Tag: PEM

Ignorance about post-exertional malaise and continued conflation of ME/CFS with chronic fatigue harms patients and stymies research progress

Dear Editor,

There are numerous issues with the opinion piece by Miller and coauthors. Most concern longstanding fallacies about the nature of ME/CFS and what patients believe about their illness, which — again — need to be corrected. I’d like to focus on just one: The defining and cardinal feature of ME/CFS is not fatigue, but rather post-exertional malaise (PEM).

PEM, sometimes referred to as post-exertional symptom exacerbation (PESE), can be defined as episodes during which people with ME/CFS experience significant worsening of existing symptoms and/or onset of new symptoms following amounts of physical or mental exertion or sensory stimuli that they could easily tolerate before the illness [1]. The length and severity of an episode of PEM are out of proportion to the amount of exertion or stimulus that triggered it; in severe or very severe ME/CFS patients, PEM may be triggered by, for example, short conversations with their carers or brief exposure to bright light, and these episodes may last week, months, or longer.

PEM remains poorly understood, but the concept and terminology have over recent years become much more mainstream, owing to the high prevalence of PEM in long covid [2]. The consensus opinion among ME/CFS patients is that daily activities and sensory input should be managed in such a way as to minimise PEM, because PEM severely impacts quality of life and can in some cases lead to further long-term deterioration in patients’ health and functional capacity. This concept forms the basis of pacing, an energy management strategy recommended by NICE [3].

In their opinion piece, Miller and coauthors ignore PEM when listing common symptoms of ME/CFS. This is an attempt to continue framing this illness as belonging to a family of ‘fatiguing conditions’, which, along with other ‘medically unexplained symptoms’, they argue can be treated with psychological interventions and rehabilitation.

Read the rest of this letter here: https://www.bmj.com/content/389/bmj.r977/rr-6

Repeated Cardiopulmonary Exercise Testing of ME/CFS Patients

Abstract:

Post-exertional malaise is a cardinal symptom present in 95% of individuals with myalgic encephalomyelitis (ME/CFS). Repeated cardiopulmonary exercise testing has been momentous in revealing that the physiological systems of those with ME/CFS are impaired or damaged and do not respond to exercise/physical activity like those without the condition. The 24-h repeated exercise test may demonstrate a reduction in peak oxygen consumption (VO2 peak), VO2 at ventilatory threshold, power output at both peak and ventilatory threshold, along with a reduction/diminished maximal heart rate commensurate with chronotropic intolerance. In this chapter, I describe the process and methods of repeated cardiopulmonary exercise testing, used to assess exercise tolerance in individuals with ME/CFS.

Source: Hodges L. Repeated Cardiopulmonary Exercise Testing of ME/CFS Patients. Methods Mol Biol. 2025;2920:163-172. doi: 10.1007/978-1-0716-4498-0_10. PMID: 40372683. https://link.springer.com/protocol/10.1007/978-1-0716-4498-0_10

Post-exertional malaise in Long COVID: subjective reporting versus objective assessment

Abstract:

Background: Post-exertional malaise (PEM) is a central feature of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and has emerged as a prominent feature of Long COVID. The optimal clinical approach to PEM is inconclusive, and studies of the impact of exercise have yielded contradictory results.

Objective: The objective of this study was to examine PEM in Long COVID by assessing the prevalence of self-reported PEM across study cohorts and symptom responses of Long COVID patients to a standardized exercise stressor. Secondarily, Long COVID symptom responses to exercise were compared to those of ME/CFS and healthy volunteers.

Methods: Data from three registered clinical trials comprised four cohorts in this study: Long COVID Questionnaire Cohort (QC; n = 244), Long COVID Exercise Cohort (EC; n = 34), ME/CFS cohort (n = 9), and healthy volunteers (HV; n = 9). All cohorts completed questionnaires related to physical function, fatigue, and/or PEM symptoms. EC also performed a standardized exercise test (cardiopulmonary exercise test, CPET), and the PEM response to CPET was assessed using visual analog scales and qualitative interviews (QIs) administered serially over 72 h. EC PEM measures were compared to ME/CFS and HV cohorts. A secondary analysis of QI explored positive responses to CPET among EC, ME/CFS and HV.

Results: Self-reported PEM was 67% in QC and estimated at 27% in EC. Only 2 of 34 EC patients (5.9%) were observed to develop PEM after a CPET. In addition, PEM responses after CPET in Long COVID were not as severe and prolonged as those assessed in ME/CFS. Twenty-two of 34 EC patients (64.7%) expressed at least one of 7 positive themes after the CPET.

Conclusion: Self-report of PEM is common in Long COVID. However, observable PEM following an exercise stressor was not frequent in this small cohort. When present, PEM descriptions during QI were less severe in Long COVID than in ME/CFS. Positive responses after an exercise stressor were common in Long COVID. Exercise testing to determine the presence of PEM may have utility for guiding clinical management of Long COVID.

Source: Stussman B, Camarillo N, McCrossin G, Stockman M, Norato G, Vetter CS, Ferrufino A, Adedamola A, Grayson N, Nath A, Chan L, Walitt B, Chin LMK. Post-exertional malaise in Long COVID: subjective reporting versus objective assessment. Front Neurol. 2025 Apr 23;16:1534352. doi: 10.3389/fneur.2025.1534352. PMID: 40337174; PMCID: PMC12055772. https://pmc.ncbi.nlm.nih.gov/articles/PMC12055772/ (Full text)

Assessing the Relationship in Symptomology of Myalgic Encephalitis/Chronic Fatigue Syndrome and Long COVID

Abstract:

The symptomology of Myalgic Encephalitis/Chronic Fatigue Syndrome (ME/CFS) shares many commonalities with Long COVID (LC). This study aimed to clearly define the comparison between ME/CFS and LC in terms of symptomology.

A cross-sectional analysis of 27,651 interviewees from a National Health Interview Survey 2022 adult dataset was conducted. The data was controlled for subject’s sex, race/ethnicity, age, life satisfaction, insurance coverage, poverty ratio, and comorbidities. A logistic regression was used to compare four groups: (1) LC individuals, (2) ME/CFS individuals, (3) LC with ME/CFS individuals, and (4) controls by symptoms of depression, anxiety, physical activity, fatigue, and memory.

The results showed that subjects with both ME/CFS and LC were more likely to report memory issues, anxiety, depression, fatigue, and difficulty with physical activity followed by subjects with ME/CFS only, LC only, and the controls (P < .01).

Our study suggests a synergistic mechanism between ME/CFS and LC in developing issues with anxiety, depression, fatigue, and physically activity in patients. The study’s conclusions highlight the need to elucidate the possible overlap in pathophysiological mechanisms of ME/CFS and LC in the symptomology of patients.

Source: Garapaty N, Reyes KM, Tehrani L, Mendoza MB, Hardigan P. Assessing the Relationship in Symptomology of Myalgic Encephalitis/Chronic Fatigue Syndrome and Long COVID. Am J Med Open. 2025 Feb 1;13:100085. doi: 10.1016/j.ajmo.2024.100085. PMID: 40271015; PMCID: PMC12017839. https://pmc.ncbi.nlm.nih.gov/articles/PMC12017839/ (Full text)

Awareness and Perception of Myalgic Encephalomyelitis and Chronic Fatigue Syndrome Among Pain Specialists: A Questionnaire-Based Study

Abstract:

Background: This study aims to explore the perceptions and clinical approaches of pain management specialists toward myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), a condition characterized by persistent fatigue, widespread pain, unrefreshing sleep, and autonomic dysfunction. Given the challenges in diagnosis and management, pain specialists may play a pivotal role in symptom relief. By identifying variations in evaluation and treatment practices, this study seeks to enhance the recognition of ME/CFS and improve its clinical management within pain medicine.

Material and methods: The questionnaire was distributed in printed form to 250 pain specialists in Turkey. Given the limited number of pain physicians in the country, the study aimed to encompass all actively practicing specialists. The survey included four demographic questions, eight true-false questions, 12 multiple-choice questions, and four rating-scale questions. Data were collected anonymously. Data were analyzed using Statistical Product and Service Solutions (SPSS, version 27.0; IBM SPSS Statistics for Windows, Armonk, NY), with descriptive statistics and chi-square (χ²) tests applied to examine the relationships between awareness levels and attitudinal variables.

Results: In Turkey, 106 pain medicine physicians (42.4%) participated in the study. The average age was 40.6±8.52 years. Among the participants, 39.6% had previously heard of myalgic encephalomyelitis. Physicians were inclined to first ask the question, “Do you think you get enough sleep at night?” when evaluating these patients, with a rate of 63.2%. The majority of participants (65.9%) stated that they “occasionally” or “rarely” considered the relationship between fatigue and orthostatic intolerance. Additionally, 37.7% believed that this disease is a subtype of depression. The statement, “chronic fatigue decreases with intense aerobic exercise,” was agreed upon by 50.9% of participants. This controversial statement was particularly more common among those who were unaware of ME/CFS’s alternative name (p=0.009) and those who did not take dysautonomic disorders into account (p=0.048). When considering an ME/CFS diagnosis, physicians most frequently referred patients to the physical medicine and rehabilitation department (32.1%). Those who preferred not to refer patients to any department (12.3%) tended to find it appropriate for a patient to seek consultation at a pain medicine clinic due to widespread body pain and fatigue (χ2=11.405, p=0.044).

Conclusion: This study is the first questionnaire-based research assessing pain physicians’ awareness and attitudes toward ME/CFS. By highlighting their perspectives on its evaluation and management, our findings may improve recognition and clinical approaches to ME/CFS. Future research should focus on education and standardized guidelines to enhance patient care.

Source: Uygun GG, Gözükızıl ST, Bilen A. Awareness and Perception of Myalgic Encephalomyelitis and Chronic Fatigue Syndrome Among Pain Specialists: A Questionnaire-Based Study. Cureus. 2025 Mar 23;17(3):e81030. doi: 10.7759/cureus.81030. PMID: 40264626; PMCID: PMC12013460. https://pmc.ncbi.nlm.nih.gov/articles/PMC12013460/ (Full text)

How I treat my patients with Myalgic Encephalomyelitis, Chronic Fatigue Syndrome (ME/CVS), fibromyalgia or “long COVID”

Abstract:

Common to Myalgic encephalomyelitis, chronic fatigue syndrome and so-called long Covid is the panoply of complaints, with Post Exertional Malaise (PEM) as the most typical symptom. Added to that are permanent feeling of fatigue, decreased capacity to concentrate, so-called brain fog, non restorative sleep, diffuse pain, and – in case of long Covid – respiratory distress.

Several recent studies have confirmed my original hypothesis that poor metabolism and energy production by the mitochondria are responsible for the majority of these phenomena. I have suggested that inhibition of Pyruvate dehydrogenase (Pdh) activity is the major reason for this. Pdh inhibition is probably caused by the excess of the phosphatase: Pyruvate Dehydrogenase Kinase (PDK). The latter results from “Systemic Immune Disorder” (what I called “SID”) and inflammation.

Based on this hypothesis I have applied oral and infusion treatment modalities which were successful in approximately 80% of 130 consecutive patients. The pivotal substances are sodium dichloroacetate, that reduces PDK, Meldonium, that facilitates intracellular glucose metabolism, and low dose Nalexone, that optimises the function of microglia.

Source: Comhaire F. How I treat my patients with Myalgic Encephalomyelitis, Chronic Fatigue Syndrome (ME/CVS),
Fibromyalgia or “long COVID”. J Clin Images Med Case Rep. 2025; 6(3): 3508. https://jcimcr.org/pdfs/JCIMCR-v6-3508.pdf (Full text)

Wearable heart rate variability monitoring identifies autonomic dysfunction and thresholds for post-exertional malaise in Long COVID

Abstract:

Objectives Patients with Long COVID experience disabling fatigue, autonomic dysfunction, reduced exercise capacity, and post-exertional malaise (PEM). Heart rate variability (HRV) can evaluate autonomic function and monitor overexertion, potentially helping to mitigate PEM. This study aimed to use continuous multi-day HRV recordings to monitor overexertion and study autonomic function in Long COVID.

Method Heart rate and HRV were continuously measured in 127 patients with long COVID (43±11 years, 32% male) and 21 healthy controls (42±13 years, 48% male), and daily life activities tracked in a logbook. Participants underwent a (sub)maximal cardiopulmonary exercise test to determine heart rate at the first ventilatory threshold (VT1) to study HRV responses to exercise at different intensities.

Results HRV was lower in patients with long COVID compared to healthy controls during various daily activities and sleep (p<0.027). HRV remained lower for 24 hours after exercise below, at or above VT1 in patients, but not in healthy controls (p=0.010). Nighttime HRV decreased with intense exercise and longer durations in patients with long COVID (p=0.018), indicative of exercise-induced diurnal disturbances of the autonomic nervous system in long COVID.

Conclusion Heart rate variability, assessed by wearables, confirms autonomic dysfunction in patients with long COVID. The delayed recovery of the sympathovagal balance after exercise close and above to VT1 suggests that VT1 can be practically interpreted as a PEM threshold.

Application These results confirm the applicability of wearables to assess autonomic function and manage overexertion in long COVID patients.

What is already known on this topic Patients with long COVID often experience fatigue, autonomic dysfunction, and post-exertional malaise (PEM). HRV can be used as a non-invasive tool to measure autonomic function and recovery. Anecdotal evidence suggests lower HRV in patients with long COVID, but measurements are usually very short.

What this study adds This study demonstrates that continuous HRV monitoring through wearables can effectively identify overexertion and autonomic dysfunction during daily activities in patients with long COVID. Patients with long COVID have a lower heart rate variability during sleep and HRV remained significantly lower for a longer period after moderate-to-heavy exercise, that is generally associated with the induction of post-exertional malaise.

How this study might affect research, practice, or policy This study supports the use of wearables for assessing autonomic function and overexertion in daily life, helping patients with long COVID in pacing daily activities to mitigate symptoms of post-exertional malaise. HRV tracking after exercise shows that VT1 is a potential threshold for PEM. Sports physicians and physiotherapists can incorporate HRV biofeedback measures into pacing advice to patients. Additional research is needed to further investigate the effect of such an intervention.

Source: Twan Ruijgt, Anouk Slaghekke, Anneke Ellens, Kasper W. Janssen, Rob C.I. Wüst.. Wearable heart rate variability monitoring identifies autonomic dysfunction and thresholds for post-exertional malaise in Long COVID. medRxiv 2025.03.18.25320115; doi: https://doi.org/10.1101/2025.03.18.25320115 https://www.medrxiv.org/content/10.1101/2025.03.18.25320115v1.full-text (Full text)

Stellate Ganglion Block reduces symptoms of SARS-CoV-2-induced ME/CFS: A prospective cohort pilot study

Abstract:

Background: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a debilitating condition characterized by fatigue, orthostatic intolerance (OI), post-exertional malaise (PEM) and unrefreshing sleep. Our previous work has shown that modulating the autonomic nervous system can alleviate symptoms of Long COVID, which shares striking similarities with ME/CFS.

Objective: Determine the effect of stellate ganglion block (SGB) on symptoms of ME/CFS.

Methods: Subjects who met the WHO criteria for Long COVID and the Institute of Medicine criteria for ME/CFS were treated with sequential bilateral SGBs separated by 18–24 hours for three consecutive weeks (n = 10). At baseline, and at 2-weeks and 2-months post-treatment, we collected subjective assessments (SF-36 and DSQ2) of symptoms, objective assessments of orthostatic intolerance and cognitive performance, and saliva to measure morning cortisol. During the entire study period, a wearable device collected physiological data several nights a week to measure sleep parameters.

Results: DSQ2 measures of PEM, Unrefreshing Sleep, Cognitive Impairment, and OI improved significantly following treatment. SF-36 measures of Vitality, Physical Function, and Social Function improved significantly following treatment. Objective symptoms of POTS associated with infectious onset resolved following treatment. Objective measures of cognitive impairment were reduced following treatment, most notably in the areas of Immediate and Delayed Recognition. Morning cortisol and measures of sleep architecture did not change significantly following treatment.

Conclusions: Symptoms of ME/CFS were reduced after treatment with SGBs in this small prospective cohort pilot study. Given the lack of FDA-approved treatments for ME/CFS, replication of results in a large clinical trial is warranted.

Source: Duricka, D. L., & Liu, L. D. (2025). Stellate Ganglion Block reduces symptoms of SARS-CoV-2-induced ME/CFS: A prospective cohort pilot study. Fatigue: Biomedicine, Health &amp; Behavior, 13(2), 97–114. https://doi.org/10.1080/21641846.2025.2455876 https://www.tandfonline.com/doi/full/10.1080/21641846.2025.2455876#d1e276 (Full text)

Recognizing the role of fibromyalgia in post-exertional malaise

Letter:

The recent opinion by Charlton et al. published in Trends in Endocrinology & Metabolism [] provides a thought-provoking discussion of the overlap between long coronavirus disease (long-COVID) and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), emphasizing the centrality of post-exertional malaise (PEM) as a shared mechanism.

Here, we suggest that fibromyalgia should be included in the discussion, given the established role of PEM in this condition []. In addition, fibromyalgia not only shares symptomatic and mechanistic overlaps with ME/CFS, but also offers a complementary perspective on the pathophysiology of PEM. Considering that PEM is a key symptom in both fibromyalgia and long COVID, exploring skeletal muscle function in fibromyalgia could provide complementary insights into the muscle-specific alterations that contribute to this debilitating phenomenon.

Source: Giollo A, Salvato M, Doria A. Recognizing the role of fibromyalgia in post-exertional malaise. Trends Endocrinol Metab. 2025 Mar 11:S1043-2760(25)00045-1. doi: 10.1016/j.tem.2025.02.005. Epub ahead of print. PMID: 40074568. https://www.cell.com/trends/endocrinology-metabolism/abstract/S1043-2760(25)00045-1

Cerebrospinal fluid metabolomics, lipidomics and serine pathway dysfunction in myalgic encephalomyelitis/chronic fatigue syndroome (ME/CFS)

Abstract:

We proposed that cerebrospinal fluid would provide objective evidence for disrupted brain metabolism in myalgic encephalomyelitis/chronic fatigue syndroome (ME/CFS). The concept of postexertional malaise (PEM) with disabling symptom exacerbation after limited exertion that does not respond to rest is a diagnostic criterion for ME/CFS. We proposed that submaximal exercise provocation would cause additional metabolic perturbations.

The metabolomic and lipidomic constituents of cerebrospinal fluid from separate nonexercise and postexercise cohorts of ME/CFS and sedentary control subjects were contrasted using targeted mass spectrometry (Biocrates) and frequentist multivariate general linear regression analysis with diagnosis, exercise, gender, age and body mass index as independent variables. ME/CFS diagnosis was associated with elevated serine but reduced 5-methyltetrahydrofolate (5MTHF).

One carbon pathways were disrupted. Methylation of glycine led to elevated sarcosine but further methylation to dimethylglycine and choline was decreased. Creatine and purine intermediates were elevated. Transaconitate from the tricarboxylic acid cycle was elevated in ME/CFS along with essential aromatic amino acids, lysine, purine, pyrimidine and microbiome metabolites. Serine is a precursor of phospholipids and sphingomyelins that were also elevated in ME/CFS. Exercise led to consumption of lipids in ME/CFS and controls while metabolites were consumed in ME/CFS but generated in controls.

The findings differ from prior hypometabolic findings in ME/CFS plasma. The novel findings generate new hypotheses regarding serine-folate-glycine one carbon and serine-phospholipid metabolism, elevation of end products of catabolic pathways, shifts in folate, thiamine and other vitamins with exercise, and changes in sphingomyelins that may indicate myelin and white matter dysfunction in ME/CFS.

Source: Baraniuk JN. Cerebrospinal fluid metabolomics, lipidomics and serine pathway dysfunction in myalgic encephalomyelitis/chronic fatigue syndroome (ME/CFS). Sci Rep. 2025 Mar 3;15(1):7381. doi: 10.1038/s41598-025-91324-1. PMID: 40025157. https://www.nature.com/articles/s41598-025-91324-1 (Full text)