title: Simulator performance, microsleep episodes, and subjective sleepiness: normative data using convergent methodologies to assess driver drowsiness.
abstract: OBJECTIVE
  Our objective was to examine a novel standardized assessment methodology of detecting impaired driving performance due to drowsiness in a normative cohort.
  
  
  METHODS
  Thirty-one healthy subjects with no significant sleep, medical, and psychiatric pathology were assessed in a driving simulation paradigm. Thirty-minute simulations were repeated at two-hourly intervals (i.e., at 1000, 1200, 1400, and 1600 h). Convergent data sources included drivers' subjective ratings of sleepiness and alertness, electroencephalogram-verified microsleep (MS) episodes, and a variety of real-time driving simulator performance measures such as speed, lane tracking, reaction time (RT), and off-road events (crashes).
  
  
  RESULTS
  Significant diurnal fluctuations were noted on objective measures of RT, velocity, tracking, and MS events, indicating the highest risk of impairment in the afternoon. By contrast, subjective ratings of sleepiness and alertness did not demonstrate significant circadian variation. The mean incidence of MS episodes and crash risk correlated highly (r = .748).
  
  
  CONCLUSIONS
  This prospective study demonstrates the relevance of multiple convergent measures for comprehensive assessment. The divergence of subjective and objective assays of impairment implies that healthy individuals may not have full insights into neurophysiologically mediated performance deficits. These results will serve as normative comparators to patients presenting with daytime somnolence and may allow a more accurate prediction of potential crash risk than noninteractive daytime polysomnogram tests such as the mean sleep latency test or the maintenance of wakefulness test.
authors.affiliation: Human Performance Laboratory and Sleep Research Unit, Neuropsychiatry Program, Toronto Western Hospital, University Health Network, University of Toronto, Toronto, Ontario, Canada. henry.moller@uhn.on.ca
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Moller
authors.forename: Leonid
authors.initials: L
authors.lastname: Kayumov
authors.forename: Eric L
authors.initials: EL
authors.lastname: Bulmash
authors.forename: Jonathan
authors.initials: J
authors.lastname: Nhan
authors.forename: Colin M
authors.initials: CM
authors.lastname: Shapiro
mesh_terms: D000063:Accidents, Traffic / Q000706:statistics & numerical data; D000328:Adult; D001334:Automobile Driving / Q000706:statistics & numerical data*; D015331:Cohort Studies; D006970:Disorders of Excessive Somnolence / Q000175:diagnosis* / Q000453:epidemiology*; D004569:Electroencephalography; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D010812:Physical Stimulation / Q000379:methods*; D017286:Polysomnography; D011930:Reaction Time; D012016:Reference Values; D012720:Severity of Illness Index; D012894:Sleep Stages; D011795:Surveys and Questionnaires