Multiple sleep latency test (MSLT)
The Multiple Sleep Latency Test (MSLT) is a sleep disorder diagnostic tool. It is used to measure the time elapsed from the start of a daytime nap period to the first signs of sleep, called sleep latency. The test is based on the idea that the sleepier people are, the faster they will fall asleep.
The MSLT can be used to test for narcolepsy, to distinguish between physical tiredness and true excessive daytime sleepiness, or to assess whether treatments for breathing disorders are working. Its main purpose is to serve as an objective measure of sleepiness.
The test consists of four or five 20-minute nap opportunities that are scheduled two hours apart. The test is often performed after an overnight sleep study. During the test, data such as the patient's brain waves, EEG, muscle activity, and eye movements are monitored and recorded. The entire test normally takes about 7 hours.
The MSLT is used extensively to test sleepiness in a number of research protocols.