Medically Reviewed by Expert Board

This page was fact checked by our expert Medical Review Board for accuracy and objectivity. Read more about our editorial policy and review process.

.
This article was last modified on

What Is Sleep Apnea?

Sleep apnea is a condition that involves disturbed breathing during sleep. An apnea is a temporary pause in breathing, and when apneas and similar breathing disruptions happen during sleep, they can worsen sleep quality, reduce the amount of oxygen in the body, and contribute to other health problems.

There are different types of sleep apnea that are classified based on the cause of breathing disruption. The two main types of sleep apnea are:

  • Obstructive sleep apnea (OSA), which occurs when the airway in the throat is partially blocked, preventing proper airflow.
  • Central sleep apnea (CSA), which involves disruption of normal signals from the brain to the muscles that control respiration.

Obstructive sleep apnea is much more common than central sleep apnea. OSA is believed to affect up to 30% of males and 15% of females in the United States while CSA is estimated to affect around 0.9% of people over age 40. Obstructive sleep apnea also occurs in around 1-5% of children.

Individual factors can increase a person’s risk of having obstructive sleep apnea. Some of these factors include older age, obesity, and certain anatomical features that narrow the upper airway. Smoking, use of certain types of drugs or medications, and a family history of obstructive sleep apnea may also lead to an elevated risk.

Obstructive sleep apnea causes many brief sleep disruptions during the night. This can cause a lack of restorative sleep and excessive daytime sleepiness. OSA has also been associated with cardiovascular problems like high blood pressure and stroke as well as anxiety and depression.

The Role of Sleep Apnea Tests

Sleep apnea tests are done primarily to diagnose a sleep-related breathing disorder like obstructive sleep apnea or central sleep apnea. Because obstructive sleep apnea is much more common and can have serious health consequences, most sleep apnea testing focuses on OSA.

A diagnosis of sleep apnea requires testing that measures breathing during sleep. This testing can confirm the occurrence of breathing disruptions and assess their frequency and severity. Some sleep apnea testing can also help determine if there are additional disorders or abnormalities affecting sleep.

Another use of sleep apnea tests is to optimize treatment. A common therapy for obstructive sleep apnea uses a continuous positive airway pressure (CPAP) device that delivers a steady stream of air through the nose or mouth to keep the airway from collapsing. Testing can help calibrate the pressure of a CPAP machine, a process known as CPAP titration.

Sleep apnea tests can also be used to track how a person’s breathing during sleep changes over time. For example, repeat testing can help determine if CPAP therapy is working. Follow-up tests can check whether sleep apnea has changed as a result of weight loss or gain.

Who should get testing?

Sleep apnea testing is typically performed as part of the diagnostic process in people who have symptoms that are consistent with a possible sleep-related breathing disorder. The primary symptoms of obstructive sleep apnea include:

  • Excessive daytime sleepiness that occurs on most days
  • Frequent loud snoring
  • Choking or gasping during sleep

Testing is often more likely to be recommended when a person has other risk factors for OSA such as obesity or high blood pressure. Testing for OSA is also a part of the diagnostic process for a number of other disorders that can cause significant daytime drowsiness.

Sleep apnea testing is not widely used for screening, which is testing in people who do not have symptoms of the condition. To date, there is a lack of evidence about whether the benefits of sleep apnea screening are greater than its potential risks, such as unnecessary tests or treatments.

Although people who are at a higher risk of obstructive sleep apnea may be asked questions during medical checkups about their sleep habits, more thorough sleep apnea testing is usually reserved for people who have symptoms.

When testing is recommended, the type of sleep apnea test that is used can depend on a patient’s specific situation including whether they are a child or adult, whether they have other health issues, and the likelihood that they have more severe sleep apnea. For any given person, a doctor or sleep specialist can best address the appropriateness of different types of sleep apnea testing.

Getting test results

Results from sleep apnea tests are usually communicated to you by a doctor or sleep specialist. A polysomnogram (PSG) is a common test for sleep apnea. It is an overnight sleep study that is conducted in a special clinic.

During a polysomnogram, sensors closely track changes in your body. You are monitored throughout the night, and after the test, a trained technologist analyzes the data from the sensors to create a detailed test report.

The test report may be sent to you by mail or made available electronically. In many cases, your doctor or someone from the sleep clinic will contact you to review the key takeaways from your sleep apnea test.

A polysomnogram produces numerous measurements related to your sleep and breathing. Some common components of the test report include your total sleep, time spent in different sleep stages, total awakenings, airflow through the nose and mouth, breathing disturbances, snoring, oxygen levels, sleep position, and movements during sleep. Within the test report, you are likely to find various graphs or tables that can help you understand what was measured.

The report also includes an interpretation section that usually addresses whether you are likely to have sleep apnea or any other sleep disorder.  Normally you will review this interpretation with your doctor over the phone or at a follow-up appointment.

When sleep apnea testing is done at home with an electronic device, some initial results may be available immediately. Full interpretation of the test, though, can only be done by a health professional with training in sleep medicine who can review the raw data that the device collected.

One of the most important measurements on an overnight sleep apnea test is the apnea-hypopnea index (AHI), which is the number of breathing disruptions that were found per hour. The AHI can be used to diagnose sleep apnea and determine its severity according to these general guidelines:

  • Normal: AHI under 5
  • Mild sleep apnea: AHI of 5 to 14
  • Moderate sleep apnea: AHI of 15 to 30
  • Severe sleep apnea: AHI of 31 or more

Some sleep studies may also calculate the respiratory disturbance index (RDI), which counts a broader range of breathing disruptions that occur per hour. The test report may also list instances of hypoventilation, a lack of sufficient oxygen that can be caused by sleep apnea.

This type of sleep study is important for the formal diagnosis of sleep apnea. A person is considered to have OSA if:

  • They have an AHI over 5 and signs or symptoms of OSA
  • They have an AHI over 15 with or without signs or symptoms of OSA

The AHI and other main findings of the test report are typically part of your post-test consultation with your doctor. In some cases, further testing may be needed to confirm the result of the initial sleep study or to plan your treatment if you have been diagnosed with obstructive sleep apnea.

Types of Sleep Apnea Tests

Several kinds of types may be used as part of diagnosis, treatment, and monitoring of sleep apnea. An overnight sleep study called a polysomnogram is the principal test for sleep apnea, but other tests are involved in typical patient assessment.

The following sections provide details about the different types of tests involved in detecting and managing sleep apnea, especially obstructive sleep apnea.

Physical exam and health review

The initial evaluation for sleep apnea includes a physical exam and a discussion of your current health and health history. During the physical exam, a doctor looks for aspects of your anatomy that may cause the airway in your throat to be narrowed, such as a large tongue or obstruction of the nose.

Along with a physical exam, your doctor will usually ask several questions about whether you have experienced symptoms of sleep apnea like excessive daytime sleepiness. You may also be asked to keep a sleep diary that tracks your sleep over a week or two.

Often a bed partner or other family member will be asked if they have observed sleep apnea symptoms that are hard for you to be aware of, including frequent snoring, gasping, or choking during sleep.

In addition, by reviewing your health history, the doctor can identify your risk factors for sleep apnea. All of this information can be factored into determining your likelihood of having obstructive sleep apnea.

Sleep apnea questionnaires

Some specific questionnaires have been developed for doctors to use as part of the health history and symptom review. These questionnaires may help identify people who are at a higher risk of obstructive sleep apnea and who should have an overnight sleep study. On their own, though, these questionnaires cannot accurately diagnose sleep apnea.

Overnight sleep study

The gold standard in sleep apnea testing is called polysomnography (PSG). During a polysomnogram, you are connected to sensors that track your eye and muscle movements, breathing, oxygen levels, heart rate, and body position. Most polysomnography also includes audio and video recording.

Taking this kind of test involves an overnight sleep study that takes place in a specially designed clinic. A technologist sets up all the sensors and then monitors them throughout the night as you sleep.

Polysomnography provides the clearest evidence about whether your breathing is interrupted during sleep, and for this reason, it is considered to be the most accurate method of diagnosing sleep apnea. In general, a health professional with expertise in sleep health is involved in analyzing a polysomnogram.

Sleep apnea testing can involve different versions of polysomnography:

  • Full-night study: In this kind of test, you are monitored throughout the night, and then your test data is analyzed. This is the most accurate way of testing for sleep apnea. If you are determined to have sleep apnea, you will return for a second sleep study for CPAP titration, which is the process of setting up and calibrating the device used for treating obstructive sleep apnea.
  • Split-night study: In a split-night study, the first part of the night is used to assess whether you have sleep apnea. If obstructive sleep apnea is detected, you will use a CPAP device for the second part of the night so that it can be properly calibrated. The main advantage of a split-night study is that it does not require a return visit to the sleep clinic for CPAP titration.
  • Nap polysomnogram: This version of the test is conducted during a shorter daytime nap. With less data, it is not as effective at detecting sleep apnea and is usually only an option for infants or very young children who frequently nap during the day.

Home sleep apnea testing

In some situations, a home sleep apnea test may be an option instead of a polysomnogram conducted in a sleep clinic. An at-home test requires specialized equipment that normally must be configured by a trained technician, and the results of this testing require interpretation by a sleep specialist.

Because it does not include all of the measurements found in a traditional sleep study, home sleep apnea testing provides less precise information than polysomnography. As a result, it is only appropriate for certain patients.

For example, home sleep apnea testing is reserved for adults who are more likely to have moderate or severe obstructive sleep apnea and who do not have other health problems. It is not recommended for pilots, bus and truck drivers, and others whose work involves heightened safety risks if sleep apnea is not diagnosed.

It is important for patients to be aware that only home sleep apnea testing directed by a health professional is validated for sleep apnea diagnosis and monitoring. Other digital devices, oxygen monitors, or app-based tools marketed for at-home sleep apnea testing have not been proven to accurately diagnose sleep-related breathing disruptions.

Tests for associated conditions

Obstructive sleep apnea has been tied to a wide range of other health issues. While there is no standard set of follow-up tests for people diagnosed with sleep apnea, the doctor may assess your cardiovascular health, thyroid function, hormone levels, or prescribe other tests based on your situation and whether or not you have signs or symptoms of conditions that could be associated with sleep apnea.

Getting Tested for Sleep Apnea

Sleep apnea testing is prescribed by a doctor. If you have symptoms of sleep apnea or are interested in sleep apnea testing, you should talk with your family doctor.

When sleep apnea testing is appropriate, specific tests may be ordered by your primary care physician, or you may be referred to a doctor with a specialty in sleep health. In most cases, a health professional with training in sleep medicine will be involved in the process of testing and interpreting your test results.

In many situations, getting tested requires going to a sleep clinic to do an overnight sleep study with polysomnography. This is considered to be the most definitive method of diagnosing sleep apnea.

In certain circumstances, though, home sleep apnea testing can be prescribed by a doctor, allowing you to use a specially designed device to collect data about your breathing during sleep.

At-home testing

At-home sleep apnea testing is available for some patients when recommended by their doctor or a sleep specialist. In order to get the most accurate results possible, you will normally pick up a testing device from your doctor’s office, or a technologist will come to your home to set it up.

Home sleep apnea testing is not recommended for children, people with certain coexisting medical issues, people who likely have only mild sleep apnea, or anyone for whom excessive daytime sleepiness at work can lead to serious safety risks.

Not all devices for at-home sleep apnea testing are equally effective at detecting obstructive sleep apnea. For this reason, you should never use an at-home sleep apnea testing device without first consulting with your doctor.

Comparing Tests

The traditional full-night polysomnogram conducted in a sleep clinic is widely regarded as the gold standard in sleep apnea testing. By collecting the widest and deepest amount of data, it is the most accurate test for diagnosing obstructive sleep apnea and many other sleep disorders.

The downsides of a full-night sleep study include its cost, the time it takes to conduct the test, and the fact that it can be uncomfortable for many people to sleep in the clinic. For this reason, other versions of testing, including the split-night sleep study and home sleep apnea testing, have increasingly become available as options for people being evaluated for sleep apnea.

Multiple factors can affect which type of test is optimal for any individual. Accordingly, a doctor or sleep specialist is in the best position to compare the pros and cons of the different types of tests for any specific patient’s situation.

Sources

A.D.A.M. Medical Encyclopedia. Pediatric sleep apnea. Updated July 3, 2019. Accessed August 10, 2021. https://medlineplus.gov/ency/article/007660.htm

A.D.A.M. Medical Encyclopedia. Central sleep apnea. Updated July 15, 2019. Accessed August 12, 2021. https://medlineplus.gov/ency/article/003997.htm

A.D.A.M. Medical Encyclopedia. Obstructive sleep apnea – adults. Updated January 29, 2020. Accessed August 10, 2021. https://medlineplus.gov/ency/article/000811.htm

A.D.A.M. Medical Encyclopedia. Polysomnography. Updated January 29, 2020. Accessed August 10, 2021. https://medlineplus.gov/ency/article/003932.htm

Brown LK, Lee W. Titration of positive airway pressure therapy for adults with obstructive sleep apnea. In: Collop N, ed. UpToDate. Updated June 28, 2021. Accessed August 10, 2021. https://www.uptodate.com/contents/titration-of-positive-airway-pressure-therapy-for-adults-with-obstructive-sleep-apnea

Chahine E. At-home sleep tests and studies. Updated May 6, 2021. Accessed August 10, 2021. https://www.sleepfoundation.org/at-home-sleep-tests

Collop N. Home sleep apnea testing for obstructive sleep apnea in adults. In: Harding SM, ed. UpToDate. Updated July 21, 2021. Accessed August 10, 2021. https://www.uptodate.com/contents/home-sleep-apnea-testing-for-obstructive-sleep-apnea-in-adults

Donovan LM, Kapur VK. Prevalence and characteristics of central compared to obstructive sleep apnea: Analyses from the sleep heart health study cohort. Sleep. 2016;39(7):1353-1359. Published 2016 Jul 1. doi:10.5665/sleep.5962

Fry A. Sleep studies. Updated June 23, 2021. Accessed August 9, 2021. https://www.sleepfoundation.org/sleep-studies

Kapur VK, Auckley DH, Chowdhuri S, et al. Clinical practice guideline for diagnostic testing for adult obstructive sleep apnea: An American Academy of Sleep Medicine clinical practice guideline. J Clin Sleep Med. 2017;13(3):479-504. Published 2017 Mar 15. doi:10.5664/jcsm.6506

Kline LR. Clinical presentation and diagnosis of obstructive sleep apnea in adults. In: Collop N, ed. UpToDate. Updated June 3, 2021. Accessed August 10, 2021. https://www.uptodate.com/contents/clinical-presentation-and-diagnosis-of-obstructive-sleep-apnea-in-adults

Kramer NR, Millman RP. Overview of polysomnography in adults. In: Harding SM, ed. UpToDate. Updated December 14, 2020. Accessed August 10, 2021. https://www.uptodate.com/contents/overview-of-polysomnography-in-adults

Paruthi S. Evaluation of suspected obstructive sleep apnea in children. In: Chervin RD, ed. UpToDate. Updated February 18, 2021. Accessed August 10, 2021. https://www.uptodate.com/contents/evaluation-of-suspected-obstructive-sleep-apnea-in-children

Rosen IM, Kirsch DB, Carden KA, et al. Clinical use of a home sleep apnea test: An updated American Academy of Sleep Medicine position statement. J Clin Sleep Med. 2018;14(12):2075-2077. Published 2018 Dec 15. doi:10.5664/jcsm.7540

Schwab RJ. Approach to the patient with a sleep or wakefulness disorder. Merck Manual Professional Version. Updated June 2020. Accessed August 10, 2021. https://www.merckmanuals.com/professional/neurologic-disorders/sleep-and-wakefulness-disorders/approach-to-the-patient-with-a-sleep-or-wakefulness-disorder

Schulman D. Polysomnography in the evaluation of sleep-disordered breathing in adults. In: Harding SM, ed. UpToDate. Updated March 19, 2020. Accessed August 10, 2021. https://www.uptodate.com/contents/polysomnography-in-the-evaluation-of-sleep-disordered-breathing-in-adults

Strohl KP. Obstructive sleep apnea. Merck Manual Professional Version. Updated September 2020. Accessed August 10, 2021. https://www.merckmanuals.com/professional/pulmonary-disorders/sleep-apnea/obstructive-sleep-apnea

Suni E. Central sleep apnea. Updated July 9, 2021. Accessed August 12, 2021. https://www.sleepfoundation.org/sleep-apnea/central-sleep-apnea

Tan HL, Kheirandish-Gozal L, Gozal D. Pediatric home sleep apnea testing: Slowly getting there!. Chest. 2015;148(6):1382-1395. doi:10.1378/chest.15-1365

UpToDate. Patient education: what is a sleep study (the basics). No date given. Accessed August 10, 2021.  https://www.uptodate.com/contents/what-is-a-sleep-study-the-basics

US Preventive Services Task Force, Bibbins-Domingo K, Grossman DC, et al. Screening for obstructive sleep apnea in adults: US Preventive Services Task Force Recommendation Statement. JAMA. 2017;317(4):407-414. doi:10.1001/jama.2016.20325

Ask a Laboratory Scientist

Ask a Laboratory Scientist

This form enables patients to ask specific questions about lab tests. Your questions will be answered by a laboratory scientist as part of a voluntary service provided by one of our partners, American Society for Clinical Laboratory Science. Please allow 2-3 business days for an email response from one of the volunteers on the Consumer Information Response Team.

Send Us Your Question