Sleep studies, also known as polysomnograms, are tests to diagnose and evaluate the severity of sleep disorders. Sleep disorders can be serious because they can elevate risk levels for medical conditions, including high blood pressure, heart disease and stroke, and have also been linked to vehicular accidents, including train derailments and airplane crashes, and to injury-causing falls, especially among the elderly.
Patients are often unaware of problems during sleep until other symptoms make them, their sleep partners or their doctors, suspicious of a sleep disorder. Such symptoms may include snoring, fatigue or sleepiness during waking hours, sleepwalking, waking up too early, or having trouble falling asleep at night. Sleep studies also evaluate how much time the patient spends in each level of sleep and what percentage of time in bed is actually spent sleeping.
Reasons for a Sleep Study
There are several types of disorders, including the following, that sleep studies can help to diagnose:
- Sleep apnea
- Sleep-related seizure disorders
- Parasomnia (abnormal movements or perceptions during sleep)
Sleep-related movement disorders may include sleepwalking, sleep talking, sleep-related eating disorder (SRED), restless leg syndrome, night terrors and sleep sex. All of these disorders not only disturb sleep patterns, but can be dangerous to the patient or others.
The Sleep Study Procedure
Prior to administration of a sleep study, the patient undergoes a thorough physical examination. A complete medical history, including a full report of sleep schedules and habits, and any symptoms related to sleep, is taken. The patient arrives at a sleep laboratory a couple of hours before his or her usual sleep time. The room is usually set up something like a motel room.
The patient is then attached to a number of machines that will monitor and record any biophysiological changes that occur during sleep. These devices typically include some or all of the following:
- Electroencephalograph (EEG)
- Electrooculograph (EOG)
- Electromyelograph (EMG)
- Electrocardiograph (EKG/ECG)
- Nasal-airflow sensor
- Snore microphone
These tests measure, respectively, brain-wave activity, eye movement, muscle movement, electrical activity of the heart, nasal airflow and snoring. In addition, belts are placed around the chest and abdomen to measure breathing, and an oximeter is placed on the finger to measure the amount of oxygen in the blood.
Other tests may be performed to measure how long it takes patients to fall asleep, how many times they awaken during the night, and how long they remain asleep. A trained sleep technician remains in the sleep lab during the testing period. A doctor who specializes in sleep medicine analyzes the resulting data to diagnose sleep disorders and their level of severity so that an appropriate treatment plan can be devised.