title: Sleep and performance in simulated Navy watch schedules.
abstract: To operate Navy ships 24h per day, watchstanding is needed around the clock, with watch periods reflecting a variety of rotating or fixed shift schedules. The 5/15 watch schedule cycles through watch periods with 5h on, 15h off watch, such that watches occur 4h earlier on the clock each day - that is, the watches rotate backward. The timing of sleep varies over 4-day cycles, and sleep is split on some days to accommodate nighttime watchstanding. The 3/9 watch schedule cycles through watch periods with 3h on, 9h off watch, allowing for consistent sleep timing over days. In some sections of the 3/9 watch schedule, sleep may need to be split to accommodate nighttime watchstanding. In both the 5/15 and 3/9 watch schedules, four watch sections alternate to cover the 24h of the day. Here we compared sleep duration, psychomotor vigilance and subjective sleepiness in simulated sections of the 5/15 and 3/9 watch schedules. Fifteen healthy male subjects spent 6 consecutive days (5 nights) in the laboratory. Sleep opportunities were restricted to an average of 6.5h daily. Actigraphically estimated sleep duration was 5.6h per watch day on average, with no significant difference between watch sections. Sleep duration was not reduced when sleep opportunities were split. Psychomotor vigilance degraded over watch days, and tended to be more variable in the 5/15 than in the 3/9 watch sections. These laboratory-based findings suggest that Navy watch schedules are associated with cumulative sleep loss and a build-up of fatigue across days. The fixed watch periods of the 3/9 watch schedule appear to yield more stable performance than the backward rotating watch periods of the 5/15 watch schedule. Optimal performance may require longer and more consistent daily opportunities for sleep than are typically obtained in Navy operations.
authors.affiliation: Sleep and Performance Research Center and Elson S. Floyd College of Medicine, Washington State University, PO Box 1495, Spokane, WA 99210-1495, USA. Electronic address: elenaskorn@gmail.com.
authors.forename: Elena
authors.initials: E
authors.lastname: Skornyakov
authors.affiliation: Naval Postgraduate School, 1411 Cunningham Road, Monterey, CA 93943, USA. Electronic address: nlshattu@nps.edu.
authors.forename: Nita L
authors.initials: NL
authors.lastname: Shattuck
authors.affiliation: Sleep and Performance Research Center and Elson S. Floyd College of Medicine, Washington State University, PO Box 1495, Spokane, WA 99210-1495, USA. Electronic address: mike.winser@wsu.edu.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Winser
authors.affiliation: Naval Postgraduate School, 1411 Cunningham Road, Monterey, CA 93943, USA. Electronic address: pmatsang@nps.edu.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Matsangas
authors.affiliation: Sleep and Performance Research Center and Elson S. Floyd College of Medicine, Washington State University, PO Box 1495, Spokane, WA 99210-1495, USA. Electronic address: amy.sparrow@wsu.edu.
authors.forename: Amy R
authors.initials: AR
authors.lastname: Sparrow
authors.affiliation: Sleep and Performance Research Center and Elson S. Floyd College of Medicine, Washington State University, PO Box 1495, Spokane, WA 99210-1495, USA. Electronic address: layton@wsu.edu.
authors.forename: Matthew E
authors.initials: ME
authors.lastname: Layton
authors.affiliation: Sleep and Performance Research Center and Elson S. Floyd College of Medicine, Washington State University, PO Box 1495, Spokane, WA 99210-1495, USA. Electronic address: rylie.gabehart@wsu.edu.
authors.forename: Rylie J
authors.initials: RJ
authors.lastname: Gabehart
authors.affiliation: Sleep and Performance Research Center and Elson S. Floyd College of Medicine, Washington State University, PO Box 1495, Spokane, WA 99210-1495, USA. Electronic address: hvd@wsu.edu.
authors.forename: Hans P A
authors.initials: HP
authors.lastname: Van Dongen
mesh_terms: D000328:Adult; D002940:Circadian Rhythm; D005221:Fatigue / Q000503:physiopathology*; D006801:Humans; D008297:Male; D011597:Psychomotor Performance / Q000502:physiology*; D012767:Ships; D012890:Sleep / Q000502:physiology*; D020178:Sleep Disorders, Circadian Rhythm; D007319:Sleep Initiation and Maintenance Disorders; D012894:Sleep Stages; D014851:Wakefulness; D014940:Work Schedule Tolerance / Q000502:physiology*
keywords: Circadian rhythm; Fatigue; Shift work; Sleep homeostasis; Sleep restriction; Wake maintenance zone