title: A new approach to the construct of alertness.
abstract: OBJECTIVE
  There are no psychometric measures to evaluate the critical construct of alertness. We, therefore, developed two questionnaires to measure alertness, the Toronto Hospital Alertness Test (THAT) and the ZOGIM-A, and evaluated their psychometric properties.
  
  
  METHODS
  We examined the correspondence between scores on the THAT and the ZOGIM-A in a sample of sleep clinic outpatients (n=96) with Maintenance of Wakefulness Test (MWT) results after an overnight sleep study, physiological sleep parameters, measures of subjective sleepiness, and two psychosocial variables (psychological well-being and emotional distress). Test-retest reliability was estimated based on responses from an independent sample of 295 sleep clinic outpatients who completed the instruments before and after an overnight sleep study.
  
  
  RESULTS
  High values were observed for both the THAT (r(tt)=.79) and the ZOGIM-A (r(tt)=.70). Internal consistency reliability (coefficient alpha) was also high: .96 for THAT and .83 for ZOGIM-A. Although neither of the new scales correlated significantly with measures derived from the MWT or nocturnal physiological measures, the two alertness scales did correlate significantly and as hypothesized with subjective measures of sleepiness and other psychosocial measures.
  
  
  CONCLUSIONS
  These results support the perspective that subjective alertness cannot be reduced to the absence of sleepiness and corroborate the psychometric adequacy of the THAT and the ZOGIM-A as unique indices of alertness that complement objective data obtained via MWT and physiological indices of sleep architecture.
authors.affiliation: Sleep and Alertness Clinic, University Health Network, Toronto, Canada.
authors.forename: Colin M
authors.initials: CM
authors.lastname: Shapiro
authors.forename: Christine
authors.initials: C
authors.lastname: Auch
authors.forename: Marlene
authors.initials: M
authors.lastname: Reimer
authors.forename: Leonid
authors.initials: L
authors.lastname: Kayumov
authors.forename: Ronald
authors.initials: R
authors.lastname: Heslegrave
authors.forename: Nada
authors.initials: N
authors.lastname: Huterer
authors.forename: Helen
authors.initials: H
authors.lastname: Driver
authors.forename: Gerald M
authors.initials: GM
authors.lastname: Devins
mesh_terms: D000293:Adolescent; D000328:Adult; D000342:Affective Symptoms / Q000175:diagnosis / Q000523:psychology; D000368:Aged; D000369:Aged, 80 and over; D001143:Arousal; D006970:Disorders of Excessive Somnolence / Q000175:diagnosis / Q000523:psychology; D005221:Fatigue / Q000175:diagnosis* / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011594:Psychometrics / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D013315:Stress, Psychological / Q000150:complications; D011795:Surveys and Questionnaires; D014851:Wakefulness