title: Non-REM sleep EEG power distribution in fatigue and sleepiness.
abstract: OBJECTIVE
  The aim of this study is to contribute to the sleep-related differentiation between daytime fatigue and sleepiness.
  
  
  METHODS
  135 subjects presenting with sleep apnea-hypopnea syndrome (SAHS, n=58) or chronic fatigue syndrome (CFS, n=52) with respective sleepiness or fatigue complaints and a control group (n=25) underwent polysomnography and psychometric assessments for fatigue, sleepiness, affective symptoms and perceived sleep quality. Sleep EEG spectral analysis for ultra slow, delta, theta, alpha, sigma and beta power bands was performed on frontal, central and occipital derivations.
  
  
  RESULTS
  Patient groups presented with impaired subjective sleep quality and higher affective symptom intensity. CFS patients presented with highest fatigue and SAHS patients with highest sleepiness levels. All groups showed similar total sleep time. Subject groups mainly differed in sleep efficiency, wake after sleep onset, duration of light sleep (N1, N2) and slow wave sleep, as well as in sleep fragmentation and respiratory disturbance. Relative non-REM sleep power spectra distributions suggest a pattern of power exchange in higher frequency bands at the expense of central ultra slow power in CFS patients during all non-REM stages. In SAHS patients, however, we found an opposite pattern at occipital sites during N1 and N2.
  
  
  CONCLUSIONS
  Slow wave activity presents as a crossroad of fatigue and sleepiness with, however, different spectral power band distributions during non-REM sleep. The homeostatic function of sleep might be compromised in CFS patients and could explain why, in contrast to sleepiness, fatigue does not resolve with sleep in these patients. The present findings thus contribute to the differentiation of both phenomena.
authors.affiliation: Brugmann University Hospital, Sleep Laboratory & Unit for Chronobiology U78, Free University of Brussels (U.L.B/V.U.B.), Brussels, Belgium; UNI, ULB Neurosciences Institute, Faculty of Medicine, Laboratory for Medical Psychology ULB312, Université Libre de Bruxelles (U.L.B.), Brussels, Belgium. Electronic address: daniel.neu@chu-brugmann.be.
authors.forename: Daniel
authors.initials: D
authors.lastname: Neu
authors.affiliation: Brugmann University Hospital, Sleep Laboratory & Unit for Chronobiology U78, Free University of Brussels (U.L.B/V.U.B.), Brussels, Belgium; UNI, ULB Neurosciences Institute, Faculty of Medicine, Laboratory for Medical Psychology ULB312, Université Libre de Bruxelles (U.L.B.), Brussels, Belgium; Department of Experimental and Applied Psychology (EXTO), Vrije Universiteit Brussel (V.U.B.), Brussels, Belgium. Electronic address: olivier.mairesse@chu-brugmann.be.
authors.forename: Olivier
authors.initials: O
authors.lastname: Mairesse
authors.affiliation: Brugmann University Hospital, Sleep Laboratory & Unit for Chronobiology U78, Free University of Brussels (U.L.B/V.U.B.), Brussels, Belgium; UNI, ULB Neurosciences Institute, Faculty of Medicine, Laboratory for Medical Psychology ULB312, Université Libre de Bruxelles (U.L.B.), Brussels, Belgium. Electronic address: paul.verbanck@chu-brugmann.be.
authors.forename: Paul
authors.initials: P
authors.lastname: Verbanck
authors.affiliation: University Clinics of Brussels, Erasme Hospital, Sleep Laboratory, Department of Psychiatry, Université Libre de Bruxelles (U.L.B.), Brussels, Belgium. Electronic address: paul.linkowski@erasme.ac.be.
authors.forename: Paul
authors.initials: P
authors.lastname: Linkowski
authors.affiliation: UNI, ULB Neurosciences Institute, Faculty of Medicine, Laboratory for Medical Psychology ULB312, Université Libre de Bruxelles (U.L.B.), Brussels, Belgium; Tivoli University Hospital, Department of Psychiatry, U.L.B., La Louvière, Belgium. Electronic address: olivier.lebon@chu-tivoli.be.
authors.forename: Olivier
authors.initials: O
authors.lastname: Le Bon
mesh_terms: D000328:Adult; D000342:Affective Symptoms / Q000209:etiology*; D000368:Aged; D004569:Electroencephalography; D005221:Fatigue / Q000209:etiology* / Q000523:psychology; D015673:Fatigue Syndrome, Chronic / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D012890:Sleep; D012891:Sleep Apnea Syndromes / Q000150:complications*; D012894:Sleep Stages; D012895:Sleep, REM
keywords: Chronic fatigue syndrome; Fatigue; NREMS power spectra; Sleep apnea; Sleepiness; Ultra slow delta