A total of 56% of 184 schools, including 48 of 98 junior high schools (response rate: 49%) and 55 of 86 high schools (response rate: 64%) took part in the survey. In total, 64,417 questionnaires were returned to the research office. After excluding the questionnaires that were blank, or had invalid/missing gender information or inconsistent responses, 64,152 questionnaires were analysed. The characteristics of the study participants are shown in Table 1.
Rates of cigarette and new tobacco-alternative product use
Broken down by product type and student gender, the age-adjusted rate of students who were ever/current/every day users of cigarettes, e-cigarettes, or HNB tobacco are shown in Table 2.
The rate of ever users of cigarettes (male/female/both) was 3.1% (95% CI: 3.1±0.1)/2.1% (95% CI: 2.1±0.1)/2.6% (95% CI: 2.6±0.1) for junior high school students, and 6.9% (95% CI: 6.9±0.3)/3.3% (95% CI: 2.1±0.1)/5.1% (95% CI: 2.6±0.3) for high school students. E-cigarette use was slightly lower than cigarette use, at 2.4% (95% CI: 2.4±0.1)/1.7% (95% CI: 1.7±0.1)/2.1% (95% CI: 2.1±0.1) among junior high school students, and 4.9% (95% CI: 4.9±0.2)/2.1% (95% CI: 2.1±0.0)/3.5% (95% CI: 3.5±0.2) among high school students. The rate of HNB tobacco users was relatively lower relative to other products, at 1.3% (95% CI: 1.3±0.0)/0.9% (95% CI: 0.9±0.0)/1.1% (95% CI: 1.1±0.1) among junior high school students, and 2.9% (95% CI: 2.9±0.1)/1.4% (95% CI: 1.4±0.0)/2.2% (95% CI: 2.2±0.2) among high school students.
The rate of current use of the three products (male/female/both) was rare. For cigarettes, the rate was 0.7% (95% CI: 0.7±0.0)/0.5% (95% CI: 0.5±0.0)/0.6% (95% CI: 0.6±0.1) among junior high school students, and 2.0% (95% CI: 2.0±0.1)/0.9% (95% CI: 0.9±0.0)/1.5% (95% CI: 1.5±0.1) among high school students. For e-cigarettes, it was 0.8% (95% CI: 0.8±0.0)/0.5% (95% CI: 0.5±0.0)/0.7% (95% CI: 0.7±0.1) for junior high school students, and 1.5% (95% CI: 1.5±0.1)/0.5% (95% CI: 0.5±0.0)/1.0% (95% CI: 1.0±0.1) for high school students. For HNB tobacco, it was 0.6% (95% CI: 0.6±0.0)/0.4% (95% CI: 0.4±0.1)/0.5% (95% CI: 0.5±0.0) for junior high school students, and 1.2% (95% CI: 1.2±0.1)/0.6% (95% CI: 0.6±0.0)/0.9% (95% CI: 0.9±0.1) for high school students.
The proportion of students who used the products every day was quite low, with the highest prevalence being that of cigarette use among high school students (male/female/both): 0.7% (95% CI: 0.7±0.1)/0.2% (95% CI: 0.2±0.0)/0.5% (95% CI: 0.5±0.1). The age-adjusted rates for the new products were 0.1% or less.
As shown in Figure 1, the use of combustible cigarettes was the most prevalent regardless of grade level. Ever use of e-cigarettes followed slightly below that of cigarettes, especially among the younger generation. A divergence was evident between ever use of HNB tobacco and that of the two other types. As for current use, the graphs of the three products overlapped each other in the younger generation, but in grades 11 and 12, combustible cigarette use was significantly higher than the use of the other two products.
Combined use of any tobacco product
The age-adjusted rates of combined use of tobacco-related products were calculated (Additional file 1), including all possible combinations of combustible cigarettes, e-cigarettes, and HNB tobacco. Across the various patterns, the exclusive users of cigarettes and exclusive users of e-cigarettes were the largest groups.
Moreover, to make comparisons more understandable, the proportions of ever and current users of any product are shown in Table 3. In terms of ever use, the proportion of exclusive users of combustible cigarettes was about 40% of users of any product in both junior high schools and high schools. Meanwhile, around 36% of users of any product used only e-cigarettes and/or HNB tobacco in junior high schools. Among high school users, around 25% of males and 32% of females ever used either one or both new alternative products. Furthermore, among junior high school students who currently used any product, exclusive e-cigarette users were the largest group among all patterns of use. In high school, exclusive combustible cigarette use, 30%, was dominant across the patterns; however, more than 30% of users currently used only new alternative products. It is worth mentioning that dual users who currently used both cigarettes and another type of products exceeded 30% in junior high school as well as in high school.
Additional file 2 shows the comparison of ever users of different products according to gender, school grade, municipality size, custom of having breakfast, participation in club activities, and future education intention. Across the different users, the proportions of males were higher than those of females. However, gender differences were smaller when comparing e-cigarette users and HNB users with cigarette users. There were upward trends from lower to higher school grades in exclusive cigarette use and cigarette use combined with other products, but the trends were not clear among new alternative products users. Regarding lifestyle, adolescents who ever used new types of products showed acceptable habits. The percentage of individuals who had breakfast every day and participated in club activities was higher among new products users than among cigarette users. The proportion of students considering further education beyond high school was higher among e-cigarette users than among other users.