Abstract
Physical activity, screen time, and sleep each represent important targets for health interventions. However, physical activity alone may not mitigate the harmful effects of excessive screen time or lack of sleep and vice versa. The purpose of our study was to examine the independent and combined effects of physical activity, screen time, and hours slept in grades 5/6, as well as the effects of change in these behaviours across 3 years, on quality of life in grades 8/9. Participants (N=918, 9-12 years old in grades 5/6) from the MATCH study completed self-report questionnaires 10 times across a 3-year period. A growth model including paths from physical activity, screen time, and hours slept in grades 5/6 and changes in these behaviours over 3 years to quality of life, provided a good fit to the data (?2(316)=803.76, p<.05, CFI=.92, RMSEA=.04, 90%CI[0.04, 0.05], R2=.20). After controlling for sex, higher physical activity (ß=.12) and hours slept (ß=.19) and lower screen time (ß=-.20) in grades 5/ 6 were associated with better quality of life in grades 8/9 (p's<.05). Increases in physical activity (ß=.22, p<.05) and hours slept (ß=.15, p=.058) and decreases in screen time (ß=-.20 p<.05) over 3 years were associated with better quality of life in grades 8/9. Youth who engaged in more physical activity, slept more, and spent less time engaging in screen-based activities during elementary school and upon entering high school experienced better quality of life in high school. Interventions targeting all three health behaviours may be more effective at promoting quality of life in youth than interventions targeting a single health behaviour.Acknowledgments: The MATCH study is supported by the New Brunswick Health Research Foundation (#20130729) and by the Social Sciences and Humanities Research Council and Sport Canada through the joint Sport Participation Research Initiative (#862-2010-0001).