What is a sleep study and why is it needed?

Have trouble sleeping? Do you snore?

If so, your doctor may suggest undergoing a sleep study to help diagnose whether you have a sleep disorder such as obstructive sleep apnea, narcolepsy, parasomnias or insomnia.

How does a sleep study work?

These are tests that record specific body functions during sleep, according to John Sand, DO, an OSF HealthCare sleep specialist.

It takes place overnight in a sleep lab, although there are situations where a home test can be conducted. As you sleep, instruments measure things like heart rate, breathing rate and airflow, brain wave activity, eye movement, blood oxygen level and muscle movement.

“They wire you up like an astronaut – there are things on your fingers to measure your pulse and blood oxygen level, electrodes on your head – you think right off the bat that you’re not going to be able to sleep, but you do,” Dr. Sand said.

What does a sleep study diagnose?

Primarily, the test is used to diagnose sleep apnea, a potentially life-threatening condition that is characterized by brief interruptions of breathing during sleep, Dr. Sand said.

There are three types of sleep apnea:

• Obstructive sleep apnea – when air can’t flow into or out of the nose or mouth although efforts to breathe continue. This is the most common sleep disorder.
• Central sleep apnea – when the brain fails to send the right signals to the muscles to start breathing.
• Complex sleep apnea – a mix of symptoms found in both central and obstructive sleep apnea.

Other conditions that could be diagnosed include:

• Narcolepsy – a disease of the central nervous system that causes excessive daytime sleepiness resulting in sleep attacks at inappropriate times and places.
• Parasomnia – a common sleep disorder characterized by strange behavior during sleep and may include nightmares, sleep terrors, sleepwalking and bedwetting.
• Insomnia – one of the most common sleep disorders which affects your ability to fall asleep, stay asleep or both.

What does a sleep study show?

“During a sleep study, you’re going to find out what an individual’s oxygen levels are doing that might be associated with their sleep disorder,” Dr. Sand said. “You can also see sleep stages – REM (rapid eye movement), and whether it’s deep or superficial. I’m not sure there’s any test in medicine that gives more data in one night.”

Other things that could be recorded include:

• Breathing patterns – the number and depth of respirations
• Oxygen saturation – the percentage of oxygen in the blood
• Acid/base balance of the stomach – the amount of acid secreted during sleep
• Sleep latency – the time it takes to fall asleep
• Sleep duration – the time a person stays asleep
• Sleep efficiency – the ratio of the total time asleep to the total time in bed

What can I expect during a sleep test?

First and foremost, Dr. Sand tells patients to do whatever they normally do, whether that’s cruising social media, reading a book or watching TV.

You can expect to have electrodes attached to your face, scalp and body. These send electrical signals and are recorded on the measuring equipment used during a study. The electrical signals are from your brain and muscles.

A nasal-oral airflow sensor measures the airflow through your nose and mouth. Belts are also placed around your chest and abdomen that measure your breathing.

During the entire study, a video camera records your body movement and a microphone records snoring.

“Someone could be watching you, but usually they’re too busy,” Dr. Sand said.

And don’t worry if you need to use the restroom. The equipment is easily removed and put back on, he said.

What if I can’t sleep during a sleep study?

No worries if you don’t sleep a solid eight hours during your overnight stay for the test, Dr. Sand said.

“Clinically speaking, we like to say we can get enough data with two hours of sleep,” he said. “It’s really not an issue ever – maybe once out of 300 times it may be an issue of not collecting enough data due to someone not getting enough sleep.”

Getting a sleep disorder diagnosis

Once the sleep test is completed, your sleep specialist will go over the results of the study. They will determine if you have a sleep disorder and what treatment or equipment you may need to help improve your sleep.

The provider who ordered your sleep study receives the results and will discuss next steps with you.