Sleep Studies: What You Need to Know Before You Go

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.
• Problems sleeping during the day because you work at night or do rotating shift work. This sleep problem is called shift work sleep disorder.
• 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.

If your doctor thinks that you may have shift work sleep disorder or another problem with your body's internal clock (circadian rhythm), you may have a test called actigraphy. For this test, you wear a device on your wrist that looks like a watch. The device measures your movement during sleep and when you are awake. It helps your doctor learn what times during the day you are active and what times you are sleeping.

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?