Images of research to illustrate the weekly research roundup

ME/CFS Research Published 23 – 29 January 2024

The weekly research round-up includes recent publications about ME/CFS and Long Covid. We highlight studies that have particularly caught our attention.


The ME Association maintains a comprehensive index of published research on ME/CFS and Long Covid that is free to use and updated weekly.

Audio Commentary by Dr Katrina Pears

It’s been a busier week with ten new ME/CFS studies and twenty-eight new Long Covid studies.

We have highlighted one of the ME/CFS studies in more detail below:

Paper ten (10) this week looks into muscle mitochondria function and morphology in ME/CFS and Post-Covid syndrome (PCS) (Long Covid).

This study used the measure of muscle mitochondrial oxidative phosphorylation (OXPHOS) capacity, which looks at the oxidation of reduced fuel substrates by electron transfer to oxygen, coupled with the conversion of ADP to ATP and accompanied by a component of respiration. The study looked at the difference between OXPHOS capacity between the three groups- ME/CFS, PCS and healthy controls. However, they only compared morphology and the shape of the mitochondria for ME/CFS and PCS.

All participants went through a standard cardiopulmonary exercise test (CPET) where skeletal muscle biopsy were taken after.

The study included 15 patients with ME/CFS, 15 with PCS and 13 healthy controls.

The study found a range of differences in the mitochondria function and morphology/structure:

  • OXPHOS capacity was reduced in PCS compared to HC.
  • The subsarcolemmal area, volume/cell, diameter, and perimeter were higher in PCS vs. ME/CFS, no difference was observed for these variables in intermyofibrillar mitochondria.
  • Both the intermyofibrillar and subsarcolemmal cristae integrity was higher in PCS compared to ME/CFS.
  • There was no difference in muscle mass per kg between both patient groups, but a higher proportion of mitochondria in the skeletal muscle of PCS patients (especially in the subsarcolemmal area).
  • Decreased mitochondrial function was found to positively correlate to disease severity in ME/CFS.
  • Both ME/CFS and PCS exhibit increased fatigue and impaired mitochondrial function, but the progressed pathological morphological changes in ME/CFS suggest structural changes due to prolonged inactivity or unknown molecular causes.
  • The increased morphological changes in ME/CFS in the subsarcolemmal area suggest long-term adaptation processes.
  • The changes found in the mitochondria of PCS patients suggests probably direct virus-induced alterations.

A few things to note about this study:

  • ME/CFS patients were diagnosed using the Canadian Consensus Criteria (CCC), although only the term CFS is used throughout the study.
  • There is a lack of detail given about the patients characteristics, especially using as the authors conclude that the differences seen in ME/CFS patients are likely due to prolonged inactivity, but illness duration is not clearly defined.
  • A large unbalance (as usual) of male: female ratios.
  • Three patients of ME/CFS and seven patients of PCS could not perform the CPET due to acute high fatigue or danger of extreme post-exertional malaise. The authors concluded that there is more apparent fatigue in PCS preventing the participants from exerting even the lighter physical loads. However, this could be due to the reduced experience of fatigue compared to those with ME/CFS or mitochondrial function.
  • Healthy controls were aged-matched unfit but otherwise healthy.
  • It’s a shame the mitochondria morphology was not studied for the healthy controls, which does limit some of the conclusions which can be drawn.
  • There is a need to compare the mitochondria function and morphology changes in ME/CFS and PCS to other chronic conditions, and not just healthy controls.

Although this was a small study, it adds to the growing evidence of mitochondrial dysfunction in ME/CFS and Long Covid, but also shows that differences exist between the two conditions. If this study was to be expanded, it could help to provide a diagnostic tool between different conditions.

You may also be interested in reading Paper one (1) in the Long Covid Reference section which is on Low Dose Naltrexone. Unfortunately, this was a retrospective study, and also included patients who had received amitriptyline, duloxetine, and physical therapy, therefore, there is still a need for randomized controlled trials. We also have a previous MEA Research Summary on this topic, which can be found here.

ME/CFS Research References

  1. Psychometric evaluation of the DePaul Symptom Questionnaire-Short Form (DSQ-SF) among adults with Long COVID, ME/CFS, and healthy controls: A machine learning approach
  2. A suffering body, hidden away from others: The experience of being long-term bedridden with severe myalgic encephalomyelitis/chronic fatigue syndrome in childhood and adolescence
  3. From Function to Physiology and Back in Adults with Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome
  4. Systemic antibody responses against gut microbiota flagellins implicate shared and divergent immune reactivity in Crohn's Disease and chronic fatigue syndrome
  5. Chronic Fatigue Syndrome, Viruses and Related Conditions in Women: The Liver Link
  6. Lipid metabolism and functional somatic disorders in the general population. The DanFunD study
  7. Repeated Hand Grip Strength is an Objective Marker for Disability and Severity of Key Symptoms in PostCOVID ME/CFS
  8. Videoconference-delivered group cognitive behavioral stress management for ME/CFS patients who present with severe PEM: a randomized controlled trial
  9. Mismatch between subjective and objective dysautonomia
  10. Functional and Morphological Differences of Muscle Mitochondria in Chronic Fatigue Syndrome and Post-COVID Syndrome

Long-COVID Research References

  1. Low-Dose Naltrexone Improves post-COVID-19 condition Symptoms
  2. Does sex modify the effect of pre-pandemic body mass index on the risk of Long COVID? Evidence from the longitudinal analysis of the Survey of Health, Ageing and Retirement in Europe
  3. Health-related quality of life in mild-to-moderate COVID-19 in the UK: a cross-sectional study from pre- to post-infection
  4. International Care programs for Pediatric Post-COVID Condition (Long COVID) and the way forward
  5. The Impact of Long COVID-19 on the Cardiovascular System
  6. Functional evaluation of physical performance, gait, balance and activities of daily living in older individuals with long COVID syndrome
  7. New Alcohol Sensitivity in Patients With Post-acute Sequelae of SARS-CoV-2 (PASC): A Case Series
  8. Case report: A case of Acute Macular Neuroretinopathy secondary to Influenza A virus during Long COVID
  9. Long COVID in pediatrics—epidemiology, diagnosis, and management
  10. Long COVID is associated with severe cognitive slowing: a multicentre cross-sectional study
  11. Clinical characteristics of female long COVID patients with menstrual symptoms: a retrospective study from a Japanese outpatient clinic
  12. Transcranial direct current stimulation (tDCS) in the treatment of neuropsychiatric symptoms of long COVID
  13. A mid‑pandemic night's dream: Melatonin, from harbinger of anti‑inflammation to mitochondrial savior in acute and long COVID‑19 (Review)
  14. COVID-19 Pediatric Follow-Up: Respiratory Long COVID-Associated Comorbidities and Lung Ultrasound Alterations in a Cohort of Italian Children
  15. Feasibility Study of Developing a Saline-Based Antiviral Nanoformulation Containing Lipid-Soluble EGCG: A Potential Nasal Drug to Treat Long COVID
  16. Post-COVID Postural Orthostatic Tachycardia Syndrome and Inappropriate Sinus Tachycardia in the Pediatric Population
  17. Guiding future research on psychological interventions in people with COVID-19 and post COVID syndrome and comorbid emotional disorders based on a systematic review
  18. Prevalence and trajectories of post-COVID-19 neurological manifestations: A systematic-review and meta-analysis
  19. Reduction in long-COVID symptoms and symptom severity in vaccinated compared to unvaccinated adults
  20. Unveiling the Clinical Spectrum of Post-COVID-19 Conditions: Assessment and Recommended Strategies
  21. Herbal Medicines for Long COVID: A Phase 2 Pilot Clinical Study
  22. Vaccination and Patient Status of Long COVID-19 Hospitalized Patients: A Cohort Observational Study
  23. Presence of SARS-CoV-2 RNA in Patients with Long-COVID: A Systematic Review
  24. The Microbiota in Long COVID
  25. Decreased risk of COVID-19 and long COVID in patients with psoriasis receiving IL-23 inhibitor: A cross-sectional cohort study from China
  26. Haematological sequelae in the post-acute phase of symptomatic SARS-CoV-2 infection
  27. HEART Rate Variability Biofeedback for LOng COVID Dysautonomia (HEARTLOC): Results of a Feasibility Study
  28. Impact of pre-existing mental health diagnoses on development of post-COVID and related symptoms: a claims data-based cohort study

Dr Katrina Pears,
Research Correspondent.
The ME Association.

Dr Katrina Pears - MEA Research Correspondent
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