[The investigation on the situation of biting pencils among part pupils in Harbin, Guangzhou, and Beijing]

Objective: To investigate the prevalence of biting pencils among pupils living in Harbin, Guangzhou, and Beijing and to compare the differences among these cases. Methods: Stratified sampling method was used to select four elementary schools in Harbin and Guangzhou from April 2015 to April 2016. Firstly, Simple random sampling method was used in every grade (grade 1-grade 5) to select 3 or 4 classes (71 classes in total).After the sample selection, questionnaire surveys were conducted among pupils and their guardians (anyone of their guardians) who belonged to these classes. Secondly, the study extracted part of these pupils to conduct a field survey. Every school was classified by grade, and every grade adopted the method of random sampling to select one classes (20 classes in total). Meanwhile, the study randomly selected pupils from 10 classes in 2 elementary schools in Beijing. All together, 1 627 pupils participated in the field survey. The questionnaire included general information about the students and their guardians, the situation of biting pencils, the awareness of the harm of biting pencils, etc.; the field survey considered if participates' pencils have tooth marks and the severity of the marks, etc. χ(2) was applied to test and compare the differences among pupils of different genders and different cities. The comparison focused on the proportion of students who bited pencils, the proportion of pencils with tooth marks and the proportion of students and guardians already awared of the harm of biting pencils, etc. Results: The number of the valid questionnaires in Harbin and Guangzhou were 1 842, and 1 210, respectively. The occurrence rate of pupils biting pencils in Harbin (18.0% (333/1 842)) was higher than that in Guangzhou (11.3% (137/1 210)) (χ(2)=29.16, P=0.001). Specifically, in Harbin, the rate of boys biting pencils was 21.9% (212/965), which was higher than girls (13.8% (121/877)) (χ(2)=27.04, P=0.001). Similarly, in Guangzhou, the rate of boys biting pencils was 14.5% (92/632), which was also higher than girls (7.7% (45/578)) (χ(2)=15.34, P=0.001). The awareness rate of the harm of biting pencils among students from these two cities were 88.5% (1 611/1 819), and 90.8% (1 098/1 208), respectively, and the difference was statistically significant as well (χ(2)=4.39, P= 0.020). Compared with these data, the awareness rate of the harm of biting pencils among guardians from these two cities were 74.7% (1 339/1 791), and 79.4% (832/1 047), respectively as well as the statistically significant difference appeared (χ(2)=9.83, P=0.007). The result of field survey showed the rate of tooth-marked pencils in Harbin, Guangzhou and Beijing was 30.5% (187/613), 14.8% (79/534), and 28.3% (136/480), respectively. The difference was also statistically significant (χ(2)=42.68, P=0.001). The degree of tooth marks was mainly mild, while the percentage of mild degree in Guangzhou (54.4%(43/79)) and Beijing (41.2% (56/136)) was apparently higher than that of Harbin (39.0% (73/187)). The difference was not statistically significant (χ(2)=7.01, P=0.136). Conclusion: The behavior of biting pencils existed universally among pupils in Harbin, Guangzhou, and Beijing , which the situation of pupils biting pencils in Harbin and Beijing was more serious than that in Guangzhou. Pupils, parents and teachers should pay attention to such a behavior.