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Comparing Idiopathic Chronic Fatigue and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) in Males: Response to Two-Day Cardiopulmonary Exercise Testing Protocol.

van Campen, C Linda M C, Visser, Frans C·Healthcare (Basel, Switzerland)·2021

This study compared how men with ME/CFS respond to exercise testing on two consecutive days versus men with chronic fatigue that doesn't meet ME/CFS criteria. When ME/CFS patients exercised on the second day, they performed worse and couldn't reach the same levels they achieved on day one. Men with chronic fatigue (but not ME/CFS) actually improved on day two, similar to healthy people.

Medical Care Situation of People with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome in Germany.

Froehlich, Laura, Hattesohl, Daniel B R, Jason, Leonard A et al.·Medicina (Kaunas, Lithuania)·2021

This study surveyed nearly 500 people with ME/CFS in Germany to understand how well they can access medical care and how satisfied they are with the care they receive. The researchers found that many patients struggle to get medical help because of cost and distance, and many are unhappy with their doctors' care. The study also created and tested a German language symptom questionnaire that could help doctors diagnose ME/CFS.

Autoantibodies to Vasoregulative G-Protein-Coupled Receptors Correlate with Symptom Severity, Autonomic Dysfunction and Disability in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.

Freitag, Helma, Szklarski, Marvin, Lorenz, Sebastian et al.·Journal of clinical medicine·2021

This study examined whether certain antibodies in ME/CFS patients' blood relate to how severe their symptoms are. The researchers tested 116 ME/CFS patients for antibodies that target receptors controlling blood vessel function and other vital processes. They found that patients whose ME/CFS started after an infection had stronger connections between these antibodies and key symptoms like fatigue and muscle pain, suggesting these antibodies might play a role in how the disease develops.

NeuroinflammationBiomarkersPost-Exertional Malaise

Exercise modifies glutamate and other metabolic biomarkers in cerebrospinal fluid from Gulf War Illness and Myalgic encephalomyelitis / Chronic Fatigue Syndrome.

Baraniuk, James N, Kern, Grant, Narayan, Vaishnavi et al.·PloS one·2021

Researchers studied the fluid around the brain and spinal cord in people with ME/CFS and Gulf War Illness to see how exercise affects certain chemicals in the body. They found that glutamate (a brain chemical) levels changed differently depending on whether someone had exercised and how their body responded, and that some fat-related molecules were different between the two conditions. This suggests that ME/CFS and Gulf War Illness may involve different problems with how the body uses energy and processes fats.

E2 ModerateCohortPEM not requiredCross-Sectional

Clinical Heterogeneity in ME/CFS. A Way to Understand Long-COVID19 Fatigue.

Murga, Iñigo, Aranburu, Larraitz, Gargiulo, Pascual A et al.·Frontiers in psychiatry·2021

This study examined 84 ME/CFS patients and 22 healthy controls using questionnaires to measure fatigue, pain, sleep quality, heart rate problems, thinking difficulties, mood, and other symptoms. Researchers used statistical clustering to group patients into five distinct subtypes based on their symptom patterns. The findings suggest that ME/CFS is not one-size-fits-all—some patients have high anxiety and depression without fibromyalgia, while others have fibromyalgia combined with heart rate regulation problems, hormone imbalances, or immune issues.

Immune SystemPost-Exertional Malaise

Patients with Persistent Polyclonal B-Cell Lymphocytosis Share the Symptomatic Criteria of Systemic Exertion Intolerance Disease.

Morizot, Romain, de Korwin, Jean-Dominique, Feugier, Pierre et al.·Journal of clinical medicine·2021

Researchers studied a rare blood condition called persistent polyclonal B-cell lymphocytosis (PPBL) and found that most patients with PPBL experience symptoms very similar to ME/CFS, including severe fatigue that doesn't improve with rest, worsening after physical activity, sleep problems, and difficulty thinking clearly. Out of 39 patients surveyed, 72% met the official criteria for ME/CFS, and nearly all reported chronic fatigue lasting more than 6 months. This finding suggests these two conditions may share common underlying features, though more research is needed to understand why.

Autonomic Nervous SystemPost-Exertional Malaise

Post-Exertional Malaise May Be Related to Central Blood Pressure, Sympathetic Activity and Mental Fatigue in Chronic Fatigue Syndrome Patients.

Kujawski, Sławomir, Słomko, Joanna, Hodges, Lynette et al.·Journal of clinical medicine·2021

This study looked at 101 ME/CFS patients to understand post-exertional malaise (PEM)—the worsening of symptoms after activity that many patients experience. Researchers measured blood pressure, nervous system function, and fatigue levels in patients with and without PEM. They found that patients with PEM had higher mental fatigue, lower central blood pressure, and greater nervous system imbalance at rest, but the researchers caution that these findings need to be confirmed by larger studies.

Characterizing long COVID in an international cohort: 7 months of symptoms and their impact.

Davis, Hannah E, Assaf, Gina S, McCorkell, Lisa et al.·EClinicalMedicine·2021

This study surveyed nearly 3,800 people from around the world who had long-lasting COVID-19 symptoms lasting more than 28 days. By seven months after illness onset, most participants had not fully recovered and experienced an average of 56 symptoms affecting multiple body systems. The three most persistent symptoms were fatigue, post-exertional malaise (feeling worse after activity), and cognitive problems, with nearly 86% experiencing relapses triggered by exercise, physical activity, mental stress, or other exertion.

E2 ModerateCohortPEM unclearObservational

Warning Signals of Post-Exertional Malaise in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Retrospective Analysis of 197 Patients.

Ghali, Alaa, Lacout, Carole, Ghali, Maria et al.·Journal of clinical medicine·2021

This study looked at whether certain new or unusual symptoms might warn ME/CFS patients that a post-exertional malaise (PEM) flare is coming. Researchers reviewed medical records from 197 ME/CFS patients and found that about 14% experienced mood changes or other new symptoms before their baseline symptoms got worse. Interestingly, these patients had less intense PEM flares than those without warning symptoms, suggesting these early signals might help patients prepare or prevent more severe crashes.

E2 ModerateCohortPEM requiredLongitudinal

COVID-19 Symptoms Over Time: Comparing Long-Haulers to ME/CFS.

Jason, Leonard A, Islam, Mohammed, Conroy, Karl et al.·Fatigue : biomedicine, health & behavior·2021

This study compared how symptoms change over time in people with long COVID versus people with ME/CFS. Researchers asked 278 long-haulers to describe their current symptoms and symptoms from about 5 months earlier, and compared them to 502 ME/CFS patients. They found that long-haulers generally improved over time, with better sleep and less post-exertional malaise, but their brain fog and memory problems actually got worse. Long-haulers started off more symptomatic than ME/CFS patients but became less symptomatic over time, though orthostatic symptoms (dizziness when standing) remained similar in both groups.

Network Analysis of Symptoms Co-Occurrence in Chronic Fatigue Syndrome.

Kujawski, Sławomir, Słomko, Joanna, Newton, Julia L et al.·International journal of environmental research and public health·2021

This study looked at how different ME/CFS symptoms appear together in patients. Researchers examined 110 Polish patients and used a network analysis method to see which symptoms tend to occur at the same time and which ones are most closely connected. They found that post-exertional malaise (feeling worse after activity), sleep problems, and memory/concentration difficulties were the most common symptoms, and that certain symptoms were strongly linked to each other.

Homebound versus Bedridden Status among Those with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.

Conroy, Karl, Bhatia, Shaun, Islam, Mohammed et al.·Healthcare (Basel, Switzerland)·2021

This study looked at over 2,100 people with ME/CFS to understand different levels of severity, focusing on those who are homebound (unable to leave home) and bedridden (unable to leave bed). The researchers found that people who are bedridden experience post-exertional malaise (PEM)—a worsening of symptoms after physical or mental activity—differently or more severely than those who are only homebound. This research helps doctors and patients better understand how severe ME/CFS can become.

Use of Cardiopulmonary Stress Testing for Patients With Unexplained Dyspnea Post-Coronavirus Disease.

Mancini, Donna M, Brunjes, Danielle L, Lala, Anuradha et al.·JACC. Heart failure·2021

This study looked at 41 people who had long-lasting breathing problems after COVID-19, even though their standard lung and heart tests appeared normal. Researchers used a special exercise test to measure how well their bodies could use oxygen and how they breathed during activity. They found that most patients had unusual breathing patterns or reduced exercise capacity, and about half met the criteria for ME/CFS.

Energy MetabolismPost-Exertional Malaise

A map of metabolic phenotypes in patients with myalgic encephalomyelitis/chronic fatigue syndrome.

Hoel, Fredrik, Hoel, August, Pettersen, Ina Kn et al.·JCI insight·2021

This study examined the chemicals in the blood of 83 ME/CFS patients compared to 35 healthy people to understand how their bodies use energy differently. Researchers found that ME/CFS patients had common metabolic changes suggesting their bodies are working harder to produce energy and are using fats and proteins differently as fuel. Interestingly, patients also fell into different subgroups with distinct metabolic patterns, suggesting ME/CFS may involve different energy problems in different people.

Hand grip strength and fatigability: correlation with clinical parameters and diagnostic suitability in ME/CFS.

Jäkel, Bianka, Kedor, Claudia, Grabowski, Patricia et al.·Journal of translational medicine·2021

This study tested hand grip strength in ME/CFS patients compared to healthy people and cancer patients to see if it could help diagnose the condition. Researchers found that ME/CFS patients had weaker grip strength and their muscles got tired much faster during repeated squeezing tests. Importantly, their muscles also recovered more slowly after resting for an hour, suggesting that muscle fatigue is a real, measurable feature of ME/CFS.

E2 ModerateCohortPEM requiredObservational

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

Nelson, Maximillian J, Buckley, Jonathan D, Thomson, Rebecca L et al.·Frontiers in physiology·2021

This study looked at how the hearts of ME/CFS patients respond to exercise on two consecutive days, comparing them to healthy people. Researchers measured heart rate patterns and recovery after exercise, finding that ME/CFS patients had slower heart rate recovery after working out. However, these measurements alone were not reliable enough to diagnose ME/CFS, suggesting that a single heart rate test may not be a useful diagnostic tool on its own.

E2 ModerateCohortPEM requiredObservational

Predicting post-exertional malaise in Gulf War Illness based on acute exercise responses.

Boruch, Alexander E, Lindheimer, Jacob B, Klein-Adams, Jacquelyn C et al.·Life sciences·2021

This study looked at how Gulf War Veterans' bodies responded during exercise and whether those responses could predict post-exertional malaise (PEM)—the worsening of symptoms after physical activity. Veterans with Gulf War Illness had more severe symptom flare-ups after exercising compared to healthy veterans, but the researchers found that common exercise measurements like breathing patterns and muscle pain didn't reliably predict who would experience worse PEM.

E2 ModerateCohortPEM unclearCase-Control

Reduced Parasympathetic Reactivation during Recovery from Exercise in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.

Van Oosterwijck, Jessica, Marusic, Uros, De Wandele, Inge et al.·Journal of clinical medicine·2021

This study examined how the nervous system controls heart rate and other body functions in ME/CFS patients compared to healthy people, both at rest and after exercise. Researchers found that while ME/CFS patients had normal nerve function at rest, their bodies had difficulty recovering after exercise—specifically, their parasympathetic nervous system (the 'rest and digest' system) didn't reactivate properly. This delayed recovery is concerning because similar patterns in other diseases are linked to worse health outcomes.