Abstract
BACKGROUND: Anxiety symptoms are common among university students in China, posing challenges to mental health. Physical activity may reduce anxiety, but the mechanisms are not fully understood. This study examines how smartphone addiction acts as a mediator and sleep quality as a moderator in the relationship between physical activity and anxiety, aiming to offer theoretical insights and practical strategies for mental health interventions. METHODS: This cross-sectional study was conducted in September 2023 at Guangxi University. A stratified sampling method was used to approach 719 students from diverse physical education classes to distribute questionnaires, and 527 valid questionnaires were returned. Validated instruments included the International Physical Activity Questionnaire-Short Form (IPAQ-SF), Smartphone Addiction Scale-Short Version (SAS-SV), Pittsburgh Sleep Quality Index (PSQI), and Self-Rating Anxiety Scale (SAS). Data analysis involved standardization, descriptive statistics, Pearson correlation, normality testing, mediation and moderation analyses, and Bootstrap validation. RESULTS: (1) Physical activity was negatively correlated with smartphone addiction (r = -0.13, p < 0.01). (2) Smartphone addiction was positively correlated with poor sleep quality (r = 0.40, p < 0.01) and anxiety (r = 0.43, p < 0.01). (3) Poor sleep quality and anxiety were significantly correlated (r = 0.57, p < 0.01). (4) A masking effect occurred as the non-significant positive direct effect (β = 0.062) was nearly canceled out by the mediation of smartphone addiction (β = -0.058), inducing total effect near-zero. (5) Sleep quality significantly influenced the link between smartphone addiction and anxiety, especially in those with poorer sleep, where the impact of smartphone addiction on anxiety was stronger (β = 0.061, p = 0.036). CONCLUSION: This study revealed a more complex relationship between physical activity and anxiety than initially hypothesized. Our findings further revealed the relationship between physical activity and university students' anxiety, and considered the mediating role of smartphone addiction between the two, as well as the moderating role of sleep quality in the relationship between mobile phone addiction and university students' anxiety.