Unveiling the Mysteries of Sleep: Your Guide to Sleep Studies

What is a sleep study?

The stages of sleep range from light to deep. Each stage has characteristics that can be measured. A sleep study is a number of tests done at the same time during sleep. The tests measure specific sleep characteristics and help to diagnose sleep disorders. A sleep study may also be called polysomnogram.

Your health care provider has referred you for a sleep study because you are having trouble getting a restful night’s sleep. A sleep study, also called a polysomnography or sleep evaluation, can determine if you are suffering from a sleep disorder like sleep apnea or restless leg syndrome. The study also provides information on which treatment option is right for you.

Sleep studies generally take place in a sleep lab during your normal sleeping hours. The goal is to record brain and body activity that happens during sleep so that sleep disorders can be diagnosed and treated.

Why might I need a sleep study?

Common reasons for a sleep study include:

  • Excessive snoring
  • Sleep apnea (periods where the breath stops)
  • Daytime sleepiness
  • Insomnia (inability to sleep)
  • Narcolepsy (sudden onset of sleep)
  • Restless legs syndrome (condition causing uncomfortable leg sensations)
  • Nightmares during nondream stages of sleep (sleep terrors), sleep walking or talking, and rapid eye movement disorders are less common conditions that may also require a sleep study.

There may be other reasons for your healthcare provider to recommend a sleep study.

What are the different types of sleep apnea?

OBSTRUCTIVE: which is the most common and occurs when the soft tissue at the back of throat relaxes and blocks airway. It is associated with snoring.

CENTRAL: which is not common and occurs when the brain doesn’t signal the muscles that control breathing- snoring is not common for people with this type.

COMPLEX: it is a combination of obstructive and central sleep apnea together.

What are the different levels sleep study?


Most are aware of level 1 sleep studies which are historically seen as the gold standard. This is usually done in laboratory and attended by a sleep technician. This allows accurate data because the sleep technician can assure the integrity of the data throughout the night. Minimum of 7 parameters monitored which include EEG, EOG, Chin EMG, airflow, respiratory effort, oxygen saturation and ECG.


Same as LEVEL 1 study. Minimum 7 parameters are monitored. But it is not attended by a sleep technician. 


Minimum of 4 parameters are monitored which include ECG/heart rate, 2 channels of respiratory effort or 1 respiratory support channel + 1 airflow channel. It often referred to as a home sleep apnea test (HSAT) is done from the comfort of your own home. It is not attended by a sleep technician.


Minimum of 3 parameters are monitored which include airflow channel, oxygen saturation and peripheral arterial tone. It is done from the comfort of your own home. It is not attended by a sleep technician.

What are the different types of sleep study?

Different types of sleep studies are available depending on one’s symptoms and the sleep disorders that may be present.

  • Polysomnography: In polysomnography, a sleep technician monitors a patient who stays overnight at a specialized clinic. A variety of functions are measured throughout the night, including eye movements, brain and muscle activity, respiratory effort and airflow, blood oxygen levels, body positioning and movements, snoring, and heart rate.
  • Multiple Sleep Latency Test: Multiple sleep latency testing measures how quickly someone falls asleep and how quickly they enter REM sleep during daytime naps. This test is primarily used to diagnose excessive daytime sleepiness that may be due to narcolepsy or an unknown cause (idiopathic hypersomnia).
  • CPAP Titration: Continuous positive airway pressure (CPAP) is a common treatment for sleep apnea. In CPAP titration, a technologist determines the amount of air pressure that patient needs from their CPAP so that their machine can be properly programmed for home use. CPAP titration usually requires a second sleep study. When sleep apnea is strongly suspected, a split-night sleep study may be an option. In a split-night study, polysomnography is used to diagnose sleep apnea during the first half of the night, and CPAP titration is performed during the second half of the night.
  • Home Sleep Apnea Testing: Home sleep apnea testing collects data about a patient’s breathing, heart rate, and other variables overnight. However, compared with polysomnography, home testing provides less information, and the process is not overseen by a technologist.

What is monitored during the sleep study?

While you sleep, a technologist monitors your:

  • Brain waves
  • Eye movements
  • Heart rate
  • Breathing pattern
  • Blood oxygen level
  • Body position
  • Limb movement
  • Snoring and other noise you may make as you sleep

These measurements are recorded on a continuous graph. The results help your sleep physician determine if treatment may improve the quality of your sleep.

What are the risks of a sleep study?

There are no known risks for a sleep study other than possible skin irritation due to the attachment of the electrodes to the skin.

How long does the test take?

In most cases, you will arrive to the sleep center in the evening and your test will take place overnight. You will remain in the hopital until aaround 7 a.m. the next day.

How to prepare for a sleep study?

Taking steps before your sleep study can help you feel comfortable and facilitate more accurate results.

Before scheduling your sleep study:

  • Speak with your doctor about medications you are taking. Certain medications can interfere with sleep study results, but don’t skip any medication doses without consulting a doctor first.
  • If you are feeling anxious about a sleep study at a clinic, request a tour of the sleep clinic ahead of time. You can also ask about having someone accompany you to the set-up portion of your sleep study.

On the day of your sleep study:

  • Follow your usual daily routine as much as you can.
  • Avoid caffeine from the afternoon on.
  • Don’t take a nap.
  • Wash any hair gel or other styling products out of your hair. They can interfere with the sleep recording.

What happens during a sleep study?

A sleep study is generally done on an outpatient basis at night. Procedures may vary based on your condition and your healthcare provider’s practices. You’ll be asleep for most of the time you’re being tested, but it’s important to know what will happen so you can do your part to ensure that the results are as accurate and useful as possible.

The technician will spend about 45 to 60 minutes setting you up for your sleep study. 

Generally, a sleep study follows this process:

  • You will need to remove any jewelry or other objects that may interfere with the procedure.
  • You will change into pajamas or a hospital gown.
  • To prepare you, the technician will measure the dimensions of your head and then use a special pencil to mark places on your scalp and face where the electrodes will be attached. (The marks wash off with soap and water.)
  • They will then use a cotton swab to apply a mildly abrasive paste to each spot in order to remove the oil from your skin so that the electrodes will adhere properly.
  • Some of the wires on your face may be taped in place. If you’re sensitive to or allergic to medical tapes or glues, let the technician know ahead of time so that they can use a type that won’t bother you.
  • A flat, plastic microphone taped to your neck to record snoring
  • Sticky pads on your chest to monitor your heart rhythm via an electrocardiogram (ECG)
  • Stretchy cloth belts that go across the chest and stomach to measure breathing
  • Sticky pads or electrodes applied to the shins or forearms to monitor muscle movements via electromyography (EMG)
  • A peripheral capillary oxygen saturation monitor (usually clipped to a finger), measuring continuous oxygen saturation
  • An electro-oculogram (EOG), which uses electrodes placed near the eye to measure eye movements

All of these wires will be connected to a small, portable box that you can easily carry with you if you need to get out of bed (for a trip to the bathroom, for example). If you use continuous positive airway pressure (CPAP) during the night, you may be fitted with a mask.

Finally, just before you go to bed, the technician will place a nasal cannula—plastic tubing that sits in the nose—that will measure airflow while you sleep. Most sleep clinics also use a thermistor, a pronged wire that sits in the nostrils and measures temperature changes. Lights will be turned off and monitoring will start before you fall asleep.

What to do after sleep study?

The technician will wake you at your regular wake-up time. They will remove your electrodes and other devices. You may be asked to fill out a questionnaire about the quality of your night’s sleep.You can also eat, drink, and take any of your regular medications.

You won’t need any special care after a sleep study. However, your healthcare provider may give you other instructions after the procedure, based on your situation.

At a follow-up appointment, your doctor reviews the results with you. Based on the data gathered, your health care provider will discuss any treatment or further evaluation that you may need.

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