Associations of reallocating time between physical activity, sedentary behavior, and sleep with mental health among Chinese adolescents: an isotemporal substitution analysis.

BACKGROUND

Depression and anxiety are important adolescent mental health concerns and may be linked to modifiable movement behaviors, including physical activity (PA), sedentary behavior (SB), and sleep. As mental health outcomes depend not only on time spent in specific behaviors but also on the trade-offs between them, this study examined the associations of reallocating 30 min between these behaviors with adolescent psychological symptoms.

METHODS

This cross-sectional study included 7,767 adolescents from Henan Province, Central China, in 2023. Daily PA, SB, and sleep duration were self-reported. Depressive symptoms were assessed using the 10-item Center for Epidemiologic Studies Depression Scale, and anxiety symptoms were measured with the 7-item Generalized Anxiety Disorder Scale. Isotemporal substitution models estimated the associations of 30-minute reallocations with depressive and anxiety symptoms. Interaction tests and subgroup analyses were conducted according to sleep status.

RESULTS

Replacing 30 min of SB with sleep or PA was associated with lower levels of depression (sleep, B = -0.47, 95%CI = -0.53~-0.41; PA, B = -0.12, 95%CI = -0.16~-0.08) and anxiety (sleep, B = -0.31, 95%CI = -0.36~-0.25; PA, B = -0.07, 95%CI = -0.10~-0.04). Reallocating PA to sleep also related to reduced depressive symptoms (B = -0.35, 95%CI = -0.42~-0.28) and anxiety symptoms (B = -0.24, 95%CI = -0.30~-0.18). Among adolescents with insufficient sleep, the associations were stronger when reallocating SB to sleep (for depression: B = -0.52, 95%CI = -0.64~-0.39; for anxiety: B = -0.40, 95%CI = -0.50~-0.28) or PA to sleep (for depression: B = -0.39, 95%CI = -0.50~-0.25; for anxiety: B = -0.32, 95%CI = -0.41~-0.19). Among those with sufficient sleep, reallocating SB to PA or sleep remained associated with lower depressive symptoms, but no significant association was observed for anxiety.

CONCLUSIONS

Reallocating time toward sleep and PA was associated with reduced depressive and anxiety symptoms, particularly among adolescents with insufficient sleep. Accounting for sleep status may help advance understanding of the associations between movement behavior reallocations and adolescent mental health.