Breakpoints of time in bed, midpoint of sleep, and social jetlag from infancy to early adulthood

Abstract

ObjectivesThe present study investigated sleep duration and sleep timing from infancy to early adulthood. MethodsA cross-sectional survey study of N = 18,323 participants (9004 female) from 0 to 25 years (M = 12.36; SD = 5.76) from kindergartens, schools and universities in SW Germany. Participants reported their usual bedtimes and rise times on weekdays/weekends. Time in bed (TIB), the midpoint of sleep, and social jetlag were calculated from these four clock times. ResultsWeekday rise times were progressively earlier until the age of 17 years, while weekend rise times contrarily were later. As a consequence, TIB during the week was progressively shorter until the age of 16 years. The midpoint of sleep (MSFsc) was increasingly later until it reached a plateau at 17 years. Social jetlag increased until 16 years to 3:18 h. Gender differences were small for sleep duration/chronotype with males sleeping less and later than girls and non-significant for social jetlag. A regression with two breakpoints explained variability in sleep duration and sleep timing by age (45–61% explained variance) better than a regression with one breakpoint (44–59%), linear regression (25–54%) or polynomial regression (43–60%). ConclusionsThe age around 16–17 years can be considered a remarkable breakpoint when sleep behavior significantly changes back towards slightly longer sleep, less socially jetlagged behavior, and the increase in eveningness is then stopped but not reversed. A somewhat softer breakpoint is identified around 5–7 years when the rapid changes in sleep behavior initiate.