title: Dimensions of pure chronic fatigue: psychophysical, cognitive and biological correlates in the chronic fatigue syndrome.
abstract: OBJECTIVE
  To investigate associated dimensions of fatigue regarding cognitive impairment, psychomotor performances, muscular effort power and circulating cytokine levels and their relations to symptom intensity in a sample of pure chronic fatigue syndrome (CFS) patients without overlapping objective sleepiness or sleep disorders.
  
  
  METHODS
  16 CFS patients were compared to 14 matched controls. We assessed structured symptom-scales, polysomnography, multiple sleep latency tests, attention (Zazzo-Cancellation ZCT, digit-symbol-substitution DSST), psychomotor vigilance and speed (PVT, finger tapping test, FTT), dynamometer handgrip force (tonic and phasic trials) and circulating cytokines (IFN-γ, IL-1b, IL-6, IL-8, IL-10, TNF-α).
  
  
  RESULTS
  In addition to fatigue, CFS patients presented with higher affective symptom intensity and worse perceived sleep quality. Polysomnography showed more slow-wave sleep and microarousals in CFS but similar sleep time, efficiency and light-sleep durations than controls. Patients presented with impaired attention (DSST, ZCT), slower reaction times (PVT) but not with lower hit rates (FTT). Notwithstanding lower grip strength during tonic and phasic trials, CFS also presented with higher fatigability during phasic trials. Cytokine levels were increased for IL-1b, IL-8, IL-10 and TNF-α and fatigue intensity was correlated to grip strength and IL-8.
  
  
  CONCLUSIONS
  In contrast to sleepiness, chronic fatigue is a more complex phenomenon that cannot be reduced to one single measured dimension (i.e., sleep propensity). Showing its relations to different measurements, our study reflects this multidimensionality, in a psychosomatic disorder such as CFS. To obtain objective information, routine assessments of fatigue should rule out sleepiness, combine aspects of mental and physical fatigue and focus on fatigability.
authors.affiliation: Sleep Laboratory and Unit for Chronobiology U78, Department of Psychiatry, Brugmann University Hospital, Université Libre de Bruxelles (U.L.B), Arthur Van Gehuchten Square, 1020, Brussels, Belgium, daniel.neu@chu-brugmann.be.
authors.forename: Daniel
authors.initials: D
authors.lastname: Neu
authors.forename: Olivier
authors.initials: O
authors.lastname: Mairesse
authors.forename: Xavier
authors.initials: X
authors.lastname: Montana
authors.forename: Medhi
authors.initials: M
authors.lastname: Gilson
authors.forename: Francis
authors.initials: F
authors.lastname: Corazza
authors.forename: Nicolas
authors.initials: N
authors.lastname: Lefevre
authors.forename: Paul
authors.initials: P
authors.lastname: Linkowski
authors.forename: Olivier
authors.initials: O
authors.lastname: Le Bon
authors.forename: Paul
authors.initials: P
authors.lastname: Verbanck
mesh_terms: D000328:Adult; D001288:Attention; D016022:Case-Control Studies; D003071:Cognition; D016207:Cytokines / Q000097:blood; D015673:Fatigue Syndrome, Chronic / Q000097:blood / Q000503:physiopathology*; D005260:Female; D018737:Hand Strength; D006801:Humans; D008297:Male; D011930:Reaction Time; D012890:Sleep
chemical_list: D016207:Cytokines