Polysomnography

An overnight sleep study, formally known as polysomnography (PSG), is a comprehensive test used to diagnose sleep disorders by monitoring various physiological parameters while a person sleeps. It is typically conducted in a sleep lab or center and is considered the gold standard for diagnosing conditions like sleep apnea, narcolepsy, insomnia, and other sleep-related issues.

What Polysomnography Measures

During a polysomnography test, a variety of bodily functions and activities are recorded throughout the night, including:

  1. Brain Waves (EEG): Electrodes placed on the scalp monitor brain activity, helping to determine sleep stages (e.g., light sleep, deep sleep, REM sleep) and sleep cycles.

  2. Eye Movements (EOG): Sensors near the eyes track movement, particularly rapid eye movement (REM), which is associated with dreaming and specific sleep phases.

  3. Heart Rate (ECG): Electrodes on the chest measure heart rate and rhythm to detect abnormalities that may occur during sleep.

  4. Breathing Patterns: Breathing effort and airflow are monitored using bands around the chest and abdomen, as well as a sensor near the nose and mouth, to detect interruptions in breathing, such as those seen in sleep apnea.

  5. Oxygen Levels (Pulse Oximetry): A sensor placed on a finger or earlobe measures blood oxygen saturation throughout the night, which is crucial for detecting conditions like obstructive sleep apnea (OSA).

  6. Limb Movements (EMG): Sensors on the legs and chin monitor muscle activity to identify issues such as restless legs syndrome or periodic limb movement disorder (PLMD), which can disrupt sleep.

  7. Body Position and Snoring: Snoring sounds are recorded, and body position is tracked to determine if sleep issues worsen in certain positions, such as lying on the back.

How the Test Works

  1. Preparation: The patient arrives at the sleep center in the evening, where they are guided by a sleep technician. Sensors are placed on the scalp, face, chest, and legs, connected by wires to a machine that records data. While the sensors may feel unusual, they are non-invasive and designed to allow for natural sleep.

  2. Monitoring Sleep: Throughout the night, the sleep technician monitors the patient's sleep from a nearby room. Data is recorded as the patient transitions through different sleep stages, and any disruptions or abnormalities are noted.

  3. Sleep Analysis: After the test, the data collected from the polysomnography is analyzed by sleep specialists to identify issues such as:

  4. Sleep apnea (breathing pauses or shallow breaths)

  5. Narcolepsy (sudden onset of REM sleep)

  6. Insomnia (difficulty falling or staying asleep)

  7. Movement disorders (such as restless leg syndrome)

  8. Parasomnias (abnormal movements or behaviors during sleep)

Results

The results of the overnight sleep study help doctors diagnose specific sleep disorders and guide treatment decisions. In the case of sleep apnea, for example, polysomnography can indicate the severity of the condition, leading to treatment options like CPAP therapy (continuous positive airway pressure).

Why Polysomnography is Important

Polysomnography provides detailed insights into the quality and structure of a person's sleep, identifying abnormalities that can affect overall health and well-being. Early detection and treatment of sleep disorders through overnight sleep studies can prevent related health problems such as heart disease, hypertension, diabetes, and daytime fatigue.

In summary, polysomnography is a key diagnostic tool used by sleep specialists to evaluate a wide range of sleep disorders, helping patients achieve better sleep and improved health.