The most common method of studying sleep disorders is polysomnography. This examination is conducted by a somnologist in a special laboratory where the patient should spend the night. During his sleep, many sensors simultaneously record the bioelectric activity of the brain (EEG), cardiac activity (ECG), respiratory movements of the chest and anterior abdominal wall, inhaled and exhaled airflow, oxygen saturation of the blood, etc. A video recording of what is happening in the ward and constant monitoring on duty doctor. Such a survey makes it possible to study the state of brain activity and the functioning of the main body systems during each of the five stages of sleep, to identify abnormalities and to find the cause of sleep disturbance.
Another method of diagnosing sleep disorders is to investigate the average sleep latency (SLE). It is used to identify the cause of drowsiness and plays an important role in the diagnosis of narcolepsy. The study consists of five attempts to fall asleep, which are carried out during waking hours. Each attempt lasts 20 minutes, the interval between attempts is 2 hours. The average latency of sleep is the time that the patient needed to sleep. If it is more than 10 minutes, then this is the norm, from 10 to 5 minutes – borderline value, less than 5 minutes – pathological drowsiness.