title: Effects of night work, sleep loss and time on task on simulated threat detection performance.
abstract: OBJECTIVE
  To investigate the effects of night work and sleep loss on a simulated luggage screening task (SLST) that mimicked the x-ray system used by airport luggage screeners.
  
  
  METHODS
  We developed more than 5,800 unique simulated x-ray images of luggage organized into 31 stimulus sets of 200 bags each. 25% of each set contained either a gun or a knife with low or high target difficulty. The 200-bag stimuli sets were then run on software that simulates an x-ray screening system (SLST). Signal detection analysis was used to obtain measures of hit rate (HR), false alarm rate (FAR), threat detection accuracy (A'), and response bias (B"(D)).
  
  
  METHODS
  Experimental laboratory study
  
  
  METHODS
  24 healthy nonprofessional volunteers (13 women, mean age +/- SD = 29.9 +/- 6.5 years).
  
  
  METHODS
  Subjects performed the SLST every 2 h during a 5-day period that included a 35 h period of wakefulness that extended to night work and then another day work period after the night without sleep.
  
  
  RESULTS
  Threat detection accuracy A' decreased significantly (P < 0.001) while FAR increased significantly (P < 0.001) during night work, while both A' (P = 0.001) and HR decreased (P = 0.008) during day work following sleep loss. There were prominent time-on-task effects on response bias B"(D) (P= 0.002) and response latency (P = 0.004), but accuracy A' was unaffected. Both HR and FAR increased significantly with increasing study duration (both P < 0.001), while response latency decreased significantly (P <0.001).
  
  
  CONCLUSIONS
  This study provides the first systematic evidence that night work and sleep loss adversely affect the accuracy of detecting complex real world objects among high levels of background clutter. If the results can be replicated in professional screeners and real work environments, fatigue in luggage screening personnel may pose a threat for air traffic safety unless countermeasures for fatigue are deployed.
authors.affiliation: Division of Sleep and Chronobiology, Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6021, USA. basner@mail.med.upenn.edu
authors.forename: Mathias
authors.initials: M
authors.lastname: Basner
authors.forename: Joshua
authors.initials: J
authors.lastname: Rubinstein
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Fomberstein
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Coble
authors.forename: Adrian
authors.initials: A
authors.lastname: Ecker
authors.forename: Deepa
authors.initials: D
authors.lastname: Avinash
authors.forename: David F
authors.initials: DF
authors.lastname: Dinges
mesh_terms: D000328:Adult; D000401:Aircraft; D001288:Attention; D003198:Computer Simulation; D005221:Fatigue / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening; D009784:Occupational Diseases / Q000175:diagnosis / Q000523:psychology*; D010364:Pattern Recognition, Visual; D012637:Security Measures; D020178:Sleep Disorders, Circadian Rhythm / Q000175:diagnosis / Q000523:psychology*; D023481:Terrorism / Q000517:prevention & control*; D014195:Travel; D014940:Work Schedule Tolerance
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