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Comparative Study
. 2018 Mar 27;60(2):172-181.
doi: 10.1539/joh.17-0070-OA. Epub 2017 Dec 19.

The effects of nighttime napping on sleep, sleep inertia, and performance during simulated 16 h night work: a pilot study

Sanae Oriyama  1 , Yukiko Miyakoshi  2
Affiliations
Comparative Study

The effects of nighttime napping on sleep, sleep inertia, and performance during simulated 16 h night work: a pilot study

Sanae Oriyama et al. J Occup Health. .

Abstract

Objectives: This study aimed to elucidate the effects of two naps taken at night on morning waking state and performance.

Methods: The participants were 12 women. The experiment was performed in a laboratory over 2 days (16:00-09:00). In this crossover comparative study, three experimental nap conditions were used (naps from 22:30 to 00:00 and from 02:30 to 03:00 (22:30-NAP), 00:30 to 02:00 and 04:30 to 05:00 (00:30-NAP), and no naps (NO-NAP), respectively). Measurement items were a Visual Analog Scale for sleepiness and fatigue, the Psychomotor Vigilance Test (PVT), and single-digit addition calculations (10 min) every hour for 18 h from 16:00 to 09:00, excluding nap times.

Results: Sleep inertia and sleepiness were noted directly after napping. Less sleepiness and fatigue were noted in the nap groups between 06:00 and 09:00 in the morning than in the NO-NAP condition and PVT response times were faster. Since participants in the nap groups were able to conduct more single-digit addition calculations, the performance of these groups appeared to be superior to that of the NO-NAP condition. Furthermore, the performance of calculations was significantly better in the 00:30-NAP than in the 22:30-NAP.

Conclusions: Taking two naps during a simulated night shift helps improve sleepiness and fatigue and maintain performance. Taking a nap in the early morning appears to be promising for improving the waking state.

Keywords: 90-min nap and 30-min nap; Night shift worker; Psychomotor vigilance task; Subjective performance.

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Conflict of interest statement

Conflicts of interest: None declared.

Figures

Fig. 1.
Fig. 1.
Schematic of the study protocol. Each row represents 24 h. The black areas indicate nap times. The diagonal hatching shows all three conditions during that time period.
Fig. 2.
Fig. 2.
Mean (± standard error of the mean) for subjective scales. (A) Visual Analog Scale (VAS) (sleepiness); (B) VAS (fatigue).
Fig. 3.
Fig. 3.
Mean (± standard error of the mean) for neurobehavioral function (A) Psychomotor Vigilance Task (PVT) response time (RT); (B) proportion of correct responses (i.e., rate of <100 ms or ≥500 ms).
Fig. 4.
Fig. 4.
Mean (± standard error of the mean) number of calculations performed.
See this image and copyright information in PMC

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