (VCAM-1) were significantly higher in ME/CFS (p < 0.05). In ME/CFS, ET-1 levels were associated with the stability of the temperature rhythm (p < 0.01), and also with the self-reported questionnaires (p < 0.001). This suggests that ME/CFS patients exhibited modifications in circadian rhythm and hemodynamic measures, which are associated with endothelial biomarkers (ET-1 and VCAM-1). Future investigation in this area is needed to assess dysautonomia and vascular tone abnormalities, which may provide potential therapeutic targets for ME/CFS.

Effect of using a structured pacing protocol on post-exertional symptom exacerbation and health status in a longitudinal cohort with the post-COVID-19 syndrome

Post-exertional symptom exacerbation (PESE) is a characteristic symptom of post-COVID syndrome (PCS). This prospective study investigated the effect of a 6-week structured World Health Organization (WHO) Borg CR-10 5-phase pacing protocol on PESE episodes and quality of life in a cohort of individuals with long-standing PCS (average duration of symptoms was 17 months). Participants received weekly telephone calls with a clinician to complete the Leeds PESE questionnaire (LPQ) and identify the appropriate phase of the pacing protocol. EQ-5D 5L was completed at the intervention's beginning and end to measure overall health. Thirty-one participants completed the 6-week protocol, with a statistically and clinically significant reduction in the average number of PESE episodes (from 3.4 episodes in Week 1 to 1.1 in Week 6), with an average decrease of 16% (95% CI: 9%-24%; p < 0.001) each week, and reduction across all three exertional triggers (physical, cognitive, and emotional). Physical activity levels showed moderate improvements during the intervention period. Mean EQ-5D 5L scores improved from 51.4 to 60.6 points (paired difference of 9.2 points, 95% CI: 3.2-15.2 points; p = 0.004). A structured pacing protocol significantly reduces PESE episodes and improves overall health in PCS.

Computer vision-based approach to detect fatigue driving and face mask for edge computing device

The fatality of road accidents in this era is alarming. According to WHO, approximately 1.30 million people die each year in road accidents. Road accidents result in significant socioeconomic losses for people, their families, and the country. The integration of modern technologies into automobiles can help to reduce the number of people killed or injured in road accidents. Most of the study and police reports claim that fatigued driving is one of the deadliest factors behind many road accidents. This paper presents a complete embedded system to detect fatigue driving using deep learning, computer vision, and heart rate monitoring with Nvidia Jetson Nano developer kit, Arduino Uno, and AD8232 heart rate module. The proposed system can monitor the driver's real-time situations, then analyze the situation to detect any fatigue conditions and act accordingly. The onboard camera module constantly monitors the driver. The frames are retrieved and analyzed by the core system that uses deep learning and computer vision techniques to verify the situation with Nvidia Jetson Nano. The driver's states are identified using eye and mouth localization approaches from 68 distinct facial landmarks. Experimentally driven threshold data is employed to classify the states. The onboard heart rate module constantly measures the heart rates and detects any fluctuation in BPM related to the drowsiness. This system uses a convolutional neural network-based deep learning framework to include additional face mask detection to cope with the current pandemic situation. The heart rate module works parallelly where the other modules work in a conditional sequential manner to ensure uninterrupted detection. It will detect any sign of drowsiness in real-time and generate the alarm. The system successfully passed the initial lab tests and some actual situation experiments with 97.44% accuracy in fatigue detection and 97.90% accuracy in face mask identification. The automatic device was able to analyze different situations of drivers (different distances of driver from the camera, various lighting conditions, wearing eyeglasses, oblique projection) more precisely and generate an alarm before the accident happened.

Phenotypic characteristics of peripheral immune cells of Myalgic encephalomyelitis/chronic fatigue syndrome via transmission electron microscopy: A pilot study

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex chronic multi-systemic disease characterized by extreme fatigue that is not improved by rest, and worsens after exertion, whether physical or mental. Previous studies have shown ME/CFS-associated alterations in the immune system and mitochondria. We used transmission electron microscopy (TEM) to investigate the morphology and ultrastructure of unstimulated and stimulated ME/CFS immune cells and their intracellular organelles, including mitochondria. PBMCs from four participants were studied: a pair of identical twins discordant for moderate ME/CFS, as well as two age- and gender- matched unrelated subjects-one with an extremely severe form of ME/CFS and the other healthy. TEM analysis of CD3/CD28-stimulated T cells suggested a significant increase in the levels of apoptotic and necrotic cell death in T cells from ME/CFS patients (over 2-fold). Stimulated Tcells of ME/CFS patients also had higher numbers of swollen mitochondria. We also found a large increase in intracellular giant lipid droplet-like organelles in the stimulated PBMCs from the extremely severe ME/CFS patient potentially indicative of a lipid storage disorder. Lastly, we observed a slight increase in platelet aggregation in stimulated cells, suggestive of a possible role of platelet activity in ME/CFS pathophysiology and disease severity. These results indicate extensive morphological alterations in the cellular and mitochondrial phenotypes of ME/CFS patients' immune cells and suggest new insights into ME/CFS biology.

The underlying sex differences in neuroendocrine adaptations relevant to Myalgic Encephalomyelitis Chronic Fatigue Syndrome

INTRODUCTION

Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome (ME/CFS) is a complex multisystem disease characterised by severe and disabling new-onset symptoms of post-exertional malaise (PEM), fatigue, brain fog, and sleep dysfunction that lasts for at least six months. Accumulating evidence suggests that sex and endocrine events have a significant influence on symptom onset and moderation of ME/CFS, with female sex being one of the most consistent and credible predictive risk factors associated with diagnosis. Such sex differences suggest sex chromosomes and sex steroids may play a part in the development of the condition or moderation of symptoms, although this has yet to be explored in detail.

METHODS/AIMS

This narrative review outlines sex differences in ME/CFS in terms of vulnerability factors and clinical phenotype and explores the known sex differences in neuroendocrine systems affected in ME/CFS and how this may relate to disease risk, onset, pathophysiology, and potential treatment avenues.

CONCLUSIONS

There is clear evidence of a sex dimorphism with regards to prevalence (3:1 female preponderance), clinical phenotypes, and aetiological triggers prior to symptom onset of ME/CFS. Endocrinological events, particularly those throughout the female lifespan, are associated with ME/CFS and include reproductive menstrual cycle fluctuations, pregnancy, post-partum and perimenopause. Further, there is evidence for gonadal sex, adrenal stress and renal neuroendocrine systems as implicated in ME/CFS, including changes in estrogen, progesterone compounds, aldosterone, and cortisol levels, of which there are established sex differences. The broad effects of steroid hormones on the physiological systems may also speak to the diversity of ME/CFS symptomatology observed in patients. Further attention must be paid to sex, age, and steroid biology in ME/CFS.

The Link Between Energy-Related Sensations and Metabolism: Implications for Treating Fatigue

Energy-related sensations include sensation of energy and fatigue as well as subjective energizability and fatigability. First, we introduce interdisciplinary useful definitions of all constructs and review findings regarding the question of whether sensations of fatigue and energy are two separate constructs or two ends of a single dimension. Second, we describe different components of the bodily energy metabolism system (e.g., mitochondria; autonomic nervous system). Third, we review the link between sensation of fatigue and different components of energy metabolism. Finally, we present an overview of different treatments shown to affect both energy-related sensations and metabolism before outlining future research perspectives.

Combination of whole body cryotherapy with static stretching exercises reduces fatigue and improves functioning of the autonomic nervous system in Chronic Fatigue Syndrome

BACKGROUND

The aim of this study was to explore the tolerability and effect of static stretching (SS) and whole body cryotherapy (WBC) upon fatigue, daytime sleepiness, cognitive functioning and objective and subjective autonomic nervous system functioning in those with Chronic Fatigue Syndrome (CFS) compared to a control population.

METHODS

Thirty-two CFS and eighteen healthy controls (HC) participated in 2 weeks of a SS + WBC programme. This programme was composed of five sessions per week, 10 sessions in total.

RESULTS

A significant decrease in fatigue was noted in the CFS group in response to SS + WBC. Some domains of cognitive functioning (speed of processing visual information and set-shifting) also improved in response to SS + WBC in both CFS and HC groups. Our study has confirmed that WBC is well tolerated by those with CFS and leads to symptomatic improvements associated with changes in cardiovascular and autonomic function.

CONCLUSIONS

Given the preliminary data showing the beneficial effect of cryotherapy, its relative ease of application, good tolerability, and proven safety, therapy with cold exposure appears to be an approach worth attention. Further studies of cryotherapy as a potential treatment in CFS is important in the light of the lack of effective therapeutic options for these common and often disabling symptoms.

Clinical overlap between fibromyalgia and myalgic encephalomyelitis. A systematic review and meta-analysis

Myalgic encephalomyelitis is an illness characterized by profound malaise after mental or physical effort occurring in patients already suffering from constant fatigue. On the other hand, widespread pain and widespread allodynia are the core fibromyalgia clinical features. There is controversy on these two syndromes alikeness. Through the years, different diagnostic and/or classification criteria have been put forward to appraise both fibromyalgia and myalgic encephalomyelitis. The epidemiology of these two illnesses, and their overlap, may vary accordingly to the used definition. The most recent Wolfe et al. 2016 fibromyalgia diagnostic criteria incorporates three myalgic encephalomyelitis features including fatigue, waking unrefreshed and dyscognition. The objective of this meta-analysis was to define the clinical overlap between fibromyalgia and myalgic encephalomyelitis based on a systematic literature review.

METHODS

PubMed, Embase, Lilacs, and Cochrane data bases were searched on January 25, 2021 linking the medical subject heading "Fibromyalgia" to the following terms "chronic fatigue syndrome", "myalgic encephalomyelitis" and "systemic exertion intolerance disease". Our review included all original articles in which the clinical overlap between fibromyalgia and myalgic encephalomyelitis could be quantified based on recognized diagnostic or classification criteria. Articles scrutiny and selection followed the PRISMA guidelines. Each study quality was assessed according to GRADE recommendations. The global clinical overlap was calculated using a fixed effect model with inverse variance-weighted average method.

RESULTS

Twenty one publications were included in the meta-analysis. Reviewed studies were highly dissimilar in their design, objectives, sample size, diagnostic criteria, and/or outcomes yielding a 98% heterogeneity index. Nevertheless, the clinical overlap between fibromyalgia and myalgic encephalomyelitis was a well defined outcome that could be reliably calculated despite the high heterogeneity value. All reviewed publications had moderate GRADE evidence level. Most evaluated articles used the old 1990 Wolfe et al. fibromyalgia diagnostic criteria. Myalgic encephalomyelitis and fibromyalgia diagnoses overlapped in 47.3% (95% CI: 45.97-48.63) of the reported cases.

CONCLUSION

This meta-analysis found prominent clinical overlap between fibromyalgia and myalgic encephalomyelitis. It seems likely that this concordance would be even higher when using the most recent Wolfe et al. 2016 fibromyalgia diagnostic criteria.

The Kidney Donor Profile Index (KDPI) Correlates With Histopathologic Findings in Post-reperfusion Baseline Biopsies and Predicts Kidney Transplant Outcome

Background

The increasing organ shortage in kidney transplantation leads to the necessity to use kidneys previously considered unsuitable for transplantation. Numerous studies illustrate the need for a better decision guidance rather than only the classification into kidneys from standard or expanded criteria donors referred to as SCD/ECD-classification. The kidney donor profile index (KDPI) exhibits a score utilizing a much higher number of donor characteristics. Moreover, graft biopsies provide an opportunity to assess organ quality.

Methods

In a single center analysis 383 kidney transplantations (277 after deceased and 106 after living donation) performed between January 1st, 2006, and December 31st, 2016, retrospectively underwent SCD/ECD and KDPI scoring. Thereby, the quality of deceased donor kidneys was assessed by using the KDPI and the living donor kidneys by using the living KDPI, in the further analysis merged as (L)KDPI. Baseline biopsies taken 10 min after the onset of reperfusion were reviewed for chronic and acute lesions. Survival analyses were performed using Kaplan-Meier analysis and Cox proportional hazards analysis within a 5-year follow-up.

Results

The (L)KDPI correlated with glomerulosclerosis (r = 0.30, p < 0.001), arteriosclerosis (r = 0.33, p < 0.001), interstitial fibrosis, and tubular atrophy (r = 0.28, p < 0.001) as well as the extent of acute tubular injury (r = 0.20, p < 0.001). The C-statistic of the (L)KDPI concerning 5-year death censored graft survival was 0.692. Around 48% of ECD-kidneys were classified as (L)KDPI<85%. In a multivariate Cox proportional hazard analysis including (preformed) panel reactive antibodies, cold ischemia time, (L)KDPI, and SCD/ECD-classification, the (L)KDPI was significantly associated with risk of graft loss (hazard ratio per 10% increase in (L)KDPI: 1.185, 95% confidence interval: 1.033–1.360, p = 0.025). Survival analysis revealed decreased death censored (p < 0.001) and non-death censored (p < 0.001) graft survival in kidneys with an increasing (L)KDPI divided into groups of <35, 35–85, and >85%, respectively.

Conclusion

With a higher granularity compared to the SCD/ECD-classification the (L)KDPI is a promising tool to judge graft quality. The correlation with chronic and acute histological lesions in post-reperfusion kidney biopsies underlines the descriptive value of the (L)KDPI. However, its prognostic value is limited and underlines the urgent need for a more precise prognostic tool adopted to European kidney transplant conditions.

Cardiopulmonary, metabolic, and perceptual responses during exercise in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): A Multi-site Clinical Assessment of ME/CFS (MCAM) sub-study

Background

Cardiopulmonary exercise testing has demonstrated clinical utility in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). However, to what extent exercise responses are independent of, or confounded by, aerobic fitness remains unclear.

Purpose

To characterize and compare exercise responses in ME/CFS and controls with and without matching for aerobic fitness.

Methods

As part of the Multi-site Clinical Assessment of ME/CFS (MCAM) study, 403 participants (n = 214 ME/CFS; n = 189 controls), across six ME/CFS clinics, completed ramped cycle ergometry to volitional exhaustion. Metabolic, heart rate (HR), and ratings of perceived exertion (RPE) were measured. Ventilatory equivalent (V˙E/V˙O2, V˙E/V˙CO2), metrics of ventilatory efficiency, and chronotropic incompetence (CI) were calculated. Exercise variables were compared using Hedges’ g effect size with 95% confidence intervals. Differences in cardiopulmonary and perceptual features during exercise were analyzed using linear mixed effects models with repeated measures for relative exercise intensity (20–100% peak V˙O2). Subgroup analyses were conducted for 198 participants (99 ME/CFS; 99 controls) matched for age (±5 years) and peak V˙O2 (~1 ml/kg/min^-1).

Results

Ninety percent of tests (n = 194 ME/CFS, n = 169 controls) met standard criteria for peak effort. ME/CFS responses during exercise (20–100% peak V˙O2) were significantly lower for ventilation, breathing frequency, HR, measures of efficiency, and CI and significantly higher for V˙E/V˙O2, V˙E/V˙CO2 and RPE (p<0.05_adjusted). For the fitness-matched subgroup, differences remained for breathing frequency, V˙E/V˙O2, V˙E/V˙CO2, and RPE (p<0.05_adjusted), and higher tidal volumes were identified for ME/CFS (p<0.05_adjusted). Exercise responses at the gas exchange threshold, peak, and for measures of ventilatory efficiency (e.g., V˙E/V˙CO2nadir) were generally reflective of those seen throughout exercise (i.e., 20–100%).

Conclusion

Compared to fitness-matched controls, cardiopulmonary responses to exercise in ME/CFS are characterized by inefficient exercise ventilation and augmented perception of effort. These data highlight the importance of distinguishing confounding fitness effects to identify responses that may be more specifically associated with ME/CFS.

Alteration of Cortical Volume and Thickness in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Myalgic Encephalomyelitis/Chronic fatigue syndrome (ME/CFS) patients suffer from neurocognitive impairment. In this study, we investigated cortical volumetric and thickness changes in ME/CFS patients and healthy controls (HC). We estimated mean surface-based cortical volume and thickness from 18 ME/CFS patients who met International Consensus Criteria (ICC) and 26 HC using FreeSurfer. Vertex-wise analysis showed significant reductions in the caudal middle frontal gyrus (p = 0.0016) and precuneus (p = 0.013) thickness in ME/CFS patients compared with HC. Region based analysis of sub-cortical volumes found that amygdala volume (p = 0.002) was significantly higher in ME/CFS patients compared with HC. We also performed interaction-with-group regressions with clinical measures to test for cortical volume and thickness correlations in ME/CFS with opposite slopes to HC (abnormal). ME/CFS cortical volume and thickness regressions with fatigue, heart-rate variability, heart rate, sleep disturbance score, respiratory rate, and cognitive performance were abnormal. Our study demonstrated different cortical volume and thickness in ME/CFS patients and showed abnormal cortical volume and thickness regressions with key symptoms of ME/CFS patients.

Markers of Cardiac Autonomic Function During Consecutive Day Peak Exercise Tests in People With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) have been shown to exhibit altered ventilatory characteristics on the second of two progressive maximal cardiopulmonary exercise tests (CPET) performed on consecutive days. However, maximal exercise can exacerbate symptoms for ME/CFS patients and cause significant post-exertional malaise. Assessment of heart rate (HR) parameters known to track post-exertional fatigue may represent more effective physiological markers of the condition and could potentially negate the need for maximal exercise testing. Sixteen ME/CFS patients and 10 healthy controls underwent a sub-maximal warm-up followed by CPET on two consecutive days. Ventilation, ratings of perceived exertion, work rate (WR) and HR parameters were assessed throughout on both days. During sub-maximal warm-up, a time effect was identified for the ratio of low frequency to high frequency power of HR variability (p=0.02) during sub-maximal warm-up, and for HR at ventilatory threshold (p=0.03), with both being higher on Day Two of testing. A significant group (p<0.01) effect was identified for a lower post-exercise HR recovery (HRR) in ME/CFS patients. Receiver operator characteristic curve analysis of HRR revealed an area under the curve of 74.8% (p=0.02) on Day One of testing, with a HRR of 34.5bpm maximising sensitivity (63%) and specificity (40%) suggesting while HRR values are altered in ME/CFS patients, low sensitivity and specificity limit its potential usefulness as a biomarker of the condition.

Orthostatic Challenge Causes Distinctive Symptomatic, Hemodynamic and Cognitive Responses in Long COVID and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Background

Some patients with acute COVID-19 are left with persistent, debilitating fatigue, cognitive impairment ("brain fog"), orthostatic intolerance (OI) and other symptoms ("Long COVID"). Many of the symptoms are like those of other post-infectious fatigue syndromes and may meet criteria for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Common diagnostic laboratory tests are often unrevealing.

Methods

We evaluated whether a simple, standardized, office-based test of OI, the 10-min NASA Lean Test (NLT), would aggravate symptoms and produce objective hemodynamic and cognitive abnormalities, the latter being evaluated by a simple smart phone-based app.

Participants

People with Long COVID (N = 42), ME/CFS (N = 26) and healthy control subjects (N = 20) were studied just before, during, immediately after, 2 and 7 days following completion of the NLT.

Results

The NLT provoked a worsening of symptoms in the two patient groups but not in healthy control subjects, and the severity of all symptoms was similar and significantly worse in the two patient groups than in the control subjects (p < 0.001). In the two patient groups, particularly those with Long COVID, the NLT provoked a marked and progressive narrowing in the pulse pressure. All three cognitive measures of reaction time worsened in the two patient groups immediately following the NLT, compared to the healthy control subjects, particularly in the Procedural Reaction Time (p < 0.01).

Conclusions

A test of orthostatic stress easily performed in an office setting reveals different symptomatic, hemodynamic and cognitive abnormalities in people with Long COVID and ME/CFS, compared to healthy control subjects. Thus, an orthostatic challenge easily performed in an office setting, and the use of a smart phone app to assess cognition, can provide objective confirmation of the orthostatic intolerance and brain fog reported by patients with Long COVID and ME/CFS.

Lessons From Heat Stroke for Understanding Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

We here provide an overview of the pathophysiological mechanisms during heat stroke and describe similar mechanisms found in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Both conditions are characterized by disturbed homeostasis in which inflammatory pathways play a central role. Splanchnic vasoconstriction, increased gut permeability, gut-related endotoxemia, systemic inflammatory response, central nervous system dysfunction, blood coagulation disorder, endothelial-cell injury, and mitochondrial dysfunction underlie heat stroke. These mechanisms have also been documented in ME/CFS. Moreover, initial transcriptomic studies suggest that similar gene expressions are altered in both heat stroke and ME/CFS. Finally, some predisposing factors for heat stroke, such as pre-existing inflammation or infection, overlap with those for ME/CFS. Notwithstanding important differences - and despite heat stroke being an acute condition - the overlaps between heat stroke and ME/CFS suggest common pathways in the physiological responses to very different forms of stressors, which are manifested in different clinical outcomes. The human studies and animal models of heat stroke provide an explanation for the self-perpetuation of homeostatic imbalance centered around intestinal wall injury, which could also inform the understanding of ME/CFS. Moreover, the studies of novel therapeutics for heat stroke might provide new avenues for the treatment of ME/CFS. Future research should be conducted to investigate the similarities between heat stroke and ME/CFS to help identify the potential treatments for ME/CFS.

Post-Acute Sequelae of COVID-19 and Cardiovascular Autonomic Dysfunction: What Do We Know?

Post-acute sequelae of SARS-CoV-2 (PASC), or long COVID syndrome, is emerging as a major health issue in patients with previous SARS-CoV-2 infection. Symptoms commonly experienced by patients include fatigue, palpitations, chest pain, dyspnea, reduced exercise tolerance, and “brain fog”. Additionally, symptoms of orthostatic intolerance and syncope suggest the involvement of the autonomic nervous system. Signs of cardiovascular autonomic dysfunction appear to be common in PASC and are similar to those observed in postural orthostatic tachycardia syndrome and inappropriate sinus tachycardia. In this review, we report on the epidemiology of PASC, discuss current evidence and possible mechanisms underpinning the dysregulation of the autonomic nervous system, and suggest nonpharmacological and pharmacological interventions to treat and relieve symptoms of PASC-associated dysautonomia.

Long COVID and Post-infective Fatigue Syndrome: A Review

Fatigue is a dominant feature of both acute and convalescent coronavirus disease 2019 (COVID-19) (sometimes termed "long-COVID"), with up to 46% of patients reporting fatigue that lasts from weeks to months. The investigators of the international Collaborative on Fatigue Following Infection (COFFI) conducted a systematic review of post-COVID fatigue and a narrative review on fatigue after other infections, and made recommendations for clinical and research approaches to assessing fatigue after COVID-19. In the majority of COVID-19 cohort studies, persistent fatigue was reported by a significant minority of patients, ranging from 13% to 33% at 16-20 weeks post-symptom onset. Data from the prospective cohort studies in COFFI and others indicate that fatigue is also a prevalent outcome from many acute systemic infections, notably infectious mononucleosis, with a case rate for clinically significant Post-infective fatigue after exclusion of recognized medical and psychiatric causes, ranging from 10%-35% at 6 months. To better characterize post-COVID fatigue, the COFFI investigators recommend the following: application of validated screening questionnaires for case detection; standardized interviews encompassing fatigue, mood, and other symptoms; and investigative approaches to identify end-organ damage and mental health conditions.

Chronic Fatigue Syndrome and Cardiovascular Disease: JACC State-of-the-Art Review

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a medically unexplained illness characterized by severe fatigue limiting normal daily activities for at least 6 months accompanied by problems with unrefreshing sleep, exacerbation of symptoms following physical or mental efforts (postexertional malaise [PEM]), and either cognitive reports or physiological evidence of orthostatic intolerance in the form of either orthostatic tachycardia and/or hypocapnia. Although rarely considered to have cardiac dysfunction, ME/CFS patients frequently have reduced stroke volume with a significant inverse relation between cardiac output and PEM severity. Magnetic resonance imaging of ME/CFS patients compared with normal control subjects found significantly reduced stroke, end-systolic, and end-diastolic volumes together with reduced end-diastolic wall mass. Another cardiovascular abnormality is reduced nocturnal blood pressure assessed by 24-hour monitoring. Autonomic dysfunction is also frequently observed with postural orthostatic tachycardia and/or hypocapnia. Two consecutive cardiopulmonary stress tests may provide metabolic data substantiating PEM.

Insights from myalgic encephalomyelitis/chronic fatigue syndrome may help unravel the pathogenesis of postacute COVID-19 syndrome

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can cause chronic and acute disease. Postacute sequelae of SARS-CoV-2 infection (PASC) include injury to the lungs, heart, kidneys, and brain that may produce a variety of symptoms. PASC also includes a post-coronavirus disease 2019 (COVID-19) syndrome ('long COVID') with features that can follow other acute infectious diseases and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Here we summarize what is known about the pathogenesis of ME/CFS and of 'acute' COVID-19, and we speculate that the pathogenesis of post-COVID-19 syndrome in some people may be similar to that of ME/CFS. We propose molecular mechanisms that might explain the fatigue and related symptoms in both illnesses, and we suggest a research agenda for both ME/CFS and post-COVID-19 syndrome.

Bioenergetic and Proteomic Profiling of Immune Cells in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients: An Exploratory Study

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a heterogeneous, debilitating, and complex disease. Along with disabling fatigue, ME/CFS presents an array of other core symptoms, including autonomic nervous system (ANS) dysfunction, sustained inflammation, altered energy metabolism, and mitochondrial dysfunction. Here, we evaluated patients' symptomatology and the mitochondrial metabolic parameters in peripheral blood mononuclear cells (PBMCs) and plasma from a clinically well-characterised cohort of six ME/CFS patients compared to age- and gender-matched controls. We performed a comprehensive cellular assessment using bioenergetics (extracellular flux analysis) and protein profiles (quantitative mass spectrometry-based proteomics) together with self-reported symptom measures of fatigue, ANS dysfunction, and overall physical and mental well-being. This ME/CFS cohort presented with severe fatigue, which correlated with the severity of ANS dysfunction and overall physical well-being. PBMCs from ME/CFS patients showed significantly lower mitochondrial coupling efficiency. They exhibited proteome alterations, including altered mitochondrial metabolism, centred on pyruvate dehydrogenase and coenzyme A metabolism, leading to a decreased capacity to provide adequate intracellular ATP levels. Overall, these results indicate that PBMCs from ME/CFS patients have a decreased ability to fulfill their cellular energy demands.

Changes in the Allostatic Response to Whole-Body Cryotherapy and Static-Stretching Exercises in Chronic Fatigue Syndrome Patients vs. Healthy Individuals

This study represents a comparison of the functional interrelation of fatigue and cognitive, cardiovascular and autonomic nervous systems in a group of Chronic Fatigue Syndrome (CFS) patients compared with those in healthy individuals at different stages of analysis: at baseline and after changes induced by whole-body cryotherapy (WBC) combined with a static-stretching (SS) program. The study included 32 patients (Fukuda criteria) and 18 healthy controls. Fatigue, cognitive, cardiovascular and autonomic function and arterial stiffness were measured before and after 10 sessions of WBC with SS. In the patients, a disturbance in homeostasis was observed. The network relationship based on differences before and after intervention showed comparatively higher stress and eccentricity in the CFS group: 50.9 ± 56.1 vs. 6.35 ± 8.72, p = 0.002, r = 0.28; and 4.8 ± 0.7 vs. 2.4 ± 1, p < 0.001, r = 0.46, respectively. Before and after intervention, in the CFS group increased fatigue was related to baroreceptor function, and baroreceptor function was in turn related to aortic stiffness, but no such relationships were observed in the control group. Differences in the network structure underlying the interrelation among the four measured criteria were observed in both groups, before the intervention and after ten sessions of whole cryotherapy with a static stretching exercise.

Analysis of Gender Differences in HRV of Patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Using Mobile-Health Technology

In a previous study using mobile-health technology (mHealth), we reported a robust association between chronic fatigue symptoms and heart rate variability (HRV) in female patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). This study explores HRV analysis as an objective, non-invasive and easy-to-apply marker of ME/CFS using mHealth technology, and evaluates differential gender effects on HRV and ME/CFS core symptoms. In our methodology, participants included 77 ME/CFS patients (32 men and 45 women) and 44 age-matched healthy controls (19 men and 25 women), all self-reporting subjective scores for fatigue, sleep quality, anxiety, and depression, and neurovegetative symptoms of autonomic dysfunction. The inter-beat cardiac intervals are continuously monitored/recorded over three 5-min periods, and HRV is analyzed using a custom-made application (iOS) on a mobile device connected via Bluetooth to a wearable cardiac chest band. Male ME/CFS patients show increased scores compared with control men in all symptoms and scores of fatigue, and autonomic dysfunction, as with women in the first study. No differences in any HRV parameter appear between male ME/CFS patients and controls, in contrast to our findings in women. However, we have found negative correlations of ME/CFS symptomatology with cardiac variability (SDNN, RMSSD, pNN50, LF) in men. We have also found a significant relationship between fatigue symptomatology and HRV parameters in ME/CFS patients, but not in healthy control men. Gender effects appear in HF, LF/HF, and HFnu HRV parameters. A MANOVA analysis shows differential gender effects depending on the experimental condition in autonomic dysfunction symptoms and HF and HFnu HRV parameters. A decreased HRV pattern in ME/CFS women compared to ME/CFS men may reflect a sex-related cardiac autonomic dysfunction in ME/CFS illness that could be used as a predictive marker of disease progression. In conclusion, we show that HRV analysis using mHealth technology is an objective, non-invasive tool that can be useful for clinical prediction of fatigue severity, especially in women with ME/CFS.

Prevalence and correlates of cancer-related fatigue in breast cancer survivors

PURPOSE

To identify potential correlates of cancer-related fatigue (CRF) after curative breast cancer (BC) treatment. The hypothesis was that fatigue would be more severe among women treated with cardiotoxic drugs, with poor physical condition and those who exercised less.

METHODS

Observational cross-sectional design. Fatigue was evaluated through PERFORM Questionnaire (multi-item, multi-dimensional). Patient-reported assessments and objective information regarding clinical data, physical activity (PA) and physical condition were analysed as potential correlates of CRF.

RESULTS

One hundred eighty women who remained free of disease were recruited. The prevalence of fatigue interfering with quality of life was 43%. Weight, resting and recovery heart rate were positively associated with fatigue. Age and time from diagnosis were negatively associated. Previous therapies, objectively assessed weekly PA, cardiorespiratory condition, muscular strength and adherence to Mediterranean diet were not associated with CRF.

CONCLUSIONS

CRF is a prevalent problem after BC treatment. Objectively assessed PA, cardiorespiratory fitness and muscular strength did not predict CRF. The association of heart rate and fatigue deserves a further insight. Future research should include longitudinal studies and determination of biomarkers.

IMPLICATIONS FOR CANCER SURVIVORS

BC survivors, especially younger and overweight women, should be informed about fatigue as a potential persistent symptom through all stages of the cancer trajectory and into survivorship. They also should be routinely screened for CRF.

Acupuncture therapy on chronic fatigue syndrome based on radar plot: A protocol for an overview of systematic reviews

BACKGROUND

Chronic fatigue syndrome (CFS) is a debilitating chronic disease of unknown etiology that is recognized by the World Health Organization (WHO) and the United States Center for Disease Control and Prevention (US CDC) as a disorder of the brain. CFS affects 1% (17-24 million people) of the world's population and is a major and costly public health problem. In traditional Chinese medicine (TCM), acupuncture can achieve a certain effect in the treatment of chronic fatigue syndrome, but evidence-based medicine is controversial. This protocol aims to multi-evaluate the literature quality and evidence quality of the current systematic reviews (SRs)/meta-analyses (MAs) of acupuncture treatment for chronic fatigue syndrome, and provide intuitive and reliable evidence synthesis and decision-making basis for clinical treatment.

METHODS

Eight databases will be searched from their inception to 1 June, 2020: the Chinese Biomedical Literature Database (CBM), China Science and Technology Journal Database (VIP), China National Knowledge Infrastructure (CNKI), WanFang Database (WF), Web of Science, Embase, PubMed, and Cochrane Library. Published systematic reviews that were reported in Chinese or English, and the included studies were randomized controlled clinical trials (RCTs) for acupuncture in people with CFS will be included. Reviews selection, data extraction and management, and assessment of the study quality will be completed independently by 2 or more reviewers. The quality of evidence, methodological quality, and reporting quality will be evaluated by using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE), A Measurement Tool to Assessment of Multiple Systematic Reviews-2 (AMSTAR-2), Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA), and Adobe Illustrator Creative Cloud (Adobe Illustrator CC) will be used to draw and optimize the radar plot.

RESULTS

The article in this overview will be submitted for publication in a peer-reviewed journal.

CONCLUSION

We hope to collect evidence from accessible and useful systematic reviews of acupuncture treatment for chronic fatigue syndrome, to provide visual and scientific decision-making methods for more clinical practice and medical research.

SYSTEMATIC REVIEW REGISTRATION

INPLASY 202060052.

The SARS-CoV-2 receptor angiotensin-converting enzyme 2 (ACE2) in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: analysis of high-throughput epigenetic and gene expression studies

Patients affected by Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) show specific epigenetic and gene expression signatures of the disease. However, it is unknown whether these signatures include abnormal levels of the human angiotensin-converting enzymes, ACE and ACE2, the latter being the main receptor described for the host-cell invasion by SARS-CoV-2. To investigate that, we first re-analyzed available case-control epigenome-wide association studies based on DNA methylation data, and case-control gene expression studies based on microarray data. From these published studies, we found an association between ME/CFS and 4 potentially hypomethylated probes located in the ACE locus. We also found another disease association with one hypomethylated probe located in the transcription start site of ACE2. The same disease associations were obtained for women but not for men after performing sex-specific analyses. In contrast, a meta-analysis of gene expression levels could not provide evidence for a differentially expression of ACE and ACE2 in affected patients when compared to healthy controls. In line with this negative finding, the analysis of a new data set on the gene expression of ACE and ACE2 in peripheral blood mononuclear cells did not find any differences between a female cohort of 37 patients and 34 age-matched healthy controls. Future studies should be conducted to extend this investigation to other potential receptors used by SARS-CoV-2. These studies will help researchers and clinicians to improve the understanding of the health risk imposed by this virus when infecting patients affected by this debilitating disease.

Relationship between Cardiopulmonary, Mitochondrial and Autonomic Nervous System Function Improvement after an Individualised Activity Programme upon Chronic Fatigue Syndrome Patients

BACKGROUND

The therapeutic effects of exercise from structured activity programmes have recently been questioned; as a result, this study examines the impact of an Individualised Activity Program (IAP) on the relationship with cardiovascular, mitochondrial and fatigue parameters.

METHODS

Chronic fatigue syndrome (CFS) patients were assessed using Chalder Fatigue Questionnaire (CFQ), Fatigue Severity Score (FSS) and the Fatigue Impact Scale (FIS). VO2peak, VO2submax and heart rate (HR) were assessed using cardiopulmonary exercise testing. Mfn1 and Mfn2 levels in plasma were assessed. A Task Force Monitor was used to assess ANS functioning in supine rest and in response to the Head-Up Tilt Test (HUTT).

RESULTS

Thirty-four patients completed 16 weeks of the IAP. The CFQ, FSS and FIS scores decreased significantly along with a significant increase in Mfn1 and Mfn2 levels (p = 0.002 and p = 0.00005, respectively). The relationships between VO2 peak and Mfn1 increase in response to IAP (p = 0.03) and between VO2 at anaerobic threshold and ANS response to the HUTT (p = 0.03) were noted.

CONCLUSIONS

It is concluded that IAP reduces fatigue and improves functional performance along with changes in autonomic and mitochondrial function. However, caution must be applied as exercise was not well tolerated by 51% of patients.

Modulatory effects of cognitive exertion on regional functional connectivity of the salience network in women with ME/CFS: A pilot study

BACKGROUND

A common symptom of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is post-exertional malaise (PEM). Various brain abnormalities have been observed in patients with ME/CFS, especially in insular and limbic areas, but their link with ME/CFS symptoms is still unclear. This pilot study aimed at investigating the association between PEM in ME/CFS and changes in functional connectivity (FC) of two main networks: the salience network (SN) and the default-mode network (DMN).

METHODS

A total of 16 women, 6 with and 10 without ME/CFS, underwent clinical and MRI assessment before and after cognitive exertion. Resting-state FC maps of 7 seeds (3 for the SN and 4 for the DMN) and clinical measures of fatigue, pain and cognition were analysed with repeated-measure models. FC-symptom change associations were also investigated.

RESULTS

Exertion induced increases in fatigue and pain in patients with ME/CFS compared to the control group, while no changes were found in cognitive performance. At baseline, patients showed altered FC between some DMN seeds and frontal areas and stronger FC between all SN seeds and left temporal areas and the medulla. Significantly higher FC increases in patients than in controls were found only between the right insular seed and frontal and subcortical areas; these increases correlated with worsening of symptoms.

CONCLUSIONS

Cognitive exertion can induce worsening of ME/CFS-related symptoms. These changes were here associated with strengthening of FC of the right insula with areas involved in reward processing and cognitive control.

The evidence base for physiotherapy in myalgic encephalomyelitis/chronic fatigue syndrome when considering post-exertional malaise: a systematic review and narrative synthesis

Background

Due to the inconsistent use of diagnostic criteria in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), it is unsure whether physiotherapeutic management regarded effective in ME/CFS is appropriate for patients diagnosed with criteria that consider post-exertional malaise (PEM) as a hallmark feature.

Purpose

To appraise current evidence of the effects of physiotherapy on symptoms and functioning in ME/CFS patients in view of the significance of PEM in the applied diagnostic criteria for inclusion.

Methods

A systematic review of randomized controlled trials published over the last two decades was conducted. Studies evaluating physiotherapeutic interventions for adult ME/CFS patients were included. The diagnostic criteria sets were classified into three groups according to the extent to which the importance of PEM was emphasized: chronic fatigue (CF; PEM not mentioned as a criterion), CFS (PEM included as an optional or minor criterion) or ME (PEM is a required symptom). The main results of included studies were synthesized in relation to the classification of the applied diagnostic criteria. In addition, special attention was given to the tolerability of the interventions.

Results

Eighteen RCTs were included in the systematic review: three RCTs with CF patients, 14 RCTs with CFS patients and one RCT covering ME patients with PEM. Intervention effects, if any, seemed to disappear with more narrow case definitions, increasing objectivity of the outcome measures and longer follow-up.

Conclusion

Currently, there is no scientific evidence when it comes to effective physiotherapy for ME patients. Applying treatment that seems effective for CF or CFS patients may have adverse consequences for ME patients and should be avoided.

Associations Between Psychological and Immunological Variables in Chronic Fatigue Syndrome/Myalgic Encephalomyelitis: A Systematic Review

Background: Little emphasis has been given to the fact that various psychological processes and behaviors in chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) have neural correlates that affect-and are affected by-the immune system. The aim of this paper is to provide a systematic review of the literature on cross-sectional and longitudinal associations between psychological and immunological variables/changes in CFS/ME. Methods: The systematic literature search was conducted on Dec 10, 2020 using PubMed. Original research studies investigating associations between a predefined set of psychological and immunological variables in CFS/ME were included. Specifically, the review was focused on studies examining the following psychological variables: executive function, emotion regulation, interpersonal function, sleep, mental health, anxiety, depression, and/or other psychiatric symptoms. In terms of immunological variables, studies investigating interleukin (IL)-1, IL-2, IL-4, IL-6, tumor necrosis factor (TNF), CD4⁺, and/or CD8⁺ were included. Besides original research papers, other potentially relevant papers (e.g., literature reviews) were carefully read and reference lists were checked in order to identify any additional relevant studies. Available data was summarized in text and tables. Results: The literature search identified 897 potentially relevant papers. Ultimately, 14 studies (807 participants in total) were included in the review of which only two were longitudinal in nature. The review indicated that executive function is associated with IL-1 and IL-6, and interpersonal function is associated with IL-6 and TNF-α. Further, the available data suggested that emotion regulation is associated with IL-2 and sleep is associated with IL-1, IL-6, TNF-α, and IL-2. Interestingly, poorer emotion regulation, interpersonal function, and sleep have all been found to be associated with higher cytokine levels. Executive function has shown both positive and negative relationships with cytokines and among these psychological constructs, it is also the only one that has been found to be associated with CD4⁺ and CD8⁺ counts/percentages. Conclusions: Correlations exist between psychological and immunological variables in CFS/ME. However, there are few consistent findings and there is almost a complete lack of longitudinal studies. This review points to a gap in existing CFS/ME research and hopefully, it will inspire to the generation of innovative, psychoneuroimmunological hypotheses within the CFS/ME research field.

Potential causal factors of CFS/ME: a concise and systematic scoping review of factors researched

BACKGROUND

Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is understood as a complex condition, likely triggered and sustained by an interplay of biological, psychological, and social factors. Little oversight exists of the field of causal research. This systematic scoping review explores potential causal factors of CFS/ME as researched by primary studies.

METHODS

We searched eight databases for primary studies that examined potential causal factors of CFS/ME. Based on title/abstract review, two researchers independently sorted each study's factors into nine main categories and 71 subordinate categories, using a system developed with input given during a 2018 ME conference, specialists and representatives from a ME patient advocacy group, and using BMJ Best Practice's description of CFS/ME etiology. We also extracted data related to study design, size, diagnostic criteria and comparison groups.

RESULTS

We included 1161 primary studies published between January 1979 and June 2019. Based on title/abstract analysis, no single causal factor dominated in these studies, and studies reported a mean of 2.73 factors. The four most common factors were: immunological (297 studies), psychological (243), infections (198), and neuroendocrinal (198). The most frequent study designs were case-control studies (894 studies) comparing CFS/ME patients with healthy participants. More than half of the studies (that reported study size in the title/abstract) included 100 or fewer participants.

CONCLUSION

The field of causal hypotheses of CFS/ME is diverse, and we found that the studies examined all the main categories of possible factors that we had defined a priori. Most studies were not designed to adequately explore causality, rather to establish hypotheses. We need larger studies with stronger study designs to gain better knowledge of causal factors of CFS/ME.

Prediction of Discontinuation of Structured Exercise Programme in Chronic Fatigue Syndrome Patients

Purpose: The purpose of this study was to assess differences in the physiological profiles of completers vs. non-completers following a structured exercise programme (SEP) and the ability to predict non-completers, which is currently unknown in this group. Methods: Sixty-nine patients met the Fukuda criteria. Patients completed baseline measures assessing fatigue, autonomic nervous system (ANS), cognitive, and cardiovascular function. Thirty-four patients completed a home-based SEP consisting of 10–40 min per day at between 30 and 80% actual HR max. Exercise intensity and time was increased gradually across the 16 weeks and baseline measures were repeated following the SEP. Results: Thirty-five patients discontinued, while 34 completed SEP. For every increase in sympathetic drive for blood pressure control as measured by the taskforce, completion of SEP decreased by a multiple of 0.1. For a 1 millisecond increase in reaction time for the simple reaction time (SRT), the probability for completion of SEP also decreases by a multiple of 0.01. For a one beat HRmax increase, there is a 4% increase in the odds of completing SEP. Conclusion: The more sympathetic drive in the control of blood vessels, the longer the reaction time on simple visual stimuli and the lower the HRmax during physical exercise, then the lower the chance of SEP completion in ME/CFS.

Cardiac Dimensions and Function are Not Altered among Females with the Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Background: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating condition associated with several negative health outcomes. A hallmark of ME/CFS is decreased exercise capacity and often profound exercise intolerance. The causes of ME/CSF and its related symptoms are unknown, but there are indications of a dysregulated metabolism with impaired glycolytic vs oxidative energy balance. In line with this, we recently demonstrated abnormal lactate accumulation among ME/CFS patients compared with healthy controls after exercise testing. Here we examined if cardiac dimensions and function were altered in ME/CFS, as this could lead to increased lactate production. Methods: We studied 16 female ME/CFS patients and 10 healthy controls with supine transthoracic echocardiography, and we assessed cardiac dimensions and function by conventional echocardiographic and Doppler analysis as well as novel tissue Doppler and strain variables. Results: A detailed analyses of key variables of cardiac dimensions and cardiac function revealed no significant differences between the two study groups. Conclusion: In this cohort of well-described ME/CFS patients, we found no significant differences in echocardiographic variables characterizing cardiac dimensions and function compared with healthy controls.