The Maintenance of Wakefulness Test (MWT) measures daytime sleepiness. It’s used to diagnose conditions like narcolepsy and to assess the effectiveness of treatment for conditions like sleep apnea.

If you have difficulty staying awake during the day, you may have a medical condition. The Maintenance of Wakefulness Test (MWT) is one method doctors use to assess how well you stay awake when you need to. This exam measures how quickly you fall asleep during what would be your typical wakeful periods of time.

This test can help diagnose medical conditions that affect your sleep or make it harder for you to stay awake when you need to. It can also help determine if treatment for conditions like sleep apnea is effective.

Read on to learn more about this noninvasive test and what to expect if you need one.

The MWT tests your ability to stay awake for a designated period of time during the day. It measures your ability to resist falling asleep. It’s also used to help diagnose and assess how effective treatment is for conditions like narcolepsy and sleep apnea.

The MWT is used to help diagnose some medical conditions that may affect sleep, like:

The test may also be helpful when assessing the effectiveness of treatments like medications or a CPAP machine, and determining whether people can safely work in safety-related jobs that require attentiveness.

An MWT is usually done in four, 40-minute sessions called wakeful periods. During each session, you will have electroencephalogram (EEG) electrodes temporarily glued to your scalp. During each wakefulness period, the EEG will measure your brain waves.

You will either be seated in a comfortable chair or lying in a bed. The room will be dark except for a dim light. You’ll be asked to sit still and look straight ahead during the test. You may not read, sing, check your phone, or do any other activity during each wakefulness period.

The session ends in 40 minutes, when you fall asleep for 90 seconds, or if you enter deep sleep for at least 30 seconds — whichever happens first.

Your first session begins 1.5 to 3 hours after you wake up in the morning. The other three sessions begin 2 hours after the start time of the previous wakefulness session.

You will be asked to follow your typical nighttime routine, take any medications you usually take, and use your CPAP if you have one.

The test measures the average time it takes you to fall asleep during each wakefulness session. A result of 20 or 30 minutes to fall asleep is typical. A significant number of people stay awake for the entire 40 minutes.

Falling asleep in less than 8 minutes is a sign of excessive sleepiness. Your sleep assessment team will interpret your specific results.

The night before your test, take your usual night-time medications unless instructed not to and use your CPAP if you have one.

Set an alarm so that you arrive at the testing center at the specified time. It’s important to start your test within 1.5 to 3 hours after you wake up.

You may need to avoid consuming:

  • tobacco
  • caffeine
  • alcohol
  • some medications

You will meet with your sleep specialist before the test, and they will ask about:

  • how much caffeine you typically consume and when
  • any prescription or over-the-counter medications or supplements you take
  • whether you use CPAP and which machine you use
  • how long and how well you typically sleep each night
  • whether you have any other medical conditions
  • anything else you want to share related to your sleep or daytime sleepiness

It’s a good idea to have someone available to drive you home following your MWT.

How is the MWT different from the Multiple Sleep Latency Test (MSLT)?

The major difference between these two assessment tests is that the Multiple Sleep Latency Test (MSLT) measures how quickly you can fall asleep for a nap during your wakeful hours, and the MWT measures how easily you can stay awake during your wakeful hours.

Can I drive after an MWT?

While you are not sedated during your MWT, it’s not a good idea to drive afterward since the test is long, and its main goal is to make you sleepy during your wakeful hours. You may be very sleepy following the test. It’s a good idea to plan for someone else to drive you home after your MWT or to arrange a safe, alternate way to get home.

Can medications affect MWT results?

Yes. Medications that induce sleepiness during daytime or wakeful hours and medications that cause increased alertness can affect the MWT results.

The American Academy of Sleep Medicine recommends that you stop taking prescription and over-the-counter medications with alerting or sedating effects before your MWT. Always consult with your primary care doctor or another healthcare professional before stopping any medication they have prescribed or recommended for you.

The MWT measures your ability to stay awake during your typical wakeful hours. This test helps doctors diagnose conditions that may cause daytime sleepiness, such as sleep apnea or narcolepsy. The MWT may also help doctors determine how effective treatment is for these conditions.

The MWT is noninvasive and is typically performed at a sleep study center, which may be an outpatient clinic or a department inside a hospital. It takes several hours. You will likely need to ask someone to drive you home afterward.