Polysomnography (sleep study)

Polysomnography, known as a sleep study, is a test used to diagnose sleep disorders. Polysomnography records your brain waves, the oxygen level in your blood, and your heart rate and breathing during sleep. It also measures eye and leg movements. A sleep study may be done at a sleep disorders unit within a hospital or at a sleep center. The test is usually performed at night. But it may be done during the day for shift workers who usually sleep in the daytime.

Polysomnography monitors your sleep stages and cycles. It can identify if or when your sleep patterns are disrupted and why. The typical process of falling asleep begins with a sleep stage called non-rapid eye movement (NREM) sleep. During this stage, brain waves slow down. This is recorded during a sleep study with a test called an electroencephalogram (EEG). After an hour or two of NREM sleep, brain activity picks up again. This sleep stage is called rapid eye movement (REM) sleep. Your eyes quickly move back and forth during REM sleep. Most dreaming occurs during this stage of sleep. You typically go through multiple sleep cycles a night. You cycle between NREM and REM sleep in about 90 minutes. But sleep disorders can interfere with this sleep process. Your health care provider may recommend a sleep study if it's suspected that you have: Sleep apnea or another sleep-related breathing disorder. In this condition, breathing stops and starts repeatedly during sleep. Periodic limb movement disorder. People with this sleep disorder flex and extend their legs while sleeping. This condition is sometimes linked to restless legs syndrome. Restless legs syndrome causes an uncontrollable urge to move the legs while you're awake, usually in the evenings or at bedtime. Narcolepsy. People with narcolepsy experience overwhelming daytime drowsiness. They can fall asleep suddenly. REM sleep behavior disorder. This sleep disorder involves acting out dreams during sleep. Unusual behaviors during sleep. This includes walking, moving around or rhythmic movements during sleep. Unexplained long-lasting insomnia. People with insomnia have trouble falling asleep or staying asleep.

Polysomnography is a noninvasive, painless test. The most common side effect is skin irritation. This can be caused by the adhesive used to attach the test sensors to your skin.

Don't consume drinks or food containing alcohol or caffeine during the afternoon and evening before a sleep study. Alcohol and caffeine can change your sleep patterns. They may make symptoms of some sleep disorders worse. Also don't nap in the afternoon before a sleep study. You may be asked to bathe or shower before your sleep study. But don't put on lotions, gels, colognes or makeup before the test. They can interfere with the test's sensors, called electrodes. For a home sleep apnea test, the equipment is delivered to you. Or you might pick up the equipment at your provider's office. You'll be given instructions on how to use the equipment. Ask questions if you're unsure about how the test or equipment works.