Circadian preferences and sleep in 15- to 20-year old Finnish students.

Purpose: Despite progress in research concerning adolescent and young adult sleep and circadian preferences, several aspects have remained unexamined. This study explored gender and diurnal rhythms in relation to several sleep-related factors: sleep duration, bedtime, wake-up time, tiredness, sleepiness, and optimal subjective sleep duration.

Methods: Circadian preferences and sleep were investigated in 555 (Females N=247) Finnish students aged 15-20.