Research abstract:

Deconstructing post-exertional malaise in myalgic encephalomyelitis/ chronic fatigue syndrome: A patient-centered, cross-sectional survey, by Lily Chu, Ian J. Valencia, Donn W. Garvert, Jose G. Montoya in PLOS one 13(6): e0197811 [Published: June 1, 2018]

Post-exertional malaise (PEM) is considered to be the hallmark characteristic of myalgic encephalomyelitis/ chronic fatigue syndrome (ME/CFS). Yet, patients have rarely been asked in formal studies to describe their experience of PEM.

To describe symptoms associated with and the time course of PEM.

One hundred and fifty subjects, diagnosed via the 1994 Fukuda CFS criteria, completed a survey concerning 11 symptoms they could experience after exposure to two different types of triggers. We also inquired about onset and duration of PEM and included space for subjects to write in any additional symptoms. Results were summarized with descriptive statistics; McNemar’s, paired t-, Fisher’s exact and chi-square goodness-of-fit tests were used to assess for statistical significance.

One hundred and twenty-nine subjects (90%) experienced PEM with both physical and cognitive exertion and emotional distress. Almost all were affected by exertion but 14 (10%) reported no effect with emotion. Fatigue was the most commonly exacerbated symptom but cognitive difficulties, sleep disturbances, headaches, muscle pain, and flu-like feelings were cited by over 30% of subjects. Sixty percent of subjects experienced at least one inflammatory/ immune-related symptom. Subjects also cited gastrointestinal, orthostatic, mood-related, neurologic and other symptoms. Exertion precipitated significantly more symptoms than emotional distress (7±2.8 vs. 5±3.3 symptoms (median, standard deviation), p<0.001). Onset and duration of PEM varied for most subjects. However, 11% reported a consistent post-trigger delay of at least 24 hours before onset and 84% endure PEM for 24 hours or more.

This study provides exact symptom and time patterns for PEM that is generated in the course of patients’ lives. PEM involves exacerbation of multiple, atypical symptoms, is occasionally delayed, and persists for extended periods. Highlighting these characteristics may improve diagnosis of ME/CFS. Incorporating them into the design of future research will accelerate our understanding of ME/CFS.

A statement from one of the authors, Lily Chu, MD, MSHS:

We have just published an article about symptoms and timing associated with post-exertional malaise (PEM) in PLOS One.

The article is open access for anyone who wants to read it in full, thanks to funding from Stanford ME/CFS Initiative supporters.

Although PEM has been discussed before in clinical articles, some studies,  and patient accounts, formal studies directly and open-endedly asking patients about their symptoms and timing of PEM are lacking.  Few studies examine the breadth of symptoms nor timing in the same study with the exception of 2 published studies by the Workwell Foundation (here and here ).  However those studies covered a younger group who were all females and could undergo back-to-back CPET (Cardiopulmonary Exercise Testing). Our study includes men, older people, and asked about PEM symptoms during the course of regular life. We also examined differential effects of physical/ cognitive vs. emotional stressors and examined timing in greater detail.

We hope the article will help mainstream clinicians better diagnose ME/CFS.

It is not enough to say that “symptoms” are exacerbated in PEM: clinicians need more specific guidance about which symptoms to recognize PEM and avoid thinking it is only post-exertional fatigue.

We also hope that the article will help inform the design, analysis, and interpretation of future PEM studies. Finally,  the published article may provide support for any work/ school accommodations and other situations when it comes to describing what symptoms commonly make up PEM and its delayed/ prolonged nature.

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