INTRODUCTION Secondhand smoke (SHS) exposure affects tobacco related health behaviors during adolescence and persists into adulthood. This study aimed to investigate the influence of SHS exposure on tobacco use among adolescents stratified by school and gender, and provide recommendations for controlling tobacco use in youth. METHODS Through stratified random cluster sampling, 12278 selected students (aged 13-18 years) from schools in China were administered questionnaires. Multiple logistic regression was used to analyze whether SHS exposure would increase the smoking risk and susceptibility of adolescents. RESULTS The prevalence of SHS exposure among the participating students was 74.8%. Adolescents exposed to SHS were at higher odds of being susceptible and currently smoking. Students with SHS exposure at both home and public places accounted for 36.6%, greatly increasing the current smoking risk and smoking susceptibility. Home SHS exposure had greater impact on the current tobacco use of boys (OR=2.13; 95% CI: 1.50-3.03) and junior school students (OR=4.67; 95% CI: 2.41-9.06). Exposure from public places increased the risk of current smoking in boys (OR=4.20; 95% CI: 2.31-7.65) and smoking susceptibility of vocational school students (OR=1.51; 95% CI: 1.07-2.15). Students with highlevel exposure to SHS had 2.25 times higher odds of e-cigarette use. CONCLUSIONS The prevalence of SHS exposure is still high among adolescents in China and is associated with increased risk for tobacco use regardless of gender and school level. Effective smoke-free strategies should be developed and strictly implemented. Boys and junior school students constitute vulnerable populations exposed to SHS at home.

E-cigarettes are widely advertised, while the potential risks of e-cigarette use have been reported among adolescents. This study assessed online e-cigarette information exposure and its association with adolescents’ e-cigarette use in Shanghai, China. A total of 12,470 students aged 13–18 years participated. A questionnaire collected information on students’ sociodemographic factors, e-cigarette information exposure, cigarette use, e-cigarette use, and e-cigarette use intention. A multivariate logistic regression was performed to assess correlates of exposure to e-cigarette information and the association between e-cigarette information exposure and e-cigarette use. Overall, 73.9% of students knew about e-cigarettes and the primary sources of information were the internet (42.4%), movies/TV (36.4%), bulletin boards in retail stores or supermarkets (34.9%), advertising flyers (33.9%), and friends (13.8%). Students who had friends using e-cigarettes were curious about e-cigarettes and showed a greater monthly allowance; smokers and females were at a higher risk of social media and website exposure. Moreover, online information exposure (social media exposure, website exposure, and total internet exposure) was significantly associated with the intention to use e-cigarettes. The enforcement of regulations on online e-cigarette content should be implemented. Moreover, efforts to prevent young people from using e-cigarettes may benefit from targeting students at a higher risk of online e-cigarette information exposure.

Weight-related status has been associated with the physical and psychological health of adolescents. This cross-sectional study evaluated three different kinds of weight-related statuses (Body Mass Index (BMI), weight self-perception and weight teasing from others) among Chinese adolescents and identified their associations with health risk behaviors (lack of healthy dietary behavior, unhealthy dietary behavior, binge eating behavior, lack of physical activity (PA), sedentary behaviors (SB) and sleep disturbance). A stratified random cluster sampling method was used to select 10,070 students aged 11–18 years old from schools in Shanghai. Self-reported questionnaires were collected, weight-related statuses were divided into three categories and six specific health risk behaviors were classified into two groups: positive or negative. Overall, 27.82% of the adolescents were classified as being overweight and obese (35.61% of boys and 18.21% of girls), 43.45% perceived themselves as too heavy and 30.46% experienced weight teasing in the past. Among overweight or obese participants, 50.55% have been teased about their weight, and 77.48% perceived themselves as too heavy. Weight perception and weight teasing were significantly associated with health risk behaviors rather than the actual body weight status based on BMI, especially regarding binge eating behavior (body weight status (BMI): p > 0.05, underweight perception: OR = 1.18, 95%CI 1.03–1.34; weight teasing for more than once a year: OR = 2.00, 95%CI 1.76–2.27). In addition, weight perception and weight teasing were significantly associated with health risk behaviors, mainly in normal and overweight/obese groups but not in underweight groups. Weight teasing and weight self-perception play an independent and stronger role than actual body weight in the health behaviors of adolescents. This calls for more attention and intervention to reduce peer bullying and stigmas on weight among adolescents.

Poor nutrition or insufficient physical activity (PA) are risk factors for obesity and chronic diseases. This 2019 cross-sectional study from the school health survey examined the dietary and PA behaviors of Chinese adolescents. A total of 12,860 adolescents aged 11–18 participated through multistage and stratified cluster random sampling. A questionnaire collected data on weight, PA, sedentary lifestyle, and eating habits. Unhealthy behaviors were identified and summed up for each behavior. Participants were then classified into high and low amounts of risk behaviors. Weight status was defined using Body Mass Index (BMI) cutoff points for Chinese individuals aged 6–18. Multinomial logistic regression was used to assess effects of lifestyle behaviors on weight status. The prevalence of overweight and obesity was 22.3% among all participants (30.6% in boys, 13.2% in girls). Females engaged in more risk physical activities (4.12 vs. 3.80, p < 0.05), while males engaged in more risk dietary activities (2.20 vs. 2.02, p < 0.05). Higher number of risk dietary, PA, and sedentary behaviors were all significantly correlated with higher BMI (dietary: r = 0.064; PA: r = 0.099; sedentary: r = 0.161; p < 0.001 for all) and body weight (dietary: r = 0.124; PA: r = 0.128; sedentary: r = 0.222; p < 0.001 for all). Risk sedentary behaviors was a significant risk factor for overweight/obesity (Adjusted Odds Ratio AOR = 1.30, 95% Confidence Interval CI 1.11–1.52). Obesity and unhealthy lifestyle behaviors remain a concern among Chinese adolescents. These results provide an update on the factors contributing to overweight/obesity among adolescents and call for efforts to address obesity among adolescents.

INTRODUCTION This study was conducted to explore the characteristics and risk factors of e-cigarette use in adolescents, aiming for tobacco control and reducing e-cigarette use in this population. METHODS Using 1:1 matching, 88 students from three vocational high schools in Shanghai were recruited to conduct a case (using e-cigarettes) - control (not using e-cigarettes) study. Group interviews and questionnaire surveys were used for this qualitative and quantitative mixed-methods study. The keywords were extracted from the interview data and analyzed by the Colaizzi seven-step method. RESULTS The characteristics of adolescents’ use of e-cigarettes include young age at first use, consumption of a large amount, as well as smoking in discrete locations in order to hide from adults. The reasons for using e-cigarettes include curiosity and wanting to replace traditional cigarettes. The risk factors of using e-cigarettes include insufficient understanding of the harm of e-cigarettes at the individual level (The positive outcome expectancy points: Z= -3.746, p<0.001; The negative outcome expectancy points: Z= -3.882, p<0.001), peer influence at the interpersonal level (χ 2 =6.510, p<0.01), and the influence of social and environmental factors such as e-cigarette sales in the stores and WeChat Moments (p<0.05 for all associations). CONCLUSIONS Having friends who use e-cigarettes, curiosity and sales exposure about e-cigarettes are important factors affecting the use of e-cigarettes by adolescents. It is necessary to strengthen the publicity of the potential hazards of e-cigarettes and to reduce overall usage by improving relevant laws and regulations.