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Abstract Introduction Sleep inertia (SI) poses challenges in safety-critical and high-performance environments. Sleep restriction is known to exacerbate SI. To minimise the experience of SI under conditions of sleep restriction, we assessed the role of two quick and easily implementable reactive countermeasures – light and odour – to increase alertness on waking. Methods N=31 (20F, 25.13±5.72y, 24.36±2.1kg/m2) were monitored at home for a week with actigraphy and then in the laboratory underwent an initial night of 7h, followed by 4 days where sleep was split across a 4h sleep opportunity at night and a 1h daytime nap, with a final night of 8h TIB for sleep. Participants were randomly allocated to one of three groups - control, light, or odour. The group allocation determined the countermeasure received on waking before commencing a battery of tests. Performance during SI was assessed using the Psychomotor Vigilance Test (PVT), and the Karolinska Sleepiness Scale (KSS) at 3, 18, 33, 48, and 63min after awakening. Outcomes included reciprocal median reaction time (RRT) and lapses (RT500ms) on the PVT, and KSS scores. Data were analysed with mixed-model ANOVAs with condition, time since awakening, time of day, and day as fixed factors, and participant as a random factor, and posthocs simple effects analysis. Results There were significant time awake by time-of-day interactions on PVT RRT and PVT Lapses p.05 and a main effect of time awake and time-of-day for KSS (p.05). Faster RRTs and fewer Lapses were found across the afternoon wake (i.e., afternoon nap) SI period compared to the morning wake (i.e., night sleep). The progress through the SI period was consistent across time of day for KSS. Condition had no significant main effect or interaction effect with time awake onto measures of SI (e.g., RRT, Lapses, and KSS) (p.05) Conclusion These findings indicate that light and odour for a short period at waking do not improve SI under conditions of sleep restriction. Instead, the findings indicate that a daytime nap may reduce the exacerbating effects of sleep restriction preventing the accumulation of SI during a 4-day simulated work week. Support (if any) Naval Postgraduate School
Owen et al. (Sat,) studied this question.