multiple sleep latency test (MSLT), a test of the propensity to fall asleep, often used to diagnose narcolepsy. The subject is given five 20-minute nap opportunities at 2-hour intervals, usually after an overnight polysomnogram. The mean latency to sleep onset and the stages of sleep that occur are determined from polygraph records. Well-rested adults have a mean MSLT of 15 minutes. A mean MSLT of less than 5 minutes indicates severe hypersomnia.
