title: Cognitive workload and sleep restriction interact to influence sleep homeostatic responses.
abstract: OBJECTIVE
  Determine the effects of high versus moderate workload on sleep physiology and neurobehavioral measures, during sleep restriction (SR) and no sleep restriction (NSR) conditions.
  
  
  METHODS
  Ten-night experiment involving cognitive workload and SR manipulations.
  
  
  METHODS
  Controlled laboratory environment.
  
  
  METHODS
  Sixty-three healthy adults (mean ± standard deviation: 33.2 ± 8.7 y; 29 females), age 22-50 y.
  
  
  METHODS
  Following three baseline 8 h time in bed (TIB) nights, subjects were randomized to one of four conditions: high cognitive workload (HW) + SR; moderate cognitive workload (MW) + SR; HW + NSR; or MW + NSR. SR entailed 5 consecutive nights at 4 h TIB; NSR entailed 5 consecutive nights at 8 h TIB. Subjects received three workload test sessions/day consisting of 15-min preworkload assessments, followed by a 60-min (MW) or 120-min (HW) workload manipulation comprised of visually based cognitive tasks, and concluding with 15-min of postworkload assessments. Experimental nights were followed by two 8-h TIB recovery sleep nights. Polysomnography was collected on baseline night 3, experimental nights 1, 4, and 5, and recovery night 1 using three channels (central, frontal, occipital [C3, Fz, O2]).
  
  
  RESULTS
  High workload, regardless of sleep duration, increased subjective fatigue and sleepiness (all P < 0.05). In contrast, sleep restriction produced cumulative increases in Psychomotor Vigilance Test (PVT) lapses, fatigue, and sleepiness and decreases in PVT response speed and Maintenance of Wakefulness Test (MWT) sleep onset latencies (all P < 0.05). High workload produced longer sleep onset latencies (P < 0.05, d = 0.63) and less wake after sleep onset (P < 0.05, d = 0.64) than moderate workload. Slow-wave energy-the putative marker of sleep homeostasis-was higher at O2 than C3 only in the HW + SR condition (P < 0.05).
  
  
  CONCLUSIONS
  High cognitive workload delayed sleep onset, but it also promoted sleep homeostatic responses by increasing subjective fatigue and sleepiness, and producing a global sleep homeostatic response by reducing wake after sleep onset. When combined with sleep restriction, high workload increased local (occipital) sleep homeostasis, suggesting a use-dependent sleep response to visual work. We conclude that sleep restriction and cognitive workload interact to influence sleep homeostasis.
authors.affiliation: Division of Sleep and Chronobiology, Department of Psychiatry, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA.
authors.forename: Namni
authors.initials: N
authors.lastname: Goel
authors.affiliation: Division of Sleep and Chronobiology, Department of Psychiatry, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA ; Japan Society for the Promotion of Science, Tokyo, Japan ; Space Biomedical Research Office, Japan Aerospace Exploration Agency, Tsukuba, Ibaraki, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Abe
authors.affiliation: Division of Sleep and Chronobiology, Department of Psychiatry, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA.
authors.forename: Marcia E
authors.initials: ME
authors.lastname: Braun
authors.affiliation: Division of Sleep and Chronobiology, Department of Psychiatry, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA.
authors.forename: David F
authors.initials: DF
authors.lastname: Dinges
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology; D003071:Cognition / Q000502:physiology*; D056344:Executive Function / Q000502:physiology; D005221:Fatigue / Q000523:psychology; D005260:Female; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D017286:Polysomnography; D011930:Reaction Time / Q000502:physiology; D012890:Sleep / Q000502:physiology*; D012892:Sleep Deprivation / Q000503:physiopathology* / Q000523:psychology*; D012894:Sleep Stages / Q000502:physiology; D013826:Theta Rhythm; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology; D016526:Workload; D055815:Young Adult
keywords: alertness; cognitive workload; fatigue; polysomnography; psychomotor vigilance task; sleep homeostasis; sleep restriction; sleepiness; slow-wave activity; slow-wave energy