What are Sleep Studies?

What Are Sleep Studies and Who Needs Them?

This page also covers:

* What To Expect Before and What To Expect During and What To Expect After
* What Do Sleep Studies Show
* What Are the Risks
* Key Points to Remember About Sleep Studies

Sleep studies allow doctors to measure how much and how well you sleep. They also help show whether you have sleep problems and how severe they are.

Sleep studies are important because untreated sleep disorders can increase your risk of high blood pressure, heart attack, stroke, and other medical conditions. Sleep disorders also have been linked to an increased risk of injury due to falls and car accidents.

People usually aren’t aware of their breathing and movements while sleeping. They may never think to talk to their doctors about sleep- and health-related issues that may be linked to sleep problems.

Doctors can diagnose and treat sleep disorders. Talk with your doctor if you snore regularly or feel very tired while at work or school most days of the week.

You also may want to talk with your doctor if you often have trouble falling or staying asleep, or if you wake up too early and aren’t able to go back to sleep. These are common signs of a sleep disorder.

Doctors can diagnose some sleep disorders by asking questions about your sleep schedule and habits and by getting information from sleep partners or parents. To diagnose other sleep disorders, doctors also use the results from sleep studies and other medical tests.

Sleep studies can help doctors diagnose:

* Sleep-related breathing disorders (such as sleep apnea)
* Sleep-related seizure disorders
* Narcolepsy

You can find more information on sleep and sleep disorders in the National Heart, Lung, and Blood Institute’s “Your Guide to Healthy Sleep.”

Who Needs a Sleep Study?

If you often feel very sleepy, even though you’ve spent enough time in bed to be well rested, talk with your doctor about whether you might benefit from a sleep study.

Doctors can diagnose some sleep disorders by asking questions about your sleep schedule and habits and by getting information from sleep partners or parents. To diagnose other sleep disorders, doctors also use the results from sleep studies and other medical tests.

Sleep studies often are used to diagnose sleep-related breathing disorders. Signs of these disorders include loud snoring, gasping, or choking sounds while you sleep or pauses in breathing during sleep.

Other common signs and symptoms of sleep disorders include the following:

* It takes you more than 30 minutes to fall asleep at night.
* You often wake up during the night and then have trouble falling back to sleep, or you wake up too early and aren’t able to go back to sleep.
* You feel sleepy during the day and fall asleep within 5 minutes if you have a chance to nap, or you fall asleep at inappropriate times during the day.
* You have creeping, tingling, or crawling feelings in your legs that are relieved by moving or massaging them, especially in the evening and when you try to fall asleep.
* You have vivid, dreamlike experiences while falling asleep or dozing.
* You have episodes of sudden muscle weakness when you’re angry, fearful, or when you laugh.
* You feel as though you can’t move when you first wake up.
* Your bed partner notes that your legs or arms jerk often during sleep.
* You regularly feel the need to use stimulants, such as caffeine, to stay awake during the day.

Talk with your doctor if you have any signs or symptoms of a sleep disorder. It’s important to note how tired you feel and whether your signs and symptoms affect your daily routine.

In infants and children, many of the same signs and symptoms of sleep disorders can occur. If your child has persistent snoring or other signs or symptoms of sleep problems, talk with his or her doctor.

If you’ve had a sleep disorder for a long time, it may be hard for you to notice how it affects your daily routine. Using a sleep diary, such as the one found in “Your Guide to Healthy Sleep,” may be helpful.

Your doctor will work with you to help decide whether you need a sleep study. A sleep study allows your doctor to observe sleep patterns and diagnose a sleep disorder, which can then be treated.

Certain medical conditions have been linked to sleep disorders. These include heart failure, coronary heart disease (also called coronary artery disease), obesity, diabetes, high blood pressure, and stroke or transient ischemic attack (TIA, or “mini-stroke”).

If you have or have had one of these conditions, talk with your doctor about whether it would be helpful to have a sleep study.

What To Expect Before a Sleep Study

Before a sleep study, your doctor may ask you about your sleep habits and whether you feel well rested and alert during the day.

You may be asked to keep a sleep diary or sleep log. You’ll record information such as when you went to bed, when you woke up, how many times you woke up during the night, and more.

You can find an example of a sleep diary in the National Heart, Lung, and Blood Institute’s “Your Guide to Healthy Sleep.”
What To Bring With You

Depending on what type of sleep study you’re having, you may need to bring:

* Notes from your sleep diary or sleep log. These may be helpful to your doctor.
* Pajamas and a toothbrush for overnight sleep studies.
* A book or something to do between testing periods if you’re having a maintenance of wakefulness test (MWT) or multiple sleep latency test (MSLT).

How To Prepare

You may need to stop or limit the use of tobacco, caffeine and other stimulants, and some medicines before having a sleep study.

Your doctor may ask you about alcohol, medicines, or other substances that you take. Make sure you tell your doctor about all of the medicines you take, including over-the-counter products. Your doctor also may ask about any allergies you have.

Talk with your doctor before the sleep study and never stop taking your medicines unless the doctor who prescribed them tells you to do so.

You should try to sleep well the night before you have an MWT because you’ll have to try to stay awake during the test. If you’re being tested as a requirement for a transportation- or safety-related job, you may be asked to take a drug-screening test.

You also should try to sleep well for a night or two before you have an MSLT because the results will be more accurate.

If you’re going to have a home-based sleep test with a portable monitor, you’ll need to visit a sleep center or your doctor’s office to pick up the equipment. Your doctor or a technician will tell you how to use the equipment.

What To Expect During a Sleep Study

Sleep studies are painless. The polysomnogram (PSG), multiple sleep latency test (MSLT), and maintenance of wakefulness test (MWT) usually are done at a sleep center.

The room the sleep study is done in may look like a hotel room. A technician makes the room comfortable for you and sets the temperature to your liking.

Most of your contact at the sleep center will be with nurses or technicians. You can ask them questions about the sleep study. They can answer questions about the test itself, but they usually can’t give you the test results.
During a Polysomnogram

Sticky patches and sensors called electrodes are placed on your scalp, face, chest, limbs, and a finger. While you sleep, these sensors record your brain activity, eye movements, heart rate and rhythm, blood pressure, and the amount of oxygen in your blood.

Elastic belts are placed around your chest and abdomen. They measure chest movements and the strength and duration of inhaled and exhaled breaths.

Wires attached to the sensors transmit the data to a computer in the next room. The wires are very thin and flexible and are bundled together so they don’t restrict movement, disrupt your sleep, or cause other discomfort.

The illustration shows the standard setup for a polysomnogram. In figure A, the patient lies in a bed with sensors attached to the body. In figure B, the polysomnogram recording shows the blood oxygen level, breathing event, and rapid eye movement (REM) sleep stage over time.

The illustration shows the standard setup for a polysomnogram. In figure A, the patient lies in a bed with sensors attached to the body. In figure B, the polysomnogram recording shows the blood oxygen level, breathing event, and rapid eye movement (REM) sleep stage over time.

If you have signs of sleep apnea, you may have a split-night sleep study. During the first half of the night, the technician records your sleep patterns. At the start of the second half of the night, he or she wakes you to fit a CPAP (continuous positive airway pressure) mask over your nose and/or mouth.

The mask is connected to a small machine that gently blows air through the mask. This creates mild pressure that keeps your airway open while you sleep.

The technician checks how you sleep with the CPAP machine. He or she adjusts the flow of air through the mask to find the setting that’s right for you.

At the end of the PSG, the technician removes the sensors. If you’re having a daytime sleep study, such as an MSLT, some of the sensors may be left on for that test.

Parents usually are required to spend the night with their child during the child’s PSG.
During a Multiple Sleep Latency Test

The MSLT is a daytime sleep study that’s usually done after a PSG. Sensors on your scalp, face, and chin usually are used for this test. These sensors record brain activity. They show various stages of sleep and how long it takes you to fall asleep. Sometimes your breathing also is checked during an MSLT.

A technician in another room watches these recordings as you sleep. He or she fixes any problems with the recordings that occur.

About 1.5 to 3 hours after you wake from the PSG, you’re asked to relax in a quiet room for about 30 minutes. The test is repeated four or five times throughout the day. This is because your ability to fall asleep changes throughout the day.

You get 2-hour breaks between tests. You need to stay awake during the breaks.

The MSLT records whether you fall asleep during the test and what types and stages of sleep you have. Sleep has two basic types: rapid eye movement (REM) and non-REM. Non-REM sleep has three distinct stages. REM sleep and the three stages of non-REM sleep occur in patterns throughout the night.

The types and stages of sleep you have during the day can help your doctor diagnose sleep disorders such as narcolepsy and idiopathic hypersomnia.
During a Maintenance of Wakefulness Test

This sleep study occurs during the day. It’s usually done after a PSG and takes most of the day. Sensors on your scalp, face, and chin are used to measure when you’re awake or asleep.

You sit quietly on a bed in a comfortable position and look straight ahead. Then you simply try to stay awake for a period of time.

An MWT typically includes four trials lasting about 40 minutes each. If you fall asleep, the technician will wake you after about 90 seconds. There usually are 2-hour breaks between trials. During these breaks, you can read, watch television, etc.

If you’re being tested as a requirement for a transportation- or safety-related job, you may need a drug-screening test before a MWT.
During a Home-Based Portable Monitor Test

If you’re having a home-based portable monitor test, you’ll need to set up the equipment at home before you go to sleep. When you pick up the equipment at the sleep center or your doctor’s office, someone will tell you how to use it.
During Actigraphy

You don’t have to go to a sleep center for this test. An actigraph is a small device that’s usually worn like a wristwatch. You can go about your normal routine while you wear it. You remove it while bathing or swimming.

The actigraph measures your sleep–wake behavior over 3 to 7 days and nights. Results give your doctor a better idea about your sleep habits, such as when you sleep or nap and whether the lights are on while you sleep.

You may be asked to keep a sleep diary while you wear an actigraph.

What To Expect After a Sleep Study

Once the sensors are removed after a polysomnogram (PSG), multiple sleep latency test, or maintenance of wakefulness test, you can go home. If you used an actigraph or a home-based portable monitor, you’ll return the equipment to a sleep center or your doctor’s office.

You won’t receive a diagnosis right away. Your primary care doctor or sleep specialist will review the results of your sleep study or sleep studies. He or she will use your medical history, your sleep history, and the test results to make a diagnosis.

It may take a couple of weeks to get the sleep study results. Usually, your doctor, nurse, or sleep specialist will explain the test results and work with you and your family to develop a treatment plan.

What Do Sleep Studies Show?

Sleep studies allow doctors to watch sleep patterns and note sleep-related problems that patients don’t know or can’t describe during routine office visits. These studies are needed to diagnose certain sleep disorders, such as narcolepsy and sleep apnea.

After your sleep study, your doctor will get the results. The results may include information about sleep and wake times, sleep stages, abnormal breathing, the amount of oxygen in your blood, and any movement during sleep.

Your doctor will use your sleep study results and your medical and sleep histories to make a diagnosis and create a treatment plan.
Results From a Polysomnogram

Polysomnogram (PSG) results are used to help diagnose:

* Sleep-related breathing disorders, such as sleep apnea
* Narcolepsy (PSG and multiple sleep latency test (MSLT) results will be reviewed together)
* Sleep-related seizure disorders

If you have sleep apnea, your doctor also may use a PSG to find the correct setting for you on a CPAP (continuous positive airway pressure) machine.

A CPAP machine gently supplies air to your nose and/or mouth through a special mask. Finding the right setting involves adding just enough extra air to create mild pressure that keeps your airway open while you sleep.

Your doctor may recommend a followup PSG to:

* Adjust your CPAP settings after weight loss or weight gain
* Recheck your sleep if symptoms return despite treatment with CPAP
* Find out how well surgery has worked to correct a sleep-related breathing disorder

Technicians also use PSGs to record the number of abnormal breathing events that occur with sleep-related breathing disorders, such as sleep apnea. These events include either pauses in breathing or dips in the level of oxygen in your blood.

In adults, when the number of events is 10 or more per hour, treatment may be needed. Children who have one to three events per hour also may need treatment.
Results From a Multiple Sleep Latency Test

MSLT results are used to help diagnose narcolepsy and idiopathic hypersomnia.

For narcolepsy, technicians study how quickly you fall asleep. The MSLT also shows how long it takes you to reach different types and stages of sleep.

Sleep has two basic types: rapid eye movement (REM) and non-REM. Non-REM sleep has three distinct stages. REM sleep and the three stages of non-REM sleep occur in patterns throughout the night.

People who fall asleep in less than 5 minutes or quickly reach REM sleep may need treatment for a sleep disorder.
Results From a Maintenance of Wakefulness Test

Maintenance of wakefulness test (MWT) results may be used to show whether your inability to stay awake is a public or personal safety concern. This study also is used to show how well treatment for a sleep disorder is working.
Results From a Home-Based Portable Monitor Test

Home-based portable monitors (PMs) may be used to help diagnose sleep apnea. PMs also can show how well some treatments for sleep apnea are working.

Sometimes, home-based PMs don’t record enough information for doctors to make accurate diagnoses. If this happens, you may be asked to take the PM home again and repeat the test, or your sleep specialist may ask you to have a PSG.
Results From Actigraphy

Actigraphy results give your doctor a better idea about your sleep habits, such as when you sleep or nap and whether the lights are on while you sleep. This test also is used to help diagnose circadian rhythm disorders.

What Are the Risks of Sleep Studies?

Sleep studies are painless. There’s a small risk of skin irritation from the sensors. The irritation will go away once the sensors are removed.

Although the risks of sleep studies are minimal, these studies take time (at least several hours). If you’re having a daytime sleep study, bring a book or something to do during the test.

Key Points

* Sleep studies allow doctors to measure how much and how well you sleep. They also help show whether you have sleep problems and how severe they are.
* Sleep studies are important because untreated sleep disorders can increase your risk of high blood pressure, heart attack, stroke, and other medical conditions. Sleep disorders also have been linked to an increased risk of injury due to falls and car accidents.
* People usually aren’t aware of their breathing and movements while sleeping. They may never think to talk to their doctors about sleep- and health-related issues that may be linked to sleep problems.
* Sleep studies can help doctors diagnose sleep-related breathing disorders (such as sleep apnea), sleep-related seizure disorders, and narcolepsy.
* To diagnose sleep-related problems, doctors may use one or more of the following sleep studies:
o A polysomnogram (PSG) is an overnight sleep study that records brain activity, eye movements, heart rate, and blood pressure. It also records the amount of oxygen in your blood, how much air is moving through your nose while you breathe, snoring, and chest movements that show whether you’re making an effort to breathe. Your doctor also may use a PSG to find the correct setting for you on a CPAP (continuous positive airway pressure) machine.
o A multiple sleep latency test (MSLT) is a daytime sleep study that measures how sleepy you are. It records brain activity to show various stages of sleep. It also shows how long it takes you to fall asleep.
o A maintenance of wakefulness test (MWT) is a daytime sleep study that measures your ability to stay awake. Results may be used to show whether your inability to stay awake is a public or personal safety concern or to check your response to treatment.
o A home-based portable monitor (PM) records some of the same information as a PSG. Results may help your doctor diagnose sleep apnea. Results also can show how well some treatments for sleep apnea are working.
* Your doctor may use a test called actigraphy if he or she thinks you have a circadian rhythm disorder. Actigraphy measures sleep–wake behavior while you go about your normal routine. Results give your doctor a better idea about your sleep habits, such as when you sleep or nap and whether the lights are on while you sleep. An actigraph is a small device that’s usually worn like a wristwatch.
* If you often feel very sleepy, even though you’ve spent enough time in bed to be well rested, talk with your doctor about whether you might benefit from a sleep study.
* Sleep studies often are used to diagnose and treat sleep-related breathing disorders. Signs of these disorders include loud snoring, gasping, or choking sounds while you sleep or pauses in breathing during sleep. Other common signs of sleep disorders are listed in “Who Needs a Sleep Study.”
* Certain medical conditions have been linked to sleep disorders. These include heart failure, coronary heart disease, obesity, diabetes, high blood pressure, and stroke or transient ischemic attack (TIA, or “mini-stroke”). If you have one of these conditions, talk with your doctor about whether it would be helpful to have a sleep study.
* Before a sleep study, your doctor may ask you to keep a sleep diary or sleep log. You’ll record information such as when you went to bed, when you woke up, how many times you woke up during the night, and more.
* You also may need to stop or limit the use of tobacco, caffeine and other stimulants, and some medicines before having a sleep study. Talk with your doctor before the sleep study and never stop taking your medicines unless the doctor who prescribed them tells you to do so.
* Sleep studies are painless. The PSG, MSLT, and MWT usually are done in a sleep center. The room the study is done in may look like a hotel room. Some people may be able to use home-based PMs to do sleep studies in their own homes.
* If you’re having actigraphy, you’ll go about your normal daily routine while you wear an actigraph on your wrist. An actigraph is a device that records data about your sleep habits.
* After a sleep study, your doctor will get the results. The results may include information about sleep and wake times, sleep stages, abnormal breathing, the amount of oxygen in your blood, and any movement during sleep.
* Your doctor will study the results and use them and your medical and sleep histories to make a diagnosis and help develop a treatment plan. You may not get the diagnosis until a few weeks after the sleep study.
* The risks of sleep studies are minimal. There is a small risk of skin irritation from the sensors. The irritation will go away once the sensors are removed.