What is an overnight sleep study?

An overnight sleep study (nocturnal polysomnogram) is a recording of brain waves (EEG), eye movements, certain kinds of muscle activity, cardiac activity, respiratory activity, nasal and oral breathing, snoring and blood oxygen concentration during a regular night of sleep.

Why is an overnight sleep study necessary?

Doctors can learn a great deal about your sleep and waking patterns from a sleep study. An overnight study reveals important information, including:

  • How many hours you slept
  • How often you woke up
  • What stages and depths of sleep you went through during the night
  • Whether you had normal rapid eye movement (REM) sleep involving dreaming

The study also tracks:

  • Unusual muscle activity (such as muscle jerks)
  • Unusual brain activity (such as mild seizures)
  • Unusual cardiac activity
  • Variations in blood oxygen concentration throughout the study
  • Unusual respiratory activity (such as sleep apnea, including the momentary stopping of breathing)

Is the test valid if I am not able to sleep in these unusual circumstances?

Yes. Most people do not sleep as well in a sleep center. In most cases, we can still get the information we need, even if you don't sleep as well as you do at home.

Does it hurt?

No. We gather all the information we need through noninvasive surface contact electrodes. No needles are used, and there is nothing painful about the test.

How are the electrodes attached?

We use various types and sizes of surface electrodes, which are like small metal cups. In most cases, electrodes are applied to several places on your head, with non-allergic conductive paste and gauze pieces. No hair will be shaved. Electrodes are also attached to your chin, near the eyes, on the shoulder and to both shins. If we are recording your respiration, we'll ask you to wear a small probe around your nose and mouth.

Bands are placed around your chest and abdomen to measure breathing, and a probe may be applied to your finger to measure the amount of oxygen in your blood. There is no pain, although on occasion, patients consider the electrodes to be a nuisance or slightly uncomfortable.

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