title: A review of short naps and sleep inertia: do naps of 30 min or less really avoid sleep inertia and slow-wave sleep?
abstract: OBJECTIVE
  Napping is a widely used countermeasure to sleepiness and impaired performance caused by sleep loss and circadian pressure. Sleep inertia, the period of grogginess and impaired performance experienced after waking, is a potential side effect of napping. Many industry publications recommend naps of 30 min or less to avoid this side effect. However, the evidence to support this advice is yet to be thoroughly reviewed.
  
  
  METHODS
  Electronic databases were searched, and defined criteria were applied to select articles for review. The review covers literature on naps of 30 min or less regarding (a) sleep inertia, (b) slow-wave sleep (SWS) and (c) the relationship between sleep inertia and SWS.
  
  
  RESULTS
  The review found that although the literature on short afternoon naps is relatively comprehensive, there are very few studies on naps of 30 min or less at night. Studies have mixed results regarding the onset of SWS and the duration and severity of sleep inertia following short naps, making guidelines regarding their use unclear. The varying results are likely due to differing sleep/wake profiles before the nap of interest and the time of the day at waking.
  
  
  CONCLUSIONS
  The review highlights the need to have more detailed guidelines about the implementation of short naps according to the time of the day and prior sleep/wake history. Without this context, such a recommendation is potentially misleading. Further research is required to better understand the interactions between these factors, especially at night, and to provide more specific recommendations.
authors.affiliation: E.P. Bradley Sleep Lab, Brown University, Providence, RI, USA; Centre for Sleep Research, University of South Australia, Adelaide, SA, Australia. Electronic address: cassie.hilditch@mymail.unisa.edu.au.
authors.forename: Cassie J
authors.initials: CJ
authors.lastname: Hilditch
authors.affiliation: Centre for Sleep Research, University of South Australia, Adelaide, SA, Australia.
authors.forename: Jillian
authors.initials: J
authors.lastname: Dorrian
authors.affiliation: Centre for Sleep Research, University of South Australia, Adelaide, SA, Australia.
authors.forename: Siobhan
authors.initials: S
authors.lastname: Banks
mesh_terms: D005260:Female; D006801:Humans; D008297:Male; D012890:Sleep; D014851:Wakefulness
keywords: Evidence-based practice; Napping policy; Performance; Shift work; Sleepiness; Slow wave sleep