The utility of a 5th nap in multiple sleep latency test

Rexford Muza, Dimosthenis Lykouras, Kate Rees


Background: This is the first study that aimed to look specifically at the utility of the 5th 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 5th nap during their MSLT from the 08th November 2011 to 12th November 2014.
Results: Fifty-three patients had a 5th nap performed out of 378 MSLT studies. In 16% of cases a diagnosis of narcolepsy was given directly due to the inclusion of the 5th nap on the MSLT. Here a 5th 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 5th nap inclusion; the mean sleep latency of the first four naps was 5.6 vs. 6.7 after inclusion of the 5th nap.
Conclusions: The 5th nap is not often performed within the MSLT studies. Our study shows that only a few patients may benefit from a 5th nap opportunity which also led to increase of the mean sleep latency at the expense of extra time, cost, labour and increased patient anxiety.