Check your sleep score! Overnight sleep study is also known as Polysomnography. Sensors are placed at different locations on the body and are connected to a computer. A sleep technician is present for attaching the electrodes and for monitoring the patient during the study.
A sleep study measures the sleep cycles with sleep stages and many body functions by recording the following information:
The main reason for getting a PSG done would be to confirm a diagnosis of obstructive sleep apnea (OSA), a sleep disorder in which a person has repeated obstruction to breathing as he sleeps. In addition, PSG is used to diagnose other sleep disorders like narcolepsy, restless legs syndrome, REM behavior disorder, parasomnias, and sleep rhythm disorders.
The study is done at a sleep laboratory with facilities for the patient to stay overnight. The following steps are recommended before a sleep study:
Typically, the patient will be asked to come to the sleep laboratory an hour or two before the patient’s usual bedtime.
The collected data in the study is reviewed in terms of "epochs" of 30 seconds each, looking for:
Sleep latency, shows the time interval between lights being switched off and the initiation of sleep in the patient. The EEG shows whether the patient was awake or was sleeping.
Sleep efficiency, which is the minutes of total sleep divided by the minutes spent on bed. In normal cases, it falls between 85%-90%.
Sleep stages, are based on the data coming from the five channels, EOG (2), EEG (usually 2 channels), and chin EMG. The stages of sleep are:
Apnea is the complete cessation of breathing for at least 10 seconds in sleep while hypopnea refers to partial cessation, again lasting for at least 10 seconds. Apnea/ hypopnea index (API) is calculated from these observations. For normal persons, it must be below 5.
"Arousals" are indicated by a sudden shift in the brain wave activity due to a variety of reasons such as leg movements, atmospheric conditions, breathing irregularities etc. A higher than normal number of "arousals" could be indicative of disturbed sleep or other symptoms like fatigue and/or sleeplessness.
Cardiac rhythm abnormalities, body position during sleep, leg movement patterns, and oxygen saturation are charted during the study.
It usually takes about two weeks to get the results of a sleep study. Once the study has been analyzed and "scored", the results are then sent to the sleep physician for interpretation. A sleep physician reaches a conclusion after considering the patient's medical and drug history, and the results are in turn sent across to the referring physician with specific recommendations based on the analysis for further treatments or tests.