Cross-sectional sleep thresholds for optimal health and well-being in Australian 4-9-year-olds

Aim. Using national Australian time-diary data, we aimed to empirically determine sleep duration thresholds beyond which children have poorer health, learning, quality of life, and weight status and parents have poorer mental health. Methods. Design/Setting: Cross-sectional data from the first three waves of the Longitudinal Study of Australian Children. Participants: A nationally representative sample of 4983 4-5-year-olds, recruited in 2004 from the Australian Medicare database and followed biennially; 3631 had analyzable sleep information and a concurrent measure of health and well-being for at least one wave. Main measures: Exposure: At each wave, a parent completed 24-h time-use diaries for one randomly selected weekday and one weekend day, including a "sleeping/napping" category. Outcomes: Parent-reported child mental health, health-related quality of life, and maternal/paternal mental health; teacher-reported child language, literacy, mathematical thinking, and approach to learning; and assessed child body mass index and girth. Results. Linear regression analyses revealed weak, inconsistent relationships between sleep duration and outcomes at every wave. For example, children with versus without psychosocial health-related quality of life problems slept slightly less at 6-7 years (adjusted mean difference 0.12 h; 95% confidence interval 0.01-0.22, p = 0.03), but not at 4-5 (0.00; -0.10 to 0.11, p = 1.0) or 8-9 years (0.09; -0.02 to 0.22, p = 0.1). Empirical exploration using fractional polynomials demonstrated no clear thresholds for sleep duration and any adverse outcome at any wave. Conclusions. Present guidelines in terms of children's short sleep duration appear misguided. Other parameters such as sleep timing may be more meaningful for understanding optimal child sleep.