What is the role of the multiple sleep latency test (MSLT) in the diagnosis of obstructive sleep apnea (OSA)?

Updated: Sep 15, 2020
  • Author: Himanshu Wickramasinghe, MD, MBBS; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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The MSLT may follow PSG. It is considered an objective measurement of excessive daytime sleepiness (EDS). The MSLT consists of 4-5 naps of 20-minute duration every 2 hours during the day. The latency to sleep onset for each nap is averaged to determine the daytime sleep latency. Normal daytime sleep latency is greater than 10-15 minutes. OSAHS is generally associated with latencies of less than 10 minutes. It is not uncommon for the MSLT to demonstrate profound daytime sleepiness in OSA patients; mean sleep latency cannot discriminate between patients with OSA and patients with narcolepsy.

Routine use of the MSLT in the evaluation of OSA has significantly decreased because sleep physicians generally treat OSA on basis of the subjective symptoms reported by the patient. The MSLT is generally used to confirm the diagnosis of narcolepsy in patients in whom narcolepsy is a consideration. As opposed to people without narcolepsy, narcoleptic patients have rapid eye movement sleep on at least 2 of the 4-5 naps during the day.

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