Sometimes people also need to have their daytime sleep tested. There are two main tests, the Multiple Sleep Latency Test (MSLT) or the Maintenance of Wakefulness Test (MWT). In sleep centers the MSLT used primarily, so that’s the one we will discuss here.
The MSLT is conducted the day following an overnight study, and begins 2 hours after waking. Patients should sleep on their regular schedule the night before, and get dressed for the day. The patient lies down in bed, and allows himself to fall asleep. After 20 minutes the nap test is over. The test is repeated every two hours for a total of 4 or 5 naps. The data from all tests is averaged.
The sleep specialist is measuring how long it takes the patient to fall asleep, and whether the patient had REM sleep. This helps assess how sleepy the person is. It is considered normal to fall asleep in 15 minutes, sleepy if sleep occurs in less than 10 minutes. Narcolepsy is characterized by a sleep onset of less than 8 minutes, with 2 sleep onset REM periods. We’ll talk more about narcolepsy in the next post.
First of all, know that almost all people sleep just fine in the sleep lab. Before and during medical school I worked as a PSG tech, so I know this is true from seeing hundreds of people sleep well.
You’ll be asked to arrive at the lab about 7pm. You will work with one staff called a PSG Tech throughout your stay. He or she will show you the bedroom, and hook the testing equipment to you. They will monitor you throughout the night and unhook the testng equipment in the morning. If you need to use the restroom in the night, no problem, simply call out to let the Tech know.
Most sleep labs have bedrooms that look like hotel rooms with a double or queen-sized bed. You are welcome to bring your most comfortable pillow, and a favorite book or movie to enjoy before bed.
Keep in mind the information gathered during the overnight sleep study is so valuable in diagnosing and treating sleep problems that it is well worth it.
What data is collected during the sleep study?
There are thin electrodes placed on your scalp with paste, at the outer corner of each eye, and on your chin. These are used to determine whether you are awake or asleep, and what stage of sleep you are in.
Additional testing equipment includes elastic bands around your chest to measure your breathing effort, EKG pads on your chest to monitor your heart, and electrodes on your legs to monitor leg movements. You will also have a sensor on one finger to measure your blood oxygen level.
From this monitoring equipment physicians can see how your sleep cycles looked, and percentage of each sleep stage. Also can see if you had any sleep breathing or movement disorder, or other more rare sleep disorder.
Next blogpost we’ll talk about ways to be most comfortable during the overnight sleep test.
Sometimes people who are sleeping poorly don’t know whether they need an overnight sleep study or not. The sleep study is also called polysomnography, or PSG for short. There are about 80 sleep disorders. Some of these sleep disorders require an overnight sleep study, though many do not. Here is a list:
Sleep study is NOT required for:
• Circadian Rhythm Disorders such as Delayed Sleep Phase Syndrome
• Most Parasomnias
• Some Hypersomnias such as
• Some movement disorders such as Restless Legs Syndrome
Overnight sleep study IS required for:
• Sleep disordered breathing, including Sleep Apnea
• Periodic Limb Movement Disorder
• Some Parasomnias, including REM Behavior Disorder
Next blog post we’ll continue this discussion by describing exactly what data is collected in the sleep study.