Polysomnography (PSG) is a comprehensive sleep study used to diagnose sleep disorders and analyze sleep patterns by recording various physiological parameters during sleep. It is widely regarded as the gold standard for assessing sleep quality and detecting abnormalities that may affect an individual’s health and well-being.
What is Polysomnography?
Polysomnography is a multi-parametric test that monitors several body functions simultaneously while a person sleeps. These functions include brain activity (electroencephalogram or EEG), eye movements (electrooculogram or EOG), muscle activity or skeletal medico del sonno muscle activation (electromyogram or EMG), heart rhythm (electrocardiogram or ECG), respiratory airflow, blood oxygen levels, and limb movements.
The primary purpose of PSG is to diagnose various sleep disorders, such as obstructive sleep apnea (OSA), narcolepsy, restless leg syndrome (RLS), periodic limb movement disorder (PLMD), and REM sleep behavior disorder (RBD). It also helps in evaluating insomnia and other conditions that disrupt normal sleep architecture.
How Does Polysomnography Work?
During a polysomnography test, a patient typically spends a night in a specialized sleep laboratory or center. The test involves attaching electrodes and sensors to the scalp, face, chest, limbs, and fingers to monitor the physiological parameters. The data collected during the night provides an in-depth view of the patient’s sleep stages, breathing patterns, oxygen saturation, and physical movements.
The test records sleep cycles, which include non-rapid eye movement (NREM) stages and rapid eye movement (REM) sleep. These stages are crucial for restorative sleep and cognitive function. Any disruption or abnormality in these stages can be detected via PSG, allowing clinicians to pinpoint the root cause of sleep disturbances.
Importance of Polysomnography in Diagnosis
Sleep disorders affect millions of people worldwide and can lead to severe health complications if untreated. Conditions such as sleep apnea, characterized by repeated interruptions in breathing during sleep, are linked with cardiovascular diseases, hypertension, diabetes, and impaired daytime functioning.
Polysomnography is instrumental in diagnosing sleep apnea by identifying episodes of apnea (cessation of breathing) or hypopnea (reduction in airflow) during sleep. It also measures oxygen desaturation events and the frequency of arousals from sleep, which can explain symptoms like excessive daytime sleepiness, fatigue, and cognitive impairment.
For patients suspected of having narcolepsy, polysomnography is often followed by a multiple sleep latency test (MSLT) to evaluate excessive daytime sleepiness and REM onset during daytime naps.
Advancements and Variations
While traditional polysomnography requires an overnight stay in a sleep center, advancements in technology have introduced portable home sleep apnea testing (HSAT). These simplified devices monitor fewer parameters but are convenient for diagnosing sleep apnea in certain patient populations.
However, comprehensive PSG remains the most reliable method for diagnosing complex sleep disorders and is preferred when other medical conditions or multiple sleep disturbances are suspected.
Preparing for the Test
Patients are advised to avoid caffeine and alcohol before the study and to follow their usual sleep schedule as much as possible. Comfortable clothing is recommended since the test requires spending the night connected to sensors.
Polysomnography is an essential tool in sleep medicine, providing valuable insights into sleep architecture and disorders. Early diagnosis through PSG can significantly improve patient outcomes by guiding appropriate treatments such as continuous positive airway pressure (CPAP) therapy for sleep apnea or medication for restless leg syndrome. As awareness about sleep health grows, polysomnography continues to be pivotal in understanding and managing sleep-related conditions.