More welcome research on post-exertional malaise (PEM) in ME/CFS

The findings reported by Lily Chu and colleagues [1] provide the blogging fodder today, and some further welcome research into the concept of post-extertional malaise (PEM) in the context of chronic fatigue syndrome / myalgic encephalomyelitis (CFS/ME).

PEM represents a cardinal feature of CFS/ME, where physical exertion - whether covering exercise or even just daily activities - brings about a period of (even more) exhaustion, weakness and fatigue. As per my previous discussion of the paper by McManimen and colleagues [2], there's still some ambiguity when it comes to clinically defining PEM (and indeed, whether the word 'malaise' covers the range of symptoms that the term includes). What is clear however is that PEM is real and can be absolutely disabling.

The Chu study, including the name Jose Montoya on the authorship list, set out to "describe symptoms associated with and the time course of PEM." Authors designed an online survey "asking subjects about the history and course of their ME/CFS" that asked a few questions about PEM. This included: "1) What symptoms, if any, are triggered or worsened by physical or mental activity?; 2) What symptoms are triggered or worsened by emotional distress?; 3) How soon usually after starting mental or physical exertion does your illness begin to worsen?; and 4) If you feel worse after activities, how long does this worsening usually last?" They also describe how they were careful not to actually use the word 'PEM' during the course of their research in order to "try to decrease the chances that subjects already diagnosed with ME/CFS would automatically answer our question based on their knowledge of or preconceived notions about PEM." Smart move.

Results: some 150 people as part of something called the MGEISD (Genetic Expression and Immune System Dynamics) study responded to the survey. While some of the participants were formally diagnosed with ME/CFS, the cohort also included those "waiting to be seen at the clinic, members of online ME/CFS forums, and participants of local ME/CFS support groups." Although all were telephone screened to see "if they fitted Fukuda 1994 CFS criteria" one does need to be a little careful with describing such a process as providing anything approaching a 'homogeneous' group.

"Most subjects (N = 129, 90%) experienced PEM with both physical/ cognitive exertion and emotional distress." There didn't seem to be any specific 'rules' in terms of the connection between the 'stressor' and onset of PEM, although around 40% of participants reported experiencing PEM within 24 hours. This was however subject to quite some variation. Symptoms reported in relation to the PEM questionnaire items were also variable. Fatigue is up there as one would expect, but also things like sleeping issues and headache were noted. Around 40% of participants also reported on a constellation of PEM symptoms: fatigue, sleep disturbance, pain and "at least one immune-related symptom."

What is becoming a little clearer from this and other research is that (a) PEM or whatever you want to call it is a real issue for many people diagnosed with CFS/ME and (b) the symptoms of PEM are not necessarily uniform in either character or timescale (onset, duration, etc.) What's still missing? Well, biology is still missing from quite a lot of the PEM literature; biology in terms of what PEM looks like on a physiological level and whether there may be something that can be done to alleviate it at a biological level aside from resting up (often for days at a time). I've talked about this before on this blog, in terms of biologically characterising PEM and how, for example, it might look in terms of defining recovery from ME/CFS (see here). To that end, lots more investigation in this area is implied...

And while on the topic of ME/CFS, I'll draw your attention to the paper by Karfakis [3] talking about the "biopolitics of CFS/ME." Yes, there has been and continues to be lots of that, including the phrase: "CFS/ME is an illness trapped between medicine and psychology". Discuss in 500 words.

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[1] Chu L. et al. Deconstructing post-exertional malaise in myalgic encephalomyelitis/ chronic fatigue syndrome: A patient-centered, cross-sectional survey. PLoS One. 2018 Jun 1;13(6):e0197811.

[2] McManimen SL. et al. Deconstructing post-exertional malaise: An exploratory factor analysis. Journal of health psychology. August 2016:1359105316664139.

[3] Karfakis N. The biopolitics of CFS/ME. Stud Hist Philos Biol Biomed Sci. 2018 Jun 8. pii: S1369-8486(17)30070-5.

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