What is a sleep study?

A sleep study is a diagnostic test that a physician may use to determine if you have a sleep disorder, what type of disorder, and the potential severity of that disorder. What many people may not realize is that there are several different types of sleep studies used for various sleep disorders.

Polysomnography (PSG) is an overnight diagnostic sleep study conducted in the sleep lab. During the study many measurements are taken, including brain activity, stages of sleep, blood oxygen, heart rate, and air flow. A PSG can identify many different sleeping conditions all during the same study, such as obstructive or central sleep apnea, periodic limb movement disorder, and parasomnias.

Titration (TITR) studies, or CPAP studies, are performed in the sleep lab for patients who have already been diagnosed with sleep apnea. This study is intended to show the physician the ideal pressure needed for the patient to control their sleep apnea. During the study, a patient will wear a CPAP throughout the night. In certain situations a physician may decide to combine the PSG and Titration studies into one night. This is known as a Split Night Study. During this type of study, a patient spends the first half of the night doing the diagnostic PSG and is later switched to the CPAP device for the remainder of the night.

Home Sleep Tests (HST) have recently become a popular and widely available option for patients. Home sleep studies are only recommended if there is a strong suspicion that the patient has sleep apnea. Not everyone is a good candidate for a home sleep test. The sleep specialist would determine during an office visit if an HST is appropriate. Home sleep tests are only able to diagnose sleep apnea, and there is a much higher chance of error or misdiagnosis with the HST than with an in-lab study. If a patient is recommended to have an HST, they are instructed on the use of the device at an office visit, after which they take home a portable monitoring device to use overnight in their home.


Multiple Sleep Latency Tests (MSLT) are sleep studies performed in the sleep lab during a patient’s normal waking hours. This test is primarily used to test for the sleep disorder Narcolepsy, however there are other indications for the test. The MSLT is generally performed during the day immediately following a PSG test. It consists of a series of naps conducted over a period of several hours. The test shows how quickly the patient falls asleep, how consistent that pattern is, and how the brain patterns appear during that time.

Maintenance of Wakefulness Tests (MWT) are also sleep lab based studies performed during a patient’s normal waking hours. The difference between this and an MSLT is that during the MWT, a patient must try to remain awake throughout the duration of the test. The test is intended to see if a patient is able to stay awake during the hours of the day when they would normally be awake. It is used to assess any safety concern there may be for the patient to conduct their day-to-day activities.

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