Why it's done

Polysomnography monitors your sleep stages and cycles to identify if or when your sleep patterns are disrupted and why.

There are different types of home sleep apnea test devices using different combinations of sensors. They generally record your breathing rate and airflow, as well as oxygen levels and heart rate. One style also incorporates information on blood vessel tone.

The normal process of falling asleep begins with a sleep stage called non-rapid eye movement (NREM) sleep. During this stage, your brain waves, as recorded by electroencephalography (EEG), slow down considerably.

Your eyes don't move back and forth rapidly during NREM, in contrast to later stages of sleep. After an hour or two of NREM sleep, your brain activity picks up again, and rapid eye movement (REM) sleep begins. Most dreaming occurs during REM sleep.

You normally go through multiple sleep cycles a night, cycling between NREM and REM sleep in about 90 minutes. Sleep disorders can disturb this sleep process.

Your doctor may recommend polysomnography if he or she suspects you have:

• Sleep apnea or another sleep-related breathing disorder. In this condition, your breathing repeatedly stops and starts during sleep.
• Periodic limb movement disorder. In this sleep disorder, you involuntarily flex and extend your legs while sleeping. This condition is sometimes associated with restless legs syndrome.
• Narcolepsy. You experience overwhelming daytime drowsiness and sudden attacks of sleep in this condition.
• REM sleep behavior disorder. This sleep disorder involves acting out dreams as you sleep.
• Unusual behaviors during sleep. Your doctor may perform this test if you do unusual activities during sleep, such as walking, moving around a lot or rhythmic movements.
• Unexplained chronic insomnia. If you consistently have trouble falling asleep or staying asleep, your doctor may recommend polysomnography.