Overnight study helps diagnose sleep apnea and other sleep disorders

A sleep study, also known as polysomnography, can help diagnose sleep disorders, which may include sleep apnea, restless leg syndrome, insomnia, sleepwalking and narcolepsy. After a visit with a sleep medicine specialist, you will be scheduled for an overnight stay at a sleep lab or sleep center. Some sleep studies can be done at home with a portable diagnostic device.

What's involved in a sleep study

If you are having a sleep study done at a sleep center, you will arrive several hours before your regular bedtime. The sleep medicine staff will help you get settled in to a comfortable bed for the night. You will be given specific instructions in advance about eating, drinking, going to the bathroom, and what articles of clothing and personal effects to bring with you.

During the study, sensors will be placed on your eyelids, chest, arms, legs and finger to measure:

  • Brain waves
  • Breathing
  • Heart rate
  • Muscle movements
  • Oxygen levels

A sleep study also measures eye movement, body position, and electrical activity of the muscles.

When measuring sleep apnea, which is the most common reason for a sleep study, sleep medicine specialists rely on the Apnea-Hypoapnea Index (AHI) to determine the severity of your condition. In the normal sleep cycle, most people will stop breathing momentarily a few times during the night. If a person stops breathing more than five times during a sleep study, the number of episodes is measured using the following scale:

  • Five to 15 times – mild sleep apnea
  • 15 to 30 times – moderate sleep apnea
  • More than 30 times – severe sleep apnea

The sleep specialist will examine the breathing results and other feedback gathered from the study. This information will be communicated to you at a later appointment. The doctor will then discuss any recommended treatments, if needed.