International ME/CFS and FM Awareness Day Is On May 12, 2018
Thomas Hennessy, Jr., selected May 12th to be our international awareness day back in 1992. He knew that May 12th had also been the birthday of Florence Nightingale. She was the English army nurse who helped to found the Red Cross as well as the first school of nursing in the world.
Discuss the article on the Forums.

Model to Explain Persistence of Fatigue in CFS (not recent but very influential)

Discussion in 'Latest ME/CFS Research' started by oceanblue, May 5, 2012.

  1. oceanblue

    oceanblue Guest

    Messages:
    1,174
    Likes:
    362
    UK
    The model put forward in this 1998 paper has been much cited by the Dutch CBT school and was explicitly used by them as the basis for their version of CBT for CFS. Yet it is a fundamentally flawed piece of work.

    The persistence of fatigue in chronic fatigue syndrome and multiple sclerosis: Development of a model, Vercoulen 1998

    JHMM Vercoulen, CMA Swanink, OR Hommes, JMD Galama, G Bleijenberg, PJH Jongen, JFM Fennis, and JWM van der Meer

    Abstract

    Objective. The cause of chronic fatigue syndrome (CFS) is unknown. With respect to factors perpetuating fatigue, on the other hand, a model has been postulated in the literature in which behavioral, cognitive, and affective factors play a role in perpetuating fatigue. In the present study this hypothesized model was tested in patients with CFS and in fatigued patients with multiple sclerosis (MS).

    Method. 51 patients with chronic fatigue syndrome and 50 patients with multiple sclerosis matched for age, sex, and education. The hypothesized model was formulated in terms of cause and effect relationships and an integral test of this model was performed by the statistical technique "structural equation modeling".

    Results. Attributing complaints to a somatic cause produced low levels of physical activity, which in turn had a causal effect on fatigue severity. In contrast, depression had to be deleted from the model. Two new causal relationships were found: sense of control over symptoms and focusing on bodily symptoms each had a direct causal effect on fatigue. The model showed excellent fit for CFS patients, but was rejected for MS patients. Therefore, a new model for MS patients had to be developed. Sense of control had a causal effect on fatigue. In the MS model no causal relationship was found between the somatic substrate as measured by the Expanded Disability Status Score and fatigue or functional impairment. Causal attributions, low level of physical activity, and focusing on bodily symptoms played an important role in the persistence of fatigue in CFS, but not in MS.

    Conclusions. The etiology of CFS is unknown, but the present study shows that cognitive and behavioral factors are involved in the persistence of fatigue. Treatment should be directed at these factors. The processes involved in the subjective experience of fatigue in CFS were different from the processes related to fatigue in MS.

    note this abstract come from JHHM Vercoulen's Doctoral Thesis (see Chapter 9) but is just a tiny edit different from the published article so I'm also assuming the paper is not materially changed from the Thesis version.

    The resulting model looks like this:
    Vercoulen 98 model.jpg


    There are several fundamental flaws to this stuy:
    1. This is a cross-sectional study (no 'before' and 'after' data) - and correlation does not mean causation, which is Game Over for the study, really. Still:
    2. The patients had Oxford-criteria defined CFS and a quarter of them did not have daily fatigue
    3. Some of the measures eg of 'functional ability' are dubious at best
    4. The authors hypothesised model failed and they had to modify it 3 separate times before it 'fitted' the data - taking post-hoc chicanery to extremes.
     
    Enid likes this.
  2. peggy-sue

    peggy-sue

    Messages:
    2,623
    Likes:
    3,258
    Scotland
    No need to go any further than their assumed "cause" merely being a correlate.
    I hope this prat does not get awarded his PhD - but if he does- more proof positive that psychology isn't science.
     
    Enid likes this.
  3. oceanblue

    oceanblue Guest

    Messages:
    1,174
    Likes:
    362
    UK
    The doctorate was awarded and the paper published so draw your own conclusions. The supervisor of the PhD and senior author on the paper was Professor Gijs Bleijenberg.
     
  4. oceanblue

    oceanblue Guest

    Messages:
    1,174
    Likes:
    362
    UK
    More detail on those 4 flaws (if anyone is still reading):

    1. The study is not suitable to draw conclusions about causation
    The big claim of this study is that it has been able to draw conclusions about what causes persistence of fatigue in CFS, because it uses Structural Equation Modelling (SEM):
    This is plain wrong. There is no statistical technique on earth that can draw causal conclusions from cross-sectional data. You need at least 'before' and 'after' data, and preferably 'during' as well to have a chance of concluding that A causes B which causes C. Here's an explanation from a relevant recent paper: Structural Equation Modeling in Medical Research: A Primer (2010)
    2. The sample of patients wasn't really suitable
    The study used 51 patients diagnosed according ot Oxford Criteria, which only requires 6 months of fatigue and no other symptoms. Tellingly, 26% of the sample did not report daily fatigue. Which means that any small effects (and this study only found small-ish effects) could be explained by inclusion of inappropriate patients. Also, the sample size of 51 is rather small. Sample size in SEM is a controversial issue, but, as the primer above says:
    3. Several of the questionnaires used as 'measures' are not appropriate
    "Somatization" was measured by the SCL-90 Somatization subscale, which actually simply asks about symptoms experienced, which might be due to CFS (eg weakness and soreness of muscles) and is not a proper measure of excessive symptom-focusing.

    "Functional Impairment" was measured soley by the Sickness Impact Profile (SIP) Home Management subscale (10 questions). The exact question list is not available but the original SIP paper gives as examples: 'I am not doing any of the maintenance or repair work around the house that I usually do' and 'I am not doing heavy work around the house'. Later studies from the same group more reasonably used a broader measure of functional impairment including 'Social', 'Rrecreation' and 'Work' (25% of patients still worked); there are 27 questions in these extra categories, giving a broader and more robust measure.

    "Physical Activity" was measured only by the SIP-Mobility subscale (10 questions, with none on walking, which is covered by the ambulation subscale). A study by the same authors on the same patients using actometers showed that SIP-mobility did not correlate well with activity measured by actometer (r=0.35).

    Again, from the primer:
    4. The model only fitted the data after tweaking it 3 separate times
    One of the strengths of a modelling approach is that the model is developed 'a priori' i.e. before the data is seen, then tested agains the data. Unfortunately, the hypothesised model failed badly. The data from the model test suggested modification i.e. dropping 5 of the original 9 'mediators' and adding 3 new ones. This radical change still didn't fit that data so they added another new mediator, which still didn't cut the mustard - so they added a 5th new mediator and finally got a fit. This is post-hoc tweaking in the extreme, with the strong possibility that the model has just been bent and twisted to fit that partiuclar group of patients. It would need replicating on an independent sample to have any meaning.

    From the primer again:
    Conclusion
    It's hard to understand how this study ever got published. The fatally flawed methodology was unsuitable to detect causal relationships, the sample was very small with a dubious diagnosis, the questionnaires were not suitable to measure what was claimed and the model was twisted and manipulated several times to get a 'fit' to the data.

    One last comment from the primer:
    How on earth could this study be used as the basis for the type of CBT promoted in the Netherlands for over a decade?
     
  5. Snow Leopard

    Snow Leopard Hibernating

    Messages:
    4,654
    Likes:
    12,564
    South Australia
    I don't mind the publishing of such a method, so long as the discussion/conclusion is reasonable (ie far more tentative than what they actually wrote).
    The bigger question is the question in the end of your post - an excellent and perhaps alarming question.
     
  6. oceanblue

    oceanblue Guest

    Messages:
    1,174
    Likes:
    362
    UK
    Vercoulen model undone

    Given the fundamental flaws in the methodology, it's not surprising that the model's findings haven't held up well in studies looking at how CBT/GET 'works', as this diagram shows:
    Vercoulen 98 model X.jpg

    So most of the proposed mechanisms haven't been supported by further studies. In particular, the large Wiborg 2010 study showed that CBT led to no change in physical activity measured by actometer (though self-reported activity did increase), while the Moss-Morris study showed that physical conditioning similarly did not improve with GET.

    Significance of 'Sense of Control' finding?
    The 'confirmatory' finding that 'sense of control' can affect fatigue less robust. However, a study of CBT for pain found a similar role for sense of control over symptoms, as did an earlier prospective study of CFS by Vercoulen. (n=298 [questionnaire validation], 18-month follow-up). Rather than 'Sense of Control' reflecting 'correct' illness beliefs it might be linked to appropriate adaptation to the illness - why else do people pace? i.e. The modest effect of 'Sense of Control' may simply be a finding that strategies like pacing are modestly helpful.


    Diagram references:
    Deale A, Chalder T, Wessely S. Illness beliefs and treatment outcome in chronic fatigue syndrome. 1998

    Moss-Morris R, Sharon C, Tobin R, Baldi JC. A Randomized Controlled Graded Exercise Trial for Chronic Fatigue Syndrome: Outcomes and Mechanisms of Change. 2005

    Wiborg JF, Knoop H, Stulemeijer M, Prins JB, Bleijenberg G. How does cognitive behaviour therapy reduce fatigue in patients with chronic fatigue syndrome? The role of physical activity. 2010

    Wiborg JF, Knoop H, Frank LE, Bleijenberg G. Towards an evidence-based treatment model for cognitive behavioral interventions focusing on chronic fatigue syndrome. 2012
     
    Waverunner and Snow Leopard like this.
  7. Enid

    Enid Senior Member

    Messages:
    3,309
    Likes:
    862
    UK
    Well it was 1998 - worst possible time for this cabal off in "la-la" land. "Correct" illness belief seems to be their problem. (No excuses for rudeness and contempt having been told it's "all in your mind" 10 years ago, much in the way of pathologies discovered since).

    Good to see your analysis here ocean.
     
  8. Esther12

    Esther12 Senior Member

    Messages:
    8,449
    Likes:
    28,530
    Nothing to add, but I just wanted to add a 'thanks' for the thread and analysis.
     
  9. oceanblue

    oceanblue Guest

    Messages:
    1,174
    Likes:
    362
    UK
    That is indeed the question; not much chance of an answer from the Dutch school, though. You are more generous than I am: I don't mind SEM on before/after data like the 2012 Wiborg study I quote below, but I don't think any paper using SEM on cross-sectional data as a basis for causal claims merits publication.

    @e12: thanks.
     
  10. roxie60

    roxie60 Senior Member

    Messages:
    1,787
    Likes:
    600
    Central Illinois, USA
    Great another 'objective' opionion telling us if we would just stop focusing on our symptoms we would feel better...yada yada
     

See more popular forum discussions.

Share This Page