ME/CFS and Post-Exertional Malaise among Patients with Long COVID.

This study sought to ascertain the prevalence of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) among a sample of 465 patients with Long COVID. The participants completed three questionnaires: (1) a new questionnaire measuring both the frequency and severity of 38 common symptoms of COVID and Long COVID, (2) a validated short form questionnaire assessing ME/CFS, and (3) a validated questionnaire measuring post-exertional malaise. The population was predominantly white, female, and living in North America. The mean duration since the onset of COVID-19 symptoms was 70.5 weeks. Among the 465 participants, 58% met a ME/CFS case definition. Of respondents who reported that they had ME/CFS only 71% met criteria for ME/CFS and of those who did not report they had ME/CFS, 40% nevertheless did meet criteria for the disease: both over-diagnosis and under-diagnosis were evident on self-report. This study supports prior findings that ME/CFS occurs with high prevalence among those who have persistent COVID-19 symptoms.