What is a sleep study?

A sleep study, also known as polysomnography, is a test that measures and records different body functions while you sleep. These include your:

• Breathing rate
• Blood oxygen level
• Heart rate
• Brain waves
• Leg movements
• Eye movements

The test checks how well you are sleeping and can diagnose sleep disorders. Sleep disorders are conditions that cause problems with sleeping. They include trouble falling asleep, getting too much sleep, and irregular breathing during sleep.

Sleep disorders can affect your overall health, safety, and quality of life. Lack of sleep may increase your risk of serious conditions such as depression, diabetes, and heart disease. Daytime sleepiness may increase your risk of an accident while driving. Early diagnosis and treatment of a sleep disorder may help you avoid health complications.

Other names: polysomnography, sleep apnea study, home sleep study

What is it used for?

A sleep study is used to diagnose sleep disorders. Common sleep disorders include:

• Sleep apnea, a disorder that causes you to repeatedly stop breathing during sleep.
• Insomnia, a disorder that can make it hard for you to fall asleep and/or stay asleep throughout the night.
• Restless leg syndrome, a condition that causes uncomfortable feelings in your legs and a strong urge to move them while you try to fall asleep.
• Narcolepsy, a neurologic condition. It causes extreme sleepiness in the daytime. You may suddenly fall asleep during the day.

Why do I need a sleep study?

You may need this test if you have symptoms of a sleep disorder, such as:

• Loud snoring during sleep
• Waking up from sleep and gasping for breath
• Trouble falling and/or staying asleep
• Daytime sleepiness

What happens during a sleep study?

A sleep study is done during your normal sleeping hours. The study may be done at a hospital, a sleep study clinic, or in your own home. A home sleep study, also known as a sleep apnea study, is used to help diagnose sleep apnea. It does not diagnose other types of sleep disorders.

During a study at a hospital or sleep clinic:

• You will arrive at the hospital or clinic in the evening and stay overnight.
• You may bring your bedclothes to wear.
• You will stay in a private, comfortable bedroom with a private bathroom, similar to a hotel room.
• Many sleep study rooms will have a low-light video camera to record your sleep movements during the night.
• A health care provider will attach electrodes (small metal disks) to your scalp, eyelids, chin, chest, and legs. After the sensors are connected, your provider may ask you to move these body parts to make sure the sensors are working well.
• The electrodes will be connected to a computer with wires. The wires will be long enough to allow you to move during sleep. If you have to get up at night to use the bathroom, you may need the staff to assist you with the wires.
• The electrodes record different body functions, such as breathing, heart rate, muscle movement, brain waves, and leg and eye movements.
• A small clip, known as a pulse oximeter, will also be placed on your finger or ear to monitor the oxygen level in your blood.
• The lights will be turned off.
• While you sleep, specially trained providers known as polysomnography technologists will monitor you through the night with video and audio equipment. They'll check for when you fall asleep and monitor your breathing, heart rate, and other body functions.
• If you need assistance during the night, you can talk to a polysomnography technologist through the monitoring equipment.
• You will be woken up in the morning, and your electrodes will be removed.
• You may be asked to fill out a questionnaire about your night's sleep.

During a home sleep study:

• You will pick up sleep study equipment at your provider's office, or it may be delivered to you.
• Your provider will provide thorough instructions on how to use the equipment. Be sure to ask if you have any questions.
• On the night of your study, you will attach the electrodes to your body and connect them to a sleep monitoring device.
• The electrodes will record different body functions, including your breathing rate, heart rate, blood oxygen levels, and snoring.
• In the morning, you'll remove the electrodes and return the sleep monitoring device as directed by your provider.

A home sleep study uses fewer sensors than a sleep study at a hospital or sleep clinic. It is used to diagnose obstructive sleep apnea. But this test is not recommended if you have other sleep disorders or health conditions that could make your breathing more difficult.

Will I need to do anything to prepare for the test?

The preparations are the same whether you are being tested at a hospital, clinic, or your home. To prepare for your sleep study:

• Avoid alcohol and caffeine during the afternoon and evening before your test. They can disrupt your normal sleep patterns.
• Don't nap during the day. It may make it harder for you to fall asleep at night.
• Don't use lotions, hair gels, or makeup before the test. They can affect the way the electrodes work.
• Avoid using nail polish or artificial nails. The pulse oximeter is attached to your finger, and this can affect the readings.

If you normally take sleep medicines, talk to your provider about whether or not you should take the medicine before the test.

Are there any risks to the test?

You may have some mild skin irritation from the electrodes. There are no other known risks to having a sleep study.

What do the results mean?

Your results may include measurements of the following:

• Apnea Hypopnea Index (AHI). This looks at how many episodes of sleep apnea happen in a night. If you have more than five episodes, it probably means you have sleep apnea.
• Sleep efficiency. This is a calculation based on the total number of minutes you sleep during the night compared with the amount of time you spend in bed. So if you spend a long time in bed without being able to sleep, you would have low sleep efficiency.
• Oxygen Desaturation Index (ODI). This measures the number of times your oxygen level drops during sleep. Lower than 90 percent oxygen is considered abnormal.
• Heart rate. A normal heart rate is between 60 and 100 beats per minute. This result will show if your heart is beating faster or slower than normal.

Your provider will review all the results and, if appropriate, provide a treatment plan. If you have questions about your results, talk to your provider.

Is there anything else I need to know about a sleep study?

You may not sleep as well during the sleep study, but a full night's sleep isn't necessary to get results.

If you've been diagnosed with sleep apnea, your provider may recommend:

• Lifestyle changes, such as losing weight, avoiding alcohol, and quitting smoking. Your provider may also recommend avoiding sleeping on your back, which may worsen your sleep apnea.
• A continuous positive airway pressure (CPAP) machine. A CPAP provides a gentle and steady pressure of air into your airway to keep it open. You wear a mask over your nose and mouth while sleeping. The mask is connected by a hose to a small machine by your bed that pumps air through the hose and mask.
• Dental devices, such as a:
  • Mouth guard, which helps prevent you from grinding your teeth during sleep (sleep bruxism). Many people with sleep apnea also have sleep bruxism.
  • Mandibular advancement device, a small plastic device that pulls the lower jaw and tongue forward. This helps keep the airways open during sleep.
  • Tongue-retaining device, which uses suction to keep the tongue forward. If the tongue moves back, it can block your airway.

If other treatments have failed, your provider may recommend a surgical procedure to correct problems in your throat, nose, or jaw.

Treatments for other sleep disorders will depend on the specific condition and your specific health needs.