A sleep study, known medically as polysomnography (PSG), is a comprehensive diagnostic procedure used to evaluate an individual’s sleep health and pinpoint underlying sleep disorders. This overnight assessment monitors multiple physiological functions while a person is asleep, providing objective data that guides diagnosis and treatment. Sleep studies capture real-time measurements of brain activity, breathing patterns, heart rate, and muscle movements to identify abnormalities. Clinicians analyze these signals to diagnose conditions such as obstructive sleep apnea, narcolepsy, restless legs syndrome, and chronic insomnia.
Professional Sleep Centers
The traditional and most comprehensive location for a sleep study is a professional sleep center, which may be a stand-alone clinic or a specialized unit within a hospital. These facilities are highly controlled environments, often featuring soundproof bedrooms that resemble comfortable hotel rooms to promote sleep. A registered sleep technician (RST) monitors the patient throughout the night from an adjacent control room.
The technician connects the patient to a comprehensive array of monitoring equipment using numerous sensors and electrodes applied to the scalp, face, chest, and limbs. This extensive setup allows for the simultaneous recording of multiple physiological parameters, defining polysomnography. The constant presence of a credentialed technician allows for immediate intervention and ensures the highest quality of recorded data.
Measurements in a Sleep Center
Brain waves (EEG) are tracked to determine sleep stages, and eye movements (EOG) are recorded to identify rapid eye movement (REM) sleep. Electrodes on the chin and legs monitor muscle activity (EMG), which can reveal disorders like restless legs syndrome or periodic limb movement disorder. Respiratory effort is measured using belts around the chest and abdomen, and airflow sensors are positioned near the nose and mouth. A pulse oximeter records blood oxygen saturation levels, and heart activity is tracked via electrocardiography (ECG).
Home Sleep Apnea Testing
Home Sleep Apnea Testing (HSAT) is conducted in the patient’s own residence. This option offers convenience and allows the patient to sleep in a familiar environment, potentially leading to a more typical night of sleep. The test is self-administered using a portable monitoring device worn for one or more nights.
HSAT devices are less complex than in-lab equipment, using a reduced number of sensors like a finger probe, nasal cannula, and chest straps. HSATs measure fewer metrics than a full PSG, focusing primarily on respiratory function, including breathing effort, airflow, heart rate, and blood oxygen saturation. The results calculate the Apnea-Hypopnea Index (AHI), which measures breathing interruptions per hour. HSAT is primarily used for diagnosing Obstructive Sleep Apnea (OSA) in adults without complicating medical factors.
Determining the Appropriate Testing Environment
The choice between a professional sleep center and a home study is a clinical decision based on the patient’s symptoms and overall health profile. Home testing is sufficient for otherwise healthy adults with a strong suspicion of moderate-to-severe Obstructive Sleep Apnea (OSA). The convenience and lower cost of HSAT make it an accessible first step for many patients.
The in-lab setting remains the gold standard because it provides a comprehensive analysis of sleep stages and a wider range of disorders. A full polysomnography is mandatory for patients with complex medical conditions, such as significant heart failure or severe pulmonary disease. The laboratory environment is also required for diagnosing non-respiratory sleep disorders, including narcolepsy, restless legs syndrome, or parasomnias. Pediatric cases, or situations where an initial home test was inconclusive, also necessitate an attended study in a professional sleep center.