Study objectives: Sleep is vital for health and development, yet inadequate sleep among children and adolescents has risen in recent decades, constituting a pressing public health problem. However, much of the existing research is predominantly based on self- or parent-report, which can be prone to bias. This study used accelerometry-based measures to describe age- and sex-specific sleep habits.
Methods: Thigh-mounted accelerometers were used to measure nocturnal total sleep time (TST), adherence to sleep duration recommendations, bedtime, wake time, chronotype, and sleep variability among 8,948 children and adolescents aged 3-17 years. Mixed-effects linear and quantile regression models fitted with fractional polynomials were used to explore the effects of age and sex on sleep.
Results: Sleep habits differed significantly from childhood through adolescence, with consistent differences between weekdays and weekends. TST rose slightly from ages 3 to 5 years and then declined through adolescence, with consistently higher adherence among girls than boys. Chronotype, bedtime and wake time became increasingly later with age. TST variability was greatest among the youngest children and oldest adolescents, bedtime variability declined with age, whereas wake time variability increased. Overall, girls exhibited earlier changes in sleep habits compared to boys, whereas boys showed a more rapid progression of sleep habit shifts during adolescence.
Conclusions: Nocturnal sleep showed gradual and continuous differences from 3 to 17 years of age, indicating stability only within relatively narrow age intervals. Variations in the rate and timing of differences between boys and girls underscore the need for refined age- and sex-specific sleep duration recommendations.
- 9926853090601891
- Accelerometer-measured sleep habits in Danish children and adolescents aged 3 to 17 years: a pooled analysis with 9,000 participants from six cross-sectional population-based studies
- Maja Sulstad JohansenJesper Schmidt-PerssonNatascha Holbæk PedersenClaus Lindenskov AndersenJan Christian BrøndPeter Lund KristensenJesper Lundbye-JensenMette ToftagerLise HestbækRandi JepsenHenriette BoyeKatrine Rich MadsenRachael TaylorKim Meredith-JonesPoul JennumAnders Grøntved
- Medicine (DSM)
- Sleep, zsag076
- Oxford University Press
- 18/03/2026
- The TRYG Foundation (115606, 130081, 114536); Novo Nordisk Foundation (NNF22SA0077224)
- The published version is not available in full-text in OUR Archive. Where available, a link to the published version is provided (check the DOI and/or the Files and links section). The full-text item may be open access on the publisher's website. An earlier version of the work (such as authors' accepted manuscript following peer-review or unreviewed preprint/author's original version) may be available in the Files and links section of this record. Alternatively, readers may have subscription access to the full-text from the publisher.
- English
- Journal article