Day type and the relationship between weight status and sleep duration in children and adolescents

Objective: This study aimed to explore sleep duration in young Australians on different types of days across weight classes. Methods: Use of time and anthropometric data were collected on 8,866 nights from 3,884 9-18 year old Australians. The association between sleep duration and weight status was examined using factorial ANOVA for four day types: S-S (to bed and waking on school days); S-NS (to bed on school day and waking on non-school day); NS-NS (to bed and waking on non-school days); NS-S (to bed on non-school day and waking on school day). Results: Sleep duration varied with weight status when all day types were considered together (p=0.0-012). Obese adolescents slept less than normal and underweight adolescents. However, the relationship varied for different day types; with the strongest relationship for NS-S days (on which obese children slept 65 min less than very underweight children, p Conclusions: The association between weight status and sleep duration showed consistent gradients across weight categories, but only for certain day types. Implications: These patterns cast light on the direction of causation in the obesity-sleep duration relationship. Findings suggest that short sleep duration contributes to obesity, or that a third unidentified factor has an impact on both. Key words: sleep, adolescent, overweight, obese, children. Aust NZ J Public Health. 201 O; 34:165-71 doi: 10.1111/j.1753-6405.2010.00502.x