Polysomnography: definition, indication and interpretation of results

Key Points	Summary
What is polysomnography?	A medical examination that analyzes a person's sleep in detail over a full night using sensors that record various physiological parameters (brain activity, eye movements, heart rate, breathing, body movements, oxygen saturation).
Why undergo polysomnography?	Mainly to detect and characterize sleep apnea, evaluate before surgery, monitor the effectiveness of a treatment, or diagnose other sleep disorders (restless legs syndrome, sleepwalking, narcolepsy, etc.).
Procedure of a polysomnography exam	Arrival at the sleep center, setting up sensors, recording parameters overnight under surveillance, possible additional tests, disconnection in the morning.
Interpreting the results	Analysis of various data (EEG, EOG, EMG, breathing, saturation, ECG) by a specialist physician to identify abnormalities and make an accurate diagnosis.
Cost of polysomnography	Between €120 and €400, partially covered by Health Insurance. High cost due to the technicality of the exam (overnight hospital stay, qualified staff, medical equipment).
Alternatives to polysomnography	Ventilatory polygraphy, actigraphy, sleep diary for more targeted assessments or initial screenings at a lower cost.

What is polysomnography?

Polysomnography is a medical examination that provides a detailed analysis of a person's sleep.

It is the most complete exploration for diagnosing sleep disorders.

Over the course of a full night, various sensors are installed on the patient to record several sleep-related physiological parameters.

What data is stored?

• Brain activity (electroencephalogram or EEG),
• Eye movements (electro-oculogram or EOG),
• Heart rhythm (electrocardiogram or ECG),
• Breathing and respiratory effort,
• Leg and body movements,
• Blood oxygen saturation (oximetry).

With these recordings, doctors can:

💊 analyze the different phases of sleep,

💊 detect apneas or other respiratory abnormalities,

💊 identify motor or behavioral disorders during sleep.

Evaluated Medical conditions

Polysomnography can be used to evaluate and diagnose many sleep disorders, including:

• Obstructive sleep apnea syndrome (OSA)
• Chronic insomnia
• Circadian rhythm disorders
• Restless legs syndrome
• Sleepwalking and other motor disorders
• Narcolepsy and hypersomnia
• Bruxism (teeth grinding during sleep)

Why have polysomnography?

Suspicion of sleep apnea

Polysomnography can detect and characterize obstructive apneas (respiratory arrest due to airway obstruction) or central apneas.

It assesses the severity of sleep apnea syndrome and its consequences (oxygen desaturation, micro-arousals, sleep fragmentation, etc.)

Assessment before surgery

Before major surgery (e.g. heart or neurological surgery), polysomnography may be prescribed to detect any sleep-disordered breathing that could complicate the operation and post-operative recovery.

Treatment follow-up

In patients already being treated for a sleep disorder (apnea, insomnia, etc.), polysomnography enables us to assess the effectiveness of treatment (continuous positive airway pressure, mandibular advancement orthosis, etc.) and adjust settings if necessary.

Diagnosis of other pathologies

The examination can also help diagnose other disorders such as:

💊 the restless legs syndrome,

💊 sleepwalking,

💊 narcolepsy,

💊 certain disorders of circadian rhythm.

It provides a detailed analysis of sleep structure and quality.

How is a polysomnography examination carried out?

Preparing for the polysomnography examination

You arrive at the sleep center in the late afternoon or early evening.

A technician greets you and installs you in a recording chamber equipped for the examination.

He explains how the night went.

Sensor installation

The technician installs numerous sensors on your body:

💊 Scalp electrodes to record brain activity (electroencephalogram)

💊 Electrodes around the eyes to detect eye movements

💊 Sensors on chin and legs to detect muscle movements

💊 Electrodes on the chest to monitor cardiac activity

💊 Nasal and thoracic sensors to measure respiration

💊 Finger oximeter for monitoring oxygen saturation

Overnight recording

Once all the connections have been made, you can go to bed and try to sleep normally.

All your physiological parameters are recorded continuously overnight by a computer system.

✅ A technician monitors the data from the adjoining control room.

Possible tests

Depending on the case, additional tests may be carried out during the night, such as :

💊 Sleep latency tests to assess sleepiness

💊 Recording of continuous positive airway pressure (CPAP) if treatment is already underway

💊 Monitoring cerebral oxygenation with near-infrared spectroscopy

Early in the morning, the technician disconnects you from the sensors.

The data is then analyzed by a sleep specialist to provide a precise diagnosis.

How to interpret the results?

➡The electroencephalogram (EEG) can be used to identify the different stages of sleep (light, deep, REM) and to detect possible micro-awakenings or sleep disturbances.

➡ The electro-oculogram (EOG) and electromyogram (EMG)provide information on eye and muscle movements, important for diagnosing certain motor disorders such as restless legs syndrome.

➡ Respiratory data (nasal/buccal airflow, thoracic and abdominal effort, oxygen saturation) are important for characterizing the presence, severity and type of sleep apnea (obstructive, central, mixed).

➡ An electrocardiogram (ECG) is used to monitor heart rhythm and detect any arrhythmias associated with respiratory disorders.

⚠ Interpretation requires great expertise to differentiate normal sleep from pathological abnormalities.

How much does polysomnography cost?

The cost of a complete polysomnographic examination performed in a sleep laboratory generally varies between 120 and 400 Euros..

This high price is explained by the technical nature of the examination, which requires:

💊 one night in hospital,

💊 qualified personnel,

💊 medical equipment.

In most cases, the Health Insurance covers a part of the cost.

The remaining cost for the patient depends on his or her complementary health insurance.

Some polysomnographies performed on an outpatient basis (without overnight hospitalization) or ventilatory polygraphies (recording limited to respiratory parameters) are less expensive, costing around 100 to 200 euros.

What are the alternatives to polysomnography?

Ventilatory polygraphy

This examination focuses solely on respiratory parameters during sleep.

It detects and quantifies obstructive apnea/hypopnea using nasal, thoracic and oximetry sensors.

It's a good initial screening for obstructive sleep apnea syndrome, less costly than a full polysomnography.

Actimetry

This is a small device worn on the wrist which records movements over a prolonged period (generally 1 to 2 weeks).

Actimetry can be used to estimate the hours:

💊 to fall asleep,

💊 wake-up call,

💊  and total sleep time.

It's a simple, inexpensive test, but provides only limited information.

Sleep diary

This tool consists of daily notes on bedtimes/wake up times, how long you fall asleep, how many times you wake up at night, and so on

Although subjective, the sleep diary provides useful information on sleep habits in the case of insomnia, for example.

The Back2Sleep solution, the intranasal orthosis

The Back2Sleep orthosis is a medical device for treating snoring and sleep apnea in a simple, low-impact way.

Placed in the nostrils, it keeps the upper airways open during sleep for free breathing and restful sleep.

FAQs on polysomnography

Q. How long does a polysomnography examination last?

The standard duration of a complete polysomnographic examination is one whole night, i.e. around 8 hours of recording.

Recording starts at bedtime and continues until you wake up the next morning.

Q. Is the examination painful or invasive?

No, polysomnography is neither painful nor invasive.

It simply involves placing several external sensors on the body (electrodes on the scalp, face and chest, nasal and thoracic sensors).

Q. What are the contraindications?

There are generally no major contraindications to polysomnography.

Certain severe pathologies may constitute a temporary contraindication, but this is rare.

Q. Where are polysomnographies performed?

Polysomnography examinations generally take place in specialized centers called "sleep laboratories" or "sleep centers".

These are dedicated hospital departments with fully equipped registration rooms.

Some general hospitals and private clinics also offer polysomnography in their pneumology or neurology departments.

Q. How do I prepare for the exam?

Here are the main recommendations for preparing for polysomnography:

- Avoid naps and alcohol in the hours preceding the exam

- Do not take sleeping pills or any other medication unless advised by your doctor

- Bring your own toiletries and nightwear (pyjamas, robe, etc.)

- Bring your own pillow if you wish

- Follow your usual sleep pattern during the day