What is an Overnight Sleep Study (Polysomnogram)?



If your doctor suspects you have a sleep disorder like sleep apnea, sleep related movements, or narcolepsy, he or she may refer you to a sleep center for an overnight sleep study, or polysomnogram. The purpose of this sleep study is to monitor you while you sleep, to get a more complete picture of what’s happening in your brain and to your body.

The goal of a sleep study is to determine whether you have a sleep disorder, and if so, to diagnose which one, so you can treat it and finally get a restful and restorative sleep.

What is an overnight sleep study test?


An overnight sleep study test, or polysomnogram, is also called a nocturnal polysomnogram (NPSG). Nocturnal means it happens at night. Polysomnogram means it measures many different body functions while you’re asleep, including: 

The purpose of a nocturnal sleep study is to use the above data to diagnose and treat sleep and arousal disorders.

At your overnight sleep study, trained sleep technologists lead you through the process and monitor the equipment that records all of your sleep data into a digital diagnostic system. These technicians (sometimes called “sleep techs”) have specialized credentials: they are Registered Polysomnographic Technologists (RPSGT).

Sleep technologists, like your referring physician, are sleep medicine professionals who work directly with your doctor to make sure you’re properly and accurately diagnosed and treated. Their work with you begins with your sleep study and sometimes continues after, with ongoing patient education and treatment. (For example, if you are diagnosed with sleep apnea, you may make continued visits to the sleep lab for CPAP fittings and follow-up visits.)

At your sleep study, you don’t need to do a thing except sleep; the lab technicians record the data. By monitoring the real-time data coming in from your wires and sensors and from in-room video, they can see how your body behaves through all the stages of sleep.

A sleep study can reveal any abnormalities in your sleep patterns; for example, if you snore, experience apneas (cessation of breathing), have any involuntary movements (like leg motions or sleepwalking), or spend too little time in any of the stages of sleep.


What’s involved with a sleep study

If all of this is new to you, you’re probably wondering what to expect from a sleep study. Though sleep labs vary, your experience should be something like this:


Many people worry that they won’t be able to fall asleep or stay asleep at an overnight sleep study. However, the rooms are designed to be restful and relaxing. Though your sleep may not be as good as usual, most patients sleep for at least part of the night, which is enough for the technologists to gather the information they need.

Getting Your Sleep Study Results

Your technologists will need to compile and review the collected information from your test. They then provide it to the sleep center’s board-certified sleep specialist, who reviews it and makes a diagnosis based on the results of the study combined with your medical history.

If a different doctor (for example, your primary care physician) ordered the sleep study, he or she will be sent a copy of the results for review with you.

After an average of about two weeks, you’ll be called to schedule a follow-up with your sleep medicine doctor. At this time, he or she will go over your results and diagnosis and determine a treatment plan.


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