Post-exertional malaise (PEM) is a worsening of chronic fatigue syndrome symptoms that occurs after exertion. PEM involves increased fatigue, and an exacerbation of other symptoms. PEM is often severe enough to be disabling, and is triggered by ordinary activities that healthy people tolerate. Post-exertional malaise typically begins 12–48 hours after the activity that triggers it, and lasts for days, but this is highly variable. Management of PEM is symptomatic, and patients are recommended to pace their activities to avoid triggering PEM.

Description

Post-exertional malaise involves fatigue, and is of such a severity that it impacts a person's functioning. Other symptoms that may be experienced during PEM include

cognitive impairment Cognitive deficit is an inclusive term to describe any characteristic that acts as a barrier to the cognition process. The term may describe * deficits in overall intelligence (as with intellectual disabilities), * specific and restricted defici ...

, flu-like symptoms, pain, weakness or trouble sleeping. While typically cast as a worsening of existing symptoms, patients may experience some symptoms exclusively during PEM. Patients often describe PEM as "crash," "relapse," or "setback." PEM is triggered by "minimal" physical or mental activities that were previously tolerated, and that healthy people tolerate, like attending a social event, grocery shopping, or even taking a shower. Emotional distress, injury, sleep deprivation, infections, and spending too long standing or sitting up are also cited as potential triggers. The resulting symptoms are disproportionate to the triggering activity and distinct from typical fatigue. PEM is often debilitating, and may render someone housebound or bedbound until they recover. The course of a crash is highly variable. The onset of symptoms typically occurs 12–48 hours after the triggering activity, but may be immediate, or delayed up to 7 days. PEM lasts "usually a day or longer," but can span hours, days, weeks, or months. The level of activity that triggers PEM, as well as the symptoms, vary from person to person, and within individuals over time. Due to this variability, people with CFS may be unable to predict what will trigger PEM.

Diagnosis

PEM is a common symptom of ME/CFS, occurring in 60 to 100% of patients, depending on how the condition is defined. PEM is also a common symptom of

long COVID Long COVID or long-haul COVID (also known as post-COVID-19 syndrome, post-COVID-19 condition, post-acute sequelae of COVID-19 (PASC), or chronic COVID syndrome (CCS)) is a condition characterized by long-term health problems persisting or appe ...

, where long COVID symptoms may get worse after exertion, in a similar manner as ME/CFS. PEM is considered a cardinal symptom by a number of the different diagnostic criteria for ME/CFS: the

International Consensus Criteria Clinical descriptions of chronic fatigue syndrome (CFS) vary. Different groups have produced sets of diagnostic criteria that share many similarities. The biggest differences between criteria are whether post-exertional malaise (PEM) is required ...

, the National Academy of Medicine criteria, and NICE's definition of CFS all require it. The Canadian Consensus Criteria require "post exertional malaise and/or ost exertionalfatigue" instead. On the other hand, the older Oxford Criteria lack any mention of PEM, and the Fukuda Criteria consider it optional. A 2-day Cardiopulmonary Exercise Test (CPET) has emerged as a helpful tool in documenting PEM, showing apparent abnormalities in the way the body responds to exercise. Still, there needs to be more attention and urgency placed on firmly establishing a diagnostic test.

Management

There is no treatment or cure for ME/CFS or PEM. Pacing, a management strategy in which someone plans their activities to stay within their limits, may help people avoid triggering PEM.

References

{{Chronic fatigue syndrome Chronic fatigue syndrome Symptoms