Overview
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.
In addition to diagnosis, a sleep study might help determine a treatment plan if you've been diagnosed with a sleep disorder. It also might be used to adjust your treatment.
Sometimes you may be able to do the sleep study at home. Home sleep apnea tests are used to help diagnose obstructive sleep apnea.
If you're doing a sleep study from home, there are different types of devices that may be used. Each device uses a different combination of sensors. Home sleep apnea tests generally record your breathing rate and airflow, as well as oxygen levels and heart rate. Home test results also may include information on blood vessels.
Risks
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.
How you prepare
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 healthcare professional's office. You'll be given instructions on how to use the equipment. Ask questions if you are not sure about how the test or equipment works.
Results
The measurements recorded during a sleep study provide a great deal of information about your sleep patterns. For example:
- Brain waves and eye movements during sleep can help your healthcare team assess your sleep stages. This helps identify disruptions in the stages. These disruptions may occur due to sleep disorders such as narcolepsy or REM sleep behavior disorder.
- Heart and breathing rate changes and changes in blood oxygen that aren't typical during sleep may suggest sleep apnea.
- Using PAP or oxygen can let your healthcare professional know which device settings work best for you. This helps if your healthcare professional would like to prescribe the device for home use.
- Frequent leg movements that disrupt your sleep may mean you have periodic limb movement disorder.
- Movements or behaviors during sleep may be signs of REM sleep behavior disorder or another sleep disorder.
The information gathered during a sleep study is evaluated first by a polysomnography technologist. The technologist uses the data to chart your sleep stages and cycles. Then the information is reviewed by your healthcare professional.
If you've had a home sleep apnea test, your healthcare professional reviews the information collected during the test. It may take a few days or weeks to get your results.
At a follow-up appointment, your healthcare professional reviews the results with you. Based on the data gathered, your healthcare professional discusses any treatment or further evaluation that you may need.
If you've had a home sleep apnea test, sometimes the results don't provide enough information. If this happens, your healthcare professional may recommend a sleep study in a sleep center.