Sleep Study (Polysomnography)
A sleep study, also known as polysomnography, is a diagnostic test used to monitor and assess sleep patterns, identify sleep disorders, and evaluate the quality of sleep. It is typically conducted in a sleep clinic or a specialized sleep center, although home sleep studies are also available for certain conditions. A sleep study provides valuable information about various stages of sleep, the body’s physiological responses during sleep, and potential disruptions.
How a Sleep Study Works:
During a sleep study, the patient is monitored overnight while they sleep, and several bodily functions are measured to understand the nature of their sleep and identify any issues. The test is non-invasive, and sensors are attached to the patient’s body to collect data without disrupting their rest.
The key components typically monitored during a sleep study include:
- Brain activity (EEG): Electrodes placed on the scalp monitor brain waves to assess the different stages of sleep (e.g., REM, deep sleep).
- Eye movements (EOG): Sensors placed near the eyes detect rapid eye movements, which occur during REM (Rapid Eye Movement) sleep.
- Muscle activity (EMG): Electrodes are placed on the chin and legs to monitor muscle tone, which helps identify conditions like sleep apnea or restless leg syndrome.
- Heart rate (ECG): The heart’s electrical activity is measured to assess cardiovascular function during sleep.
- Respiratory effort: Sensors around the chest and abdomen monitor how well a person is breathing during sleep, helping to detect issues like sleep apnea.
- Oxygen levels (pulse oximetry): A clip is placed on the finger or earlobe to measure blood oxygen saturation, which helps identify any drops in oxygen levels during sleep.
- Leg movements: Electromyography (EMG) detects abnormal leg movements, which can be a sign of conditions like restless leg syndrome or periodic limb movement disorder.
Types of Sleep Studies:
- Polysomnography (PSG): The most comprehensive sleep study, which involves the monitoring of brain activity, heart rate, muscle movements, eye movements, and respiratory functions. It is typically used to diagnose disorders like sleep apnea, narcolepsy, or parasomnias (e.g., sleepwalking).
- Home Sleep Apnea Test (HSAT): A simplified version of a sleep study that is done at home. It primarily measures breathing patterns, oxygen levels, and heart rate to diagnose obstructive sleep apnea (OSA). This test is typically prescribed for patients suspected to have OSA and is not suitable for other sleep disorders.
- Multiple Sleep Latency Test (MSLT): This test is often done the day after a polysomnography to assess daytime sleepiness and diagnose narcolepsy or other excessive daytime sleep disorders.
- Actigraphy: This involves wearing a wristwatch-like device that monitors sleep-wake patterns over a period of time. It’s commonly used for patients with suspected insomnia or circadian rhythm disorders.
Common Sleep Disorders Diagnosed by a Sleep Study:
- Obstructive Sleep Apnea (OSA): A common condition where the airway becomes blocked during sleep, causing brief periods of interrupted breathing.
- Central Sleep Apnea: A less common type of sleep apnea where the brain does not send the correct signals to the muscles that control breathing.
- Narcolepsy: A disorder that causes excessive daytime sleepiness, often with sudden episodes of falling asleep.
- Restless Leg Syndrome (RLS): A condition characterized by uncomfortable sensations in the legs, leading to an irresistible urge to move them, particularly at night.
- Parasomnias: Sleep disorders involving abnormal behaviors during sleep, such as sleepwalking, night terrors, or REM sleep behavior disorder.
