Overnight Sleep Tests

Overnight sleep tests diagnose types and causes of sleep disorders. Learn about various types of sleep tests, including the wrist actigraphy test and the nocturnal polysomnogram.

Nocturnal Polysomnogram

The nocturnal polysomnogram is used to diagnose conditions like sleep apnea, narcolepsy and sleep-related seizures. If you’re slated for this sleep test, you may be asked to arrive at the sleep study center—many of which have rooms similar to those in hotels—about two hours before bedtime.

A technician will place electrodes on your scalp, face and chest to record vital signs such as blood pressure and heart rate, and fit elastic belts on your chest and abdomen to measure chest movements and breathing.

During a polysomnogram, the electrodes monitor how long it takes you to fall asleep, as well as how long it takes for you to enter rapid eye movement (REM) sleep. The heart rate and breathing monitors record if you either stop or almost stop breathing. A test technician monitors the exam, which is sometimes video recorded, in a separate room.

If you exhibit signs of sleep apnea, the technician may fit you with a continuous positive airway pressure (CPAP) mask to keep your airway open while you sleep.

Home-Based Portable Monitor

In order to diagnose sleep apnea or determine the best treatment for this condition, a patient may use a home-based portable monitor (PM) on his own. You must obtain this device and instructions from either a doctor’s office or a sleep study center.

The PM consists of a recording mechanism, sensors, belts and cables. The belt, which is placed around the chest or stomach, measures breathing, while the sensors placed near the mouth and nose measure airflow. The PM can also track blood oxygen level through a pulse monitor on the fingertip.

Wrist Actigraphy

Wrist actigraphy is another type of home overnight sleep study that monitors individuals during both sleep and active hours. It can help determine if a sleep disorder is attributable to a problem with the circadian rhythm.

A wrist actigraphy allows a physician to track a patient’s behavior as she performs her normal, daily routines. Worn like a wristwatch, the actigraph device records data over three to seven days and nights to help doctors better understand a patient’s sleep habits and behaviors.


National Heart Lung and Blood Institute. (n.d.). What to expect during a sleep study. Retrieved December 15, 2010, from http://www.nhlbi.nih.gov/health/dci/Diseases/slpst/slpst_during.html

Riverside Health System. (n.d.). Portable home monitor: What to expect. Retrieved December 15, 2010, from http://www.riversideonline.com/services/sleep_disorders/portable-home-monitor-expect.cfm

U.S. National Library of Medicine. (2010). Polysomnography. Retrieved December 15, 2010, from http://www.nlm.nih.gov/medlineplus/ency/article/003932.htm