In sleep studies, your heart rate, breathing, brain and muscle activity, and other body functions are monitored as you sleep. Typically, you are observed by means of electrocardiography, electroencephalography, electromyography, and oximetry.

Purpose of the Sleep Studies

  • To diagnose sleep disorders, including apnea (recurrent episodes of breathing cessation during sleep), in people who display typical symptoms such as excessive snoring, daytime sleepiness, and chronic fatigue, as well as those who have documented abnormal heart rhythms (arrhythmias) during sleep
  • To record brain waves (EEG), electrical activity of muscles, eye movement, breathing rate, blood pressure, blood oxygen saturation and heart rhythm; these are used to evaluate sleep cycles and stages
  • To evaluate sleeping problems such as trouble falling or staying asleep (insomnia), breathing that stops during sleep (apnea), nightmares and sleepwalking and problems with arm or leg movement during sleep

Who Performs It

  • A nurse or a technician in a special sleep study center.

Special Concerns

  • None

Before the Sleep Studies

  • Your eating habits don’t need to change in preparation, so eat as you normally would with two exceptions: avoid caffeine and alcohol for several days before the test.
  • When making the appointment for the sleep study, ask whether you should keep taking them in the days before the test. Bring your medications with you when you go.
  • Pack comfortable clothing to bring with you. (Pajamas are appropriate.)

What You Experience

  • The test takes place during your normal sleeping hours in a specially designed sleep laboratory. The lab is constructed to block out external sounds and the temperature is easily controlled.
  • Electrodes (small wires) are applied to your skin. They will monitor your heart rate and rhythm (ECG), brain waves (EEG), and muscle activity (EMG). This may require shaving areas of body hair in some men.
  • You are attached to monitors that measure your air flow, breathing effort, and the amount of oxygen present in your blood. This equipment is not uncomfortable and should not disturb your sleeping pattern. A video camera records your movements during sleep.
  • The monitors and electrodes are removed when you wake.

Risks and Complications

  • There are no risks or complications associated with this test.

After the Sleep Studies

  • Most patients can go home right after the study and resume their usual activities.


  • Your doctor will examine and interpret the results. Based on this analysis, you may be diagnosed with a sleep disorder, such as obstructive sleep apnea (caused by complete obstruction of the upper airway that stops breathing for at least 10 seconds at a time during sleep) or central sleep apnea (characterized by the cessation of breathing not due to an obstructed airway).
  • Depending on which type of sleep apnea is diagnosed, your doctor will make treatment recommendations.


The Johns Hopkins Consumer Guide to Medical Tests

Simeon Margolis, M.D., Ph.D., Medical Editor

Updated by Remedy Health Media

Publication Review By: the Editorial Staff at

Published: 24 Jan 2012

Last Modified: 27 Feb 2015