Association between screen time and physical activity on mental health among preschoolers: a cross-sectional study from Southwest China.

Background: Screen time and physical activity behaviors undergo development during early childhood and impact mental health. However, there is limited knowledge regarding the associations between physical activity, screen time, and mental health problems (MHP) in preschoolers. This study examines these associations using a large sample size and brief measures.

Methods: A multistage cluster stratified sampling method was used to conduct an observational cross-sectional study of 19,015 Chinese preschoolers in 2020. Information on physical activity, and screen time was collected by a self-administered questionnaire; MHP was assessed by the parent-reported Strengths and Difficulties Questionnaire (SDQ). Logistic regression models were used to obtain the odds ratios (ORs) and 95% confidence intervals (95% CIs) of preschoolers' MHP associated with screen time, total physical activities, moderate to vigorous physical activity (MVPA), and outdoor physical activities.

Results: A total of 19,015 participants from the 19,548 recruited population were included in the analyses (missing rate: 2.73%), 52.60% were boys. 64.01%, 57.96%, 35.98%, and 82.64% of preschoolers were reported to meet total physical activities, MVPA, and outdoor activities with screen time recommendations level. The results of multivariable-adjusted ORs (95% CIs) of preschoolers' MHP for comparisons of different levels of screen time (< 2 h/day, 2-4 h/day,≥4 h/day) show that screen time positively associated with MHP after adjusting for confounders (P < 0.05), but the association was not significant among girls with screen time ≥ 4 h/day. In addition, increased engagement in physical activity was reversely linked to MHP (P < 0.05). A stronger association between MHP and MVPA was observed in boys, however, this association was weakened when the total time spent engaging in MVPA exceeded two hours per day (P < 0.05).

Conclusion: Less physical activity and more screen time positively relate to MHP, but the relationship differs by type of physical activity, total time, and gender. These findings provide novel insights and evidence supporting for guidelines on physical activity, screen time, and improvement of mental health for preschoolers.