Evidence browser

Autonomic Nervous SystemCognitive Impairment

Impairments in cognitive performance in chronic fatigue syndrome are common, not related to co-morbid depression but do associate with autonomic dysfunction.

Robinson, Lucy J, Gallagher, Peter, Watson, Stuart et al.·PloS one·2019

This study found that people with ME/CFS often experience slowing in thinking speed and processing information, particularly in tasks requiring quick reactions. Importantly, these cognitive difficulties are not caused by depression—even patients without depression showed the same thinking problems. The researchers discovered that problems with heart rate regulation (how the body's autonomic nervous system works) were linked to these cognitive difficulties.

Orthostatic intolerance in chronic fatigue syndrome.

Garner, Richard, Baraniuk, James N·Journal of translational medicine·2019

This study looked at dizziness and lightheadedness symptoms in ME/CFS patients when lying down versus standing up. Researchers found that these symptoms were very common in ME/CFS (occurring in 72% of patients when standing) and that they often happened even while lying down—something doctors don't usually check for. Importantly, these symptoms weren't simply caused by a rapid heart rate, suggesting a different mechanism is at play in ME/CFS.

E2 ModerateCohortPEM not requiredObservational

A cluster analysis of serious adverse event reports after human papillomavirus (HPV) vaccination in Danish girls and young women, September 2009 to August 2017.

Ward, Daniel, Thorsen, Nicklas Myrthue, Frisch, Morten et al.·Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin·2019

This study examined adverse event reports submitted to Danish health authorities after HPV vaccination between 2009 and 2017. Researchers found that fatigue, dizziness, and headache were common symptoms reported, and noticed that some clusters of reports—particularly those mentioning cognitive problems and sleep issues—were submitted during periods of increased media coverage about vaccine safety concerns.

Autonomic Nervous SystemCognitive Impairment

E2 ModerateCohortPEM unclearObservational

Relationship Between Exercise-induced Oxidative Stress Changes and Parasympathetic Activity in Chronic Fatigue Syndrome: An Observational Study in Patients and Healthy Subjects.

Polli, Andrea, Van Oosterwijck, Jessica, Nijs, Jo et al.·Clinical therapeutics·2019

This study looked at whether oxidative stress (cellular damage from normal metabolism) is related to pain in ME/CFS patients, and how it connects to the vagus nerve, which helps control the body's relaxation response. Researchers had ME/CFS patients and healthy people do a mild exercise test and measured their pain, oxidative stress levels, and nerve activity before and after. They found that oxidative stress was linked to pain in ME/CFS patients, but unlike healthy people, ME/CFS patients didn't show improvements in pain or oxidative stress after exercise.

Pain and SensitizationAutonomic Nervous System

E2 ModerateCohortPEM unclearLongitudinal

Long Term Follow up of Young People With Chronic Fatigue Syndrome Attending a Pediatric Outpatient Service.

Rowe, Katherine S·Frontiers in pediatrics·2019

This study followed 784 young people with ME/CFS for an average of 8 years to understand how the illness progresses over time. About half of the young people reported recovery within 5 years, and by 10 years, 68% reported feeling recovered. Most young people improved in their ability to function daily, though a small group (5%) remained very unwell. Having supportive doctors, staying involved in school with flexible accommodations, and developing personal management plans were all important for long-term improvement.

E2 ModerateCohortPEM unclearObservational

Low Sensitivity of Abbreviated Tilt Table Testing for Diagnosing Postural Tachycardia Syndrome in Adults With ME/CFS.

van Campen, C Linda M C, Rowe, Peter C, Visser, Frans C·Frontiers in pediatrics·2018

Many people with ME/CFS experience dizziness and rapid heartbeat when standing up, a condition called POTS. This study found that when doctors use shortened tilt table tests (lasting only 2 minutes) to diagnose POTS, they miss more than half of the patients who actually have it. The researchers recommend using the full 10-minute test instead of the abbreviated version to properly identify POTS in ME/CFS patients.

E2 ModerateCohortPEM unclearObservational

Verification of exercise-induced transient postural tachycardia phenotype in Gulf War Illness.

Garner, Richard S, Rayhan, Rakib U, Baraniuk, James N·American journal of translational research·2018

Researchers found that about one-fourth of Gulf War Illness patients developed an unusual heart rate response after exercise: their heart raced when they stood up, even though this didn't happen before exercise. This temporary condition, called the START phenotype, appeared around 2 hours after exercise and was different from a similar condition called POTS that some patients had continuously. This discovery suggests that exercise can trigger a specific cardiovascular problem in some Gulf War Illness patients.

Intracranial compliance is associated with symptoms of orthostatic intolerance in chronic fatigue syndrome.

Finkelmeyer, Andreas, He, Jiabao, Maclachlan, Laura et al.·PloS one·2018

Many people with ME/CFS experience dizziness or lightheadedness when standing up—a condition called orthostatic intolerance. This study used brain imaging to measure how well the brain's blood vessels and fluid systems adjust to position changes. Researchers found that ME/CFS patients with worse symptoms had less flexible brain spaces and higher blood flow at rest, suggesting their brains may struggle to maintain proper blood flow when standing.

Cardiovascular characteristics of chronic fatigue syndrome.

Bozzini, Sara, Albergati, Andrea, Capelli, Enrica et al.·Biomedical reports·2018

This study looked at heart and blood pressure problems in people with ME/CFS. Researchers found that patients with ME/CFS tend to have lower blood pressure than expected, which may explain some common symptoms like dizziness, fatigue, and difficulty concentrating. Most other heart measurements were similar between people with and without ME/CFS.

Pain and SensitizationSleepAutonomic Nervous System

Poor self-reported sleep quality and health-related quality of life in patients with chronic fatigue syndrome/myalgic encephalomyelitis.

Castro-Marrero, Jesús, Zaragozá, Maria C, González-Garcia, Sergio et al.·Journal of sleep research·2018

This study looked at sleep problems in 1,455 Spanish ME/CFS patients and found that nearly all of them reported poor sleep quality that wasn't refreshing, even when they slept. The researchers discovered that poor sleep was strongly linked to worse pain, fatigue, anxiety, depression, and lower quality of life overall. Several factors—including pain intensity, mood problems, fibromyalgia, and autonomic nervous system dysfunction—were particularly associated with sleep difficulties.

E2 ModerateCohortPEM not requiredObservational

The effects of warm water immersion on blood pressure, heart rate and heart rate variability in people with chronic fatigue syndrome.

Parker, Romy, Higgins, Zeenath, Mlombile, Zandiswa N P et al.·The South African journal of physiotherapy·2018

This study looked at how warm water bathing affects heart function in people with ME/CFS compared to healthy people. Researchers found that people with ME/CFS had less stable heart rate patterns before entering warm water, but this improved during the water immersion. The heart rate stayed slightly elevated in the ME/CFS group even after leaving the water. Overall, warm water immersion appeared safe and may help with managing ME/CFS symptoms.

Urodynamic characteristics might be variable in bladder pain syndrome/interstitial cystitis patients with different non-bladder co-morbid conditions.

Cheng, Wei-Ming, Fan, Yu-Hua, Lin, Alex T L·Journal of the Chinese Medical Association : JCMA·2018

This study looked at how other health conditions that often occur alongside bladder pain syndrome (interstitial cystitis) might affect bladder function. Researchers tested 111 patients with bladder pain and found that 78% also had at least one other condition, such as irritable bowel syndrome, fibromyalgia, or chronic fatigue syndrome. They discovered that patients with both bladder pain and irritable bowel syndrome had different bladder function patterns than those with bladder pain alone.

The etiologic relation between disequilibrium and orthostatic intolerance in patients with myalgic encephalomyelitis (chronic fatigue syndrome).

Miwa, Kunihisa, Inoue, Yukichi·Journal of cardiology·2018

This study looked at 44 ME/CFS patients to understand why they struggle to stay upright (orthostatic intolerance). Researchers found that balance problems—difficulty staying steady when standing with eyes closed—were common and seemed to make orthostatic intolerance worse. Patients with balance problems were more likely to have trouble completing a 10-minute standing test than those with only heart rate changes, suggesting balance issues may be just as important as blood pressure and heart rate problems in ME/CFS.

Latent class analysis of a heterogeneous international sample of patients with myalgic encephalomyelitis/chronic fatigue syndrome.

Huber, Kayla A, Sunnquist, Madison, Jason, Leonard A·Fatigue : biomedicine, health & behavior·2018

This study looked at 1,210 ME/CFS patients to see if there are different types or subtypes of the illness based on their symptoms. Researchers found six distinct groups of patients, each experiencing different combinations of symptoms like heart and blood pressure problems, dizziness when standing, and digestive issues. Importantly, patients in different groups had very different abilities to function in daily life, suggesting that tailored treatment approaches might work better than one-size-fits-all care.

Circadian rhythm abnormalities and autonomic dysfunction in patients with Chronic Fatigue Syndrome/Myalgic Encephalomyelitis.

Cambras, Trinitat, Castro-Marrero, Jesús, Zaragoza, Maria Cleofé et al.·PloS one·2018

This study compared daily activity patterns and skin temperature regulation in 10 women with ME/CFS and 10 healthy women over a week in both winter and summer. While sleep patterns were similar between groups, people with ME/CFS had lower overall daily activity levels and their bodies showed weaker responses to the normal daily rhythm patterns that healthy people display (like a post-lunch energy dip). The findings suggest that ME/CFS may involve problems with how the body's internal clock and temperature regulation systems work.

E2 ModerateCohortPEM requiredCase-Control

Autonomic Nervous System Functioning Related to Nocturnal Sleep in Patients With Chronic Fatigue Syndrome Compared to Tired Controls.

Orjatsalo, Maija, Alakuijala, Anniina, Partinen, Markku·Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine·2018

This study examined how the nervous system controls heart rate and blood pressure during sleep in ME/CFS patients compared to people without the condition. Researchers found that ME/CFS patients showed unusual patterns during sleep: their sympathetic nervous system (the 'fight or flight' system) was more active than normal, while their parasympathetic nervous system (the 'rest and digest' system) was less active, especially during deep sleep. This abnormal nervous system activity during sleep may help explain why ME/CFS patients often wake up feeling unrefreshed.

E2 ModerateBehavioralPEM not requiredCross-Sectional

Negative Affectivity, Depression, and Resting Heart Rate Variability (HRV) as Possible Moderators of Endogenous Pain Modulation in Functional Somatic Syndromes.

Van Den Houte, Maaike, Van Oudenhove, Lukas, Van Diest, Ilse et al.·Frontiers in psychology·2018

This study looked at how the body's natural pain-blocking system works in people with fibromyalgia and chronic fatigue syndrome (CFS), and whether mood, depression, or heart rate variability might affect this system. Researchers compared 78 patients with these conditions to 33 healthy people using a test where they applied cold and electrical stimuli to see if pain would decrease. Unfortunately, the main pain-blocking effect the researchers expected to find did not appear in either group, so they could not draw clear conclusions about what affects pain modulation.

Pain and SensitizationAutonomic Nervous System

Blood Volume Status in ME/CFS Correlates With the Presence or Absence of Orthostatic Symptoms: Preliminary Results.

van Campen, C Linda M C, Rowe, Peter C, Visser, Frans C·Frontiers in pediatrics·2018

This study measured the amount of blood circulating in the bodies of 20 adults with ME/CFS and found that those with symptoms of dizziness or lightheadedness when standing up had significantly less blood volume than those without these symptoms. On average, all ME/CFS patients had about 11 milliliters less blood per kilogram of body weight than expected, but the drop was much more pronounced in patients with orthostatic symptoms. This finding suggests that reduced blood volume may be connected to specific symptoms some ME/CFS patients experience.

E2 ModerateCohortPEM not requiredCase-Control

Are current chronic fatigue syndrome criteria diagnosing different disease phenotypes?

Maclachlan, Laura, Watson, Stuart, Gallagher, Peter et al.·PloS one·2017

This study looked at whether different diagnostic criteria for ME/CFS are actually identifying the same disease or different versions of it. Researchers tested 49 ME/CFS patients and 10 healthy controls using questionnaires and objective tests of heart function and thinking ability. They found that patients reported more autonomic and cognitive symptoms than controls, but objective heart tests didn't show clear differences—though different patient subgroups did show different levels of impairment on cognitive testing.

Autonomic Nervous SystemDiagnosticsCognitive Impairment

Stress vulnerability in adolescents with chronic fatigue syndrome: experimental study investigating heart rate variability and skin conductance responses.

Rimes, Katharine A, Lievesley, Kate, Chalder, Trudie·Journal of child psychology and psychiatry, and allied disciplines·2017

This study looked at how adolescents with ME/CFS respond to stress compared to young people with asthma and healthy teenagers. Researchers measured physical stress responses (heart rate and skin sweating) while young people gave a speech. Adolescents with ME/CFS showed signs of being more stressed before, during, and after the task, and their bodies took longer to calm down afterward compared to the other groups.