title: A new EEG biomarker of neurobehavioural impairment and sleepiness in sleep apnea patients and controls during extended wakefulness.
abstract: OBJECTIVE
  To explore the use of detrended fluctuation analysis (DFA) scaling exponent of the awake electroencephalogram (EEG) as a new alternative biomarker of neurobehavioural impairment and sleepiness in obstructive sleep apnea (OSA).
  
  
  METHODS
  Eight patients with moderate-severe OSA and nine non-OSA controls underwent a 40-h extended wakefulness challenge with resting awake EEG, neurobehavioural performance (driving simulator and psychomotor vigilance task) and subjective sleepiness recorded every 2-h. The DFA scaling exponent and power spectra of the EEG were calculated at each time point and their correlation with sleepiness and performance were quantified.
  
  
  RESULTS
  DFA scaling exponent and power spectra biomarkers significantly correlated with simultaneously tested performance and self-rated sleepiness across the testing period in OSA patients and controls. Baseline (8am) DFA scaling exponent but not power spectra were markers of impaired simulated driving after 24-h extended wakefulness in OSA (r=0.738, p=0.037). OSA patients had a higher scaling exponent and delta power during wakefulness than controls.
  
  
  CONCLUSIONS
  The DFA scaling exponent of the awake EEG performed as well as conventional power spectra as a marker of impaired performance and sleepiness resulting from sleep loss.
  
  
  CONCLUSIONS
  DFA may potentially identify patients at risk of neurobehavioural impairment and assess treatment effectiveness.
authors.affiliation: Sleep and Circadian Research Group and NHMRC Centre for Integrated Research and Understanding of Sleep, Woolcock Institute of Medical Research, The University of Sydney, Australia. angela.drozario@sydney.edu.au
authors.forename: Angela L
authors.initials: AL
authors.lastname: D'Rozario
authors.forename: Jong Won
authors.initials: JW
authors.lastname: Kim
authors.forename: Keith K H
authors.initials: KK
authors.lastname: Wong
authors.forename: Delwyn J
authors.initials: DJ
authors.lastname: Bartlett
authors.forename: Nathaniel S
authors.initials: NS
authors.lastname: Marshall
authors.forename: Derk-Jan
authors.initials: DJ
authors.lastname: Dijk
authors.forename: Peter A
authors.initials: PA
authors.lastname: Robinson
authors.forename: Ronald R
authors.initials: RR
authors.lastname: Grunstein
mesh_terms: D000328:Adult; D001288:Attention; D001334:Automobile Driving; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012146:Rest; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology* / Q000628:therapy; D012894:Sleep Stages; D014851:Wakefulness
keywords: Detrended fluctuation analysis; Neurobehavioural function; Obstructive sleep apnea; Power spectral analysis; Quantitative EEG; Sleep deprivation