Social Jetlag Emerges in Preadolescent Children Despite Adequate Sleep Duration: Evidence for Child-Mother Circadian...

Social jetlag, the misalignment between behaviourally expressed circadian timing and social schedules, has been extensively studied in adults but remains poorly characterized in preadolescent children. This cross-sectional survey examined sleep-wake patterns in 972 Israeli children (mean age: 5.8 ± 1.6 years, range: 4-10) and their mothers (mean age: 37.1 ± 5.7 years, range: 22-49), who reported sleep behaviours using adapted Munich Chronotype Questionnaire items and an item about evening screen exposure between 16:00 and sleep onset. Children's mean sleep duration was 10.45 h, with 57.1% showing 30 min or less variation between free and school days. Surprisingly, children exhibited higher social jetlag than their mothers (64.9 ± 47.7 vs. 46.6 ± 52.9 min, p < 0.001), increasing from 54.5 min at age 4 to 107.1 min at age 10. Positive correlations existed between mother-child chronotypes (ρ = 0.224, p < 0.001) and social jetlag (ρ = 0.222, p < 0.001). Evening screen exposure averaged 84 ± 66 min and correlated with age (ρ = 0.240, p < 0.001). Later chronotype was the strongest predictor of child social jetlag; higher body mass index was associated with greater social jetlag, whereas older age, secular lifestyle, longer sleep, more consistent sleep duration and screen exposure were associated with lower social jetlag. Maternal social jetlag independently predicted greater child social jetlag. Young children experience substantial social jetlag, challenging assumptions about sleep timing regularity in preadolescence. Adequate sleep duration coexisting with high social jetlag, a marker linked to adverse metabolic and behavioural outcomes, suggests paediatric guidelines may need to incorporate weekly sleep timing consistency. Child-mother sleep interconnections highlight the necessity of exploring family-based interventions beyond focus on sleep quantity.