Multiple Sleep Latency Test (MSLT)

Most people with excessive sleepiness have a disorder that is detectable on an overnight sleep study. In a small number of people, the cause for excessive sleepiness is not clear after an overnight sleep study and, it may be necessary to measure the ease with which they fall asleep during the day and the type of sleep experienced. This test is called a Multiple Sleep Latency Test (MSLT). The need for an MSLT is always discussed before arranging the study.

The MSLT is performed during the day after an overnight sleep study. Some of the sensors placed for the overnight sleep study are left in place and, following breakfast and a period of recreation, a series of 4 or 5 naps is scheduled at 2-hourly intervals commencing about 9.00 am with completion by 3.00 to 5.00 pm. Thus a full day is occupied. The naps typically last for about 20 minutes; each nap starts with the patient in bed and following a request to “lie quietly, close your eyes and try and fall asleep”. Between naps, the leads are disconnected from the amplifiers and the patient is free to move about.

Breakfast and lunch are provided in the cafeteria. Patients having an MSLT may choose to bring their own pillow and something to occupy them between naps.

Patients are advised to abide by the following rules to ensure that the MSLT is valid:

  1. After sufficient overnight sleep, the patient must ring the buzzer so that the overnight technologists can end the overnight study and document the time. The MSLT will start 1.5 to 3 hours after this time.
  2. The technologists will then remove some overnight sensors, leaving most of the facial sensors in place. The patient will then be advised to dress in day clothes. It is best to have loose, comfortable clothes to wear during the MSLT.
  3. The patient will be asked to provide a urine sample in a yellow-topped container before the MSLT, and this will be sent to a pathology company for analysis. The patient will receive an account (about $40) from the pathology company for the cost of the analysis.
  4. Once out of bed, the patient should avoid lying or sitting on the bed except when requested by the technologist for each nap test.
  5. Carbonated drinks and caffeine (eg. coffee, tea, Coke) must be avoided prior to and during the MSLT.
  6. The technologist will check all medications normally taken in the morning to ensure that they do not interfere with the MSLT. Some medication may be withheld until after the MSLT.
  7. Cigarette smokers should not smoke for at least 30 minutes prior to each nap.
  8. Vigorous activity should be avoided for at least 15 minutes prior to each nap.