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Daytime Sleep Studies

Multiple Sleep Latency Test

image of patient results

This daytime sleep study measures how sleepy you are. It typically is 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 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.

The types and stages of sleep you have can help your doctor diagnose 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.

An MSLT takes place over the course of a full day. This is because your ability to fall asleep changes throughout the day.

Maintenance of Wakefulness Test

This daytime sleep study measures your ability to stay awake and alert. It's usually done the day after a PSG and takes most of the day.

Results can show whether your inability to stay awake is a public or personal safety concern. Results also can show how you're responding to treatment.

Source: National Heart, Lung, and Blood Institute