Polysomnography is an overnight recording of your sleep made in a sleep laboratory. Sensors track brain waves, eye movements, muscle tone, breathing, oxygen level, heart rhythm, snoring, leg movements and body position while a technician watches from another room.
It is the reference test for sleep apnoea and for several other sleep disorders. It shows what happens during one night in an unfamiliar bed, so an unusually poor night can limit how much it tells you.
What Polysomnography (Sleep Study) shows
The study counts how often your breathing stops or becomes shallow each hour (the apnoea-hypopnoea index), whether the pauses are obstructive or central, how far your oxygen falls, and how these events fragment your sleep. It maps your sleep stages and shows how long you take to fall asleep and to reach REM sleep. It also detects periodic limb movements, acting out of dreams in REM sleep behaviour disorder, abnormal heart rhythms during sleep, and, with extended EEG, night-time seizures. When followed by a daytime nap test, it helps diagnose narcolepsy.
When Polysomnography (Sleep Study) is recommended
- Loud snoring with witnessed pauses in breathing, choking awakenings or unrefreshing sleep
- Marked daytime sleepiness, especially in drivers and machine operators
- Resistant high blood pressure, atrial fibrillation or heart failure with suspected sleep apnoea
- Assessment before bariatric surgery or surgery for snoring
- Suspected narcolepsy, REM sleep behaviour disorder or violent behaviour during sleep
- Titration of CPAP pressure or review when CPAP is not working
Limits and situations where another test is better:
- Simple insomnia, which is diagnosed from your history and a sleep diary rather than a laboratory night
- Straightforward suspected obstructive apnoea in an otherwise healthy adult, where a home sleep apnoea test is often enough
- Restless legs syndrome, which is a clinical diagnosis
- People who cannot sleep at all away from home may get more from a home-based recording
How to prepare
- Avoid caffeine after midday and alcohol on the day of the test
- Do not nap that day
- Wash your hair and avoid gels, oils and heavy face creams so sensors stick
- Bring nightwear, your usual medicines and anything that helps you sleep, such as your own pillow
- Tell the team about sleeping tablets or sedating medicines; do not stop them without advice
What happens during the test
You arrive in the evening, around 8 to 9 pm. A technician spends about 45 minutes attaching small electrodes to your scalp, face, chest and legs, elastic belts around your chest and abdomen, a nasal airflow sensor and a finger oxygen probe. Nothing hurts and you can turn over and visit the toilet. The room is private and recorded on infrared video. You are woken at about 6 to 7 am and can leave after the sensors come off.
Results and next steps
A sleep technologist scores the recording by hand in 30-second segments and a sleep physician interprets it. A written report is usually ready in 2 to 7 days. Depending on the result, the next step may be CPAP or a mandibular advancement device, weight and position advice, an ENT opinion about the airway, or a second night to set CPAP pressure.
- Test time: One night, about 10 hours in the laboratory
- Results ready: Report in 2 to 7 days
- Back to everyday activity: None
Safety and risks
- Skin irritation from electrode paste or tape
- A poorer night's sleep than usual, which may underestimate or occasionally overestimate the problem
- Tiredness the next morning; take care with driving
Arranging Polysomnography (Sleep Study) in Türkiye
A sleep study alone is rarely worth a flight, since most countries offer home testing. It makes sense as part of a wider visit: before bariatric or airway surgery, within a cardiac or executive check-up, or when you want diagnosis, CPAP titration and device fitting completed in one week. Ongoing CPAP follow-up should then be arranged where you live.
Send your previous reports and the question you want answered and a Clinic-Y coordinator replies within 24 hours with suitable teams and written, all-inclusive proposals side by side. Reviewing your case is free.
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What if I cannot fall asleep?
Most people sleep less well than at home but still enough. About 4 hours of recorded sleep normally gives a usable result.
Is a home test just as good?
For uncomplicated obstructive sleep apnoea it is often adequate. It does not record brain activity, so it cannot stage sleep or diagnose other sleep disorders, and it can miss mild disease.
Can the study and CPAP fitting happen on the same night?
Sometimes. In a split-night study, if severe apnoea is obvious in the first hours, CPAP is started and adjusted in the second half.