Sedentary Behavior And Its Association With Overweight And Obesity Among Secondary School Students Of Yuhang District In Hangzhou City

[OBJECTIVE] To assess the situation of sedentary behavior and its association with the prevalence of overweight and obesity among junior middle school students in Yuhang district, and to provide the scientific evidence for preventing overweight and obesity.[METHODS] The sample was selected using a cluster sampling, included1139students in three secondary schools. The survey was conducted among the students and their parents. The questionnaire was consisted of the basic information of the student and the family, time spent on sedentary behavior, dietary behavior, physical activity, sleeping hours and academic stress. The time of sedentary behavior was divided into two groups according to P50or P75. Overweight and obesity was classified with BMI cutoff points from WGOC. Group comparisons were performed using χ2test. Multiple logistic regression was used to study the influence of sedentary behavior on overweight and obesity.[RESULTS] Among of the1,139student,49.5%were boys and50.5%were girls. They were all was between10and16years old and the average age was12.78(SD=0.66). Most of the parents’ education levels were junior high school or below, most of the parents had jobs. Overall,9.9%was overweight,4.0%was obesity. The overweight rate (χ2=15.792, P<0.001) and obesity rate (χ2=20.053, P<0.001) in boys were both higher than girls.On weekdays, written homework every day normally took a relatively long time, and the median was120minutes (quartile range:90-170minutes). On weekend, the median of written homework time was180minutes (quartile range:120-240minutes), and the median of screen entertainment time was180minutes(quartile range:120-300minutes).On weekdays, girls spent more time in homework, learning using computer than boys, and boys spent more time in screen entertainment than girls. On weekend, girls spent more time in reading and learning using computer.The screen entertainment time was significantly higher in the student whose written homework time was no more than2hours than the student more than2hours on weekdays(boys χ2=11.416, P<0.001, girls χ2=4.177, P=0.041). The girls whose written homework time was longer, the time of learning by using computer was longer(weekday χ2=9.392, P=0.002, weekend χ2=24.040, P<0.001). Screen entertainment time in weekend was significantly associated with boys’ overweight and obesity(χ2=16.981, P<0.001). Screen entertainment both weekdays and weekend was significantly associated with girls’ overweight and obesity (weekday χ2=9.091, P=0.003, weekend χ2=4.249, P=0.039). The time of learning by using computer was significantly associated with girls’ overweight and obesity (χ2=5.236, P=0.021).Compared the risk factor of overweight and obesity between groups which sedentary behavior time was different, we found that on weekdays, screen entertainment time was associated with the feeding frequency of fried food(χ2=17.904, P<0.001) and carbonated drinks(χ2=29.937, P<0.001). The time of learning by using computer was associated with biscuits sweets feeding frequency(χ2=4.258, P=0.039). On weekend, screen entertainment time was associated with the feeding frequency of fried food(χ2=15.266, P<0.001), carbonated drinks(χ2=16.712, P<0.001) and biscuits sweets(χ2=4.507, P=0.034). There was significant difference in physical activity between the students whose screen entertainment time, or reading time, or the time of learning using computer was difference. Written homework time was associated with adequate sleep. The students whose written homework time was longer had more academic stress.In a logistic regression model, after control diet, physical activity, sleeping hours and academic stress, reported that screen entertainment time more than3hour on weekend was the risk factor of boys’ overweight and obesity(aOR=2.227,95%CI:1.439～3.4453), screen entertainment time more than30minutes on weekdays(aOR=2.533,95%CI:1.349～4.758),3hours on weekends (aOR=1.923,95%CI:1.034～3.577) and learning using computer more than50minutes on weekends(aOR=2.073,95%CI:1.094～3.928) were the risk factors of girls’ overweight and obesity.[CONCLUSION] The sedentary behavior time of Yuhang District students was too long, especially written work time and screen entertainment time. Screen entertainment on weekend was closely associated with overweight and obesity of boys. Screen entertainment on both weekday and weekend was closely associated with overweight and obesity of girls. The influence of sedentary behavior on overweight and obesity was not found to be mediated by diet, physical activity, sleeping hours and academic stress.