Sleep / Sleep test
The night of a sleep test: what happens, and how to prepare
Why is it ordered?
Your doctor may want to know whether your breathing stops during sleep. This is called sleep apnea. Snoring, witnessed pauses in breathing or excessive daytime sleepiness can raise this suspicion. Questionnaires and examination point the way but cannot give a diagnosis on their own. The expert guideline recommends a sleep test for diagnosis.2
A sleep test can also look at other sleep problems. Leg movements during sleep or irregularities in sleep stages are examples.1
Full test in a laboratory (polysomnography)
Polysomnography is the recording of many body signals together through a night. You usually go to the centre in the evening. There are no other patients in your room.1
Where do the wires go? A technologist attaches the sensors with tape or adhesive. They go on the scalp for brain waves, beside the eyes for eye movements and on the chin for muscle tension. A thin tube that follows airflow is placed in front of the nose. Flexible belts that follow breathing movements are wrapped around the chest and belly. A clip that measures oxygen goes on a finger. Heart rhythm and leg movements are recorded as well.1 If you are allergic to adhesive, tell the technologist.
How does the night go? At the start you are asked to move your eyes, clench your teeth and move your legs. This checks that the sensors work. The wires are long enough for you to turn over in bed. After the lights go out, the technologist watches you from the next room with a camera that works in low light. If you need to get up to use the toilet, or a wire comes off, they help. In the morning the sensors are removed and you go home.1
What if I cannot sleep? This is the most common worry. Most people do not sleep as well in a laboratory as at home; this usually does not affect the result. Almost everyone falls asleep at some point. A full night's sleep is often not needed for a diagnosis.1 If not enough was recorded, your doctor decides what to do.
Some centres also try treatment on the same night. The diagnosis is made in the first half of the night, and air pressure is adjusted with a mask in the second half. This is called a split night test.2
Test at home (home sleep apnea test)
A home test has fewer sensors. Usually an airflow tube in front of the nose, chest and belly belts and a finger clip are used. You collect the device from the centre, put it on yourself and sleep in your own bed.
Who is it suitable for? According to the 2017 guideline of the American Academy of Sleep Medicine (AASM), a home test can be used in adults whose symptoms suggest moderate or severe sleep apnea and who have no other serious illness.2
Who is it not suitable for? The same guideline recommends a laboratory test in the following cases: serious heart or lung disease, nerve and muscle diseases that cause muscle weakness, suspected inadequate breathing during sleep, long-term use of opioid painkillers, a past stroke, and severe insomnia.2 If a home test comes back clear but the suspicion remains, a laboratory test is recommended.2
For experts
Kapur et al. 2017 AASM guideline: clinical tools and questionnaires should not be used for diagnosis without PSG or HSAT (strong recommendation). In an uncomplicated adult whose signs and symptoms suggest moderate or severe OSA, PSG or a technically adequate HSAT for diagnosis (strong). If a single HSAT is negative, inconclusive or technically inadequate, PSG (strong). PSG rather than HSAT in significant cardiorespiratory disease, respiratory muscle weakness due to neuromuscular disease, suspected awake hypoventilation or sleep-related hypoventilation, chronic opioid use, history of stroke and severe insomnia (strong). A split night protocol instead of a full night when clinically appropriate (weak). A second PSG may be considered if the first PSG is negative and suspicion remains (weak). Because HSAT uses recording time rather than sleep time as the denominator, it may underestimate the index.2
Preparation list
- Keep your daily routine as normal as you can on the day, and do not nap.1
- Do not have caffeinated drinks such as coffee, tea or cola in the afternoon.13
- Unless your doctor says otherwise, do not take alcohol or sleeping pills.13
- Wash and dry your hair; do not use products such as spray or gel. They can interfere with the recording.1
- Take a list of the medicines you use regularly. Ask your doctor beforehand which ones to continue; do not stop any on your own.1
- Bring comfortable pyjamas, a toothbrush and clean clothes for the morning. Something to read may help too.1
What does the results report say?
Scoring and assessing the recording can take up to two weeks.1 In Türkiye, the polysomnography report requested for a device prescription is also expected to include the headings below.8 The most common ones are:
- AHI (apnea hypopnea index): Shows how many times per hour of sleep your breathing stopped or became clearly weaker. Experts group this number as follows: 5 to 15 mild, 15 to 30 moderate, 30 and above severe.4
- Lowest oxygen: The lowest value the oxygen in your blood reached during the night. The average value may be shown next to it.
- Sleep stages: Show the time spent in light sleep (N1, N2), deep sleep (N3) and dreaming sleep (REM). Total sleep time and the time it took to fall asleep are also included.
- Sleeping position: Can show whether pauses in breathing increased when lying on the back.
These numbers mean little on their own. Your doctor assesses them together with your symptoms and examination. Leave the interpretation to your doctor, and ask about anything on your mind.
For experts
Severity thresholds (AHI events per hour): 5 to <15 mild, 15 to 30 moderate, >30 severe; AASM 1999 task force report.4 AASM 2012 scoring rules: apnea, a drop in flow of 90% or more on the thermal sensor for at least 10 seconds; hypopnea, a drop of 30% or more in nasal pressure for at least 10 seconds together with a desaturation of at least 3% or an arousal (recommended rule; the 4% desaturation rule is acceptable).5 When reading the report, check which hypopnea rule was used: the same recording can give a different AHI under a different rule.
Where to go in Türkiye?
The Turkish Sleep Medicine Society accredits the sleep disorders centres it inspects and publishes the list.6 We have gathered this list by province on our sleep centres page.
At state hospitals you can book an appointment through the Central Physician Appointment System (MHRS). The website, the mobile app or the ALO 182 line can be used for this.7 The sleep test is usually ordered by the specialist who examines you. You can also ask your family doctor which department and which centre to go to. Before you go, have a look at what you can bring and what you can ask.
Sources
- American Academy of Sleep Medicine. Sleep study. Sleep Education. sleepeducation.org/patients/sleep-study · Patient information page. Accessed: 18.10.2026.
- Kapur VK, Auckley DH, Chowdhuri S et al. Clinical practice guideline for diagnostic testing for adult obstructive sleep apnea: an American Academy of Sleep Medicine clinical practice guideline. Journal of Clinical Sleep Medicine. 2017;13(3):479-504. doi:10.5664/jcsm.6506 · Clinical guideline.
- MedlinePlus. Polysomnography. U.S. National Library of Medicine. medlineplus.gov/ency/article/003932.htm · Patient information page. Accessed: 18.10.2026.
- American Academy of Sleep Medicine Task Force. Sleep-related breathing disorders in adults: recommendations for syndrome definition and measurement techniques in clinical research. Sleep. 1999;22(5):667-689. doi:10.1093/sleep/22.5.667 · Expert task force report.
- Berry RB, Budhiraja R, Gottlieb DJ et al. Rules for scoring respiratory events in sleep: update of the 2007 AASM Manual for the Scoring of Sleep and Associated Events. Journal of Clinical Sleep Medicine. 2012;8(5):597-619. doi:10.5664/jcsm.2172 · Scoring rules.
- Turkish Sleep Medicine Society. Sleep disorders centres accredited by TUTD (in Turkish). tutd.org.tr · Accessed: 18.10.2026.
- Ministry of Health of the Republic of Türkiye. Central Physician Appointment System (MHRS). mhrs.gov.tr · Accessed: 18.10.2026.
- Social Security Institution (SGK). Health Implementation Communiqué, article 3.3.6.A-1 (4): principles for providing NIMV devices in sleep-disordered breathing (in Turkish). mevzuat.gov.tr · Current text. Accessed: 18.10.2026.
Correction history: 18.10.2026 first published. 24.10.2026 English version published.
Disclosure: This article has no sponsor.
Cite: Nefesly. The night of a sleep test: what happens, and how to prepare. nefesly.com/en/guide/sleep-test/, 2026.