ME/CFS Evidence Browser — Classified Studies on Myalgic Encephalomyelitis

141–160 of 736 studies

E2 ModerateCohortPEM unclearLongitudinal

Post-Acute Sequelae of COVID-19 Persist Over 3 Years in Acute Lung Injury/Acute Respiratory Distress Syndrome Survivors But Are Not Associated With Persistent Thromboinflammation or Endothelial Dysfunction.

Jones, Ansley E, Khan, Zain, McGroder, Claire F et al.·Critical care explorations·2026

This study followed people who were hospitalized with severe COVID-19 for 3 years after they left the hospital. About one-quarter of them continued to experience long COVID symptoms like fatigue, brain fog, and difficulty with physical activity. Surprisingly, when researchers measured inflammation and blood vessel markers in their blood, these markers were not elevated and did not explain why some people had ongoing symptoms.

BiomarkersImmune SystemPost-Exertional Malaise

E2 ModerateCohortPEM unclearObservational

Cardiopulmonary exercise test results do not change over two sequential days in patients with chronic fatigue syndrome.

Mancini, Donna M, Cook, Dane B, Brunjes, Danielle L et al.·Frontiers in physiology·2026

Researchers asked whether doing two exercise tests on consecutive days could reliably detect post-exertional malaise (PEM) in ME/CFS patients. They found that oxygen consumption and other key exercise measures did not change between Day 1 and Day 2 in either ME/CFS patients or healthy controls. However, ME/CFS patients reported much greater fatigue during exercise and had lower maximum heart rates. One study's findings do not establish whether this two-day test method is truly useful for measuring PEM in clinical practice.

DiagnosticsPost-Exertional Malaise

E2 ModerateCohortPEM requiredObservational

[The Role of ME/CFS Phenotype in Outpatient Post-COVID Rehabilitation].

Kaiserseder, Moritz, Prüfer, Ferdinand, Untersmayer-Elsenhuber, Eva et al.·Pneumologie (Stuttgart, Germany)·2026

This study looked at 216 people recovering from COVID-19 in rehabilitation programs to see how many had ME/CFS—a condition with severe fatigue and worsening after physical activity. The researchers found that about 7% of these patients met the criteria for ME/CFS. These patients were typically younger, mostly women, and experienced much more severe fatigue that didn't improve with rehabilitation compared to other COVID-19 patients.

Post-Exertional Malaise

E2 ModerateCohortPEM unclearCross-Sectional

Symptom, Functional, and Work Participation Profiles Among Racialized Canadians with Pre-Existing Mental Health Challenges and Long COVID: A Cross-Sectional Study.

Shahzad, Maryam, Siddiqui, Sana, Lau, Chloe et al.·Healthcare (Basel, Switzerland)·2026

This study observed symptom burden, functional impairment, and mental health outcomes in 51 Canadian adults with long COVID who also identified as racialized and had pre-existing mental health conditions. Participants reported moderate overall symptoms, notable fatigue and post-exertional malaise, cognitive difficulties, and mild-to-moderate anxiety and depression, alongside moderate functional limitations in work, social, and daily activities. However, this is a small, self-selected group, and the findings may not generalise to all long COVID patients.

Cognitive ImpairmentLong COVID OverlapPost-Exertional Malaise

E2 ModerateCohortPEM unclearCross-Sectional

Central noradrenergic deficiency in post-infectious chronic fatigue: neurobehavioral correlates.

Aregawi, Lillian, Walitt, Brian, Sullivan, Patti et al.·Brain communications·2026

Researchers measured levels of norepinephrine (a brain chemical) in cerebrospinal fluid from people with ME/CFS, Long COVID, and Parkinson's disease, comparing them to healthy volunteers. They observed that norepinephrine pathway activity was lower in all three patient groups, and in Long COVID patients with post-exertional malaise, this reduction was particularly pronounced. This is one study in a small sample, and it remains unclear whether these findings fully explain fatigue and brain fog or apply directly to ME/CFS.

BiomarkersCognitive ImpairmentLong COVID OverlapPost-Exertional Malaise

E2 ModerateCohortPEM not requiredObservational

Post-Exertional Malaise in Post-COVID-19 Syndrome: A Shift in the Frequency Across Pandemic Phases.

Ghali, Alaa, Lavigne, Christian, Ghali, Maria et al.·Journal of clinical medicine·2026

A French hospital study observed that post-COVID patients infected in 2020–2021 reported post-exertional malaise (PEM) more often than those infected later, and that PEM was associated with higher fatigue levels. By analogy, this may be relevant to ME/CFS patients, though the study examined post-COVID populations and the reasons for these differences remain uncertain—they could reflect changes in the virus, vaccination, immunity, or other unmeasured factors.

Long COVID OverlapPost-Exertional Malaise

E2 ModerateCohortPEM unclearCross-Sectional

Raman Spectroscopy Combined with Machine Learning Reveals Myalgic Encephalomyelitis-Associated Biomolecular Signatures at Rest and After Standardized Stress.

Heidarifard, Maryam, Moezzi, Atefeh, Dallaire, Frédérick et al.·International journal of molecular sciences·2026

Researchers used a laboratory technique called Raman spectroscopy combined with computer learning to identify chemical signatures in blood plasma that are associated with ME/CFS. They collected blood samples from 115 ME/CFS patients and 45 healthy controls both at rest and 90 minutes after a standardized stress test, and found the method could distinguish between the two groups with moderate-to-good accuracy (79–84%). However, this is an early-stage study and much more work is needed before such a test could be used in clinical practice.

BiomarkersDiagnosticsPost-Exertional Malaise

E2 ModerateCohortPEM unclearCase-Control

Interpreting hand grip strength in hospital employees with post-COVID syndrome compared to non-infected controls: a case-control study.

Tack, Matthias, Gruber, Rosalie, Betting, Leia et al.·Scientific reports·2026

This small study compared hand grip strength in 19 hospital workers with post-COVID syndrome (including 7 who met ME/CFS criteria) to 23 healthy controls. Researchers found that grip strength tended to be lower in the post-COVID group, particularly when tested a second time after a 60-minute break, which might suggest difficulty recovering after repeated effort. However, these are preliminary findings from a small group, and the authors note that grip strength alone is not reliable enough to diagnose post-COVID syndrome.

DiagnosticsPost-Exertional Malaise

E2 ModerateCohortPEM not requiredLongitudinal

Long COVID longitudinal symptoms burden clusters within a national community-based cohort.

Shen, Yanhan, Shahn, Zach, Robertson, McKaylee M et al.·BMC infectious diseases·2026

This study followed over 500 people with long COVID for up to a year, tracking their symptoms over time. Researchers identified three groups based on symptom burden: one with persistent severe symptoms (including fatigue, brain fog, post-exertional malaise, and pain), one with moderate symptoms that improved, and one with minimal symptoms. The findings are preliminary and based on self-reported data, so the stability and generalisability of these groups to other long COVID populations remain to be confirmed.

Pain and SensitizationSleepAutonomic Nervous SystemCognitive Impairment

E2 ModerateCohortPEM requiredCross-Sectional

Identifying post-exertional malaise subtypes: Differentiating physical and mental PEM manifestations.

Tuzzolino, Katherine, Jason, Leonard A, Furst, Jacob·Journal of health psychology·2026

This study looked at how post-exertional malaise (PEM)—the worsening of symptoms after activity—shows up differently in people with ME/CFS. Researchers divided patients into groups based on whether their PEM affected them physically (like muscle pain), mentally (like brain fog), both ways, or neither way severely. They found that people experiencing both physical and mental PEM had the worst overall symptoms, while those with neither type of severe PEM were less affected, though still much more disabled than healthy people.

Post-Exertional Malaise

E2 ModerateCohortPEM unclearCross-Sectional

Cardiopulmonary Exercise Testing Reveals Functional Limitations and Work Disability in Severe Post-COVID-19 and ME/CFS Patients.

Tomaskovic, Aleksandar, Weber, Vincent, Ochmann, David T et al.·Sports medicine - open·2026

A cross-sectional study of 92 severely ill post-COVID patients found that those meeting ME/CFS criteria had lower measured aerobic capacity (oxygen uptake and power output) on exercise testing compared to post-COVID patients without ME/CFS. Two-thirds of all patients showed objective signs of work disability on testing, and these measurements correlated with patients' own reports of disability and their employment status. The relevance of these findings specifically to ME/CFS requires caution, as the study enrolled primarily post-COVID patients, and the overlap between these conditions remains incompletely understood.

Severe MEDiagnosticsLong COVID OverlapPost-Exertional Malaise

E2 ModerateCohortPEM requiredLongitudinal

Post-discharge sequelae of Lassa fever survivors in Nigeria: an analysis of the LASCOPE prospective cohort.

Guichard, Eva, Juchet, Sylvain, Etafo, Ijeoma Chukwudumebi et al.·The Lancet. Infectious diseases·2026

This study followed 882 people who recovered from Lassa fever (a serious viral infection) after hospital discharge to see what long-term symptoms they experienced. Most survivors felt better within about 3 weeks after leaving the hospital, with the most common lingering symptoms being tiredness, headaches, and difficulty with physical activity. The good news is that serious complications like hearing loss were rare, affecting only 2% of survivors.

Post-Exertional Malaise

E2 ModerateCohortPEM requiredObservational

Postexertional Symptom Exacerbation after Submaximal Exercise in Individuals with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Postacute Sequelae of COVID-19.

Berardi, Giovanni, Janowski, Adam, McNally, Samuel et al.·Medicine and science in sports and exercise·2026

This study looked at what happens when people with ME/CFS or long COVID do moderate exercise. Researchers asked 60 patients and 30 healthy people to exercise for 25 minutes, then tracked their symptoms for a week. Most patients with ME/CFS experienced worsening fatigue, mental fog, and other symptoms in the days after exercise, but the severity and which symptoms got worse varied from person to person.

Post-Exertional Malaise

E2 ModerateCohortPEM requiredCross-Sectional

Exploration of Intersections and Divergences of Long COVID and Chronic Fatigue Syndrome.

Kouyoumdjian, Joao A, Yamamoto, Leticia A, Graca, Carla R·Cureus·2025

This study looked at how Long COVID and ME/CFS might be related by comparing people with Long COVID symptoms to those without and healthy controls. While many Long COVID patients experienced symptoms that overlap with ME/CFS—like post-exertional malaise (feeling worse after activity), brain fog, and sleep problems—only about 1 in 5 Long COVID patients actually met the official diagnostic criteria for ME/CFS. The findings suggest that Long COVID and ME/CFS are related but distinct conditions.

Post-Exertional Malaise

E2 ModerateCohortPEM unclearCross-Sectional

A patient-centered view of symptoms, functional impact, and priorities in post-COVID-19 syndrome: cross-sectional results from the Québec Action Post-COVID cohort.

Mayo, Nancy E, Brouillette, Marie-Josée, Falcone, Emilia Liana et al.·BMC infectious diseases·2025

This study surveyed 535 people in Quebec living with long-term COVID symptoms to understand what symptoms they experience, how much these symptoms affect their daily lives, and what treatments matter most to them. The most common symptom was fatigue, and people reported symptoms affecting multiple body systems. Most participants had been dealing with symptoms for over a year, and the impact on their quality of life was significant.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredObservational

Replicated blood-based biomarkers for myalgic encephalomyelitis not explicable by inactivity.

Beentjes, Sjoerd Viktor, Miralles Méharon, Artur, Kaczmarczyk, Julia et al.·EMBO molecular medicine·2025

Researchers found multiple blood markers that distinguish ME/CFS patients from healthy people, including signs of inflammation, insulin problems, and liver issues. Importantly, these differences were NOT caused by patients being physically inactive—they are genuine biological changes related to the disease itself. While no single blood test can diagnose ME/CFS yet, these findings suggest that a combination of blood markers could eventually provide objective diagnosis.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Abnormal breathing patterns and hyperventilation are common in patients with chronic fatigue syndrome during exercise.

Mancini, Donna M, Brunjes, Danielle L, Cook, Dane et al.·Frontiers in medicine·2025

Researchers studied how patients with ME/CFS breathe during exercise and found that many breathe abnormally in ways that healthy people do not. Specifically, 42% of ME/CFS patients showed irregular breathing patterns, and 32% were breathing too fast and too deeply (hyperventilation). These breathing problems were much more common in ME/CFS patients than in the healthy control group, suggesting that abnormal breathing may be contributing to the fatigue and breathlessness patients experience.

Post-Exertional Malaise

E2 ModerateCohortPEM requiredObservational

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

Stussman, Barbara, Camarillo, Nathan, McCrossin, Gayle et al.·Frontiers in neurology·2025

This study looked at post-exertional malaise (PEM)—the symptom worsening that happens after activity—in people with Long COVID. Researchers asked patients about PEM symptoms and had some patients do an exercise test to see if PEM actually occurred. While 67% of patients reported having PEM symptoms, only 6% actually showed clear PEM after the exercise test. When PEM did occur in Long COVID, it was less severe than what the researchers saw in ME/CFS patients.

Severe MEPost-Exertional Malaise

E2 ModerateCohortPEM unclearLongitudinal

Exploring DNA methylation, telomere length, mitochondrial DNA, and immune function in patients with Long-COVID.

Polli, Andrea, Godderis, Lode, Martens, Dries S et al.·BMC medicine·2025

This study followed 358 people who had COVID-19 to understand why some develop Long-COVID with symptoms like extreme fatigue, sleep problems, and post-exertional malaise (feeling much worse after activity). Researchers measured biological markers in blood and found that two factors—elevated troponin T (a heart protein) and shortened telomeres (the protective caps on DNA)—were most strongly linked to Long-COVID, particularly the fatigue cluster. The study shows that Long-COVID is not a single illness but has different symptom patterns, suggesting different underlying causes may be at play.

BiomarkersPost-Exertional Malaise

E2 ModerateCohortPEM unclearLongitudinal

Relationship between post-COVID-19 symptoms and daily physical activity.

Sarmento, Antonio, Webber, Sandra, Sargent, Shelley et al.·Frontiers in rehabilitation sciences·2025

This study tracked 18 people with post-COVID symptoms (11 of whom also had ME/CFS-like symptoms) for a week using smartwatches and daily surveys to see how their symptoms related to how much they walked each day. The researchers found that dizziness had the strongest connection to reduced activity—people with more dizziness walked fewer steps both on the same day and the next day. They also discovered that when people had lower fatigue or chest pain the previous day, they were more likely to walk 5,000 or more steps the next day.

Post-Exertional Malaise

← Previous Next 20 studies →

Or browse by topic

PEM Immune Neuro Metabolic Biomarkers Severe ME Long COVID Cognitive

Evidence Atlas

Evidence browser

Post-Acute Sequelae of COVID-19 Persist Over 3 Years in Acute Lung Injury/Acute Respiratory Distress Syndrome Survivors But Are Not Associated With Persistent Thromboinflammation or Endothelial Dysfunction.

Cardiopulmonary exercise test results do not change over two sequential days in patients with chronic fatigue syndrome.

[The Role of ME/CFS Phenotype in Outpatient Post-COVID Rehabilitation].

Symptom, Functional, and Work Participation Profiles Among Racialized Canadians with Pre-Existing Mental Health Challenges and Long COVID: A Cross-Sectional Study.

Central noradrenergic deficiency in post-infectious chronic fatigue: neurobehavioral correlates.

Post-Exertional Malaise in Post-COVID-19 Syndrome: A Shift in the Frequency Across Pandemic Phases.

Raman Spectroscopy Combined with Machine Learning Reveals Myalgic Encephalomyelitis-Associated Biomolecular Signatures at Rest and After Standardized Stress.

Interpreting hand grip strength in hospital employees with post-COVID syndrome compared to non-infected controls: a case-control study.

Long COVID longitudinal symptoms burden clusters within a national community-based cohort.

Identifying post-exertional malaise subtypes: Differentiating physical and mental PEM manifestations.

Cardiopulmonary Exercise Testing Reveals Functional Limitations and Work Disability in Severe Post-COVID-19 and ME/CFS Patients.

Post-discharge sequelae of Lassa fever survivors in Nigeria: an analysis of the LASCOPE prospective cohort.

Postexertional Symptom Exacerbation after Submaximal Exercise in Individuals with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Postacute Sequelae of COVID-19.

Exploration of Intersections and Divergences of Long COVID and Chronic Fatigue Syndrome.

A patient-centered view of symptoms, functional impact, and priorities in post-COVID-19 syndrome: cross-sectional results from the Québec Action Post-COVID cohort.

Replicated blood-based biomarkers for myalgic encephalomyelitis not explicable by inactivity.

Abnormal breathing patterns and hyperventilation are common in patients with chronic fatigue syndrome during exercise.

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

Exploring DNA methylation, telomere length, mitochondrial DNA, and immune function in patients with Long-COVID.

Relationship between post-COVID-19 symptoms and daily physical activity.

Curated Collections

Neuroinflammation Evidence

Metabolism & Mitochondria

Biomarkers

PEM-Specific Research