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 repeated muscle twitching 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.