0143 Effects of Optimal-timed Automatic Awakening from a Short Daytime Nap on Cognitive Performance and Fatigue

Introduction Daytime naps, although known to improve performance, can impair performance if overextended, as slow-wave sleep causes sleep inertia. Hayashi et al. (2014) showed that a nap duration of 9 min after N2 onset maximized performance. However, awakening 9 min after N2 is challenging, other than in sleep laboratories, because it requires manual polysomnography (PSG) scoring. We developed a system that automatically awakens 9 min after N2 by an automatic sleep stage estimator using a blood flow meter and investigated whether this improved performance, sleepiness, and fatigue compared to no napping and also its effectiveness as compared to manual awakening. Methods Eighty-one healthy adults (33.6±12.8 years [mean ± standard deviation], 47 women) were randomly assigned to three groups of 27 participants each: automatic awakening, manual awakening, and rest. The digit symbol substitution test (DSST) was used to evaluate cognitive speed and visual detection task (VDT) to evaluate attention. The Karolinska Sleepiness Scale and the visual analog scale were used for the sleepiness and fatigue evaluation; the tasks were performed thrice after attaching the PSG and used as a baseline. The automatic and manual awakening groups napped wearing the blood-flow-meter device. The latter group was awakened 9 min after the N2 onset. The participants in the rest group remained awake for 22 minutes. After the nap or rest, the task was performed again for six sessions consisting of three times tasks. Groups were compared for the changes detected from the baseline in each session. Results The automatic awakening group woke up 19.6 ± 6.0 (mean ± standard deviation) [min-max 7.9–27.1] min from N2. Subjective sleepiness and fatigue in the automatic awakening group decreased compared to the rest group in all sessions and were comparable to those in the manual awakening group; the number of correct answers on the DSST increased in the sixth session for manual awakening compared to rest. VDT did not differ between groups. Conclusion Napping with the automatic awakening device improved sleepiness and fatigue comparable to manual awakening. Support (if any) This work was funded by Kyocera Corporation.