Purpose of review: Unexplained fatigue is commonly reported in the general population, with varying severity. Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) sits at the extreme of the fatigue continuum, yet more individuals experience unexplained prolonged fatigue (1-6-month duration) or chronic fatigue (> 6 months) that, although debilitating, does not fulfil ME/CFS criteria. This review examines the empirical literature comparing symptoms for those with prolonged fatigue, chronic fatigue and ME/CFS.
Recent findings: Substantial overlap of self-reported psychological, physical and functional impairments exists between chronic fatigue and ME/CFS. The conversion rate from prolonged or chronic fatigue to ME/CFS is not understood. Current research has failed to uncover factors accounting for differences in fatigue trajectories, nor incorporate comprehensive, longitudinal assessments extending beyond self-reported symptoms. Distinguishing factors between prolonged fatigue, chronic fatigue and ME/CFS remain poorly understood, highlighting a need for longitudinal studies integrating biopsychosocial approaches to inform early management and targeted rehabilitation strategies.
Keywords: Autonomic; Chronic fatigue syndrome; Fatigue; Function; Myalgic encephalomyelitis.