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Capturing post-exertional exacerbation of fatigue after physical & cognitive challenge in CFS

Simon

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

Andrew Keech ,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.
 

Simon

Senior Member
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Monmouth, UK
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.
 

duncan

Senior Member
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2,240
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.
 
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jimells

Senior Member
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2,009
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northern Maine
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?
 

Dolphin

Senior Member
Messages
17,567
It's Andrew Lloyd so I'd read it closely given his form
The main, possibly only bit I found annoying was this bit (see last sentence):
A novel finding was the gradual and reasonably linear increase in the perception of exertion over the course of each challenge, despite the constant level of task demand. This inability to habituate to the task was not reflected physiologically; for example, during the exercise challenge all participants exercised at the same relative heart rate and other markers of physiological capacity, such as VO2and respiratory markers, plateaued permanently once‘steady-state’ was achieved early in the challenge. As such, this suggests that an abnormal perception of effort during physical or cognitive activity is a component of CFS.
 

Dolphin

Senior Member
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17,567
Interestingly he has chosen to focus on only "fatigue" as being PEM
Yes, it is frustrating. I don't think a good reason is given. It does make me a bit suspicious.

Frequently-used terms deemed to be describing independent symptoms (e.g. ‘painful’, ‘sleepy’, and‘aching’) or functional impact (e.g.‘unable to think’) were also excluded from the frequency analysis.

The environment is:
All patients were diagnosed with CFS by a specialist physician according to the consensus international diagnostic criteria[1], and were recruited from those attending the Fatigue Clinic, University of New South Wales, in Sydney, Australia for management of CFS via a 12-week outpatient treatment programme incorporating cognitive–behavioural therapy, activity pacing and graded exercise therapy.
which may be influencing where the researchers "want to go".
 

Dolphin

Senior Member
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17,567
For each study, patients attended the laboratory only for the challenges and the assessments on that day (immediately before and after challenges, and post-1 h and post-4 h assessments). All other assessments were performed at the patient's home so as to minimise the confounding effect of exacerbated fatigue induced by travel.
Makes sense.
 

Dolphin

Senior Member
Messages
17,567
For the first hour following the cognitively demanding challenge, participants undertook an assessment of cognitive function and interoception (to be reported in a supporting paper).
"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).
 

Dolphin

Senior Member
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17,567
Table 1
Word frequency analysis of the descriptors of fatigue nominated by patients with CFS.

1) Descriptor

2) No. of mentions

3) Positive or negative

4) Physical or cognitive

5) Example quote

Exhausted/tired
54
+
Both
“I think fatigue is totally the wrong word 'cause everyone's been tired. Exhaustion feels more like it…like bone-shattering exhaustion.”(4:3)
Heaviness in the limbs or whole body
22
+
Physical
“I'm heavy. It's like I weigh 10 tonnes. It's like I'm made out of bricks and I'm walking through water.”(2:1)

Fogginess in the head
20
+
Cognitive
“I feel constantly foggy. I don't get that nice, clear sharp….if I'm reading something, I have to read something over and over again.”(5:1)

Weakness in the muscles
12

Physical
“I feel kind of weak, physically very weak. I don't feel like, I might be able to walk but I don't feel like I have much muscle strength.”(5:2)

Drained of energy
12

Both
“…although‘drained’ sounds a bit wussy, it's the [concept of] having absolutely nothing left…nothing physically, emotionally, mentally…just having nothing.”(3:9)
Note: abbreviations after each quote refer to the focus group session number (ranging from 1 to 5) followed by the number denoted to the participant in that session.
 

Simon

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Monmouth, UK
"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).
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)
Converging evidence indicates that primates have a distinct cortical image of homeostatic afferent activity that reflects all aspects of the physiological condition of all tissues of the body.

This interoceptive system, associated with autonomic motor control, is distinct from the exteroceptive system (cutaneous mechanoreception and proprioception) that guides somatic motor activity.

The primary interoceptive representation in the dorsal posterior insula engenders distinct highly resolved feelings from the body that include pain, temperature, itch, sensual touch, muscular and visceral sensations, vasomotor activity, hunger, thirst, and 'air hunger'.

In humans, a meta-representation of the primary interoceptive activity is engendered in the right anterior insula, which seems to provide the basis for the subjective image of the material self as a feeling (sentient) entity, that is, emotional awareness.

Insula-006.png

Position-of-the-Insula.png


also:
How do you feel? Interoception: the sense of the physiological condition of the body : Abstract : Nature Reviews Neuroscience
Recent functional anatomical work has detailed an afferent neural system in primates and in humans that represents all aspects of the physiological condition of the physical body
 
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Marco

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A novel finding was the gradual and reasonably linear increase in the perception of exertion over the course of each challenge, despite the constant level of task demand. This inability to habituate to the task was not reflected physiologically; As such, this suggests that an abnormal perception of effort during physical or cognitive activity is a component of CFS.

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.
 

Snow Leopard

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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.

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?)
 
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aimossy

Senior Member
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1,106
That is very close isnt it to the right anterior fasiculus (excuse any spelling errors) that was highlighted in the stanford brain imaging @Simon ?
 

A.B.

Senior Member
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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.

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

Marco

Grrrrrrr!
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2,386
Location
Near Cognac, France
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?)

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.