The impact of short night-time naps on performance, sleepiness and mood during a simulated night shift

ABSTRACT

Short naps on night shift are recommended in some industries. There is a paucity of evidence to verify the sustained recovery benefits of short naps in the last few hours of the night shift. Therefore, the current study aimed to investigate the sustained recovery benefits of 30 and 10-min nap opportunities during a simulated night shift. Thirty-one healthy participants (18F, 21–35 y) completed a 3-day, between-groups laboratory study with one baseline night (22:00–07:00 h time in bed), followed by one night awake (time awake from 07:00 h on day two through 10:00 h day three) with random allocation to: a 10-min nap opportunity ending at 04:00 h, a 30-min nap opportunity ending at 04:00 h or no nap (control). A neurobehavioral test bout was administered approximately every 2 h during wake periods. There were no significant differences between nap conditions for post-nap psychomotor vigilance performance after controlling for pre-nap scores (p > 0.05). The 30-min nap significantly improved subjective sleepiness compared to the 10-min nap and no-nap control (p < 0.05). The 10-min nap significantly worsened negative mood compared to the 30-min nap and no-nap control (p < 0.01). Contrary to some evidence suggesting “power naps” can help to alleviate performance decrements, a 30-min nap opportunity at approximately 04:00 h was found to improve subjective, but not objective sleepiness. A 10-min nap may lead to increased negative mood in the hours following the nap due to a “short nap aversion” effect.

KEYWORDS:

• Napping
• performance
• shift work

Acknowledgements

The authors would like to thank Professor Hans Van Dongen for his mentorship, input into the design of the study and interpretation of data and analyses and Professor Gary Wittert, and staff and students who assisted in running the project.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article. The authors also acknowledge financial support from a University of South Australia Divisional Research Performance Fund seeding grant.