Reallocating 24-hour movement behaviors and its impact on mental health in preschool children: a compositional data and dose-response analysis.

Abstract

Background: Mental health issues in preschool children are a significant public health concern with long-term developmental implications. Understanding how reallocations of time among different 24-hour movement behaviors-moderate-to-vigorous physical activity (MVPA), light physical activity (LPA), sedentary behavior (SED), and sleep (SLP)-affect various dimensions of mental health is essential for designing effective interventions.

Methods: In this cross-sectional study, 828 Chinese preschool children aged 3 to 6 years were assessed. Physical activity and sleep were objectively measured using accelerometers to capture MVPA, LPA, SED, and SLP. Mental health was evaluated using the Strengths and Difficulties Questionnaire (SDQ), assessing Total Difficulties, Internalizing Problems, Externalizing Problems, and Prosocial Behavior. Compositional data analysis was conducted using isometric log-ratio (ilr) transformation, followed by multivariate linear regression to assess associations. Additionally, isotemporal substitution modeling and dose-response analysis were applied to examine the effects of reallocating time between behaviors on mental health outcomes, adjusting for age, gender, BMI, parental education, and parental attitudes toward physical activity.

Results: Increased MVPA was significantly associated with lower Total Difficulties (ß_MVPA= - 1.587; P < 0.001) and Internalizing Problems (ß_MVPA= - 0.663; P = 0.017). Increased SED was associated with higher Total Difficulties (ß_SED= 1.512; P < 0.05), while increased SLP was linked to improved Externalizing Problems (ß_LPA= - 1.792; P = 0.008). Reallocating as little as 1 min from LPA or SED to MVPA or SLP significantly reduced Total Difficulties and Internalizing Problems (P < 0.05). Conversely, replacing SED or SLP with LPA increased Externalizing Problems, particularly Conduct Problems and Hyperactivity/Inattention (P < 0.05). A critical threshold at 30 min was identified, beyond which the effects on mental health outcomes became more pronounced.

Conclusions: Reallocating time from LPA or SED to MVPA or SLP significantly improves Total Difficulties and Internalizing Problems in preschool children, even with brief substitutions. However, increasing LPA at the expense of SED or SLP exacerbates Externalizing Problems, especially Conduct Problems and Hyperactivity/Inattention. Interventions should promote MVPA and adequate sleep while considering the critical 30-minute threshold where effects become more pronounced to enhance emotional and behavioral well-being.