This month the chosen study was “The Impact of a Structured Exercise Programme upon Cognitive Function in Chronic Fatigue Syndrome Patients” (Zalewski et al, 2019).
Quick summary
People with ME showed improved visual attention following a 16 week exercise programme.
However…
None of the statistically significant results survived after FDR correction
Only 64% of participants were able to complete the programme.
Critique
A detailed critique of this study has been discussed over on the “Science for ME” forums, which is well worth reading through.
The selection criteria used was “Fukuda” which does not require the presence of post exertional malaise and therefore may not be a clear representation of ME.
Many comments in our journal club immediately picked up on the main issue with this paper, which was the drop-out rate. Of 69 patients, 35 dropped out of the study, either following the preliminary cardio-pulmonary exercise test to select participants, or part-way through the 16 week exercise programme. The paper – and most of the comments in our journal club – hypothesised that this drop-out was due to the triggering of post exertional malaise, suggesting the intervention had caused a symptom exacerbation.
The paper does discuss post exertional malaise in detail, and concludes; “It is therefore important, that those who are engaging in a structured exercise programme where there might be potential benefits are fully informed of possible detrimental effects.”
However, the other area most commented on was how the data was presented in the abstract, which states “ME/CFS patients able to complete the SEP showed improved visual attention both in terms of reaction time and correctness of responses and processing speed of simple visual stimuli” and includes the line "Statistically significant improvement was noted..." whereas in the discussion; "none of the effects remained significant after FDR correction."
This led to the following quote, which was a great summary;
‘The abstract giveth and the data taketh away’.
Implications for practice
While some patients appeared to have benefits to their cognition following an exercise plan, the high drop-out rate and issues with selection criteria mean that the outcome cannot be safely applied in clinical practice.
This study is an example of the importance of reading beyond an abstract, taking note of factors such as drop-out rates before making a clinical decision.
Lived experience
We asked people with ME how exercise affected their cognitive symptoms, or “brain fog", to see whether there was replication of the small improvements noted in the small number of this study’s participants.
The majority of responses are summarised as; “Exercise makes my cognitive problems worse.”
Many people with ME also picked up on the term “exercise”, discussing how activities such as taking a shower, preparing a meal, housework, or even just sitting upright, will impact on their cognitive function.
Symptoms described included issues with word finding, speech and comprehension; “My thoughts have to wade through concrete”.
One person said that becoming confused was their first indicator of post exertional malaise. Another said that while exercise made their cognition worse, rest and managing their orthostatic intolerances helped to improve it.
Summary
This study was an example of the importance of considering a drop-out rate when looking at the evidence for ME, and using critical appraisal skills when assessing the evidence.
The discussion also highlighted the range of cognitive impairments of people with ME and the significant impact they have on quality of life and daily function.