What Happens During a Sleep Study?

A sleep study — medically called a polysomnogram — is an overnight test that records what your body does while you sleep. It is painless, takes one night in most cases, and gives your doctor objective data about your breathing, brain activity and body movements.

What is measured

Small sensors placed on your skin and scalp record several signals at once: brain waves (EEG), eye movements, heart rhythm, blood oxygen level, breathing effort through your nose and mouth, and leg movement. A small belt around your chest and abdomen measures how your body moves air in and out.

How the night usually goes

You arrive in the evening, change into comfortable clothes, and a technologist attaches the sensors with gentle adhesive. Each sensor is about the size of a coin or smaller. Then you sleep in a private, hotel-like room while the equipment records. If you need to get up during the night, a technologist helps you disconnect briefly.

How to prepare

Avoid caffeine after midday, do not use lotions or hair products (sensors stick better to clean skin), take your regular medications unless your doctor says otherwise, and bring comfortable sleepwear and your own pillow if that helps you rest.

After the study

A sleep physician reads thousands of data points and prepares a report, usually within a week or two. If the study shows sleep apnea, common next steps include a CPAP machine, an oral appliance, or weight and position therapy — your doctor will match treatment to your results. Ready to book one? Browse sleep clinics near you.

Home sleep tests

Some patients qualify for a home sleep apnea test with a portable monitor. It records fewer signals but is convenient. Your clinic can tell you which type of sleep study fits your situation.