Physical Activity, Sedentary Time, and Sleep from Childhood to Young Adulthood: A Seven-Wave Cohort Study of Within-person Relations.

Study objectives: To determine whether within-person changes in total physical activity (PA), moderate-to-vigorous physical activity (MVPA), and sedentary time from ages 6 to 18 predict changes in sleep duration and insomnia symptoms, and vice versa.

Methods: Seven waves of biennially collected data from a birth cohort study were used, capturing ages 6 to 18 years (N = 880). Every second year, objective data on PA, sedentary time, and sleep duration were collected using accelerometers, while insomnia symptoms were assessed through clinical interviews. Random Intercept Cross-Lagged Panel Models (RI-CLPMs) were estimated to test the within-person relations between PA/MVPA/sedentary time and sleep. Potential sex- and age-differences were also examined.

Results: We found no evidence for within-person relations between the study variables, nor for any sex- or age-differences.

Conclusions: Children and adolescents who become more physically active or spend less time in sedentary activities are probably not more likely to sleep longer or better than they typically would.