title: The utility of a 5(th) nap in multiple sleep latency test.
abstract: BACKGROUND
  This is the first study that aimed to look specifically at the utility of the 5(th) nap in the multiple sleep latency test (MSLT), a test used to assist in the diagnosis of narcolepsy.
  
  
  METHODS
  Data was retrospectively collected from the Sleep Disorders Centre of a Tertiary Hospital on patients that had a 5(th) nap during their MSLT from the 08(th) November 2011 to 12(th) November 2014.
  
  
  RESULTS
  Fifty-three patients had a 5(th) nap performed out of 378 MSLT studies. In 16% of cases a diagnosis of narcolepsy was given directly due to the inclusion of the 5(th) nap on the MSLT. Here a 5(th) nap allowed diagnostic criteria of mean sleep latency <8 minutes and >2 SOREMPS to be met. In 53% of cases the mean sleep latency increased due to 5(th) nap inclusion; the mean sleep latency of the first four naps was 5.6 vs. 6.7 after inclusion of the 5(th) nap.
  
  
  CONCLUSIONS
  The 5(th) nap is not often performed within the MSLT studies. Our study shows that only a few patients may benefit from a 5(th) nap opportunity which also led to increase of the mean sleep latency at the expense of extra time, cost, labour and increased patient anxiety.
authors.affiliation: 1 Sleep Disorders Centre, Nuffield House, Guy's and St Thomas' NHS Trust, London, UK ; 2 Department of Pulmonary Medicine, University Hospital of Patras, Rio Patras, Greece ; 3 School of Medical Education, King's College London, London, UK.
authors.forename: Rexford
authors.initials: R
authors.lastname: Muza
authors.affiliation: 1 Sleep Disorders Centre, Nuffield House, Guy's and St Thomas' NHS Trust, London, UK ; 2 Department of Pulmonary Medicine, University Hospital of Patras, Rio Patras, Greece ; 3 School of Medical Education, King's College London, London, UK.
authors.forename: Dimosthenis
authors.initials: D
authors.lastname: Lykouras
authors.affiliation: 1 Sleep Disorders Centre, Nuffield House, Guy's and St Thomas' NHS Trust, London, UK ; 2 Department of Pulmonary Medicine, University Hospital of Patras, Rio Patras, Greece ; 3 School of Medical Education, King's College London, London, UK.
authors.forename: Kate
authors.initials: K
authors.lastname: Rees
keywords: Narcolepsy; multiple sleep latency test (MSLT); sleep diagnostics; sleep onset rapid eye movement (SOREM)