Source: PlosOne Vol 14, #2, p e0210394 Date: February 5, 2019 URL: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0210394 Impairments in cognitive performance in chronic fatigue syndrome are common, not related to co-morbid depression but do associate with autonomic dysfunction ---------------------------------------------------------- Lucy J. Robinson(1), Peter Gallagher(2), Stuart Watson(3), Ruth Pearce(4), Andreas Finkelmeyer(2), Laura Maclachlan(4), Julia L. Newton(4,5,*) 1 School of Psychology, Newcastle University, Newcastle, United Kingdom, and Northumbria Healthcare NHS Foundation Trust, Newcastle, United Kingdom. 2 Institute of Neuroscience, Newcastle University, The Henry Wellcome Building, Framlington Place, Newcastle upon Tyne, United Kingdom. 3 Academic Psychiatry and Regional Affective Disorders Service Newcastle University, Newcastle upon Tyne, United Kingdom, and Northumberland, Tyne and Wear Foundation Trust, Wolfson Research Centre, Campus for Ageing and Vitality, Newcastle upon Tyne, United Kingdom. 4 Institute of Cellular Medicine, Newcastle University, Newcastle, United Kingdom. 5 Newcastle Hospitals NHS Foundation Trust, Newcastle, United Kingdom. * Corresponding author. Email: julia.newton@ncl.ac.uk Received: June 7, 2018 Accepted: December 21, 2018 Published: February 5, 2019 Abstract Objectives To explore cognitive performance in chronic fatigue syndrome (CFS) examining two cohorts. To establish findings associated with CFS and those related to co-morbid depression or autonomic dysfunction. Methods Identification and recruitment of participants was identical in both phases, all CFS patients fulfilled Fukuda criteria. In Phase 1 (n=48) we explored cognitive function in a heterogeneous cohort of CFS patients, investigating links with depressive symptoms (HADS). In phase 2 (n=51 CFS & n=20 controls) participants with co-morbid major depression were excluded (SCID). Furthermore, we investigated relationships between cognitive performance and heart rate variability (HRV). Results Cognitive performance in unselected CFS patients is in average range on most measures. However, 0-23% of the CFS sample fell below the 5th percentile. Negative correlations occurred between depressive symptoms (HAD-S) with Digit-Symbol-Coding (r=-.507, p=.006) and TMT-A (r=-.382, p=.049). In CFS without depression, impairments of cognitive performance remained with significant differences in indices of psychomotor speed (TMT-A: p=0.027; digit-symbol substitution: p=0.004; digit-symbol copy: p=0.007; scanning: p=.034) Stroop test suggested differences due to processing speed rather than inhibition. Both cohorts confirmed relationships between cognitive performance and HRV (digit-symbol copy (r=.330, p=.018), digit-symbol substitution (r=.313, p=.025), colour-naming trials Stroop task (r=.279, p=.050). Conclusion Cognitive difficulties in CFS may not be as broad as suggested and may be restricted to slowing in basic processing speed. While depressive symptoms can be associated with impairments, co-morbidity with major depression is not itself responsible for reductions in cognitive performance. Impaired autonomic control of heart-rate associates with reductions in basic processing speed.
But no mention of PEM. PEM being an optional symptom for Fukuda so we don't know if they were looking at ME patients.
Hads isn't reliable for this the questions some questions don't distinguish between fatigue and depression
Whatever HADS is measuring, it didn't show up as causing the cognitive dysfunction in ME. The association found was between HRV which they say is a measure of autonomic dysfunction, and cognitive tasks, specifically reduction in basic processing speed. I thought this deduction from the results was interesting:
An interesting hypothesis would investigate whether PEM related cognitive deficits are associated with short term alterations in blood volume and/or blood flow in the brain...
It would have made sense to repeat the tests several times in short space of a time (24-48hrs) to investigate the effect of PEM on congnitive function. Speaking of which I could see no mention of the sequence they administered the tests in; if it was the same order for every participant then their results may have been skewed with mental exhaustion towards the end of the experiment?
Also, isn't this rather meaningless - when there is no mentioning of either severity of illness, or how long they've been sick? In an illness where illness severity is varying so much, and no-one has assesed the long time impact. Since the norwegian 4 day mindfullness study, I'm beginning to see this as an weakness - it all comes down to one persons view of how to apply the diagnostic criteria. Would this person agree with for instance Stubbhaug about which patients fullfill Fukuda?
One of the problems is selection bias. Participation in studies like this tends to be skewed towards people with above average (pre-illness) IQs and hence claims about normality or lackthereof is questionable. The most valid methodology would require prospective participants before they become ill in the first place, to compare before and after, but no one seems to want to fund very expensive prospective population based epidemiological studies like this.
IMHO the conclusion does not reflect the method and observations and deductions arising from them. What they appear to have done is to examine a group of Fukuda CFS patients with normal cognition on average and show that if they exclude depression then the remaining CFS patients have a real cognitive problem relating to processing speed which is correlated with autonomic dysfunction (which is regarded as a neurological phenomenon) and demonstrably not inhibition which might otherwise be interpreted as a psychological cause e.g. due to pathological ideation or addictive neurosis. This indicates that the codiagnosing of depression and ME as CFS using Fukuda is leading to statistical insignificance of cohort data which neatly demonstrates the subtypes problem with current criteria as this shows Fukuda CFS criteria are not specific enough to distinguish between depression and other conditions which include ME. Instead of demonstrating the evidence of this flaw in Fukuda the conclusion pulls its punches and returns to Fukuda as the standard for CFS and discusses the idea that the Fukuda CFS cohort do not all have cognitive difficulties and co-morbid depression does not cause them, which to my mind perversely fails to enunciate the obvious common sense conclusion that Fukuda is too broad a diagnostic criteria and is flawed because it includes enough depressive illness that it makes it impossible to draw statistical data on ME from cohorts. IMHO the written conclusion is not the logical conclusion and represents a diversion of the truths and insights which should arise from such experiments. (EDIT I have rewritten this paragraph because the first draft was a bit garbled.) From a political and legal perspective, which I feel must be a consideration, while broadly speaking they appear to be addressing the same reality I inhabit, it is disappointing that they are not willing make logical inferences from the results they published which could influence ME research towards better criteria and diagnosis. IMHO the authors have avoided saying something which stands out plainly as a conclusion and needs to be said. I dont trust that, as I dont see a scientific reason for it. It looks like obfuscation, a continuation of a concerted agenda to confound ME with affective disorder diagnosese. Since bias in the interpretation and design of ME CFS experiments has been a longstanding problem among certain schools of psychology, IMHO the failure to engage evident in this paper's conclusions probably results from more of the same kind of bias. Fukuda is broken QED.
Doesn't Jason's four-symptom Empiric Criteria (different to the Empirical Criteria, which are the Reeves/CDC criteria) suggest otherwise? He puts neurocognitive symptoms as a core symptom based on GPS analysis: https://me-pedia.org/wiki/Four-symptom_criteria
Any study that concludes this is flawed beyond repair. It is one of the most common complaints and one of the most severe. It is by far the most impactful thing for me and has preceded any significant fatigue by years. Even if I just shambled on a broken body but still had my cognitive faculties intact it would manageable. They are devastating to me in the very same sense as an athlete having their legs crushed and pulped would be devastating to their career. On the most basic assessment (circle the horse) there would obviously be little to no difference. The choice of what to measure is critical here.
