Yet unpublished preliminary results, that we present in close collaboration with research advisor as a background of this prospective study, indicate that multiple sleep latency test (MSLT) measured sleepiness increases between ages 11-15 years, and then remains relatively stable until the age of 21 years, raising the possibility that adolescents may be unique in their responses to sleep duration. To determine if the objective sleepiness peaks in adolescence and stays elevated or decreases in young adulthood, and thus define whether or not adolescence is a transitional period of sleep need, we propose to evaluate effects of varied sleep duration (sleep restriction – 7 hours of sleep; sleep extension - 10 hours of sleep) on daytime sleepiness measured with MSLT, maintenance of wakefulness test (MWT) and Karolinska Sleepiness Scale (KSS), and on psychomotor vigilance test (PVT) measured performance, spanning wider age range (12-27 years) from adolescence to young adulthood.

Six cohorts, 12 subjects in each (mean age: 12, 15, 18, 21, 24, 27 years) will be studied. Each participant will complete two different time in bed (TIB) schedules (Actigraphy/sleep dairies applied) -  7 days habitual TIB, 3 days - 8.5 hours TIB, four days with either 7 or 10 hours of TIB (3 nights at home, 4th night - Laboratory PSG recording), followed by PVT, KSS, MSLT, and MWT performed at two hour intervals during the day. The proposed study is innovative in providing data on relation of varied sleep duration to daytime sleepiness/performance from adolescence through young adulthood using MSLT and MWT measures of sleepiness simultaneously.