Chronic fatigue syndrome
Last reviewed: December 2017
Last updated: November 2017
....
Definition
Definitions of chronic fatigue syndrome (CFS) have evolved from a focus on fatigue and impairment as described in the Centers for Disease Control (CDC) criteria,
[1] to postexertional malaise (PEM)/exertional exhaustion in myalgic encephalomyelitis (ME)/CFS as defined by the Canadian Consensus Criteria,
[2] [3] and systemic exertion intolerance disease (SEID) introduced by the US Institute of Medicine.
[4] [5] These 3 definitions have compatible criteria that focus on PEM, disability, sleep, pain, and cognition.
[6] [7]
Exertional exhaustion is the critical aspect that distinguishes ME/CFS from other nociceptive, interoceptive, and fatiguing illnesses. .....Consideration of “fatigue” as mental or physical tiredness is too simplistic to encompass the scope of impairment in CFS, and belies the inadequacy of the vocabulary of fatigue.
CFS is characterized by a sudden or gradual onset of persistent disabling fatigue, postexertional malaise (PEM, exertional exhaustion), unrefreshing sleep, cognitive and autonomic dysfunction, myalgia, arthralgia, headaches, and sore throat and lymph nodes, with symptoms lasting at least 6 months.
[8]PEM is the hallmark of CFS. The fatigue is not related to other medical conditions, and symptoms do not improve with sleep or rest.
ME is more strictly defined than CFS. ME is defined by: disabling fatigue; postexertional malaise; sleep, pain, cognitive and autonomic dysfunction; and chemical irritant sensitivity.
[6] [7]
Systemic exertion intolerance disease (SEID) was defined by the US Institute of Medicine (IOM). Diagnosis of SEID requires disabling fatigue, PEM, unrefreshing sleep, and cognitive and autonomic dysfunction that is persisting, moderate or severe, and present at least 50% of the time in order to denote the unique symptom spectrum.
[4]
It is inappropriate to use the 1991 Oxford criteria of fatigue as an alternative for CFS because the Oxford criteria are based on “mild fatigue", do not require postexertional malaise, and allow inclusion of chronic idiopathic fatigue, depression, and other fatiguing conditions. [9] Up to 30.5% of the population have chronic fatigue
[10] and would meet Oxford criteria for study inclusion. Studies that used the Oxford criteria are not representative of the more severe and restricted definitions of CFS that the CDC, Canadian Consensus, or SEID criteria define. Exercise and cognitive behavioral therapy studies that used the Oxford criteria for study inclusion are biased and misleading because people with true CFS are underrepresented, with excessive recruitment of people with chronic idiopathic fatigue and depression who are known to respond well to these modalities.
[11]