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Sleep Studies

(Polysomnography)

What is it?

A sleep study is a diagnostic test that involves recording multiple systems in your body while you sleep. Key body systems monitored include your brain, heart, breathing and more. This test isn’t painful and usually only takes one night to complete. This test is also very common and can help diagnose many sleep-related conditions.

Overview

What is a sleep study?

A sleep study, formally known as a polysomnogram (pronounced “poly-som-no-gram”), is a diagnostic test that tracks and records how multiple body systems work while you’re asleep. This test involves sensors that track the activity of multiple body systems, including your heart, brain and respiratory system, giving healthcare providers a comprehensive view of the quality of your sleep.

When is a sleep study necessary?

A sleep study is a diagnostic test, meaning that healthcare providers use it to diagnose or rule out health issues. Healthcare providers usually recommend this test when you have symptoms of conditions that affect sleep, to determine how to treat those conditions or to see if completed treatments worked. These are generally conditions that affect or disrupt your brain, nervous system, breathing and heart function.

Conditions that a sleep study can diagnose include:

Sleep apnea (obstructive and central).

Narcolepsy.

Periodic limb movement disorder (including restless legs syndrome).

Insomnia.

Certain types of seizures and epilepsy.

Night terrors (also known as sleep terrors).

Nocturnal panic attacks.

Sleepwalking or other sleep behavior-related disorders.

Sleep paralysis.

Other types of parasomnias and disruptive sleep disorders.

The National Heart, Lung, and Blood Institute (NHLBI) warns that if sleep disorders go untreated, they can raise your risk of:

Heart disease

High blood pressure

Stroke

Depression

There’s also a link between sleep disorders and an increased risk of injuries related to falling and car accidents.

When is a sleep study performed?

Most sleep studies take place during your normal sleeping hours. Because most people sleep during nighttime hours, facilities that perform sleep studies (known as sleep labs) schedule most people for overnight sleep studies. However, people who work overnight hours and shifts — meaning they sleep during the day — can often schedule a daytime sleep study if necessary.

How common are sleep studies?

Sleep studies are very common. In 2014, people on Medicare accounted for more than 800,000 sleep studies. That doesn’t count the studies for people who aren’t on Medicare.

Who performs a sleep study?

A sleep study involves several healthcare professionals. The people performing the sleep study are often medical technicians, technologists, assistants and nurses (including registered nurses and licensed practice nurses).

After you complete a sleep study, a physician (such as a pulmonologist or sleep medicine specialist) will review the test records for signs of any problems. They may also work cooperatively with other providers, such as a neurologist, primary care specialist or another provider you see, to get more info about your medical history or circumstances. They may also follow up with a provider you see to share the results so both providers can provide seamless, coordinated care.

At-home sleep apnea testing

An at-home sleep apnea test and a sleep study are similar but aren’t the same thing. An at-home sleep study typically doesn’t involve all of the sensors used in a sleep study. Some of the sensors that might not be used are those that detect brain wave activity, eye movement or your heart’s electrical activity.

An at-home sleep study usually involves sensors that detect breathing through your nose or mouth and movement of the breathing-related muscles in your chest and belly. These are usually reserved for cases where a provider strongly suspects sleep apnea or for follow-up testing to see if you still have sleep apnea after corrective surgery, weight loss, etc.

Test Details

How does a sleep study work?

A sleep study involves these different sensors because the quality of your sleep can depend on many factors. Using multiple types of sensors, each tracking a specific body system or process, lets healthcare providers take an in-depth look at your sleep. That can make a big difference in diagnosing certain sleep-related conditions.

A sleep study involves the following sensors and monitoring methods:

Electroencephalography (EEG): These sensors have a sticky, electrically conductive gel coating. The coating helps the sensors stick to your head while they detect and record the electrical activity of your brain, known as brain waves, while you’re asleep. Different wave types happen during different stages of sleep. That’s a key way to identify sleep disorders and issues.

Electrocardiography (EKG or ECG): During a sleep study, you wear a single EKG sensor on your chest to pick up the electrical activity of your heart. Examining heart activity allows a healthcare provider to see if there’s any issue with your heart’s beating pattern (rhythm) and internal electrical system.

Electromyogram (EMG): These sensors attach to the skin, usually on your face and a leg, to track muscle movement. Unlike a standard EMG, these sensors are for monitoring only. Unlike a standard diagnostic EMG, the sensors don’t also activate any muscles.

Electro-oculography (EOG): This test involves placing adhesive sensors on the skin around your eye. These sensors detect eye activity. You’ll wear four of these sensors for a sleep study, two around each eye.

Breathing sensors: These include sensors that detect air movement through your mouth and nose.

Respiratory inductive plethysmography (RIP) belt: A RIP belt is a device that detects the expansion of your torso, especially around your chest and belly, when you breathe.

Pulse oximeter: This is a small adhesive sensor that sticks to the tip of your index finger. It reads your pulse and the level of oxygen in your blood.

Video and audio monitoring: This allows sleep lab staff and providers to see and hear what’s happening while you sleep. Providers can use this if any of the above sensors give them unusual or concerning readings. The recordings also synchronize with sensor data, so a provider trying to interpret sensor readings can see and hear what was happening at that exact time.

What should I expect before a sleep study? How do I prepare for a sleep study?

A healthcare provider, usually a pulmonologist (a physician specializing in lung and breathing conditions) or a sleep medicine specialist, will recommend a sleep study based on your symptoms and health history. Once they do, they can often provide you with options for sleep labs in your area, and they may even be able to help you directly schedule with a sleep lab.

The scheduled time for your sleep study depends on your regular sleep habits, preferences, schedule and circumstances. Providers are most likely to recommend that you schedule your study at a time when you’re normally sleeping. It’s also common that sleep labs can schedule studies for people who sleep overnight or people who work at night and sleep during the day.

Preparing for a sleep study involves packing for an overnight stay and bathing/grooming for a medical procedure. While there might be some variations depending on sleep lab procedures and capabilities, the following are generally helpful to keep in mind while preparing:

Follow your provider’s guidelines on bathing and grooming. A common recommendation for a sleep study is to bathe or shower beforehand. However, you should avoid using creams, lotions, hair care products, etc., afterward. Clean skin without any additional products on it is best, so the sensors that are part of a sleep study can stay attached and get clear readings. Likewise, hair products such as hair gel or hairspray can make it harder for the adhesive gel on the EEG sensors to stick to your head. You should also avoid using nail polish or fake nails, as these can affect the pulse oximeter readings from your finger.

Pack like you’re staying the night at a hotel. Bring a toothbrush, pajamas or sleepwear, clothes to wear the morning after your sleep study and any other hygiene or personal grooming items you might need. If you have questions about other items you could need, sleep lab staff or your healthcare provider can provide more information and guidance on what you can expect. Bringing makeup remover is also a good idea if you wear makeup or other cosmetics.

Take your medications as usual unless your provider says otherwise. Your provider will guide you on which medications to keep taking and which to stop temporarily before your sleep study. If you have any questions about this, be sure to talk to your provider. Stopping some medications suddenly can have unpleasant or dangerous effects. Talking to your provider can help you avoid these before your sleep study.

Tell your healthcare provider about any skin allergies you have. Some adhesives used with sensors for a sleep study can cause irritation or an allergic skin reaction. Knowing about these allergies in advance can help your provider find alternatives that won’t cause a reaction.

What should I expect on the date of a sleep study?

On the day of your sleep study, you should mostly go about your usual routine. But there are also a few things you should keep in mind (unless your provider tells you otherwise):

Avoid caffeine and alcohol for at least eight hours before your sleep study. Both can disrupt your normal sleep patterns and affect the results of your sleep study.

Don’t nap. Taking a nap can make it harder for you to fall asleep during your sleep study.

Stick to your routine as best you can. The more naturally you sleep during a sleep study, the more accurately a healthcare provider can interpret the results, diagnose any condition's) you have and treat you accordingly.

What should I expect during a sleep study?

After you arrive at the location where the sleep study is taking place, the healthcare providers who’ll oversee the study will take you to the room where you’ll stay the night. Once there, you’ll change into your sleepwear, and then the staff will go through the process of attaching the sensors to the various places on your body. Most of the sensors either have adhesive on them or need tape to attach them (if you have sensitive skin or adhesive allergies, be sure to tell the staff before they begin attaching the sensors).

After staff attach the sensors, they’ll have you do a few tasks to help them check that the sensors are working and calibrated correctly. The tasks are simple and include moving your eyes, opening/closing your mouth and moving your legs.

The sensor wires should be long enough to allow you to move comfortably in bed. However, if you need to get out of bed, a staff member may need to assist you in unplugging the wires. Don’t unplug them unless a staff member tells you how to do so correctly, or it might affect the sleep study results.

After staff members calibrate the sensors, you can relax and watch TV or read before going to sleep. Most people don’t sleep as well during a sleep study because it’s an unfamiliar environment or because of the sensors they’re wearing. However, this usually won’t impact your study’s results.

While you sleep, providers and personnel monitoring your sleep study may check on you under certain circumstances.

These include:

If a wire or sensor comes loose, staff will usually come in, wake you and reattach the sensor.

If they see signs that you’re having a serious problem during your sleep study, such as a seizure or other potential medical emergency.

What should I expect after a sleep study?

After polysomnography in a sleep center, the sensors are removed and you may leave the sleep center. You're given an appointment for a follow-up visit with the healthcare professional who recommended the test. You can return to your usual activities after polysomnography.

In the morning following a home sleep apnea test, you can remove the sensors when you wake. You'll return the testing equipment to your provider's office or by mail. Some home sleep apnea tests are now disposable, so they can be discarded when the test is over.

What are the risks and side effects of a sleep study?

Very few side effects or complications can happen with a sleep study. These are most likely to be irritation from — or a reaction to — adhesives/tapes used to attach sensors. Another common effect is that people don’t sleep as well or for as long because they’re in an unfamiliar place.

There may be other possible complications, but these are uncommon and vary from person to person. A healthcare provider is the best person to tell you more about what’s likely in your case.

Results and Follow-Up

What type of results do you get, and what do the results mean?

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.

To identify sleep apnea, your doctor will review the results of the polysomnography to look for:

the frequency of apnea episodes, which occur when breathing stops for 10 seconds or longer

the frequency of hypopnea episodes, which occur when breathing is partially blocked for 10 seconds or longer

With this data, your doctor can measure your results with the apnea-hypopnea index (AHI). An AHI score lower than 5 is normal.

This score, along with normal brain wave and muscle movement data, usually indicates that you don’t have sleep apnea.

An AHI score of 5 or higher is considered abnormal. Your doctor will chart abnormal results to show the degree of sleep apnea:

An AHI score of 5 to 15 indicates mild sleep apnea.

An AHI score of 15 to 30 indicates moderate sleep apnea.

An AHI score greater than 30 indicates severe sleep apnea.

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.

Additional Common Questions

How long do you stay for a sleep study?

For most people, a single night in a sleep lab (or the equivalent of a night, for those who get a daytime sleep study) is all it takes. Experts and healthcare providers generally consider a sleep study valid if you sleep a total of two hours or more (but the more you sleep like normal, the more useful the data gathered).

For some people, more than one night in a sleep lab is necessary. That can be for multiple reasons, ranging from the condition suspected to whether or not the readings from the first night were sufficient for interpretation. A healthcare provider can tell you more about what they recommend for you and why.

Does someone watch me during a sleep study?

Sleep studies do involve low-light cameras that can record video and audio. However, the sleep lab staff won’t watch you the whole time while you sleep. The cameras are mostly there so sleep lab staff can look at what’s happening if they get unusual or concerning readings. The cameras are also there to record what’s happening so providers can compare the recording to the readings from the sensors. That means unless a staff member has a specific reason to look at you through the camera, they probably aren’t watching you.

Can I get up and use the bathroom during a sleep study?

Yes, you can wake up at night to use the bathroom during a sleep study. But sleep lab staff will tell you whether or not you can do so without a staff member helping you. This varies depending on the sleep lab’s equipment, policies and room layout. You can ask about this if a sleep lab staff member doesn’t tell you before your sleep study begins.

Do I have to do a sleep study alone?

Under almost all circumstances, a sleep study is something you do alone. There are cases, such as for children or people with special circumstances and needs, where a caregiver or loved one can also stay at the sleep lab. However, they’ll usually need to use another room to keep from affecting the readings and results of the sleep study.

In rare instances, a caregiver or loved one may be able to stay in the same room, but they can’t sleep in the same bed as the person undergoing the sleep study. This varies depending on the lab, type of test and more, so it’s best to talk to your healthcare provider or sleep lab staff.

Does a sleep study hurt?

No, a sleep study is painless. None of the sensors or other equipment will cause you any pain during the study. Taking off some of the sensors, which use tape or adhesives to stick to your skin, might cause mild discomfort, but staff can help minimize or prevent that when the study is over.

One Final Note..

A sleep study is a common diagnostic test that can help diagnose many conditions and sleep-related issues. Hundreds of thousands of sleep studies happen annually, and they’re a key part of diagnosing and treating conditions like sleep apnea, narcolepsy, restless leg syndrome and more.

While many people feel anxious or worried about this test, healthcare staff and providers who specialize in or participate in sleep study testing can help you relax and rest easy. That way, you can sleep, the test can gather info about how you sleep, and providers can determine if there’s a cause for concern and what they can do to help.

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