What happens during a sleep study?

Not everyone needs the same amount of sleep, but it can really affect your physical and mental health if you regularly do not get enough sleep, or have trouble falling asleep or sleeping through the night. Sleep is a complex process that is directed by processes in our brain. There are many different causes of sleep problems and they aren’t always easy to detect. Outside influences like light or noise can make it difficult to sleep, but ongoing sleep disorders are commonly caused by emotional stress, physical illness or working night shifts.

If you’ve had a sleep disorder for a very long time and previous medical examinations and advice have not helped, a sleep study is the usual next step. In the study, your sleep will be monitored for one or more nights monitor using special instruments. Sleep studies demand a bit of time and are carried out in a hospital or specialized sleep center. You’ll usually need to have a referral from a doctor.

When can a sleep study help?

Sleep studies are done by doctors from many different fields working together, including internal medicine, neurology, cardiology, pulmonology and psychology. The studies most commonly involve sleep disorders that have been treated unsuccessfully for more than six months and severely affect a person’s mental state or general performance. Possible causes of these disorders may include:

  • Heart problems
  • Nighttime breathing pauses (sleep apnea)
  • Restless legs syndrome
  • Recurring nightmares

How do you prepare for a sleep study?

If you notice that you have problems falling asleep or sleeping through the night, you can start keeping a sleep diary: in it you can fill in a table each morning detailing when you went to bed and got up, any medication you took, how you’d rate your own sleep and how often and how long you were awake during the night. The table can also include what you had to eat or drink and whether you were physically active after four p.m. It’s also important to make note of any exceptional events or unusual emotional stress.

You’ll need to pack for two or three nights before you leave for the sleep study. On the day you arrive avoid drinking any coffee, black tea or alcohol after two p.m. and try not to sleep before bedtime.

What happens during the study?

A sleep study starts with an in-depth discussion of the problem. Your doctor will ask about the specific difficulties you have and any pre-existing conditions. They’ll also want to find out about physical exercise you do, special habits and your patterns of coffee and alcohol consumption. You might find it helpful to have your partner there to answer questions about nighttime breathing pauses or snoring.

When going to bed in the evening, you’ll be connected to several different instruments through electrodes and cables. None of these attachments hurt, and they won’t prevent you from sleeping in any position you like. It may seem strange to fall asleep being in this kind of situation, but it’s usually easier than you might think.

After you fall asleep, your sleep will be monitored and analyzed the entire night. The following measurements will be made:

  • Electroencephalography (EEG) to measure brain activity
  • Electrocardiography (ECG) to record your heart rate
  • Electrooculography (EOG) for eye movements
  • Electromyography (EMG) to measure muscle activity
  • Pulse oximetry to track oxygen saturation in the blood stream, usually using a sensor attached to the tip of your finger

Video recording is also possible.

This type of nighttime examination is also called polysomnography. Sometimes, other studies or interviews also need to be done during the day. But the rest of the time you’re free to go as you please inside the hospital. If no other tests are needed, you may be allowed to go home during the day and then return towards evening.

What happens afterwards?

A large amount of data is collected during the sleep study, and it can take a while to analyze all of it, so you usually won’t get any results right away. Usually, an appointment will be scheduled for you to come back to talk with one of the doctors about the and your treatment options.

Andreae S. Lexikon der Krankheiten und Untersuchungen. Stuttgart: Thieme; 2008. Pschyrembel W. Klinisches Wörterbuch. Berlin: De Gruyter; 2014.

Deutsche Gesellschaft für Schlafforschung und Schlafmedizin (DGSM). S3-Leitlinie „Nicht erholsamer Schlaf / Schlafstörungen“, in Überarbeitung. October 2009 (AWMF-Leitlinien; Volume 063-001).

Deutsche Gesellschaft für Schlafforschung und Schlafmedizin (DGSM). Patientenratgeber: Die Untersuchung im Schlaflabor. October 2011.

Ohayon MM, Carskadon MA, Guilleminault C, Vitiello MV. Meta-analysis of quantitative sleep parameters from childhood to old age in healthy individuals: developing normative sleep values across the human lifespan. Sleep 2004; 27(7): 1255-1273.

Stuck B, Maurer J. Praxis der Schlafmedizin. Heidelberg: Springer; 2009.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Updated on March 9, 2016
Next planned update: 2022


Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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