Exercise Pathophysiology in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Postacute Sequelae of SARS-CoV-2: More in Common Than Not?

Factors associated with the presence and intensity of ongoing symptoms in Long COVID

OBJECTIVE

Identification of modifiable factors associated with symptom intensity among people seeking care for Post-Acute Sequelae of SARS-CoV-2 infection (PASC) could help guide the development of comprehensive, whole-person care pathways to alleviate symptoms irrespective of potential underlying pathophysiologies. We aimed to better define the key contributors to PASC, and sought the factors associated with PASC symptom presence and intensity.

METHODS

In this cross-sectional study, 249 patients presenting for PASC care at a dedicated Post-COVID-19 clinic completed a standardized screening assessment prior to initial visit and evaluation by a general internist or nurse practitioner. We measured 46 symptoms based on the WHO's Global COVID-19 Clinical Platform Case Report Form for Post COVID Condition and performed a factor analysis and item response theory based 2-parameter logistic model to develop a population-based t-score to measure PASC symptom presence and intensity (PASC-SPI). A multivariable linear regression analysis was used to assess factors associated with PASC-SPI, accounting for demographics, comorbidities, COVID-19 infection duration and severity, and mental health.

RESULTS

Greater PASC-SPI was associated with greater symptoms of anxiety, a longer duration of COVID-19 infection, and hypercholesterolemia. Lower PASC-SPI was associated with older age, self-reported 1-3 units of alcohol per week, and self-reported clinician confirmation of COVID-19 diagnosis. Symptoms of anxiety accounted for a considerably higher proportion of variation in PASC-SPI than other variables.

CONCLUSION

Symptoms of anxiety were the strongest correlate of PASC-SPI, highlighting it as both a potential neuroinflammatory marker of PASC and a modifiable component of the illness. This emphasizes the need for comprehensive, whole person treatment strategies that integrate evidence-based interventions to address the multifaceted nature of PASC.

Effectiveness and tolerance of exercise interventions for long COVID: a systematic review of randomised controlled trials

OBJECTIVES

To examine the effectiveness of exercise interventions to improve long COVID symptoms and the tolerance of exercise interventions among people with long COVID.

DESIGN

Systematic review.

DATA SOURCES

Medline via EBSCOhost, Embase via OVID and CENTRAL via the Cochrane Library up to 28 February 2023.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Inclusion criteria were: (1) participants with long COVID, as defined by study authors; (2) random assignment to either an exercise intervention or a comparison group and (3) a quantitative measure of at least 1 of the 12 core long COVID outcomes. Exclusion criteria were: (1) signs or symptoms not reasonably attributable to prior SARS-CoV-2 infection; (2) pre-exposure or postexposure prophylaxis for COVID-19 or the prevention of long COVID symptoms and (3) interventions where the primary exercise component is breathing or respiratory muscle training.

DATA EXTRACTION AND SYNTHESIS

Two reviewers independently extracted data, and studies were narratively synthesised.

RESULTS

Eight studies were included. Follow-up periods ranged from 2 to 28 weeks (mean=8.5 weeks). Sample sizes ranged from 39 to 119 (mean=56). All studies were in adults (mean age=49.9 years) and both sexes (mean female proportion=53.9%). Four studies were at low risk of bias, two were unclear and two were high. The evidence suggests that exercise interventions lead to short-term improvements in dyspnoea, fatigue, physical function and the physical domain of quality of life among people with long COVID. Of the five studies that reported adverse events, rates were low and, when reported, mild. Of the seven studies that reported sufficient relevant information, 1 of 252 participants who received exercise discontinued the intervention due to tolerance-related issues.

CONCLUSION

Available evidence suggests that exercise interventions may be beneficial and tolerable among some people with long COVID. However, the evidence base consists of a limited number of studies with small sample sizes and short follow-up periods.

Analysis of 977 Long COVID Patients Reveals Prevalent Neuropathy and Association with Anti-Ganglioside Antibodies

Background

Long COVID (LC) is a novel condition that is characterized by persistent symptoms that last from months to years following a SARS-CoV-2 infection. While LC symptoms vary widely, neuropathy is one of the most prevalent symptoms and drastically affects patients' quality of life. However, the underlying pathophysiology of LC neuropathy remains poorly understood. Here, we investigated the prevalence and potential mechanisms of LC neuropathy in the largest LC neuropathy cohort to date.

Methods

We conducted an observational study of 977 adults with LC at Dell Medical School. Participants underwent clinical assessments, skin punch biopsy, and comprehensive metabolic, endocrine and immunological profiling. A subset of patients received treatment with intravenous immunoglobulin (IVIG).

Findings

Neuropathic symptoms were reported by 55% (534/977) participants, with skin biopsy confirming small fiber neuropathy in 56.5% (48/85) cases, affecting both epidermal and autonomic nerve fibers. Common risk factors for neuropathy, including metabolic and endocrine disorders, did not fully explain neuropathic symptoms. While general immunological markers (lymphocyte, T cell, and B cell count and C reactive protein were unremarkable, unexpectedly, we detected anti-ganglioside antibodies (AGAs) in 25% of patients with LC neuropathy, a comparable rate to other AGA-associated neuropathies. Longitudinal testing revealed persistent AGA positivity, and multiple elevated AGAs in a subset of patients. In a pilot treatment cohort of eight patients, IVIG treatment resulted in improvement of patient reported neuropathic symptoms.

Interpretation

Our findings reveal a high prevalence of small fiber neuropathy in LC, with evidence suggesting an autoimmune mechanism involving AGAs in one in four LC neuropathy patients. The therapeutic response to IVIG further supports an autoimmune pathophysiology, suggesting potential benefits of immunomodulation in LC neuropathy patients.

Poor Association Between Clinical Characteristics and Seropositivity in Children With Suspected Long COVID-A Single-Centre Study

AIM

We aimed to compare characteristics and clinical presentation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody positive or negative children attending a specialist outpatient clinic for suspected paediatric long COVID.

METHODS

A cross-sectional study was conducted of 113 children and adolescents enrolled between 1 December 2020 to 14 September 2021 in a multidisciplinary programme. Clinical and epidemiological data were collected with standardised interviews and laboratory tests including SARS-CoV-2 spike antibody measurement.

RESULTS

A serological link to SARS-CoV-2 infection was found in 52%. Most patients (94.7%) reported several symptoms. Fatigue, post-exertional malaise, dizziness, nausea, headache, and concentration difficulties were the most common. Seronegative children had a higher number of individual symptoms. School absence and drop-out from leisure activities was substantial in both groups with higher numbers for the seronegative group. Self-reported health was low in both groups.

CONCLUSION

Children attending a specialist paediatric long COVID clinic experienced multiple symptoms and poor self-reported health. The symptomatology was similar regardless of serological status, implying multifactorial causes. A multidisciplinary assessment of this cohort was essential considering the broad spectrum of symptoms displayed and their substantial impact on everyday functioning.

A Narrative Review of the Efficacy of Long COVID Interventions on Brain Fog, Processing Speed, and Other Related Cognitive Outcomes

In the years following the global emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), or COVID-19, researchers have become acutely aware of long-term symptomology associated with this disease, often termed long COVID. Long COVID is associated with pervasive symptoms affecting multiple organ systems. Neurocognitive symptoms are reported by up to 40% of long COVID patients, with resultant effects of loss of daily functioning, employment issues, and enormous economic impact and high healthcare utilization. The literature on effective, safe, and non-invasive interventions for the remediation of the cognitive consequences of long COVID is scarce and poorly described. Of specific interest to this narrative review is the identification of potential interventions for long COVID-associated neurocognitive deficits. Articles were sourced from PubMed, EBSCO, Scopus, and Embase following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Articles published between the dates of January 2020 and 30 June 2024 were included in the search. Twelve studies were included in the narrative review, including a feasibility study, a pilot study, a case series, a case study, and an observational study, in addition to three randomized clinical trials and four interventional studies. Overall, treatment interventions such as cognitive training, non-invasive brain stimulation therapy, exercise rehabilitation, targeted pharmacological intervention, and other related treatment paradigms show promise in reducing long COVID cognitive issues. This narrative review highlights the need for more rigorous experimental designs and future studies are needed to fully evaluate treatment interventions for persistent cognitive deficits associated with long COVID.

Towards an understanding of physical activity-induced post-exertional malaise: Insights into microvascular alterations and immunometabolic interactions in post-COVID condition and myalgic encephalomyelitis/chronic fatigue syndrome

BACKGROUND

A considerable number of patients who contracted SARS-CoV-2 are affected by persistent multi-systemic symptoms, referred to as Post-COVID Condition (PCC). Post-exertional malaise (PEM) has been recognized as one of the most frequent manifestations of PCC and is a diagnostic criterion of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Yet, its underlying pathomechanisms remain poorly elucidated.

PURPOSE AND METHODS

In this review, we describe current evidence indicating that key pathophysiological features of PCC and ME/CFS are involved in physical activity-induced PEM.

RESULTS

Upon physical activity, affected patients exhibit a reduced systemic oxygen extraction and oxidative phosphorylation capacity. Accumulating evidence suggests that these are mediated by dysfunctions in mitochondrial capacities and microcirculation that are maintained by latent immune activation, conjointly impairing peripheral bioenergetics. Aggravating deficits in tissue perfusion and oxygen utilization during activities cause exertional intolerance that are frequently accompanied by tachycardia, dyspnea, early cessation of activity and elicit downstream metabolic effects. The accumulation of molecules such as lactate, reactive oxygen species or prostaglandins might trigger local and systemic immune activation. Subsequent intensification of bioenergetic inflexibilities, muscular ionic disturbances and modulation of central nervous system functions can lead to an exacerbation of existing pathologies and symptoms.

Neurovascular dysregulation in systemic sclerosis: novel insights into pathophysiology, diagnosis, and treatment utilizing invasive cardiopulmonary exercise testing

PURPOSE OF REVIEW

Pathologic abnormalities in skeletal muscle and the systemic vasculature are common in patients with systemic sclerosis (SSc). These abnormalities may lead to impaired systemic peripheral oxygen extraction (EO 2 ), known as neurovascular dysregulation, which may be because of abnormal blood flow distribution in the vasculature, microvascular shunting, and/or skeletal muscle mitochondrial dysfunction. Findings from invasive cardiopulmonary exercising testing (iCPET) provide important insights and enable diagnosis and treatment of this SSc disease manifestation.

RECENT FINDINGS

Recent findings from noninvasive cardiopulmonary exercise testing (niCPET) support the existence of neurovascular dysregulation in patients with SSc. Invasive cardiopulmonary exercise testing (iCPET) has pointed to reduced systemic vascular distensibility as a possible mechanism for neurovascular dysregulation in patients with connective tissue diseases, including SSc.

SUMMARY

Neurovascular dysregulation is likely an underappreciated cause of exercise impairment and dyspnea in patients with SSc in the presence or absence of underlying cardiopulmonary disease. It is posited to be related to microcirculatory and muscle dysfunction. Further studies are needed to clarify the pathophysiology of neurovascular dysregulation in SSc and to identify novel treatment targets and additional therapies.

Post-Acute Sequelae of SARS-CoV-2 Infections: Exercise Limitation and Rehabilitation

Patients with prior SARS-CoV-2 infections can develop chronic symptoms; this clinical presentation has been called post-acute sequelae of SARS-CoV-2 infection, post-COVID condition, and long COVID. It can develop in both outpatient cases and in hospital cases; the frequency depends on the severity of infection and comorbidity. Many of these patients have exercise limitation when tested using cardiopulmonary exercise tests. The potential explanations for reduced exercise capacity include cardiac limitations, respiratory limitations, skeletal muscle weakness, deconditioning, and limiting symptoms out of proportion to any measured physiological limitation, and many patients have more than one explanation for the exercise limitation. Since these patients may have required prolonged hospitalization, deconditioning has been considered a potential explanation for their post-hospitalization limitations. Patients with deconditioning have a low oxygen uptake per minute (VO2) maximum with no obvious cardiac or respiratory limitation, but some do have measurable muscle weakness. One complex study reported that these patients had a high proportion of high-fatigable glycolytic fibers, reduced mitochondrial function, atrophic fibers, and focal necrosis in skeletal muscle. Some post-COVID patients have chronic fatigue and post-exertional malaise and meet the clinical criteria for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Most patients with post-COVID syndrome do improve with conventional cardiopulmonary rehabilitation. However, patients with post-exertional malaise need special attention to their exercise programs and careful monitoring for adverse effects. In summary, patients with long COVID can have complex presentations with a broad range of symptoms and several possible exercise limitations. Their rehabilitation program should be based on their physical capacity and their symptom profile.

From the armchair to contemporary cardiac rehabilitation: the remarkable ongoing journey of exercise training in ischemic heart disease

Exercise is an important physiological activity with several health benefits. In the setting of ischemic heart disease (IHD), the view toward exercise has greatly evolved throughout the years, concurrently to several major advances in the management of this complex entity. Currently, exercise training has broad applications across the IHD continuum as a powerful tool in its overall management, being a core component of comprehensive cardiac rehabilitation programs. Beyond this, exercise has also been incorporated as an integral part of contemporary methodologies aiming to provide diagnostic and prognostic data, such as cardiopulmonary exercise stress testing or stress echocardiography. In this article, we provide a pragmatic overview concerning the role of exercise in IHD, with a focus on its incorporation in cardiac rehabilitation frameworks, while also discussing some of the challenges and unmet needs concerning these interventions.

Two-day cardiopulmonary exercise testing in long COVID post-exertional malaise diagnosis

BACKGROUND

Long COVID patients present with a myriad of symptoms that can include fatigue, exercise intolerance and post exertional malaise (PEM). Long COVID has been compared to other post viral syndromes, including myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), where a reduction in day 2 cardiopulmonary exercise test (CPET) performance of a two-day CPET protocol is suggested to be a result of PEM. We investigated cardiopulmonary and perceptual responses to a two-day CPET protocol in Long COVID patients.

METHODS

15 Long COVID patients [n=7 females; mean (SD) age: 53(11) yr; BMI = 32.2(8.5) kg/m2] performed a pulmonary function test and two ramp-incremental CPETs separated by 24 hr. CPET variables included gas exchange threshold (GET), peak oxygen uptake (V̇O2peak) and peak work rate (WRpeak). Ratings of perceived dyspnoea and leg effort were recorded at peak exercise using the modified 0-10 Borg Scale. PEM (past six months) was assessed using the modified DePaul Symptom Questionnaire (mDSQ). One-sample t-tests were used to test significance of mean difference between days (p<0.05).

RESULTS

mDSQ revealed PEM in 80 % of patients. Lung function was normal. Responses to day 1 CPET were consistent with the presence of aerobic deconditioning in 40 % of patients (V̇O2peak <80 % predicted, in the absence of evidence of cardiovascular and pulmonary limitations). There were no differences between day-1 and day-2 CPET responses (all p>0.05).

CONCLUSION

PEM symptoms in Long COVID patients, in the absence of differences in two-day CPET responses separated by 24 hours, suggests that PEM is not due to impaired recovery of exercise capacity between days.

A practical framework for Long COVID treatment in primary care

Long COVID is a complex, multisystem illness with a poorly understood pathophysiology, absence of specific diagnostic tests or criteria, or evidence-based treatments. With over 200 identified symptoms and approximately 10% of COVID-19 cases resulting in Long COVID, it is a challenge to provide comprehensive treatment at a scale commensurate with the illness burden. The diverse manifestations of Long COVID, encompassing numerous medical specialties, typically place primary care providers (PCPs) at the forefront of management, navigating an evolving landscape of research and lack of evidence-based guidelines. This paper presents a pragmatic, structured framework for Long COVID management in primary care, integrating current knowledge and best practices. The approach is individualized, addressing Long COVID's broad symptomatology through a four-step framework. The first step focuses on energy management strategies, emphasizing the prevention of post-exertional malaise, a cardinal feature of Long COVID. The second step, intentional rehabilitation, employs carefully titrated multidisciplinary modalities to address physical, cognitive, and emotional domains. The third step utilizes symptomatic management through both pharmacological and non-pharmacological interventions, targeting debilitating symptoms like fatigue, insomnia, and chronic pain. The fourth step outlines an approach to trialing experimental, targeted therapies that may impact Long COVID's underlying pathophysiology. These treatments, while experimental and lacking quality evidence in Long COVID, may be available off-label on an individual basis following a thorough risk-benefit discussion. This stepwise framework can equip PCPs to effectively address the most common and disabling symptoms of Long COVID, individualize care, and remain attuned to the evolving scientific understanding of the condition.

The metabolic and physiologic impairments underlying long COVID associated exercise intolerance

Data from invasive CPET (iCPET) revealed long COVID patients have impaired systemic oxygen extraction (EO2), suggesting impaired mitochondrial ATP production. However, it remains uncertain whether the initial severity of SARS-CoV-2 infection has implications on EO2 and exercise capacity (VO2) nor has there been assessment of anerobic ATP generation in long COVID patients. iCPET was performed on 47 long COVID patients (i.e., full cohort; n = 8 with severe SARS-CoV-2 infection). In a subset of patients (i.e., metabolomic cohort; n = 26) metabolomics on venous and arterial blood samples during iCPET was performed. In the full cohort, long COVID patients exhibited reduced peak EO2 with reduced peak VO2 (90 ± 17% predicted) relative to cardiac output (118 ± 23% predicted). Peak VO2 [88% predicted (IQR 81% - 108%) vs. 70% predicted (IQR 64% - 89%); p = 0.02] and EO2 [0.59(IQR 0.53-0.62) vs. 0.53(IQR 0.50-0.48); p = 0.01) were lower in severe versus mild infection. In the metabolomic cohort, 12 metabolites were significantly consumed, and 41 metabolites were significantly released (p-values < 0.05). Quantitative metabolomics demonstrated significant increases in inosine and succinate arteriovenous gradients during exercise. Peak VO2 was significantly correlated with peak venous succinate (r = 0.68; p = 0.0008) and peak venous lactate (r = 0.49; p = 0.0004). Peak EO2 and consequently peak VO2 impact long COVID patients in a severity dependent manner. Exercise intolerance associated with long COVID is defined by impaired aerobic and anaerobic energy production. Peak venous succinate may serve as a potential biomarker in long COVID.

Characterizing Long COVID in Children and Adolescents

Importance

Most research to understand postacute sequelae of SARS-CoV-2 infection (PASC), or long COVID, has focused on adults, with less known about this complex condition in children. Research is needed to characterize pediatric PASC to enable studies of underlying mechanisms that will guide future treatment.

Objective

To identify the most common prolonged symptoms experienced by children (aged 6 to 17 years) after SARS-CoV-2 infection, how these symptoms differ by age (school-age [6-11 years] vs adolescents [12-17 years]), how they cluster into distinct phenotypes, and what symptoms in combination could be used as an empirically derived index to assist researchers to study the likely presence of PASC.

Design, Setting, and Participants

Multicenter longitudinal observational cohort study with participants recruited from more than 60 US health care and community settings between March 2022 and December 2023, including school-age children and adolescents with and without SARS-CoV-2 infection history.

Exposure

SARS-CoV-2 infection.

Main Outcomes and Measures

PASC and 89 prolonged symptoms across 9 symptom domains.

Results

A total of 898 school-age children (751 with previous SARS-CoV-2 infection [referred to as infected] and 147 without [referred to as uninfected]; mean age, 8.6 years; 49% female; 11% were Black or African American, 34% were Hispanic, Latino, or Spanish, and 60% were White) and 4469 adolescents (3109 infected and 1360 uninfected; mean age, 14.8 years; 48% female; 13% were Black or African American, 21% were Hispanic, Latino, or Spanish, and 73% were White) were included. Median time between first infection and symptom survey was 506 days for school-age children and 556 days for adolescents. In models adjusted for sex and race and ethnicity, 14 symptoms in both school-age children and adolescents were more common in those with SARS-CoV-2 infection history compared with those without infection history, with 4 additional symptoms in school-age children only and 3 in adolescents only. These symptoms affected almost every organ system. Combinations of symptoms most associated with infection history were identified to form a PASC research index for each age group; these indices correlated with poorer overall health and quality of life. The index emphasizes neurocognitive, pain, and gastrointestinal symptoms in school-age children but change or loss in smell or taste, pain, and fatigue/malaise-related symptoms in adolescents. Clustering analyses identified 4 PASC symptom phenotypes in school-age children and 3 in adolescents.

Conclusions and Relevance

This study developed research indices for characterizing PASC in children and adolescents. Symptom patterns were similar but distinguishable between the 2 groups, highlighting the importance of characterizing PASC separately for these age ranges.

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.

Functional neurological disorder, physical activity and exercise: What we know and what we can learn from comorbid disorders

Functional neurological disorder (FND) is a common neurologic disorder associated with many comorbid symptoms including fatigue, pain, headache, and orthostasis. These concurrent symptoms lead patients to accumulate multiple diagnoses comorbid with FND, including fibromyalgia, chronic fatigue syndrome, postural orthostatic tachycardia syndrome, persistent post-concussive symptoms, and chronic pain. The role of physical activity and exercise has not been evaluated in FND populations, though has been studied in certain comorbid conditions. In this traditional narrative literature review, we highlight some existing literature on physical activity in FND, then look to comorbid disorders to highlight the therapeutic potential of physical activity. We then consider abnormalities in the autonomic nervous system (ANS) as a potential pathophysiological explanation for symptoms in FND and comorbid disorders and postulate how physical activity and exercise may provide benefit via autonomic regulation.

Long COVID and post-acute sequelae of SARS-CoV-2 pathogenesis and treatment: A Keystone Symposia report

In 2023, the Keystone Symposia held the first international scientific conference convening research leaders investigating the pathology of post-acute sequelae of COVID-19 (PASC) or Long COVID, a growing and urgent public health priority. In this report, we present insights from the talks and workshops presented during this meeting and highlight key themes regarding what researchers have discovered regarding the underlying biology of PASC and directions toward future treatment. Several themes have emerged in the biology, with inflammation and other immune alterations being the most common focus, potentially related to viral persistence, latent virus reactivation, and/or tissue damage and dysfunction, especially of the endothelium, nervous system, and mitochondria. In order to develop safe and effective treatments for people with PASC, critical next steps should focus on the replication of major findings regarding potential mechanisms, disentangling pathogenic mechanisms from downstream effects, development of cellular and animal models, mechanism-focused randomized, placebo-controlled trials, and closer collaboration between people with lived experience, scientists, and other stakeholders. Ultimately, by learning from other post-infectious syndromes, the knowledge gained may help not only those with PASC/Long COVID, but also those with other post-infectious syndromes.

Head-down tilt reduces the heart rate in postural tachycardia syndrome in acute setting: a pilot study

BACKGROUND

Reduced preload and thoracic blood volume accompany postural tachycardia syndrome (POTS). Head-down tilt (HDT) increases both preload and intrathoracic blood volume. The objective of this study was to assess the safety and efficacy of HDT in POTS in acute settings.

METHODS

This retrospective study evaluated POTS patients. Analyzed data included heart rate, blood pressure, cerebral blood flow velocity (CBFv) in the middle cerebral artery, and capnography. The baseline supine hemodynamic data were compared with the data obtained at the second minute of the -10° HDT. A linear mixed-effects model was used to assess the effect of HDT on hemodynamic variables.

RESULTS

The HDT was explored in seven POTS patients and an additional seven POTS patients without HDT served as controls. In the HDT arm, four POTS patients had overlapping diagnoses of myalgic encephalopathy/chronic fatigue syndrome (ME/CFS) and one patient had comorbidity of post-acute sequelae of SARS-CoV-2 infection (PASC). HDT lowered heart rate by 10% and increased end-tidal CO2 by 8%. There was no change in other cardiovascular variables.

CONCLUSIONS

In the acute setting, HDT is safe. HDT reduces the heart rate presumably by modulating baroreflex by enhancing preload and stroke volume, which in turn increases thoracic blood volume with a net effect of parasympathetic cardiovagal activation and/or sympathetic withdrawal. This pilot study provides a foundation to proceed with longitudinal studies exploring the long-term effect of repetitive HDT in conditions associated with preload failure such as POTS, ME/CSF, and PASC.

Personalized pulmonary rehabilitation program for patients with post-acute sequelae of COVID-19: A proof-of-concept retrospective study

Long-COVID patients present with a decline in physical fitness. The aim of this study is to reveal the impact of pulmonary rehabilitation (PR) on physical fitness, quality of life (QoL), and parameters of quantified thorax CT. Long-COVID patients enrolled in a 3-month PR program were retrospectively studied. PR included endurance and resistance training three times a week. Assessments pre- and post-rehabilitation included quantified chest CT, pulmonary function tests (PFT), six-minute walk test (6MWT), cardiopulmonary exercise test, and questionnaires: Hospital Anxiety and Depression Scale, post-COVID-19 Functional Status scale, Borg score, and EuroQol. Seventeen subjects (5M/12F), mean age 42 ± 13 years, were included. PR improved all questionnaires' results significantly. Only significant difference in PFT parameters was correlation between baseline total lung capacity (TLC) and difference in TLC pre- and post-rehabilitation (p = 0.002). 6MWT increased from 329 to 365 m (p < 0.001), VO2max changed from 21 to 24 mL/kg/min (p = 0.007), peak load increased from 116 to 141 Watt (p < 0.001). Blood volume in small pulmonary vessels of 1.25 to 5 mm2 in cross-sectional area (BV5%) was higher than observed in patients with acute COVID-19 infection. After rehabilitation, BV5% decreased from 65% to 62% (p = 0.020). These changes correlated directly with changes in TLC (p = 0.039). Quantified CT airway volume increased after rehabilitation (p = 0.013). After rehabilitation, TLC tended to normalize due to (re)opening of small airways, with decline in air trapping and recruitment of alveoli. Furthermore, this study revealed that pulmonary rehabilitation can improve QoL and physical fitness in long-COVID patients.

Disentangling the effects of PTSD from Gulf War Illness in male veterans via a systems-wide analysis of immune cell, cytokine, and symptom measures

BACKGROUND

One-third of veterans returning from the 1990-1991 Gulf War reported a myriad of symptoms including cognitive dysfunction, skin rashes, musculoskeletal discomfort, and fatigue. This symptom cluster is now referred to as Gulf War Illness (GWI). As the underlying mechanisms of GWI have yet to be fully elucidated, diagnosis and treatment are based on symptomatic presentation. One confounding factor tied to the illness is the high presence of post-traumatic stress disorder (PTSD). Previous research efforts have demonstrated that both GWI and PTSD are associated with immunological dysfunction. As such, this research endeavor aimed to provide insight into the complex relationship between GWI symptoms, cytokine presence, and immune cell populations to pinpoint the impact of PTSD on these measures in GWI.

METHODS

Symptom measures were gathered through the Multidimensional fatigue inventory (MFI) and 36-item short form health survey (SF-36) scales and biological measures were obtained through cytokine & cytometry analysis. Subgrouping was conducted using Davidson Trauma Scale scores and the Structured Clinical Interview for Diagnostic and statistical manual of mental disorders (DSM)-5, into GWI with high probability of PTSD symptoms (GWIH) and GWI with low probability of PTSD symptoms (GWIL). Data was analyzed using Analysis of variance (ANOVA) statistical analysis along with correlation graph analysis. We mapped correlations between immune cells and cytokine signaling measures, hormones and GWI symptom measures to identify patterns in regulation between the GWIH, GWIL, and healthy control groups.

RESULTS

GWI with comorbid PTSD symptoms resulted in poorer health outcomes compared with both Healthy control (HC) and the GWIL subgroup. Significant differences were found in basophil levels of GWI compared with HC at peak exercise regardless of PTSD symptom comorbidity (ANOVA F = 4.7, P = 0.01,) indicating its potential usage as a biomarker for general GWI from control. While the unique identification of GWI with PTSD symptoms was less clear, the GWIL subgroup was found to be delineated from both GWIH and HC on measures of IL-15 across an exercise challenge (ANOVA F > 3.75, P < 0.03). Additional differences in natural killer (NK) cell numbers and function highlight IL-15 as a potential biomarker of GWI in the absence of PTSD symptoms.

CONCLUSION

We conclude that disentangling GWI and PTSD by defining trauma-based subgroups may aid in the identification of unique GWI biosignatures that can help to improve diagnosis and target treatment of GWI more effectively.

Physical Activity and Fatigue Symptoms: Neurotypical Adults and People with Chronic Multisymptom Illnesses

For neurotypical adults, a single bout of low-to-moderate intensity physical activity usually transiently improves feelings of energy. Similar bouts of exercise have the opposite effect of increased feelings of fatigue when performed by samples with chronic multisymptom illnesses (CMIs) such as Long-COVID, Gulf War Illness (GWI), or Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). The short-term adoption of regular moderate intensity physical activity (typical experiments are 1 to 6 months) among neurotypical adults results in small-to-moderate improvements in self-reported feelings of fatigue, energy, and vitality. Small improvements in these feelings, or no change at all, occur for CMIs, but limited data precludes strong conclusions. The mechanisms of exercise effects on fatigue, whether acute or chronic, are poorly understood but likely involve multiple neural circuits and associated transmitters. For CMIs, the mechanisms of acute worsening of fatigue with exercise may be driven by the yet unknown pathophysiological mechanisms of the disease (perhaps involving brain, immune and autonomic system dysfunction, and their interactions). Likewise, fatigue improvements may depend on whether chronic physical activity is a disease-modifying treatment.

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.

Focus on post-exertional malaise when approaching ME/CFS in specialist healthcare improves satisfaction and reduces deterioration

Background

Post-exertional malaise (PEM) is considered a hallmark characteristic of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). This may also apply to subgroups of patients with long COVID-induced ME/CFS. However, it is uncertain to what extent PEM is acknowledged in routine specialist healthcare for ME/CFS patients, and how this affects patient outcomes.

Objective

This study aims to evaluate to what extent ME/CFS patients experienced focus on PEM in specialist healthcare practice and its significance for outcome and care quality.

Methods

Data from two online cross-sectional surveys covering specialist healthcare services for ME/CFS patients at rehabilitation institutes in Norway and two regional hospitals, respectively, were analyzed. Evaluations of 788 rehabilitation stays, 86 hospital consultations, and 89 hospital interventions were included. Logistic regression models and Mann-Whitney U-tests were used to quantify the impact of addressing PEM on health and functioning, care satisfaction, or benefit. Spearman's rank correlation and Cronbach's alpha of focus on PEM with the respondents' perception of healthcare providers' knowledge, symptom acknowledgment, and suitability of intervention were assessed as measures for care quality and their internal consistency, respectively.

Results

PEM was addressed in 48% of the rehabilitation stays, 43% of the consultations, and 65% of the hospital interventions. Failure to address PEM roughly doubled the risk of health deterioration, following rehabilitation (OR = 0.39, 95% CI 0.29-0.52; 40.1% vs. 63.2% P = <0.001) and hospital intervention (OR = 0.34, 95% CI 0.13-0.89; 22.4% vs. 45.2%, p = 0.026). The focus on PEM (PEM-focus) during the clinical contact was associated with significantly higher scores on patients' rated care satisfaction and benefit of both consultation and intervention. Furthermore, addressing PEM was (inter)related to positive views about healthcare providers' level of knowledge of ME/CFS, their acknowledgment of symptoms, obtained knowledge, and the perceived suitability of intervention (Cronbach's alpha ≥0.80).

Discussion

PEM is still frequently not acknowledged in specialist healthcare practice for ME/CFS patients in Norway. Not addressing PEM substantially increased the probability of a decline in health and functioning following the intervention and was strongly associated with reduced perceived care quality, satisfaction, and benefit. These findings may be related to the applied explanatory models for ME/CFS and are most likely of relevance to long COVID.

Yeast Beta-Glucan Supplementation with Multivitamins Attenuates Cognitive Impairments in Individuals with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Randomized, Double-Blind, Placebo-Controlled Trial

This research aimed to examine the potential alleviative effects of beta-glucan administration on fatigue, unrefreshing sleep, anxiety/depression symptoms and health-related quality of life in ME/CFS. A 36-week unicenter, randomized, double-blind, placebo-controlled trial was conducted in 65 ME/CFS patients, who were randomly allocated to one of two arms to receive four capsules each one of 250 mg beta-glucan, 3.75 µg vitamin D3, 1.05 mg vitamin B6, and 7.5 mg zinc (n = 35), or matching placebo including only microcrystalline cellulose as an excipient (n = 30) once daily. The findings showed that the beta-glucan supplementation significantly improved cognitive fatigue (assessed with FIS-40 scores) after the 36-week treatment compared to the baseline (p = 0.0338). Taken together, this study presents the novel finding that yeast-derived beta-glucan may alleviate cognitive fatigue symptoms in ME/CFS. Thus, it offers valuable scientific insights into the potential use of yeast beta-glucan as a nutritional supplement and/or functional food to prevent or reduce cognitive dysfunction in patients with ME/CFS. Further interventions are warranted to validate these findings and also to delve deeper into the possible immunometabolic pathomechanisms of beta-glucans in ME/CFS.

Observational Study of Repeat Immunoadsorption (RIA) in Post-COVID ME/CFS Patients with Elevated ß2-Adrenergic Receptor Autoantibodies-An Interim Report

There is increasing evidence for an autoimmune aetiology in post-infectious Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). SARS-CoV-2 has now become the main trigger for ME/CFS. We have already conducted two small proof-of-concept studies on IgG depletion by immunoadsorption (IA) in post-infectious ME/CFS, which showed efficacy in most patients. This observational study aims to evaluate the efficacy of IA in patients with post-COVID-19 ME/CFS. The primary objective was to assess the improvement in functional ability. Due to the urgency of finding therapies for post-COVID-Syndrome (PCS), we report here the interim results of the first ten patients, with seven responders defined by an increase of between 10 and 35 points in the Short-Form 36 Physical Function (SF36-PF) at week four after IA. The results of this observational study will provide the basis for patient selection for a randomised controlled trial (RCT), including sham apheresis, and for an RCT combining IA with B-cell depletion therapy. Trial registration number: NCT05629988.