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Sleep Study (Polysomnography) in Gangnam, Seoul

Medically reviewed by Dr. Kim Yoo Suk, MD · Board-certified otolaryngologist · Former professor, Yonsei & Ajou University · Consultations in English

What is polysomnography?

Polysomnography (PSG) is the reference standard test for diagnosing sleep-disordered breathing. During a full overnight study, sensors record multiple signals at once:

• Brain waves (EEG), eye movements and chin muscle tone to stage sleep
• Airflow through the nose and mouth
• Chest and abdominal breathing effort
• Blood oxygen saturation (pulse oximetry)
• Heart rhythm (ECG), snoring sounds, body position and leg movements

The key result is the apnea-hypopnea index (AHI), the average number of breathing pauses and partial obstructions per hour of sleep. In adults, an AHI of 5 to 15 is commonly classed as mild, 15 to 30 as moderate, and above 30 as severe obstructive sleep apnea. The report also lists the lowest oxygen level, how much time was spent with low oxygen, and whether events cluster when lying on the back, which is called positional sleep apnea.

In-lab and home studies

A full in-laboratory study records the most signals and is supervised overnight. Simplified home sleep apnea tests measure fewer channels and can be suitable for some adults with a high likelihood of moderate to severe apnea, but they may underestimate severity.

Who is it for?

A sleep study is recommended for people with:

• Loud, habitual snoring with witnessed breathing pauses or gasping
• Suspected obstructive sleep apnea, especially with daytime sleepiness, morning headaches or poor concentration
• High blood pressure or heart rhythm problems alongside snoring
• Planned snoring surgery, to confirm severity and later assess the result
• Evaluation before choosing CPAP or an oral appliance

How it fits into care at our Gangnam clinic

Dr. Kim Yoo Suk, a board-certified otolaryngologist and former university professor, has published research on long-term outcomes of sleep apnea surgery and on heart rate variability in sleep apnea. The clinic's sleep evaluation brings together:

1. A detailed sleep history, ideally including a bed partner's observations
2. Examination of the nose, palate, tonsils and tongue base with endoscopy
3. A cephalogram and, when needed, CT
4. Polysomnography to measure apnea severity

The logistics of the overnight study are explained at your consultation. Dr. Kim then reviews the full report with you in English, connecting the numbers to your symptoms and anatomy.

What to expect on the night

Sensors are attached with adhesive and elastic belts; none are painful. Follow your usual routine, avoid caffeine in the afternoon and avoid alcohol that evening unless advised otherwise. Many people worry they won't sleep with sensors on, but enough sleep is usually recorded for a valid result.

Risks and limitations

Polysomnography is noninvasive, with only minor skin irritation from adhesives. A single night may not perfectly represent every night, and sleeping in an unfamiliar setting can affect sleep quality. Results are interpreted together with symptoms and examination. Seek medical advice promptly if you feel dangerously sleepy while driving, and avoid driving when drowsy.

Practical information for foreign patients

Bring any previous sleep study reports from home for comparison. Reports and an English medical certificate are available for your records or insurer. Learn about Dr. Kim's sleep apnea research and visit the international patient guide.

Frequently asked questions

What does my AHI number mean?

The apnea-hypopnea index counts breathing pauses and partial obstructions per hour of sleep. In adults, 5 to 15 is commonly considered mild, 15 to 30 moderate, and over 30 severe. Dr. Kim interprets your number alongside symptoms and oxygen levels.

Can snoring be harmless?

Some snoring occurs without sleep apnea and is mainly a social problem. However, loud snoring with pauses, gasping or daytime sleepiness suggests sleep apnea, which is linked to cardiovascular risk. A sleep study clarifies which situation applies.

Should I take my usual medications on the night of the study?

Generally, continue your regular medications unless the doctor advises otherwise. Mention sleeping pills, sedatives and alcohol use during consultation, because they can affect breathing during sleep and the interpretation of results.

This page is general medical information written and reviewed by an ENT specialist. It is not a diagnosis or a guarantee of results; every treatment carries risks, and suitability is decided only after an examination. In an emergency in Korea, call 119.