More than just sleeping in: a late timing of sleep is associated with health problems and unhealthy behaviours in adolescents

Abstract

ObjectiveNew research suggests that the timing of sleep, or chronotype, affects the mental well-being of adolescents, however evidence of its links to physical health is limited. We investigated the associations between chronotype and various health outcomes and behaviours in a national sample of Canadian adolescents. MethodsData were from the 2014 Canadian Health Behaviour in School-Aged Children survey (29,470 students; ages 10–18). Chronotype was estimated using the midpoint of sleep on weekends, corrected for catch-up sleep. We tested the associations with physical health (headache, stomach ache, back ache, dizziness, overweight, self-rated health) and health behaviours (consumption of fruits, vegetables, sweets, soft drinks, and energy drinks, smoking, physical activity, screen time) using random-effects regressions adjusted for sleep duration and individual, family, and school characteristics. ResultsThe average chronotype was 4:11 a.m. for boys and 4:10 for girls. Each 1-h delay in chronotype was associated with more headaches, stomach aches, and back aches [proportional odds ratios (PropORs) 1.08, 1.08, 1.07, respectively (boys), 1.10, 1.10, 1.08, respectively (girls)], and dizziness and worse self-rated health in girls (PropORs 1.10 and 1.09, respectively), but not overweight. A 1-h delay in chronotype also related to daily soft drink consumption [ORs 1.17 (boys), 1.11 (girls)], smoking [ORs 1.23 (boys), 1.37 (girls)], screen time [additional 0.64 h (boys), 0.74 h (girls)], less vegetable consumption in boys (OR 0.96), and daily energy drink consumption in girls (OR 1.42). ConclusionA later chronotype related to worse physical health and unhealthy behaviours in Canadian adolescents. Studies are needed to clarify the underlying mechanisms.