title: Actigraphy-assessed sleep during school and vacation periods: a naturalistic study of restricted and extended sleep opportunities in adolescents.
abstract: School-related sleep restriction in adolescents has been identified by studies comparing weekday and weekend sleep. This study compared weekday and vacation sleep to assess restricted and extended sleep opportunities. One-hundred and forty-six adolescents (47.3% male) aged 16.2 ± 1.0 years (M ± SD) from the general community wore an actigraph continuously for 4 weeks: the last week of a school term (Time-E), the following 2-week vacation, and the first week of the next term. Self-reported sleep was assessed for each of the three time intervals, and chronotype was assessed using the Morningness-Eveningness Questionnaire at Time-E. Daily actigraphy bedtime, rise-time, time-in-bed, total sleep time, sleep onset latency, sleep efficiency, and % wake after sleep onset were analysed using latent growth curve modelling. The removal of school-related sleep restriction was associated with an abrupt delay in sleep timing and increase in sleep duration. Subsequently, bedtime and rise-time showed further linear delays throughout the vacation, while changes in time-in-bed were non-significant. Sleep onset latency increased linearly, peaking in the middle of the second vacation week. Across the first vacation week, total sleep time and sleep efficiency linearly decreased, while % wake after sleep onset increased. These changes stabilized during the second vacation week. Older age and eveningness were associated with later bedtime and rise-time, whilst females had longer time-in-bed, total sleep time and sleep onset latency. Compared with school days, sleep during the vacation was characterized by later timing, longer duration, lower quality and greater variability. Recovery from school-related sleep restriction appeared to be completed within the 2 weeks of naturalistic extended sleep.
authors.affiliation: Melbourne School of Psychological Sciences, University of Melbourne, Melbourne, Vic., Australia.
authors.forename: Bei
authors.initials: B
authors.lastname: Bei
authors.forename: Nicholas B
authors.initials: NB
authors.lastname: Allen
authors.forename: Christian L
authors.initials: CL
authors.lastname: Nicholas
authors.forename: Paul
authors.initials: P
authors.lastname: Dudgeon
authors.forename: Greg
authors.initials: G
authors.lastname: Murray
authors.forename: John
authors.initials: J
authors.lastname: Trinder
mesh_terms: D056044:Actigraphy; D000293:Adolescent; D001071:Appointments and Schedules; D005260:Female; D006693:Holidays; D006801:Humans; D008297:Male; D012574:Schools; D057566:Self Report; D012890:Sleep / Q000502:physiology*; D012892:Sleep Deprivation / Q000503:physiopathology; D011795:Surveys and Questionnaires; D013997:Time Factors; D014739:Victoria
keywords: adolescence; latent growth curve modelling; sleep duration; sleep recovery; sleep variability; vacation