Sleep studies are tests that watch what happens to your body during sleep. The studies are done to find out what is causing your sleep problems. Sleep problems include:

• Sleep apnea, when an adult regularly stops breathing during sleep for 10 seconds or longer. This may be caused by blocked airflow during sleep, such as from narrowed airways. Or it may be caused by a problem with how the brain signals the breathing muscles to work.
• Problems staying awake, such as narcolepsy.
• Problems with nighttime behaviors, such as sleepwalking, night terrors, or bed-wetting.
• Problems sleeping at night (insomnia). This may be caused by stress, depression, hunger, physical discomfort, or other problem.
• Conditions such as periodic limb movement disorder, which is continuous or wild movements of the feet, arms, or legs during sleep.

Sleep studies can also determine whether you have a problem with your stages of sleep. The two stages of sleep are non-rapid eye movement (NREM) and rapid eye movement (REM). Normally, NREM and REM alternate 4 to 5 times during a night's sleep. A change in this cycle may make it hard for you to sleep soundly.

The most common sleep studies are:

• Polysomnogram. This test records several body functions during sleep, including brain activity, eye movement, oxygen and carbon dioxide blood levels, heart rate and rhythm, breathing rate and rhythm, the flow of air through your mouth and nose, snoring, body muscle movements, and chest and belly movement.
• Multiple sleep latency test (MSLT). This test measures how long it takes you to fall asleep. A video camera is used to record movements during sleep.
• Multiple wake test (MWT). This test measures whether you can stay awake during a time when you are normally awake.

Sleep studies usually are done in a sleep lab. Sleep labs are often located in hospitals.

Should I have a sleep study to diagnose obstructive sleep apnea?

Health Tools

Health tools help you make wise health decisions or take action to improve your health.

Decision Points focus on key medical care decisions that are important to many health problems.

Why It Is Done

Sleep studies are done to find sleep problems, including:

• Sleep apnea. For more information, see the topic Sleep Apnea.
• Hypopnea, which is an abnormal decrease in air flow to your lungs.
• Excessive snoring.
• Insomnia.
• Narcolepsy.
• Heart rhythm problems.
• Periodic limb movement disorder.

How To Prepare

You likely will be asked to keep a sleep diary for 1 to 2 weeks before your sleep study. Try to follow your normal sleep routine during this time so you will not be too tired or too rested for your sleep test. Do not take any naps for 2 to 3 days before your test. See an example of a sleep diary(What is a PDF document?).