Multiple Sleep Latency Test: technical aspects and normal values.

Excessive daytime sleepiness is now recognized as an important medical problem. This paper describes the Multiple Sleep Latency Test (MSLT), a direct, objective method of measuring daytime sleepiness. The standard methodology of the MSLT is outlined, including a description of possible and sources of error in conducting an MSLT. Data regarding the reliability and validity of the MSLT are presented. Finally, normal values are offered, and clinical MSLT results in patients with disorders of excessive daytime sleepiness are interpreted.