title: A 30-Minute, but Not a 10-Minute Nighttime Nap is Associated with Sleep Inertia.
abstract: OBJECTIVE
  To assess sleep inertia following 10-min and 30-min naps during a simulated night shift.
  
  
  METHODS
  Thirty-one healthy adults (aged 21-35 y; 18 females) participated in a 3-day laboratory study that included one baseline (BL) sleep (22:00-07:00) and one experimental night involving randomization to either: total sleep deprivation (NO-NAP), a 10-min nap (10-NAP) or a 30-min nap (30-NAP). Nap opportunities ended at 04:00. A 3-min psychomotor vigilance task (PVT-B), digit-symbol substitution task (DSST), fatigue scale, sleepiness scale, and self-rated performance scale were undertaken pre-nap (03:00) and at 2, 17, 32, and 47 min post-nap.
  
  
  RESULTS
  The 30-NAP (14.7 ± 5.7 min) had more slow wave sleep than the 10-NAP (0.8 ± 1.5 min; P < 0.001) condition. In the NO-NAP condition, PVT-B performance was worse than pre-nap (4.6 ± 0.3 1/sec) at 47 min post-nap (4.1 ± 0.4 1/sec; P < 0.001). There was no change across time in the 10-NAP condition. In the 30-NAP condition, performance immediately deteriorated from pre-nap (4.3 ± 0.3 1/sec) and was still worse at 47 min post-nap (4.0 ± 0.5 1/sec; P < 0.015). DSST performance deteriorated in the NO-NAP (worse than pre-nap from 17 to 47 min; P < 0.008), did not change in the 10-NAP, and was impaired 2 min post-nap in the 30-NAP condition (P = 0.028). All conditions self-rated performance as better than pre-nap for all post-nap test points (P < 0.001).
  
  
  CONCLUSIONS
  This study is the first to show that a 10-min (but not a 30-min) nighttime nap had minimal sleep inertia and helped to mitigate short-term performance impairment during a simulated night shift. Self-rated performance did not reflect objective performance following a nap.
authors.affiliation: Centre for Sleep Research, University of South Australia, Adelaide, South Australia, Australia.
authors.forename: Cassie J
authors.initials: CJ
authors.lastname: Hilditch
authors.affiliation: Centre for Sleep Research, University of South Australia, Adelaide, South Australia, Australia.
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Centofanti
authors.affiliation: Centre for Sleep Research, University of South Australia, Adelaide, South Australia, Australia.
authors.forename: Jillian
authors.initials: J
authors.lastname: Dorrian
authors.affiliation: Centre for Sleep Research, University of South Australia, Adelaide, South Australia, Australia.
authors.forename: Siobhan
authors.initials: S
authors.lastname: Banks
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology; D005221:Fatigue / Q000175:diagnosis / Q000503:physiopathology; D005260:Female; D006801:Humans; D020179:Jet Lag Syndrome / Q000175:diagnosis / Q000503:physiopathology*; D008297:Male; D011597:Psychomotor Performance; D057566:Self Report; D012890:Sleep / Q000502:physiology*; D012892:Sleep Deprivation / Q000503:physiopathology; D012894:Sleep Stages / Q000502:physiology; D013647:Task Performance and Analysis; D013997:Time Factors; D014940:Work Schedule Tolerance / Q000502:physiology; D055815:Young Adult
keywords: alertness; fatigue countermeasure; nap sleep; night shift work; psychomotor vigilance task; sleep deprivation; sleep inertia; subjective performance