title: Circadian preferences and sleep in 15- to 20-year old Finnish students.
abstract: OBJECTIVE
  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. The self-report measures included a shortened version of the Horne-Östberg Morningness-Eveningness Scale, the Epworth Sleepiness Scale as well as items probing feelings of tiredness, optimal subjective sleep durations, and bedtime and wake-up time on the most recent day and a typical weekend. Data were collected from Tuesday to Thursday during an ordinary school week.
  
  
  CONCLUSIONS
  The most frequent chronotype was the intermediate type (54%), and compared to previous studies, the prevalence of evening-oriented individuals was high (37%), whereas only 9% of the participants were classified as morning oriented. No gender-specific or chronotype-specific differences in sleep durations were observed, but girls/women and evening-orientated individuals reported suffering more from sleepiness, compared to boys/men and more morning-typed participants, respectively. About 20% of the total sample indicated that their subjective need for sleep was not satisfied during the weekdays nor the weekend, indicating chronic sleep deprivation. Among girls/women and evening-oriented individuals, the subjective sleep need was greater for weekday nights.
authors.affiliation: Open University, University of Helsinki, Finland.
authors.forename: Juhani E
authors.initials: JE
authors.lastname: Lehto
authors.affiliation: Open University, University of Helsinki, Finland.
authors.forename: Outi
authors.initials: O
authors.lastname: Aho
authors.affiliation: Open University, University of Helsinki, Finland.
authors.forename: Mari
authors.initials: M
authors.lastname: Eklund
authors.affiliation: Open University, University of Helsinki, Finland.
authors.forename: Marika
authors.initials: M
authors.lastname: Heinaro
authors.affiliation: Open University, University of Helsinki, Finland.
authors.forename: Sari
authors.initials: S
authors.lastname: Kettunen
authors.affiliation: Open University, University of Helsinki, Finland.
authors.forename: Aila
authors.initials: A
authors.lastname: Peltomäki
authors.affiliation: Open University, University of Helsinki, Finland.
authors.forename: Katja
authors.initials: K
authors.lastname: Ylä-Kotola
authors.affiliation: Open University, University of Helsinki, Finland.
authors.forename: Kaarina
authors.initials: K
authors.lastname: Öst
authors.affiliation: Department of Health, National Institute for Health and Welfare, Helsinki, Finland.
authors.forename: Timo
authors.initials: T
authors.lastname: Partonen
keywords: Chronotype; Diurnal; Gender; Optimal sleep length; Sleep deprivation; Sleepiness