Professor & patients' paper on the solvable biological challenge of ME/CFS: reader-friendly version
Simon McGrath provides a patient-friendly version of a peer-reviewed paper which highlights some of the most promising biomedical research on ME/CFS ...
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Capturing post-exertional exacerbation of fatigue after physical & cognitive challenge in CFS

Discussion in 'Latest ME/CFS Research' started by Simon, Sep 14, 2015.

  1. Simon

    Simon

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    Capturing the post-exertional exacerbation of fatigue following physical and cognitive challenge in patients with chronic fatigue syndrome - Journal of Psychosomatic Research

    Andrew Keech [​IMG],Carolina X. Sandler,Ute Vollmer-Conna, Erin Cvejic, Benjamin K. Barry, Andrew R. Lloyd

    Highlights
    • •Provides a new self-report measure of fatigue in patients with chronic fatigue syndrome
    • •Uniquely captures fatigue in real time with descriptive anchors derived from focus groups
    • •Captures exacerbations following challenge tasks in the laboratory and in daily living
    • •Distinct scale domains capture exacerbations following physical and cognitive tasks.

    Objective
    To design and validate an instrument to capture the characteristic post-exertional exacerbation of fatigue in patients with chronic fatigue syndrome (CFS).

    Methods
    Firstly, patients with CFS (N = 19) participated in five focus group discussions to jointly explore the nature of fatigue and dynamic changes after activity, and inform development of a self-report instrument — the Fatigue and Energy Scale (FES). The psychometric properties of the FES were then examined in two case–control challenge studies: a physically-demanding challenge (moderate-intensity aerobic exercise; N = 10 patients), and a cognitively-demanding challenge (simulated driving; N = 11 patients). Finally, ecological validity was evaluated by recording in association with tasks of daily living (N = 9).

    Results
    Common descriptors for fatigue included ‘exhaustion’, ‘tiredness’, ‘drained of energy’, ‘heaviness in the limbs’, and ‘foggy in the head’. Based on the qualitative data, fatigue was conceptualised as consisting of ‘physical’ and ‘cognitive’ dimensions. Analysis of the psychometric properties of the FES showed good sensitivity to the changing symptoms during a post-exertional exacerbation of fatigue following both physical exercise and driving simulation challenges, as well as tasks of daily living.

    Conclusion
    The ‘fatigue’ experienced by patients with CFS covers both physical and cognitive components. The FES captured the phenomenon of a post-exertional exacerbation of fatigue commonly reported by patients with CFS. The characteristics of the symptom response to physical and cognitive challenges were similar. Both the FES and the challenge paradigms offer key tools to reliably investigate biological correlates of the dynamic changes in fatigue.
     
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  2. Simon

    Simon

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    There are a number of things I really like about this study
    • Focus on post-exertional, not general fatigue, and 'challenge' tests of both moderate exercise and a driving simulator a cognitive challenge. I'd like to see a lot more studies using this approach
    • Involvement of patients in discussing what should be be in the fatigue scale (by contrast, Simon Wessley said he came up with the fatigue questions for the Chalder Fatigue scale all by himself).
    • The descriptors for post-exertional fatigue seem - from memory- similar to those that came up in studies by Lennny Jason and colleagues.
    I wish they'd looked at post-exertional malaise more generally, rather than just focusing on fatigue. And while this study seems like a good start I don't think you can validate any questionnaire on such a small sample. Added: the authors acknowledge this: "While the analysis of the psychometric properties of the FES was conducted across several patient groups and assessment conditions, each analysis involved only small samples of patients with CFS; investigation of the validity and reliability of the instrument in larger samples, and especially in patients with more severe symptomology, is required").

    This paper is part of a series using the challenge tests (another one here), and I know of two others that sound pretty interesting, including one that aims to replicate work done elsewhere.

    I have a copy of the paper but don't yet have the energy to read it, but will post when I do.
     
  3. duncan

    duncan Senior Member

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    Curious Journal in which to publish a paper about a real disease...

    I wonder, are they saying this vehicle reliably captures perceptions of false illness beliefs? It must be accurate because they used focus groups. :) I've been part of a few focus group selection processes - so I am double worried.

    The full study might address that question, but it appears to be behind a paywall.
     
    Last edited: Sep 14, 2015
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  4. ukxmrv

    ukxmrv Senior Member

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    It's Andrew Lloyd so I'd read it closely given his form

    Interestingly he has chosen to focus on only "fatigue" as being PEM
     
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  5. jimells

    jimells Senior Member

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    I have a hard time getting exciting about another subjective questionnaire about fatigue. How many different fatigue scales are needed? One for each "CFS" definition?

    Since our symptom severity usually fluctuates wildly over a very short period of time, I fail to see how this study answers any of the important questions like, what biochemical processes are behind PEM?
     
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  6. Dolphin

    Dolphin Senior Member

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  7. Dolphin

    Dolphin Senior Member

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    The main, possibly only bit I found annoying was this bit (see last sentence):
     
  8. Dolphin

    Dolphin Senior Member

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    Yes, it is frustrating. I don't think a good reason is given. It does make me a bit suspicious.

    The environment is:
    which may be influencing where the researchers "want to go".
     
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  9. Dolphin

    Dolphin Senior Member

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    Makes sense.
     
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  10. Dolphin

    Dolphin Senior Member

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    "Interoception" is a loaded term. Peter White has tried to promote it as an important issue with regard to ME/CFS, that patients supposedly pay too much attention to normal bodily sensations (as opposed to the more likely reality, that the body is producing abnormal sensations).
     
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  11. Dolphin

    Dolphin Senior Member

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  12. Simon

    Simon

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    Fair point, and I've seen other do the same. But I am fascinated by the idea of interoception, a distinct neural network and brain sensing area for measuring the physiological condition of the body. As you say, the sensing may be normal, it's the signalling that's abnormal instead, as implied by the Lights' work on gene expression afterr exercise, but I do think this area deserved more attention to try to find out what's going on.

    Interoception: the sense of the physiological condition of the body. (Craig 2003)
    [​IMG]
    [​IMG]

    also:
     
    Last edited: Sep 24, 2015
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  13. A.B.

    A.B. Senior Member

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    Yes, absence of measured abnormalities doesn't mean that it's all a matter of perception - it could just mean that they are not measuring the right things.

    It's the absence of evidence is evidence of absence fallacy.
     
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  14. Marco

    Marco Grrrrrrr!

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    I actually find these comments intriguing as 'an inability to habituate' sensory input is something I'd noticed and started me down a path of 'research' where 'fatigue' wasn't the core problem.
     
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  15. Snow Leopard

    Snow Leopard Hibernating

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    How does that account for the drop in performance when we feel severe fatigue after some exertion? The part of the brain that receives this sensory input would have to directly inhibit the motor control parts of the brain directly. This could be observed and I haven't actually seen any high quality evidence showing that such a thing happens (can be in anyone who is severely fatigued, not just patients), though maybe I haven't looked hard enough.

    Lastly, why would a pathogen (or autoimmune component) just interfere with this part of the brain and nothing else?

    Lastly, all the drugs that have been tried so far that act centrally on the brain (eg anticonvulsants, antidepressants etc.) have not shown any benefit. (Other possibilities?)
     
    Last edited: Sep 23, 2015
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  16. Snow Leopard

    Snow Leopard Hibernating

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  17. aimossy

    aimossy Senior Member

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    That is very close isnt it to the right anterior fasiculus (excuse any spelling errors) that was highlighted in the stanford brain imaging @Simon ?
     
  18. A.B.

    A.B. Senior Member

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    The drop in VO2max on a second CPET in other studies shows a real reduction in exercise capacity.
     
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  19. Sean

    Sean Senior Member

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    Which would suggest that habituation, i.e. behavioural adaption, is not the answer.

    ?
     
  20. Marco

    Marco Grrrrrrr!

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    I'm pretty sure it's not as straighforward as that i.e. fatigue triggers inhibitory motor control circuits. We're all aware of examples where fatigue signals can be overridden by motivational factors (marathon runners, in instances of extreme danger etc). But an inability to habituate (over time to screen out or inhibit sensory information) could plausibly result in a similar type of cumulative 'wind-up' as found in neuropathic pain.

    I don't see any reason in particular why a pathology (pathogen or autoimmunity) wouldn't interfere with signalling either peripherally, centrally or both.
     

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