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.