Cross-sectional and prospective associations between children's 24-h time use and their health-related quality of life: a compositional isotemporal substitution approach

Background Promoting active, balanced lifestyles among children may be an important approach to optimising their health-related quality of life (HRQoL). However, the relationships between children's movement behaviours and HRQoL remain unclear. Methods We examined the associations between movement behaviours (sleep, inactivity, light and moderate-to vigorous intensity physical activity) assessed using accelerometers at ages 8 and 10 years and self-reported HRQoL scores (overall, and physical and emotional well-being, self-esteem, relationship with family and friends, and school functioning domains) at age 10 years among 370 children in a local birth cohort using compositional isotemporal substitution techniques.Findings Cross-sectionally, light and moderate-to-vigorous intensity physical activities were associated with better selfesteem (0 = 15.94 [2.71, 29.18]) and relationship with friends (0 = 10.28 [3.81, 16.74]) scores respectively. Prospectively, inactivity was associated with lower overall HRQoL (0 = -10.00 [-19.13, -0.87]), relationship with friends (0 = -16.41 [-31.60, -1.23]) and school functioning (0 = -15.30 [-29.16, -1.44]) scores, while sleep showed a positive trend with overall HRQoL (0 = 10.76 [-1.09, 22.61]) and school functioning (0 = 17.12 [-0.87, 35.10]) scores. Children's movement behaviours were not associated with their physical and emotional well-being, or relationship with family scores. The isotemporal substitution analyses suggest that increasing time spent in physical activity and/or sleep at the expense of inactivity may benefit children's HRQoL.Interpretation Our findings suggest that sleep and physical activity may be associated with better HRQoL, with the inverse for inactivity. However, the relationship between children's movement behaviours and HRQoL is complex and warrants further research.