Focus on Fatigue

Focus on Fatigue, Issue 39: Napping on the night shift

By January 10, 2016 No Comments

Welcome to Focus on Fatigue,

Welcome to the first issue of Focus on Fatigue for 2016. We here at InterDynamics hope you had a restful holiday period and have been enjoying the first months of this new year. We are looking forward to bringing you more newsletters packed with useful information regarding many aspects of fatigue risk management.

Best wishes for the year ahead.

The FRMS Team

InterDynamics - Navigating Complexity. Delivering Clarity.

InterDynamics Pty Ltd
320 Adelaide Street Brisbane Qld 4000
Tel +61 2 8404 0400 Ext 23

Views expressed in articles and links provided are those of the individual authors, and do not necessarily represent the views of InterDynamics (except where directly attributed).

Feature Articles

Napping on the Night Shift

For some people, the idea of employees sleeping during work hours evokes stereotypical images of a person dozing off in their work chair while emergency lights flash unheeded in the background. Others may believe naps are just an excuse to sleep on the job and call it work. If the culture of a workplace is not supportive, then nappers may be viewed as weak or lazy.

It must be recognized that in some jobs, especially in the area of shift work, the use of strategic naps are an important, and sometimes critical, part of fatigue management.

What is the different between strategic napping and dozing off on the job?

Strategic napping is one of many tools shift workers can use to manage fatigue in the workplace. Unlike a doze, a strategic nap is planned in advance. The timing and duration of the nap is determined by weighing the benefits of the nap against the potential negative consequences. Considerations include variables such as the number of hours the person has already been awake and the work requirements of the shift. A strategic nap also allows workers to coordinate with their colleagues and possibly arrange for any essential work activities to be covered while the planned nap is taking place. All of this helps workers to manage their fatigue effectively, and thus reduces risk.
What are the benefits of napping?

Over several decades, researchers have studied the effects of napping during periods of sustained wakefulness. This research has been conducted in laboratory settings, using simulated shift work, and in real-life operational settings. Some of the benefits of napping include improvements in alertness, performance, and mood.

Workers may not perform as well as they would if they were fully rested, but there is often a significant improvement from the level of performance achieved if they did not nap at all. The benefits to alertness and performance can last for up to 12 hours following the nap.

What are the downsides of napping?

There are two potential negative effects of napping that should be considered when deciding if, when and long to nap for. These are: sleep inertia and the potential disruption to subsequent sleep.

Sleep inertia – This is the grogginess and disorientation we feel when first waking from a nap. Depending on the length of the nap, sleep inertia can last from a few minutes up to 35 minutes, though in most cases the effects will dissipate in about 10-15 minutes. While under the effects of sleep inertia, task performance can be worse than if the person had not napped at all. Therefore it is imperative when planning a nap, to ensure that adequate time is allowed to recover from sleep inertia before resuming work.

Disruption to subsequent sleep – Recovery sleep between shifts is essential to ensure that workers are ready for their next shift. Napping for long periods, or at certain times during a shift, can disrupt the quantity and quality of this recovery sleep.

Types of napping

There are two types of naps shift workers can use to enhance their work performance. These include pre-shift napping and napping during shifts.

Pre-shift napping – This most commonly occurs before the first night shift, as workers taking a nap in the late afternoon/early evening in preparation for the sustain wakefulness ahead. This type of nap can delay the onset of performance decrements normally associated with sustained wakefulness. Indeed, one study found that pre-shift napping reduced the risk of accidents while working by 48%.

Napping during shifts – Appropriate use of napping can be used to maintain job performance during shifts, and relieve some of the homeostatic sleep pressure caused by long periods of sustained wakefulness. Improvements have been seen even when the sleep achieved was short and of a poor quality.

How long should my nap be?

The duration of naps will always be heavily dependent on the type of work in which a shift worker is involved. However, even a 20-minute nap has been shown to improve alertness and performance. Napping for longer than 30 minutes will increase the effects of sleep inertia, and so requires extra time after waking before returning to work tasks. Longer naps are more likely to have an effect on subsequent sleep, but are also more likely to result in better performance once sleep inertia has dissipated. Naps are most likely to be of benefit on the first night shift.

When could napping be a bad idea?

If a worker’s scheduled nap is interrupted by an emergency requiring a quick response with a high level of performance, that person may end up responding to the emergency while suffering the effects of sleep inertia. In this case, their job performance may be worse than if they had not napped at all.

Therefore, if this possibility exists, it will be necessary to weigh up the benefits of improved alertness and performance during regular work, with the potential likelihood of an emergency occurring during the period when sleep inertia is an issue.


  • Garbarino, S., Mascialino, B., Penco, M. A., Squarcia, S., De Carli, F., Nobili, L., Beeelke, M., Cuomo, G. and Ferrillo, F. (2004) Professional shift-work drivers who adopt prophylactic naps can reduce the risk of car accidents during night work. Sleep, 27(7), 1295-1302.
  • Knauth, P. & Hornberger, S. (2003) Preventative and compensatory measures for shift workers. Occupational Medicine, 53, 109-116.
  • Purnell, M. T., Feyer, A. M. and Herbison, G. P. (2002) The impact of a nap opportunity during the night shift on the performance and alertness of 12-hour shift workers. Journal of Sleep Research, 11, 219-227.
  • Rosekind, M. R., Smith, R. M., Miller, D. L., Co, E. L., Gregory, K. B., Webbon, L. L., Gander, P. H. and Lebacqz, J. V. (1995) Alertness management: Strategic naps in operational settings. Journal of Sleep Research, 4, 62-66.
  • Signal, T. L., Gander, P. H., Anderson, H. and Brash, S. (2009) Scheduled napping as a countermeasure to sleepiness in air traffic controllers. Journal of Sleep Research, 18, 11-19.
  • Signal, T. L., van den Berg, M. J., Mulrine, H. M. and Garder, P. H. (2012) Duration of sleep inertia after napping during simulated night work and in extended operations. Chronobiology International, 29(6), 769-779.
  • Takahashi, M. (2012) Prioritizing sleep for healthy work schedules. Journal of Physiological Anthropology, 31(6).

In the News

Provided below are a selection of articles from around the web on the issues associated with fatigue. We hope you find them useful and interesting.

Article: Protected ‘power naps’ prove helpful for doctors in training to fight fatigue

by Medical Xpress (4 December 2012)

Research from the Perelman School of Medicine at the University of Pennsylvania and the Philadelphia VA Medical Center indicates that the implementation of protected sleep periods for residents who are assigned to overnight shifts in a hospital represent a viable tool in preventing fatigue and alleviating the physiological and behavioral effects of sleep deprivation among these doctors in training.

Video: The Facts of Napping

by Stanfordsdprod (23 May 2013)

This video, produced for a Stanford University class called ‘Sleep and Dream,’ examines the benefits of napping for our health and productivity.


Article: Scheduled napping as a countermeasure to sleepiness in air traffic controllers

Signal, T. L., Gander, P. H., Anderson, H. and Brash, S. (2009) Scheduled napping as a countermeasure to sleepiness in air traffic controllers. Journal of Sleep Research, 18, 11-19.


The aims of this study were to measure sleep during a planned nap on the night shift; and to use objective measures of performance and alertness to compare the effects of the nap opportunity versus staying awake. Twenty-eight air traffic controllers (mean age 36 years, nine women) completed four night shifts (two with early starts and two with late starts). Each type of night shift (early/late start) included a 40-min planned nap opportunity on one occasion and no nap on the other. Polysomnographic data were used to measure sleep and waking alertness [spectral power in the electroencephalogram (EEG) during the last hour of the night shift and the occurrence of slow rolling eye movements (SEMs) subsequent to the nap]. Psychomotor performance task [Psychomotor Vigilance Task (PVT)] was completed at the beginning and end of the shift, and after the nap (or an equivalent time if no nap was taken). Nap sleep latencies were relatively long (mean = 19 min) and total sleep time short (mean = 18 min), with minimal slow wave sleep (SWS, mean = 0%), and no rapid eye movement sleep. Nap sleep resulted in improved PVT performance (mean and slowest 10% of reaction time events), decreased spectral power in the EEG and reduced the likelihood of SEMs. The occurrence of SWS in the nap decreased spectral power in the EEG. This study indicates that although sleep taken at work is likely to be short and of poor quality it still results in an improvement in objective measures of alertness and performance.

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