What happens in a sleep study?

It is normal for different people to need different amounts of sleep. But it can really affect your physical and mental health if you often don't get enough sleep or have trouble falling asleep. Sleep is a complex process that is regulated by processes in our brain. Sleep problems can be caused by many different things and they aren’t always easy to detect. Common causes include emotional stress, physical illness and working night shifts. Outside influences like light or noise can make it difficult to sleep too.

If you’ve had sleep problems for a while, and previous medical examinations and advice haven't helped, a sleep study is usually the next step. In the study, your sleep will be monitored for one or more nights using special instruments. Sleep studies take a bit of time, and are often carried out in a hospital or special sleep center. You will usually need to have a referral from a doctor.

When are sleep studies considered?

Sleep studies are done by a team of doctors from many different fields – including internal medicine, neurology, cardiology (heart specialists), pulmonology (lung specialists) and psychology. They are typically prescribed for people who have sleep problems that have been treated unsuccessfully for more than six months, and that are greatly affecting their mental health or general performance. The possible causes of these sleep problems include:

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

How can you prepare for a sleep study?

You can start by keeping a daily sleep diary for a while. There you can make a note of when you went to sleep and when you got up, any medications you took and how you would rate your sleep and your wake periods in the night. You can also use it to keep a note of what you ate and drank, and whether you did any exercise or other activities in the evenings. Other important points to be included are whether anything out of the ordinary happened during the day or whether you were particularly stressed.

People who go for a sleep study usually need to stay at a sleep center for two or three nights. On the day you arrive, you shouldn't drink any coffee, tea or alcohol after 2 p.m. or sleep during the day. It is a good idea to wash your hair beforehand and avoid using hairstyling products. This helps the electrodes stay on your scalp properly.

What happens during the sleep study?

A sleep study starts with an in-depth talk. The doctor will ask about your specific sleep problems and any medical conditions you have. They’ll also ask about the physical exercise you do, any special habits you may have, and how much coffee and alcohol you drink. You might find it helpful to have your partner there to answer questions about nighttime breathing pauses or snoring.

When it's time to go to bed in the evening, you’ll be connected to several different instruments. You will have electrodes on your scalp and body, and special straps around your stomach and chest. The electrodes and straps may feel a little uncomfortable to start with but they're not painful. In some sleep centers, a wireless system is used to measure your body's signals during sleep. If the instruments do have wires, they'll be tied together so you're not too restricted and can get into your usual sleeping positions. It may seem strange to fall asleep 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 all night. The following things will be measured:

  • Brain activity, using electroencephalography (EEG)
  • Heart rate, using electrocardiography (ECG)
  • Eye movements, using electrooculography (EOG)
  • Muscle activity, using electromyography (EMG)
  • Oxygen levels in your blood, using pulse oximetry (typically with a sensor attached to the tip of your finger)

Your sleep may also be monitored and recorded using a video camera.

This type of nighttime examination is known as polysomnography. Sometimes, the sleep center staff will do other tests or ask you questions during the day, too. If you are staying several nights and no other tests are needed during the day, you may be allowed to go home 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. In most cases, you will be given an appointment to come back and talk with one of the doctors about the and your treatment options.

Deutsche Gesellschaft für Schlafforschung und Schlafmedizin (DGSM). Patientenratgeber: Die Untersuchung im Schlaflabor (AG Methodik). 2021.

Pschyrembel. Klinisches Wörterbuch. Berlin: De Gruyter; 2017.

Riemann D, Baum A, Cohrs S et al. S3 Leitlinie Nicht erholsamer Schlaf/Schlafstörungen. Kapitel „Insomnie bei Erwachsenen“. AWMF-Registernr.: 063-003. Somnologie 2017; 21(2): 2-44.

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 14, 2022

Next planned update: 2025


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

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