Evidence browser

Prevalence of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) in Australian primary care patients: only part of the story?

Orji, Nneka, Campbell, Julie A, Wills, Karen et al.·BMC public health·2022

This study looked at how many people in Australia have ME/CFS by examining medical records from primary care clinics between 2015-2019. Researchers found that roughly 95-104 people per 100,000 have ME/CFS in Australia, but they also discovered that many patients avoid visiting their doctors because of stigma, disbelief in the condition, and lack of available treatments. The researchers concluded that the real number of people with ME/CFS is likely much higher than what their numbers show.

Long COVID OverlapPost-Exertional Malaise

ME/CFS and Post-Exertional Malaise among Patients with Long COVID.

Jason, Leonard A, Dorri, Joseph A·Neurology international·2022

Researchers studied 465 people with long-term COVID symptoms to see how many also had ME/CFS (a serious condition causing extreme fatigue and worsening after activity). They found that about 6 in 10 people with long COVID met the medical criteria for ME/CFS. Interestingly, some people thought they had ME/CFS when they didn't, while others had ME/CFS without realizing it—showing that self-diagnosis alone isn't reliable.

Chronic Fatigue and Postexertional Malaise in People Living With Long COVID: An Observational Study.

Twomey, Rosie, DeMars, Jessica, Franklin, Kelli et al.·Physical therapy·2022

This study looked at 213 people with long COVID to measure how severe their fatigue and postexertional malaise (PEM—worsening of symptoms after activity) were. Researchers found that over 71% had chronic fatigue as severe as or worse than other serious illnesses, and nearly 59% experienced PEM similar to what people with ME/CFS report. The study highlights that fatigue and symptom flare-ups after activity are major problems that need careful monitoring and should shape how doctors design rehabilitation programs.

E2 ModerateCohortPEM requiredObservational

A 2-day cardiopulmonary exercise test in chronic fatigue syndrome patients who were exposed to humidifier disinfectants.

Leem, Jong-Han, Jeon, Hyoung-Eun, Nam, Hun et al.·Environmental analysis, health and toxicology·2022

This study tested whether a special two-day exercise test could detect post-exertional malaise (PEM)—the worsening of symptoms after physical activity—in people with ME/CFS who had been exposed to humidifier disinfectants. The researchers had 29 participants complete an exercise test, rest for 24 hours, then repeat it. They found that performance noticeably declined on the second day, showing that PEM is real and measurable.

Immune SystemPost-Exertional Malaise

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Post-COVID Syndrome: A Common Neuroimmune Ground?

Ryabkova, Varvara A, Gavrilova, Natalia Y, Fedotkina, Tamara V et al.·Diagnostics (Basel, Switzerland)·2022

This Russian study looked at 56 people with ME/CFS and 14 people with post-COVID syndrome to understand how their bodies function differently. The researchers found that both groups had similar patterns of immune system problems, heart rate changes when standing up, and reduced blood flow in small vessels. Importantly, fatigue severity was linked to many other ME/CFS symptoms but not to anxiety or depression.

E2 ModerateCohortPEM unclearObservational

Pain Burden in Post-COVID-19 Syndrome following Mild COVID-19 Infection.

Bileviciute-Ljungar, Indre, Norrefalk, Jan-Rickard, Borg, Kristian·Journal of clinical medicine·2022

This study looked at 100 people who had mild COVID-19 but developed long-lasting symptoms afterward. Researchers asked about their pain, fatigue, sleep problems, and quality of life. Three-quarters of the participants reported widespread pain in various parts of their body, and many showed signs of fibromyalgia. The study found that pain is a major problem for people with long COVID and needs better treatment.

E2 ModerateCohortPEM unclearCase-Control

Genetic risk factors for ME/CFS identified using combinatorial analysis.

Das, Sayoni, Taylor, Krystyna, Kozubek, James et al.·Journal of translational medicine·2022

Researchers identified 199 genetic variations in 14 genes that are associated with ME/CFS by analyzing genetic data from thousands of people in UK Biobank. These genetic variations work together in groups to influence ME/CFS risk and were found in 91% of people with ME/CFS in the study. The identified genes are involved in processes the body uses to handle stress, infection, energy production in cells, sleep, and immune function—all areas that scientists think may go wrong in ME/CFS.

Immune SystemPost-Exertional Malaise

E2 ModerateMechanismPEM requiredObservational

Plasma metabolomics reveals disrupted response and recovery following maximal exercise in myalgic encephalomyelitis/chronic fatigue syndrome.

Germain, Arnaud, Giloteaux, Ludovic, Moore, Geoffrey E et al.·JCI insight·2022

Researchers studied 60 ME/CFS patients and 45 healthy people by measuring thousands of chemical substances in their blood before and after intense exercise tests done 24 hours apart. They found that ME/CFS patients had very different chemical patterns in their blood, especially after exercise and during the 24-hour recovery period, suggesting their bodies struggle to respond to and recover from physical exertion in ways that may explain post-exertional malaise (the worsening of symptoms after activity).

Energy MetabolismPost-Exertional Malaise

Long-term sequelae of COVID-19 (myalgic encephalomyelitis): An international cross-sectional study.

Shaheen, Nour, Shaheen, Ahmed·Medicine·2022

This study examined how COVID-19 affects people's health long after the initial infection, including whether some people develop ME/CFS (myalgic encephalomyelitis) as a result. Researchers planned to survey 20,000 people worldwide about their ongoing symptoms weeks to months after COVID-19 infection, using detailed questionnaires to capture a wide range of both common and unusual long-term effects. The goal was to understand who develops long-term problems and whether COVID-19 can trigger ME/CFS in previously healthy people.

E2 ModerateCohortPEM requiredObservational

Long-term neuromuscular consequences of SARS-Cov-2 and their similarities with myalgic encephalomyelitis/chronic fatigue syndrome: results of the retrospective CoLGEM study.

Retornaz, Frédérique, Rebaudet, Stanislas, Stavris, Chloé et al.·Journal of translational medicine·2022

This study found that long-COVID patients and ME/CFS patients have very similar symptoms and muscle problems. Researchers measured electrical activity in leg muscles during and after exercise in both groups and found comparable patterns of muscle fatigue. This suggests that COVID-19 infection may trigger ME/CFS-like illness in some people.

Endothelial dysfunction and altered endothelial biomarkers in patients with post-COVID-19 syndrome and chronic fatigue syndrome (ME/CFS).

Haffke, Milan, Freitag, Helma, Rudolf, Gordon et al.·Journal of translational medicine·2022

This study looked at whether blood vessel function is damaged in people with long COVID and ME/CFS. Researchers tested blood vessel function and measured specific proteins in the blood that reflect endothelial (blood vessel lining) health. They found that some patients with both conditions showed signs of blood vessel dysfunction, and had abnormal levels of certain proteins compared to healthy people.

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.

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.

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

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.

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.

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.

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 not requiredLongitudinal

Relationship between Cardiopulmonary, Mitochondrial and Autonomic Nervous System Function Improvement after an Individualised Activity Programme upon Chronic Fatigue Syndrome Patients.

Kujawski, Sławomir, Cossington, Jo, Słomko, Joanna et al.·Journal of clinical medicine·2021

This study tested whether a personalized activity program could help ME/CFS patients feel less tired and function better. Thirty-four patients followed a 16-week program tailored to their individual abilities. After the program, patients reported significant improvements in fatigue, and blood tests showed improvements in mitochondrial markers (Mfn1 and Mfn2)—the energy-producing components of cells. However, about half of the patients found exercise difficult to tolerate.

Autonomic Nervous SystemPost-Exertional Malaise