Multiple Sleep Latency Test (MSLT)
This daytime sleep study measures how sleepy you are. It is typically done the day after a PSG. You relax in a dark, quiet room for about 30 minutes while a technician checks your brain activity. The MSLT is used to typically diagnose narcolepsy and to measure the degree of daytime sleepiness. The types and stages of sleep you have can further help your doctor diagnose other sleep disorders, such as, narcolepsy, idiopathic hypersomnia (id-ee-o-PATH-ick HI-per-SOM-ne-ah), and other sleep disorders that cause daytime tiredness.
The MSLT measures how quickly you fall asleep in quiet situations during the day. It also monitors how quickly and how often you enter REM sleep. To ensure accurate results, it is performed two hours after waking up from the PSG and having breakfast. The MSLT takes place over the course of a full day, this is because of your ability to fall asleep changes throughout the day.
The study records whether you fall asleep during the test and what types and stages of sleep you're having. Sleep has two basic types: rapid eye movement (REM) and non-REM. Non-REM sleep has three distinct stages. REM sleep and the three stages of non-REM sleep occur in regular cycles throughout the night.