Evidence browser

Stroop task and practice effects demonstrate cognitive dysfunction in long COVID and myalgic encephalomyelitis / chronic fatigue syndrome.

Baraniuk, James N, Thapaliya, Kiran, Inderyas, Maira et al.·Scientific reports·2024

This study tested how quickly people with Long COVID and ME/CFS could complete a simple task involving reading color words displayed in different colored inks. Both patient groups were noticeably slower at this task than healthy people, and unlike healthy people, they didn't get faster with practice. This suggests that ME/CFS and Long COVID may involve a problem with how different parts of the brain communicate during problem-solving.

Cognitive reserve as a protective factor against cognitive impairment in chronic fatigue syndrome.

Surendran, Gopika, Jose, Tony P·Applied neuropsychology. Adult·2024

This study examined whether people's life experiences and education—called 'cognitive reserve'—help protect them from the thinking and memory problems common in ME/CFS. Researchers tested 91 people with ME/CFS and found that those with more cognitive reserve had fewer cognitive problems. The severity of someone's ME/CFS was the main factor affecting both cognitive reserve and cognitive problems, rather than age or gender.

Investigating brain cortical activity in patients with post-COVID-19 brain fog.

Wojcik, Grzegorz M, Shriki, Oren, Kwasniewicz, Lukasz et al.·Frontiers in neuroscience·2023

This study looked at brain electrical activity in people who had COVID-19 and experienced 'brain fog'—persistent mental cloudiness that can last several months. Researchers compared three groups using advanced brain scans while people performed thinking tasks, and used computer algorithms to see if they could distinguish between those with brain fog, those without it, and healthy controls. They found measurable differences in brain activity patterns between the groups, suggesting brain fog has a detectable physical basis in the brain.

E2 ModerateCohortPEM requiredCross-Sectional

Connectivity Between Salience and Default Mode Networks and Subcortical Nodes Distinguishes Between Two Classes of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.

Su, Jiasheng, Thapaliya, Kiran, Eaton-Fitch, Natalie et al.·Brain connectivity·2023

This study used brain imaging (fMRI) to examine how different brain networks communicate in people with ME/CFS compared to healthy controls. Researchers found that people with ME/CFS have different patterns of brain connectivity, particularly in networks involved in attention and the brain's rest-state activity. Importantly, the study discovered that two different diagnostic criteria for ME/CFS (ICC and Fukuda) appear to identify distinct brain differences, suggesting they may represent different disease types.

Subcortical and default mode network connectivity is impaired in myalgic encephalomyelitis/chronic fatigue syndrome.

Inderyas, Maira, Thapaliya, Kiran, Marshall-Gradisnik, Sonya et al.·Frontiers in neuroscience·2023

This study used advanced brain imaging to compare how different brain regions communicate in people with ME/CFS versus healthy people. Researchers found that certain connections between the brainstem (the lower part of the brain) and cerebellum (involved in balance and coordination) are weakened in ME/CFS patients. These brain communication problems may help explain why people with ME/CFS experience fatigue, memory problems, and other symptoms.

E2 ModerateCohortPEM unclearObservational

Physical Activity Effects on Muscle Fatigue in Sport in Active Adults with Long COVID-19: An Observational Study.

Coscia, Francesco, Mancinelli, Rosa, Gigliotti, Paola Virginia et al.·Diagnostics (Basel, Switzerland)·2023

This study looked at how physical activity affected fatigue and other symptoms in people with Long COVID-19. Researchers compared people who stayed active with those who were sedentary and tracked their symptoms over 6 to 12 months. They found that people who remained physically active experienced a larger drop in fatigue over time compared to those who were inactive, though both groups still had muscle weakness and sleep problems.

SleepCognitive Impairment

E2 ModerateCohortPEM unclearObservational

Cognitive impairment in post-acute sequelae of COVID-19 and short duration myalgic encephalomyelitis patients is mediated by orthostatic hemodynamic changes.

Day, Heather, Yellman, Brayden, Hammer, Sarah et al.·Frontiers in neuroscience·2023

This study examined why people with ME/CFS and long COVID experience 'brain fog' and memory problems. Researchers tested how well people could think and remember before and after standing up quickly (which can make blood pressure drop). They found that people with these illnesses had more trouble thinking clearly after the standing test, and this was linked to unusual changes in their heart rate and blood pressure. The findings suggest that problems with blood flow to the brain during physical stress may be contributing to cognitive difficulties.

Autonomic Nervous SystemCognitive Impairment

Autonomic Nervous SystemCognitive Impairment

Dysautonomia and small fiber neuropathy in post-COVID condition and Chronic Fatigue Syndrome.

Azcue, N, Del Pino, R, Acera, M et al.·Journal of translational medicine·2023

This study compared how the nervous system works differently in people with ME/CFS, people with long COVID, and healthy people. Researchers tested heart rate responses, sweating patterns, and how nerves respond to temperature. They found that people with ME/CFS had more severe problems with heart rate regulation and nerve fiber damage than those with long COVID, and both groups had more problems than healthy controls.

E2 ModerateCohortPEM not requiredCase-Control

Post-acute sequelae of COVID-19 in young adults: Mental fatigue and decreased cognitive flexibility.

Sedat, Yasin, Erman, Altunisik, Yasemin, Firat Ekmekyapar·Ideggyogyaszati szemle·2023

This study looked at young adults who had COVID-19 and compared them to those who hadn't. Researchers found that people who had COVID-19 reported more mental fatigue (difficulty concentrating and feeling mentally tired) and had more trouble switching between different tasks. These problems lasted long after the initial infection, suggesting COVID-19 may have lasting effects on how the brain works.

E2 ModerateBehavioralPEM not requiredCross-Sectional

A comparison of pain, fatigue, and function between post-COVID-19 condition, fibromyalgia, and chronic fatigue syndrome: a survey study.

Haider, Saman, Janowski, Adam J, Lesnak, Joseph B et al.·Pain·2023

This study surveyed 707 people with post-COVID-19, fibromyalgia, and/or ME/CFS to compare their symptoms. Researchers found that all three conditions share similar patterns of pain, fatigue, brain fog, anxiety, and depression that impact daily life. People with post-COVID-19 reported somewhat less severe pain and fatigue than those with fibromyalgia or ME/CFS, but those with multiple diagnoses had worse symptoms overall.

Pain and SensitizationCognitive Impairment

SleepAutonomic Nervous SystemCognitive Impairment

Urine Metabolite Analysis to Identify Pathomechanisms of Long COVID: A Pilot Study.

Taenzer, Maja, Löffler-Ragg, Judith, Schroll, Andrea et al.·International journal of tryptophan research : IJTR·2023

This study examined urine samples from people with Long COVID and ME/CFS to look for chemical imbalances that might explain their symptoms. Researchers found that both groups had lower levels of certain amino acids and neurotransmitters (brain chemicals) compared to healthy people, particularly affecting energy production, mood, and sleep. These chemical signatures could potentially be used as simple urine tests to help doctors understand what is happening in patients and create personalized treatments.

The association between the number of symptoms and the severity of Post-COVID-Fatigue after SARS-CoV-2 infection treated in an outpatient setting.

Schmidbauer, Lena, Kirchberger, Inge, Goßlau, Yvonne et al.·Journal of neurology·2023

This study looked at 425 people who had mild-to-moderate COVID-19 treated as outpatients and followed them for about 8 months afterward. Researchers found that 37% of these people developed long-lasting fatigue (Post-COVID-Fatigue), and those who had more symptoms during their initial infection and ongoing symptoms were more likely to experience severe fatigue. The more symptoms someone had, the worse their fatigue tended to be.

The Conners Continuous Performance Test CPT3™: Is it a reliable marker to predict neurocognitive dysfunction in Myalgic encephalomyelitis/chronic fatigue syndrome?

Fernández-Quirós, Judith, Lacasa-Cazcarra, Marcos, Alegre-Martín, Jose et al.·Frontiers in psychology·2023

This study tested whether a computer-based attention test called CPT3™ can reliably detect thinking and concentration problems in ME/CFS patients. Researchers compared 158 ME/CFS patients with 67 healthy people and found that ME/CFS patients performed significantly worse on measures of attention, focus, and reaction speed. The test successfully identified differences between the two groups, suggesting it could be a useful tool for doctors to help diagnose or monitor ME/CFS.

Neurocognitive screening in patients following SARS-CoV-2 infection: tools for triage.

Blackmon, Karen, Day, Gregory S, Powers, Harry Ross et al.·BMC neurology·2022

Many people recovering from COVID-19 report trouble thinking clearly or remembering things. This study tested 102 COVID-19 patients (some who were hospitalized, some who weren't) within about 3-4 weeks of infection to see how common these cognitive problems really were and what might cause them. The researchers found that while most patients felt foggy-headed, people who had been hospitalized showed more measurable problems with memory and thinking speed than those who recovered at home.

E2 ModerateCohortPEM requiredCross-Sectional

Alteration of Cortical Volume and Thickness in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.

Thapaliya, Kiran, Marshall-Gradisnik, Sonya, Staines, Donald et al.·Frontiers in neuroscience·2022

Researchers used brain imaging to compare the brains of people with ME/CFS to healthy people. They found that people with ME/CFS had some areas of the brain that were thinner and other areas that were larger, particularly in regions involved in thinking and emotion. These brain differences were also connected to how severe symptoms like fatigue, sleep problems, and cognitive difficulties were in each person.

E2 ModerateCohortPEM not requiredObservational

Incidence of post-COVID syndrome and associated symptoms in outpatient care in Bavaria, Germany: a retrospective cohort study using routinely collected claims data.

Donnachie, Ewan, Hapfelmeier, Alexander, Linde, Klaus et al.·BMJ open·2022

This study looked at health insurance records from nearly 400,000 people in Germany who had COVID-19 to see how many developed long COVID symptoms lasting at least 12 weeks. About 14% of COVID-19 patients received a diagnosis of post-COVID syndrome, with the most common symptoms being fatigue, breathing problems, and loss of taste or smell. These symptoms occurred much more often in COVID-19 patients compared to people who had other respiratory infections or no respiratory illness.

E2 ModerateCohortPEM not requiredLongitudinal

Chronic fatigue syndrome and cognitive deficit are associated with acute-phase neuropsychiatric manifestations of COVID-19: A 9-month follow-up study.

Mirfazeli, Fatemeh Sadat, Sarabi-Jamab, Atiye, Pereira-Sanchez, Victor et al.·Neurological sciences : official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology·2022

This study followed 95 COVID-19 patients for 9 months to see which ones developed long-COVID symptoms like fatigue and brain fog. The most common symptom was extreme tiredness (affecting about half the patients), followed by anxiety, shortness of breath, and headaches. Interestingly, how sick someone was during acute COVID didn't predict whether they'd have long-COVID problems—but certain early warning signs (like psychiatric symptoms during the acute phase) did predict who would develop chronic fatigue and memory problems later.

E2 ModerateCohortPEM not requiredObservational

Characteristics of Sleep Disturbance in Patients with Long COVID: A Retrospective Observational Study in Japan.

Sunada, Naruhiko, Nakano, Yasuhiro, Otsuka, Yuki et al.·Journal of clinical medicine·2022

This study looked at sleep problems in 363 long COVID patients in Japan and found that about 16.5% had significant sleep disturbance. People infected during the Omicron wave were twice as likely to have sleep problems compared to those infected during the Delta wave. Patients with sleep disturbance also reported more fatigue, brain fog, headaches, and anxiety, and had abnormal stress hormone levels suggesting their bodies were under persistent stress.

SleepCognitive Impairment

Cognitive Task Performance and Subjective Cognitive Symptoms in Individuals With Chronic Fatigue Syndrome or Fibromyalgia: A Cross-Sectional Analysis of the Lifelines Cohort Study.

Joustra, Monica L, Hartman, Catharina A, Bakker, Stephan J L et al.·Psychosomatic medicine·2022

This study looked at thinking and memory problems in people with ME/CFS and fibromyalgia by testing nearly 80,000 people. Researchers found that people with ME/CFS reported significantly more trouble concentrating and had slightly slower performance on thinking tasks compared to healthy people and those with other diseases like multiple sclerosis. These cognitive complaints remained even when researchers accounted for depression, anxiety, and physical symptom severity.

Bright, but allergic and neurotic? A critical investigation of the "overexcitable genius" hypothesis.

Fries, Jonathan, Baudson, Tanja Gabriele, Kovacs, Kristof et al.·Frontiers in psychology·2022

This study looked at whether highly intelligent people (members of MENSA) experience more health problems than the general population. Researchers surveyed over 600 high-IQ individuals across five European countries and found that chronic fatigue syndrome was about 5.7 times more common in this group compared to the general public. Other conditions like depression, anxiety, and autism spectrum disorders were also significantly more common, but surprisingly, allergies and autoimmune diseases were not.