title: Sleep inertia associated with a 10-min nap before the commute home following a night shift: A laboratory simulation study.
abstract: Night shift workers are at risk of road accidents due to sleepiness on the commute home. A brief nap at the end of the night shift, before the commute, may serve as a sleepiness countermeasure. However, there is potential for sleep inertia, i.e. transient impairment immediately after awakening from the nap. We investigated whether sleep inertia diminishes the effectiveness of napping as a sleepiness countermeasure before a simulated commute after a simulated night shift. N=21 healthy subjects (aged 21-35 y; 12 females) participated in a 3-day laboratory study. After a baseline night, subjects were kept awake for 27h for a simulated night shift. They were randomised to either receive a 10-min nap ending at 04:00 plus a 10-min pre-drive nap ending at 07:10 (10-NAP) or total sleep deprivation (NO-NAP). A 40-min York highway driving task was performed at 07:15 to simulate the commute. A 3-min psychomotor vigilance test (PVT-B) and the Samn-Perelli Fatigue Scale (SP-Fatigue) were administered at 06:30 (pre-nap), 07:12 (post-nap), and 07:55 (post-drive). In the 10-NAP condition, total pre-drive nap sleep time was 9.1±1.2min (mean±SD), with 1.3±1.9min spent in slow wave sleep, as determined polysomnographically. There was no difference between conditions in PVT-B performance at 06:30 (before the nap). In the 10-NAP condition, PVT-B performance was worse after the nap (07:12) compared to before the nap (06:30); no change across time was found in the NO-NAP condition. There was no significant difference between conditions in PVT-B performance after the drive. SP-Fatigue and driving performance did not differ significantly between conditions. In conclusion, the pre-drive nap showed objective, but not subjective, evidence of sleep inertia immediately after awakening. The 10-min nap did not affect driving performance during the simulated commute home, and was not effective as a sleepiness countermeasure.
authors.affiliation: Centre for Sleep Research, University of South Australia, Adelaide, South Australia 5001, Australia. Electronic address: cassie.hilditch@mymail.unisa.edu.au.
authors.forename: Cassie J
authors.initials: CJ
authors.lastname: Hilditch
authors.affiliation: Centre for Sleep Research, University of South Australia, Adelaide, South Australia 5001, Australia.
authors.forename: Jillian
authors.initials: J
authors.lastname: Dorrian
authors.affiliation: Centre for Sleep Research, University of South Australia, Adelaide, South Australia 5001, Australia.
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Centofanti
authors.affiliation: Sleep and Performance Research Center, Washington State University, Spokane, WA, USA.
authors.forename: Hans P
authors.initials: HP
authors.lastname: Van Dongen
authors.affiliation: Centre for Sleep Research, University of South Australia, Adelaide, South Australia 5001, Australia.
authors.forename: Siobhan
authors.initials: S
authors.lastname: Banks
mesh_terms: D000328:Adult; D001334:Automobile Driving; D002940:Circadian Rhythm; D005221:Fatigue / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D017286:Polysomnography; D011597:Psychomotor Performance / Q000502:physiology*; D012890:Sleep / Q000502:physiology*; D012892:Sleep Deprivation / Q000503:physiopathology*; D020178:Sleep Disorders, Circadian Rhythm / Q000503:physiopathology*; D012894:Sleep Stages; D014851:Wakefulness
keywords: Alertness; Fatigue countermeasure; Nap sleep; Night shift work; Psychomotor vigilance test; Simulated driving