Objective: To describe the prevalence and relationship between screen time and sub-health status among middle school students in weekdays and weekends.
Methods: With multistage stratified random cluster sampling, 14 400 students from junior and senior middle schools in 288 classes of 30 schools in 4 cities( Shenyang, Chongqing, Xinxiang, Guangzhou) were investigated in October, 2011. A total of 13 817 valid questionnaires were retained for analysis. Survey content includes general demographic information, screen time, sub-health state. Logistic regression model was used to analyze the relationship between screen time and sub-health status.
Results: The screen time among middle school students > 2 h/d on weekdays and weekends were 15.1% (2 085/13 817) and 58.5% (8 077/13 817) , respectively. Among them, the boys' screen time > 2 h/d on weekdays and weekends were 17.9% (1 187/6 644) and 61.3% (4 070/6 644), which were higher than girls (12.5% (898/7 173), 55.9% (4 007/7 173) )(χ² values were 76.95 and 41.35, respectively. P < 0.01). The prevalence of physical sub-health status, psychological sub-health status and sub-health status were 24.8% (3 431/13 817), 21.7% (2 997/13 817) and 22.1% (3 051/13 817), respectively. Among them, the girls' prevalence of physical sub-health status, psychological sub-health status and sub-health status were 26.0% (1 863/7 173), 22.9% (1642/7 173) and 23.1% (1 658/7 173) ), respectively, which were higher than boys' (23.6% (1 568/6 644), 20.4% (1 355/6 644) and 21.0% (1 393/6 644)) (χ² values were 10.39, 12.66 and 9.25, respectively. P < 0.05). The senior students' prevalence of physical sub-health status, psychological sub-health status and sub-health status were 31.6% (2 176/6 884) , 28.3% (1 946/6 884) and 28.9% (1 990/6 884), respectively, which were higher than junior students' (18.1% (1 255/6 933), 15.2% (1 051/6 933) and 15.3% (1 061/6 933)) (χ² values were 337.65, 349.46 and 371.54, respectively, P < 0.05). After adjusting on demographic characteristics, compared with screen time ≤ 2 h/d on weekday, screen time > 2 h/d on weekday was significantly associated with physical sub-health status, psychological sub-health status and sub-health status (OR (95% CI): 1.39 (1.25-1.55), 1.62 (1.45-1.81) and 1.59 (1.43-1.78)). And compared with screen time ≤ 2 h/d on weekend, screen time > 2 h/d on weekend was also significantly associated with physical sub-health status, psychological sub-health status and sub-health status (OR(95% CI):1.49 (1.37-1.61), 1.81 (1.66-1.98), and 1.71 (1.57-1.87)).
Conclusion: The rate of the screen time > 2 h/d and the detection ratio of sub-health among the middle school students in Shenyang, Chongqing, Xinxiang, Guangzhou in 2011 were high. Screen time >2 h/d on weekdays or weekends was a risk factor for sub-health status.