What is the Multiple Sleep Latency Test?

The multiple sleep latency test is a study used to help doctors accurately diagnose different sleep disorders, including narcolepsy and excessive daytime sleepiness. The day-long test takes place in an accredited sleep study center, and it is overseen by certified technicians, nurses, and doctors. A patient is given a comfortable, quiet private room and allowed to take four or five naps during the day with about two hours between each. Monitoring equipment is used to detect changes in brain and eye activity and determine if a disorder exists.

Different sleep centers and labs may have their own versions of the multiple sleep latency test, but most tests are administered very similarly. Before the multiple sleep latency test can take place, the patient usually needs to stay a night in the sleep center so doctors can monitor night-long patterns in a procedure called polysomnography. Results from the overnight test are used as a baseline for the daytime tests to track changes.

During both the multiple sleep latency test and the polysomnography study, electrodes are affixed to the chest, forehead, chin, underneath the eyes. Data on brain wave activity, heart rate, eye movement, and facial muscle contractions are collected by an electronic monitoring machine. The testing procedure is completely painless, and sleep technicians try to make the sensors and wires as comfortable to wear as possible.

After the night of the polysomnography test, a patient is encouraged to stay awake for about two hours in the morning. He or she is then asked to try to fall asleep again. The sleep technician records the time it takes for the patient to actually enter sleep, and then tracks brain and eye activity to determine when deep sleep, or rapid eye movement (REM) sleep, is reached. The patient is woken up about 15 or 20 minutes into the nap and instructed to stay awake for another two hours. Most sleep centers conduct four or five nap tests per patient, so a person can expect to be at the center for at least seven hours.

Once testing is completed, a patient is allowed to go home and technicians, psychologists, and doctors can begin analyzing results. Information about how long it took the patient to fall asleep during each nap can help doctors assess the possibility of narcolepsy or another chronic sleepiness problem. In general, a multiple sleep latency test that shows a person falling asleep within five minutes and quickly entering the REM phase is indicative of an underlying disorder. Once findings are carefully reviewed, a doctor can explain the results to the patient and discuss treatment options.