Research Digest 10/07/20

Welcome to the 51st Emerge Australia Research Digest, where you will find summaries of some of the latest research and information about ME/CFS, with links to the complete articles.

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Epidemiological and clinical factors associated with post-exertional malaise severity in patients with myalgic encephalomyelitis/chronic fatigue syndrome

Authors: Ghali A, Richa P, Lacout C, Gury A, Beucher AB, Homedan C, Lavigne C, Urbanski G

Post-exertional malaise (PEM) is a well-known feature of ME/CFS, occurring after exposure to a stressor. It is characterised as a worsening of symptoms such as fatigue, cognitive function, and pain, and is not alleviated by rest or sleep. The aim of this study was to define possible factors that could be associated with the severity of PEM.

This study included 197 participants (diagnosed according to the International Consensus Criteria), with a median age of 32 years at disease onset. The authors collected epidemiological data, as well as data on fatigue features, ME/CFS symptoms, and possible triggers for ME/CFS. The severity of PEM was determined by the Centre for Disease Control and Prevention Symptom Inventory (CDC SI). As there are no standardised thresholds for PEM severity, the authors divided the participants’ PEM severity scores into quartiles: mild, moderate, severe and very severe. 

Results showed that that older age at disease onset (≥ 32 years), susceptibility to viral infections during the course of the disease, and gastrointestinal infections prior to disease onset were independently associated with PEM severity. Fatigue scale scores revealed high levels of fatigue and fatigue-related impairment across the sample, and there were no significant differences in fatigue scores across the PEM severity quartiles. 

The authors suggest that these findings may be used to individualise disease management. For example, older patients could be advised to adhere more strictly to pacing strategies, and specific measures against infections together with pacing should be recommended for those who display recurrent and/or persistent infections. The authors suggest that this may prevent PEM occurrence, or at least help reduce its severity, to improve disease course and patients’ quality of life.

Predicting GP visits: A multinomial logistic regression investigating GP visits amongst a cohort of UK patients living with Myalgic encephalomyelitis

Authors: Walsh RS, Denovan A, Drinkwater K, Reddington S, Dagnall, N

Healthwatch is an independent UK organisation which seeks to understand the needs and concerns of healthcare users in the UK, and advocate on their behalf. Following a complaint from an ME/CFS patient about their treatment from a general practitioner (GP), a local Healthwatch undertook a survey of ME/CFS patients to better understand what factors predict the number of visits people with ME/CFS have with their GP in a year.

Data was collected via a survey of 476 individuals who identified as living with ME/CFS (411 women and 65 men) in the UK. Of these, 463 indicated that they had received a formal diagnosis (the diagnostic criteria used were not reported). 

Length of time living with ME/CFS, geographical location, trust in their GP and gender were all found to be significant predictors of the number of GP visits an individual with ME/CFS would have per year. Those who had lived the longest with ME/CFS tended to see their GP less frequently than those with shorter illnesses. Women and those who reported trust in their GP also visited their GP more often than men or those who reported that they didn’t trust their GP. The survey also revealed that around half of the participants lacked trust in their GP.

The doctor-patient relationship and the presence of mutual respect is fundamental to patient wellbeing and the effectiveness of care delivered. The authors suggest that potential barriers to doctor-patient interaction in the context of ME/CFS should be identified and addressed to improve patient outcomes.

Paradigm shift to disequilibrium in the genesis of orthostatic intolerance in patients with myalgic encephalomyelitis and chronic fatigue syndrome

Author: Miwa K, Inoue Y

Orthostatic intolerance (OI) is a significant symptom of ME/CFS which affects patient activities. OI is the inability to be upright, with “cardiovascular symptoms correlated with cerebral hypo-perfusion and exaggerated sympathetic activation”. These authors hypothesised that postural instability, or disequilibrium, possibly related to central vestibular dysfunction, may be involved in the development of OI in ME/CFS.

The study comprised 72 patients with ME/CFS (18 men and 54 women, diagnosed according to the International Consensus Criteria) who underwent neurological examinations, including both standing-on-one-leg and Romberg (standing feet together with eyes shut) tests for disequilibrium, and a conventional 10 minute standing test for OI.

Results showed that 32% of patients had disequilibrium, 22% had postural orthostatic tachycardia (POT) and 26% failed the standing test. Disequilibrium was much higher among those who failed the standing test (89%) than among those who passed (11%). POT occurred at similar rates (22% vs 23%) in those who failed and those who completed the standing test.

The authors conclude that disequilibrium could be a contributing factor in the development of OI among ME/CFS patients. However, they acknowledge that there is still no direct evidence to show a causal relationship between disequilibrium and OI. The authors also acknowledge that it’s not known whether therapeutic recovery from disequilibrium leads to an elimination of OI, and that the mechanism by which disequilibrium develops in ME/CFS patients is also still unknown. Given that the results of the neurological tests varied among the patients with disequilibrium, the authors posit that the underlying mechanism may vary between patients.

Skeletal Muscle Weakness Often Occurs in Patients with Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (ME/CFS)

Author: Jammes Y, Retornaz F

This paper provided commentary on these authors’ previously reported findings of reduced maximal handgrip strength in patients with ME/CFS (see Research Digest 21/02/20, 41st edition). The previous paper found that ME/CFS patients had reduced maximal handgrip strength which was proportional to their reduced performance on a maximal cycle test, and the authors concluded that the maximal handgrip strength test is a reasonable indication of overall reduced maximal physical performance in ME/CFS patients.

This paper explored two possible causes of muscle weakness in ME/CFS: ‘central fatigue’, wherein the observed reduction in maximal physical performance was due to a reduction in central nervous system command to skeletal muscles; and ‘peripheral fatigue’, wherein altered muscle membrane excitability could be the result of an imbalance of oxidant/anti-oxidant status. The authors provide some evidence for both hypotheses and suggest that muscle fatigue in ME/CFS may be due to a combination of both central and peripheral fatigue.

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