title: Multiple caffeine doses maintain vigilance during early morning operations.
abstract: BACKGROUND
  When used to counteract the effects of sleep deprivation, multiple doses of caffeine are typically ingested across an extended period of time. The goal of this study was to determine the optimal dose of caffeine for sustaining performance during sleep loss with administration of multiple doses.
  
  
  METHODS
  There were 48 subjects (28 men, 20 women) who were randomly assigned to 1 of 4 groups (placebo, 50, 100, or 200 mg caffeine). After an overnight 8-h sleep period, subjects were required to remain awake for the ensuing 29 h. Control data were collected until 03:00 (Day 3), followed by three 2-h test blocks. At 03:00, 05:00, and 07:00 subjects chewed two sticks of gum (Stay Alerts chewing gum) containing caffeine or placebo. Six 10-min sessions on a version of the Psychomotor Vigilance Test (PVT) were completed during each 2-h test block. The Stanford Sleepiness Scale (SSS) was administered after each PVT.
  
  
  RESULTS
  Lapses on the PVT were categorized as response times greater than 1, 3, or 5 s. Lapses in all categories significantly increased in the placebo group. Caffeine significantly reduced the number of lapses in a dose-related manner; and performance was maintained at baseline levels for the entire sleep loss period with multiple doses of 200 mg caffeine. There was a significant main effect for session on the SSS, the score increasing over time, but no significant differences between groups.
  
  
  CONCLUSIONS
  These results indicate that a bi-hourly administration of 200 mg of caffeine maintains vigilance performance across a single night without sleep.
authors.affiliation: Department of Behavioral Biology, Walter Reed Army Institute of Research, Washington, DC, USA. Gary.Kamimori@us.army.mil
authors.forename: Gary H
authors.initials: GH
authors.lastname: Kamimori
authors.forename: Dagny
authors.initials: D
authors.lastname: Johnson
authors.forename: David
authors.initials: D
authors.lastname: Thorne
authors.forename: Gregory
authors.initials: G
authors.lastname: Belenky
mesh_terms: D000337:Aerospace Medicine; D000704:Analysis of Variance; D002110:Caffeine / Q000008:administration & dosage*; D000697:Central Nervous System Stimulants / Q000008:administration & dosage*; D002638:Chewing Gum; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D008297:Male; D011597:Psychomotor Performance; D012892:Sleep Deprivation / Q000188:drug therapy*
chemical_list: D000697:Central Nervous System Stimulants; D002638:Chewing Gum; D002110:Caffeine