ME Association August Summary of ME/CFS Published Research | 03 September 2019


Charlotte Stephens, Research Correspondent, ME Association.

The Index of Published ME/CFS Research has been updated to take account of the research that has been published during August 2019.

It’s is a convenient way to locate and read the most recent research or research that was published decades ago.

It’s free to download and comes with an interactive contents table.

This is an A-Z list of all the most important ME/CFS research studies (and selected key documents and articles).

They are listed by subject matter and author, with links to PubMed or the relevant Journal.

You can also find the index in the Research section of the website together with all the summary research reviews that we have published.

ME/CFS Research Published in August 2019

1. Antcliff D et al. (2019)
Survey of activity pacing across healthcare professionals informs a new activity pacing framework for chronic pain/fatigue.
Musculoskeletal Care 1– 11. 

Abstract
Introduction: Activity pacing is considered a key component of rehabilitation programmes for chronic pain/fatigue. However, there are no widely used guidelines to standardize how pacing is delivered. This study aimed to undertake the first stage in developing a comprehensive evidence‐based activity pacing framework.

Methods: An online survey across pain/fatigue services in English National Health Service trusts explored healthcare professionals’ opinions on the types/uses of pacing, aims, facets and perceived effects. Data were analysed using descriptive statistics for closed‐ended questions and thematic analysis for open‐ended questions. Purposeful recruitment with a snowball effect engaged 92 healthcare professionals (physiotherapists, occupational therapists, nurses, doctors and psychologists) to the study.

Results: Pacing was highly utilized, with perceived long‐term benefits for patients (n = 83, 90.2% healthcare professionals instructed pacing). The most endorsed aim of pacing was “achievement of meaningful activities” (24.5% of ranked votes). The least endorsed aim was “to conserve energy” (0.1% of ranked votes). The most frequently supported facet of pacing was “breaking down tasks” (n = 91, 98.9%). The least supported facet was “stopping activities when symptoms increase” (n = 6, 6.5%). Thematic analysis showed recurring themes that pacing involved flexibility and sense of choice.

Conclusions: Pacing is a multidimensional coping strategy and complex behaviour. The message is clear that pacing should enable increases in meaningful activities, as opposed to attempting to avoid symptoms. The survey findings have informed the development of an activity pacing framework to guide healthcare professionals on the multiple components of pacing. This will help to standardize and optimize treatments for chronic pain/fatigue and enable future investigations.

2. Blomberg J et al. (2019)
Antibodies to Human Herpesviruses in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients.
Frontiers in Immunology 10: 1946.

Abstract
Myalgic encephalomyelitis, also referred to as chronic fatigue syndrome (ME/CFS) is a debilitating disease characterized by myalgia and a sometimes-severe limitation of physical activity and cognition. It is exacerbated by physical and mental activity. Its cause is unknown, but frequently starts with an infection. The eliciting infection (commonly infectious mononucleosis or an upper respiratory infection) can be more or less well diagnosed.

Among the human herpesviruses (HHV-1-8), HHV-4 (Epstein-Barr virus; EBV), HHV-6 (including HHV-6A and HHV-6B), and HHV-7, have been implicated in the pathogenesis of ME/CFS. It was therefore logical to search for serological evidence of past herpesvirus infection/reactivation in several cohorts of ME/CFS patients (all diagnosed using the Canada criteria). Control samples were from Swedish blood donors.

We used whole purified virus, recombinant proteins, and synthetic peptides as antigens in a suspension multiplex immunoassay (SMIA) for immunoglobulin G (IgG). The study on herpesviral peptides based on antigenicity with human sera yielded novel epitope information.

Overall, IgG anti-herpes-viral reactivities of ME/CFS patients and controls did not show significant differences. However, the high precision and internally controlled format allowed us to observe minor relative differences between antibody reactivities of some herpesviral antigens in ME/CFS versus controls. ME/CFS samples reacted somewhat differently from controls with whole virus HHV-1 antigens and recombinant EBV EBNA6 and EA antigens.

We conclude that ME/CFS samples had similar levels of IgG reactivity as blood donor samples with HHV-1-7 antigens. The subtle serological differences should not be over-interpreted, but they may indicate that the immune system of some ME/CFS patients interact with the ubiquitous herpesviruses in a way different from that of healthy controls.

3. Collard S and Murphy J (2019)
Management of chronic fatigue syndrome/myalgic encephalomyelitis in a pediatric population: A scoping review.
Journal of Child and Health Care [Epub ahead of print].

Abstract
Chronic fatigue syndrome (CFS)/myalgic encephalomyelitis (ME) negatively impacts the quality of life for children with the condition. Although up to 2% of children have CFS/ME, the bulk of research investigates adults with CFS/ME. Using the PRISMA extension for a scoping review and the work of Arksey and O’Malley (2005), a scoping review was conducted of all relevant peer-reviewed research investigating nutrition, exercise, and psychosocial factors within a pediatric population diagnosed with CFS/ME.

Key themes found were nutrition and dietary components, exercise therapy, psychosocial factors, and multifaceted treatment. Nutrition was explored on its own as a tool to decrease symptoms; however, there were very few studies found to examine nutritional deficiency or treatment with those under the age of 18. Graded exercise and resistance training improved fatigue severity and symptoms of depression in adolescents with CFS/ME. Research exploring psychosocial factors of CFS/ME presented attributes that could lead to being diagnosed as well as barriers to treatment.

The multifaceted treatment undertaken typically consists of graded activities/exercise, cognitive behavioral therapy, nutritional advice, and family sessions. This has shown to increase school attendance and decrease the severity of the fatigue for adolescents.

Minimal literature exploring CFS/ME within a prepubescent population presents the need for further research.

4. Collin S et al. (2019)
Depressive symptoms at age 9–13 and chronic disabling fatigue at age 16: A longitudinal study.
Journal of Adolescence 75: 123-129.

Abstract
Introduction: We investigated whether depressive symptoms at ages 9–13 years were associated with chronic disabling fatigue (CDF) at age 16 among children in the Avon Longitudinal Study of Parents & Children (ALSPAC) birth cohort.

Methods: Depressive symptoms at ages 9, 10, 11, 12, and 13 years were defined as a child- or parent-completed Short Mood and Feelings Questionnaire (SMFQ) score ≥11 (range 0–26). SMFQ score was also analysed as a continuous exposure. Chronic disabling fatigue at 16 was defined as fatigue of ≥6 months’ but <5 years’ duration which prevented school attendance or activities, for which other causes were not identified, and with a Chalder Fatigue Questionnaire score ≥19. Logistic regression was used with multiple imputation to correct for missing data bias. We performed sensitivity analyses in which children who had CDF and depressive symptoms at age 16 were reclassified as not having CDF.

Results: In fully adjusted models using imputed data (N = 13,978), depressive symptoms at ages 9, 11, and 13 years were associated with 2- to 3-fold higher odds of CDF at age 16. Each one-point increase in SMFQ score at ages 9, 10, 11, 12, and 13 years was associated with 6–11% higher odds of CDF at age 16. Depressive symptoms and continuous SMFQ scores at each age were not associated with CDF if the outcome was reclassified to exclude children with comorbid depressive symptoms at age 16.

Conclusions: Depressive symptoms at ages 9–13 were associated with chronic disabling fatigue at age 16, but causality is not certain.

5. Corbitt M et al. (2019)
A systematic review of cytokines in chronic fatigue syndrome/myalgic encephalomyelitis/systemic exertion intolerance disease (CFS/ME/SEID).
BMC Neurology 19 (207).

Abstract
Background: Cytokines in Chronic Fatigue Syndrome/Myalgic Encephalomyelitis/Systemic Exertion Intolerance Disease (CFS/ME/SEID) patients compared with healthy controls have been extensively studied. However, the evidence regarding whether a baseline difference between CFS/ME/SEID patients and the normal population remains unclear. The aim of this study was to conduct a systematic review of the literature regarding cytokines in CFS/ME/SEID and whether there is a significant difference in cytokine levels between this patient group and the normal population.

Methods: Pubmed, Scopus, Medline (EBSCOHost), and EMBASE databases were searched to source relevant studies for CFS/ME/SEID. The review included any studies examining cytokines in CFS/ME/SEID patients compared with healthy controls. Results of the literature search were summarised according to aspects of their study design and outcome measures, namely, cytokines. Quality assessment was also completed to summarise the level of evidence available.

Results: A total of 16,702 publications were returned using our search terms. After screening of papers according to our inclusion and exclusion criteria, 15 studies were included in the review. All the included studies were observational case control studies. Ten of the studies identified measured serum cytokines in CFS/ME/SEID patients, and four measured cytokines in other physiological fluids of CFS/ME/SEID patients. The overall quality assessment revealed most papers included in this systematic review to be consistent.

Conclusions: Despite the availability of moderate quality studies, the findings of this review are inconclusive as to whether cytokines play any definitive role in CFS/ME/SEID, and consequently, they would not serve as reliable biomarkers. Therefore, in light of these results, it is recommended that further efforts toward a diagnostic test and treatment for CFS/ME/SEID continue to be developed in a range of research fields.

6. Hyland M et al. (2019)
Symptom frequency and development of a generic functional disorder symptom scale suitable for use in studies of patients with irritable bowel syndrome, fibromyalgia syndrome or chronic fatigue syndrome.
Chronic Diseases and translational Medicine 5 (2): 129-138.

Abstract
Objectives: To describe the extent to which irritable bowel syndrome (IBS), fibromyalgia syndrome (FMS), and chronic fatigue syndrome (CFS) exhibit symptom overlap, and to validate a patient-derived, generic symptom questionnaire.

Methods: A patient-derived 61-item symptom-frequency questionnaire was completed by participants recruited through IBS, FMS and CFS self-help websites. Principal axis factor analysis with oblimin rotation was performed separately for those reporting an IBS, FMS or CFS diagnosis.

Results: Questionnaires were completed by 1751 participants of whom 851 reported more than one of the three diagnoses.

  • Stomach pain on at least a weekly basis was reported by 79% of IBS, 52% of FMS, and 43% of CFS single diagnosis participants.
  • Pain increasing the day after activity was reported by 32% of IBS, 94% of FMS, and 85% of CFS single diagnosis participants.
  • Waking still tired at least once weekly was reported by 75% of IBS, 97% of FMS, and 95% of CFS single diagnosis participants.

Exploratory factor analysis produced consistent results across all three diagnostic groups, the 61 items loading on 12 correlated factors with a single higher order factor on which all items loaded.

Frequency analysis led to the rejection of one item (cold sores on or near lips), and freeform reporting by participants of additional symptoms identified an additional five, namely, restless legs, hair loss/brittle hair/thinning, dizziness/balance problems, blurred vision and urination problems.

Conclusions: IBS, FMS and CFS are polysymptomatic spectrum disorders with a wide range of overlapping symptoms, many of which are unrelated to diagnostic criteria. Frequency analysis and factor analysis confirm the validity of using the same questionnaire across different diagnostic categories. The 65-item general symptom questionnaire (GSQ-65) is a valid generic symptom scale suitable for assessing the many different symptoms of people with IBS, FMS and CFS.

7. Larson B et al. (2019)
Reproducibility of Measurements Obtained During Cardiopulmonary Exercise Testing in Individuals With Fatiguing Health Conditions: A Case Series.
Cardiopulmonary Physical Therapy Journal [Epub ahead of print].

Abstract
Purpose: Measurements obtained during maximal cardiopulmonary exercise testing (CPET) demonstrate high test–retest reliability, which indicates low error variance. However, measurements obtained from people with myalgic encephalomyelitis/ chronic fatigue syndrome (ME/CFS) may depart from typically observed high reproducibility, which could represent functionally relevant biological variability that is characteristic of the underlying pathophysiology. The purpose of this case series was to document individual experiences with test–retest variability in CPET measurements in individuals with ME/CFS compared with other fatiguing health conditions.

Methods: In this case series, 6 women matched for age and body mass index underwent 2 maximal CPETs spaced 24 hours apart. Clients comprised 1 sedentary individual without fatigue, 1 active individual without fatigue, 1 individual with multiple sclerosis (MS), 1 individual diagnosed with HIV, 1 individual with ME/CFS and low maximal volume of oxygen consumed (VO2max), and 1 high-functioning individual with ME/CFS and high VO2max. Percent change in CPET measurements between tests was calculated for each client.

Results: Nondisabled clients and clients with MS and HIV reproduced or improved in their volume of oxygen consumed (VO2), workload (WL), heart rate (HR), and minute ventilation (VE) at ventilatory anaerobic threshold (VAT) and at peak exercise (except peak WL and VE for the individual with HIV). Neither individual with ME/CFS reproduced VO2, WL, HR, or VE at VAT within literature estimates.

Conclusions: Measurements during CPET for individual patients may relate to potential condition-specific deficits in cardiac, pulmonary, and metabolic functioning.

8. Milrad S et al. (2019)
Relationship satisfaction, communication self-efficacy, and chronic fatigue syndrome-related fatigue.
Social Science and Medicine 237.  

Abstract
Rationale: Relationship dissatisfaction has been linked with worse health outcomes in many patient populations, though the mechanism(s) underlying this effect are unclear. Among patients with chronic fatigue syndrome (CFS) and their partners, there is evidence for a bi-directional association between poorer relationship satisfaction and the severity of CFS-related fatigue.

Objective: Here, we hypothesized that relationship dissatisfaction negatively impacts fatigue severity through greater depression and less patient satisfaction about communication about symptoms to partners.

Method: Baseline data were drawn from diagnosed CFS patients (N = 150) participating in a trial testing the efficacy of a stress management intervention. Data derived from fatigue severity (Fatigue Symptom Index, FSI), depression (Center for Epidemiologic Survey-Depression, CES-D), relationship quality (Dyadic Adjustment Scale, DAS) and communication satisfaction (Patient Symptom Disclosure Satisfaction, PSDS) questionnaires were used for bootstrapped indirect effect analyses using parallel mediation structural equation modeling in Mplus (v8). Age and BMI were entered as covariates.

Results: Greater relationship satisfaction predicted greater communication satisfaction (p < 0.01) and lower CES-D scores (p < 0.01), which in turn were each significantly related to greater fatigue severity (p < 0.05). Tests of the indirect paths indicated that relationship satisfaction had a significant effect on fatigue severity through both constructs, but primarily via depression. There was no direct association between relationship satisfaction and fatigue severity after the intermediate variables (depression, communication satisfaction) were included in the model.

Conclusion: Results highlight the importance of considering depression and communication-related factors when examining the effects of relationship satisfaction on CFS symptoms such as fatigue. Further mechanism-based, longitudinal research might identify relationship-related mediating variables that can be targeted therapeutically.

9. Petersen M et al. (2019)
Prevalence of functional somatic syndromes and bodily distress syndrome in the Danish population: the DanFunD study.
Scandinavian Journal of Public Health [Epub ahead of print].

Abstract
Aims: Little is known about the prevalence and characteristics of functional somatic syndromes (FSS) such as irritable bowel syndrome (IBS), fibromyalgia (FM), chronic fatigue syndrome (CFS), whiplash associated disorders (WAD), multiple chemical sensitivity (MCS), and bodily distress syndrome (BDS) in the general population when they are investigated simultaneously. 

Method: This cross-sectional study is based on the Danish Study of Functional Disorders (DanFunD) cohort consisting of 9656 adults from the general population. FSS and BDS were identified by questionnaires and characterized by age, sex, vocational training, physical health and comorbidity with physical and psychiatric disease. 

Results: In total, 16.3% (95% CI: 15.6–17.1) of the participants fulfilled the criteria for at least one FSS, ranging from 1.7% for WAD to 8.6% for CFS, and 16.1% (95% CI: 15.4–16.9) fulfilled the criteria for BDS. Cases had a high risk of poor self-perceived health, limitations in daily activities, and a high psychiatric comorbidity, all increasing with the number of syndromes in each individual. However, the associations differed across the various FSS. Mutual overlaps of IBS, FM and CFS were greater than could be expected by chance. 

Conclusions: FSS and BDS are prevalent in the adult Danish population, and cases have high risk of poor self-perceived health, limitation in daily activities, and psychiatric comorbidity. These associations were particularly strong for cases with multiple FSS and multi-organ BDS.

10. Rivera C et al. (2019)
Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Comprehensive Review.
Diagnostics 9 (3).

Abstract
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating chronic disease of unknown aetiology that is recognized by the World Health Organization (WHO) and the United States Center for Disease Control and Prevention (US CDC) as a disorder of the brain. The disease predominantly affects adults, with a peak age of onset of between 20 and 45 years with a female to male ratio of 3:1.

Although the clinical features of the disease have been well established within diagnostic criteria, the diagnosis of ME/CFS is still of exclusion, meaning that other medical conditions must be ruled out. The pathophysiological mechanisms are unclear but the neuro-immuno-endocrinological pattern of CFS patients gleaned from various studies indicates that these three pillars may be the key point to understand the complexity of the disease.

At the moment, there are no specific pharmacological therapies to treat the disease, but several studies’ aims, and therapeutic approaches have been described in order to benefit patients’ prognosis, symptomatology relief, and the recovery of pre-existing function.

This review presents a pathophysiological approach to understanding the essential concepts of ME/CFS, with an emphasis on the population, clinical, and genetic concepts associated with ME/CFS.

11. Stevelink S et al. (2019)
Factors associated with work status in chronic fatigue syndrome.
Occupational Medicine [Epub ahead of print].

Abstract
Background: Work status in people with chronic fatigue syndrome (CFS) has not been extensively researched.

Aims: To explore occupational outcomes in patients with CFS by socio-demographic, well-being and disease characteristics.

Methods: We assessed cross-sectional data from patients attending a UK specialist CFS treatment service between 1 January 2007 and 31 December 2014. The main outcome was self-reported current employment status: currently in employment, temporarily interrupted employment or permanently interrupted employment. Other variables included sex, age, ethnicity, education, marital status, CFS duration, fatigue severity, anxiety, depression, activity limitations and functional impairment. We used multinominal logistic regression models to identify factors associated with current work status.

Results: Two hundred and seventy-nine (55%) patients were currently working, with 83 (16%) reporting temporarily interrupted employment and 146 (29%) stopping work altogether.

Factors strongly associated with permanently interrupted employment were older age (adjusted odds ratio (AOR) 5.24; 95% CI 2.67-10.28), poorer functioning (AOR 6.41; 95% CI 3.65-11.24) and depressive symptoms (AOR 2.89; 95% CI 1.82-4.58) compared to patients currently working.

Higher educated patients (AOR 0.60; 95% CI 0.37-0.97) and being in a relationship (AOR 0.34; 95% CI 0.21-0.54) were associated with being currently employed. Anxiety symptoms were common; 230 patients (45%) met caseness criteria.

Conclusions: Many patients with CFS were not working. This was exacerbated by high levels of depressive symptoms. Health professionals should assess co-morbid mental health conditions and consider treatment options when patients with CFS present themselves. The early involvement of occupational health practitioners is recommended to maximize the chances of maintaining employment.

12. Strawbridge R et al. (2019)
Inflammatory proteins are altered in chronic fatigue syndrome – a systematic review and meta-analysis.
Neuroscience and Biobehavioural Reviews [Epub ahead of print].

Abstract
Immune dysfunction has been posited as a key element in the aetiology of chronic fatigue syndrome (CFS) since the illness was first conceived. However, systematic reviews have yet to quantitatively synthesise inflammatory biomarkers across the literature. We undertook a systematic review and meta-analysis to quantify available data on circulating inflammatory proteins, examining studies recruiting patients with a CFS diagnosis and a non-affected control group.

Results were meta-analysed from 42 studies. Patients with CFS had significantly elevated tumour necrosis factor (ES = 0.274, p < 0.001), interleukin-2 (ES = 0.203, p = 0.006), interleukin-4 (ES = 0.373, p = 0.004), transforming growth factor-β (ES = 0.967, p < 0.001) and c-reactive protein (ES = 0.622, p = 0.019). 12 proteins did not differ between groups.

These data provide some support for an inflammatory component in CFS, although inconsistency of results indicates that inflammation is unlikely to be a primary feature in all those suffering from this disorder. It is hoped that further work will elucidate whether there are subgroups of patients with clinically-relevant inflammatory dysfunction, and whether inflammatory cytokines may provide a prognostic biomarker or moderate treatment effects.

13. Tomas C et al. (2019)
Assessing cellular energy dysfunction in CFS/ME using a commercially available laboratory test.
Scientific Reports 9.
Note: This attempt at replication has been covered by a recent MEA review that featured comment from the authors. The MEA Ramsay Research Fund provided the finance for this research.

Abstract
The mitochondrial energy score (MES) protocol, developed by the Myhill group, is marketed as a diagnostic test for chronic fatigue syndrome/Myalgic Encephalomyelitis (CFS/ME). This study assessed the reliability and reproducibility of the test, currently provided by private clinics, to assess its potential to be developed as an NHS accredited laboratory test.

The mitochondrial energy score (MES) protocol, developed by the Myhill group, is marketed as a diagnostic test for chronic fatigue syndrome/Myalgic Encephalomyelitis (CFS/ME). This study assessed the reliability and reproducibility of the test, currently provided by private clinics, to assess its potential to be developed as an NHS accredited laboratory test.

We replicated the MES protocol using neutrophils and peripheral blood mononuclear cells (PBMCs) from CFS/ME patients (10) and healthy controls (13). The protocol was then repeated in PBMCs and neutrophils from healthy controls to investigate the effect of delayed sample processing time used by the Myhill group.

Experiments using the established protocol showed no differences between CFS/ME patients and healthy controls in any of the components of the MES (p ≥ 0.059). Delaying blood sample processing by 24 hours (well within the 72-hour time frame quoted by the Myhill group) significantly altered many of the parameters used to calculate the MES in both neutrophils and PBMCs.

The MES test does not have the reliability and reproducibility required of a diagnostic test and therefore should not currently be offered as a diagnostic test for CFS/ME. The differences observed by the Myhill group may be down to differences in sample processing time between cohorts.

14. Vuong Q et al. (2019)
Brain Responses in CFS and TMD to Autonomic Challenges: An Exploratory fMRI Study.
JDR Clinical and Translational Research [Epub ahead of print].

Abstract
Introduction: Dysfunction of the autonomic nervous system (ANS) is seen in chronic fatigue syndrome (CFS) and temporomandibular disorders (TMDs). Both conditions have poorly understood pathophysiology. Several brain structures that play a role in pain and fatigue, such as the insular cortex and basal ganglia, are also implicated in autonomic function.

Objectives: ANS dysfunction may point to common neurophysiologic mechanisms underlying the predominant symptoms for CFS and TMD. No studies to date have investigated the combination of both conditions. Thus, our aim was to test whether patients with CFS with or without TMD show differences in brain responses to autonomic challenges.

Methods: In this exploratory functional imaging study, patients with CFS who screened positive for TMD (n = 26), patients who screened negative for TMD (n = 16), and age-matched control participants (n = 10) performed the Valsalva maneuver while in a 3-T magnetic resonance imaging scanner. This maneuver is known to activate the ANS.

Results: For all 3 groups, whole-brain F test showed increased brain activation during the maneuver in the superior and inferior frontal gyri, the left and right putamen and thalamus, and the insular cortex. Furthermore, group contrasts with small-volume correction showed that patients with CFS who screened positive for TMD showed greater activity in the left insular cortex as compared with patients who screened negative and in the left caudate nucleus as compared with controls.

Conclusion: Our results suggest that increased activity in the cortical and subcortical regions observed during autonomic challenges may be modulated by fatigue and pain. ANS dysfunction may be a contributing factor to these findings, and further work is required to tease apart the complex relationship among CFS, TMD, and autonomic functions.

15. White P (2019)
A perspective on causation of the chronic fatigue syndrome by considering its nosology.
Journal of Evaluation in Clinical Practice [Epub ahead of print].

Abstract
The causes of chronic fatigue syndrome (CFS) remain unknown, with many failures to replicate new findings. This may be because the condition is hard to diagnose, difficult to classify, or because of its heterogeneous nature.

Authors have problems in differentiating CFS from myalgic encephalomyelitis (ME), which leads many to label it as a hybrid CFS/ME or ME/CFS. Attempts to validate the many published criterion-based definitions have ended in failure. The International Classification of Diseases provide several different descriptions to choose from, although the latest 11th edition has narrowed this down.

This paper describes conventional attempts to define and classify the illness, suggesting that this may be what leads to a failure to replicate putative causes. The approach to CFS/ME may require a shift in the assumption that the illness is homogeneous. An alternative approach is provided by studies suggesting that the condition is heterogeneous.

The way forward may be to be over-inclusive regarding the diagnosis as a first step, while subdividing the condition into likely subgroups as a means of finding valid and reliable associations with potential causes. Studies of aetiology must involve prospective designs since cross-sectional studies cannot inform either aetiology or pathophysiology.

16. Zielinski M et al. (2019)
Fatigue, Sleep, and Autoimmune and Related Disorders.
Frontiers of Immunology 10: 1827.

Abstract
Profound and debilitating fatigue is the most common complaint reported among individuals with autoimmune disease, such as systemic lupus erythematosus, multiple sclerosis, type 1 diabetes, celiac disease, chronic fatigue syndrome, and rheumatoid arthritis.

Fatigue is multi-faceted and broadly defined, which makes understanding the cause of its manifestations especially difficult in conditions with diverse pathology including autoimmune diseases.

In general, fatigue is defined by debilitating periods of exhaustion that interfere with normal activities. The severity and duration of fatigue episodes vary, but fatigue can cause difficulty for even simple tasks like climbing stairs or crossing the room.

The exact mechanisms of fatigue are not well-understood, perhaps due to its broad definition. Nevertheless, physiological processes known to play a role in fatigue include oxygen/nutrient supply, metabolism, mood, motivation, and sleepiness – all of which are affected by inflammation.

Additionally, an important contributing element to fatigue is the central nervous system – a region impacted either directly or indirectly in numerous autoimmune and related disorders.

This review describes how inflammation and the central nervous system contribute to fatigue and suggests potential mechanisms involved in fatigue that are likely exhibited in autoimmune and related disease.

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