Obesity has been identified as a major risk factor for a large number of chronic diseases. Understanding factors related to adolescent obesity is critical for prevention of chronic diseases. The associations between sleep duration and obesity among adolescents in the existing literature are controversial. Our study was designed to determine the prevalence of short sleep duration, and assess the association of sleep duration and obesity, among middle and high school students in Zhejiang, China. 18,403 Students in 442 schools were recruited and surveyed using an anonymous, self-administered questionnaires. Weighted multivariable logistic regression models were used for data analyses. The mean (SD) age of the students was 15.9 (1.8) years. 49.7% of students were girls. The mean (SD) height and weight were 166.2 (8.5) cm and 54.6 (11.1) kg, respectively. The overall prevalence of obesity and overweight were 3.4% (95% CI: 3.0–3.8) and 7.8% (95% CI: 7.4–8.3), respectively. The overall prevalence of short sleep duration among students was 66.0% (95% CI: 63.8–68.1), higher among girls than boys (69.8% vs. 62.1%) (P < 0.0001). The figures for middle school, academic high school, and vocational high school were 59.0, 82.4 and 59.7%, respectively (P < 0.0001). As compared with girls who sleep 8 h per day (reference), the odds ratios (95% CI) of obesity for girls who sleep < 7 h, 7 h, 9 h and ≥ 10 h were 1.97 (1.15–3.38), 1.90 (1.18–3.04), 1.38 (0.86–2.20) and 2.12 (1.22–3.67) respectively, after adjustment for socio-demographic status, lifestyle factors, and mental health. The corresponding figures among boys were 1.45 (0.97–2.16), 1.13 (0.81–1.57), 1.25 (0.89–1.74), and 1.12 (0.81–1.54), respectively. Insufficient sleep is prevalent among students in Zhejiang China. A U-shaped relationship was found between sleep duration and obesity risk among girls, with the lowest risk among those who slept for 8 h, but not among boys. Adequate sleep duration may be an important component of obesity prevention initiatives among adolescents.

Background: Diabetes was a major risk factor for numerous chronic diseases. However, the associations between daytime napping and diabetes in the existing literature is still inconsistent. Methods: The analysis included 53,916 participants aged 30–79 years of the China Kadoorie Biobank prospective study from Tongxiang. Incident diabetes were identified through linkage with incident diabetes surveillance systems, health insurance system, and death registries. Cox regressions were used to estimate the associations of daytime napping with diabetes. Results: 5.11% of participants reported habitual daytime napping. During 488,233 person-years (median 9.4 years) of follow-up, 3333 incident diabetes, including 1249 males and 2084 females, were documented. After adjusting for socio-demographic status, behavioral lifestyle, BMI, waist circumference and snoring, as comparison with those without daytime napping, the hazard ratios for risk of diabetes were 1.39 (95% CI 1.21–1.59). The corresponding figures for males and females were 1.45 (95% CI 1.20–1.74) and 1.30 (95% CI 1.05–1.59), respectively. The corresponding figures for postmenopausal and premenopausal females were 1.41 (95% CI 1.08–1.80) and 1.13 (95% CI 0.78–1.59), respectively. Conclusions: Habitual daytime napping is positively associated with risk of diabetes in adults, except premenopausal females.

Objective: This study aimed to explore the relationship between breakfast consumption frequency and both depression and anxiety symptoms among middle and high school students in Eastern China. Methods: In this school-based cross-sectional study, 27,001 middle and high school students were investigated in 2022. Multivariable logistic regression models were used to examine the relationship between breakfast consumption frequency and both depression and anxiety symptoms. Results: The percentages of students who consumed breakfast daily, 6 days/week, 4–5 days/week, and ≤3 days/week were 71.0% (95%CI: 69.9–72.2), 8.3% (95%CI: 7.8–8.6), 11.9% (95%CI: 11.2–12.6), and 8.8% (95%CI: 8.2–9.5), respectively. After adjusting for socio-demographic and lifestyle factors, academic performance, self-reported health, and bullying victimization, compared to those consuming breakfast daily, the odds ratios (95%CI) for depression symptoms were 1.32 (1.15–1.52) for those consuming breakfast 6 days/week, 1.66 (1.49–1.84) for those consuming breakfast 4–5 days/week, and 1.74 (1.54–1.97) for those consuming breakfast ≤3 days/week, respectively (p < 0.001). The corresponding figures for anxiety symptoms were 1.31 (1.14–1.51), 1.35 (1.20–1.52), and 1.43 (1.23–1.66), respectively (p < 0.001). Conclusions: Breakfast skipping is common among middle and high school students in Eastern China. The frequency of breakfast consumption is inversely associated with both depression symptoms and anxiety symptoms among adolescents.

Suicide is the second leading cause of death among 15–29 year old youths globally, and the third most common external cause of death in China. School bullying can cause serious consequences among adolescents, including psychosocial problems, low self-esteem and post-traumatic stress disorder. Most studies examining the associations between being bullied in school and suicide are from Western, developed countries. Moreover, few studies focus on being threatened or injured with a weapon, which may cause serious body injury. Our study aimed to explore the relationship of being threatened or injured with a weapon in school with suicidal ideation and attempt among middle and high school students in Zhejiang Province, China. A cross-sectional study of 23,543 students in grades 7–12 from 442 schools was carried out through an anonymous self-administered questionnaire between April and May 2017. Multivariable logistic regression models were used to examine the relationship of being threatened or injured with a weapon in school with suicidal ideation and attempt. 51.3% of participants were boys, and mean (SD) age was 15.6 (1.7) years. The overall prevalence of suicidal ideation and attempt were 16.1% (95%CI: 15.3–16.9) and 3.6% (95%CI: 3.3–4.0), respectively. Prevalence was higher among girls than boys (ideation: 19.1% vs. 13.3%. attempt: 4.4% vs. 2.9%). 13.2% of students reported being threatened or injured with a weapon in school in the past 12 months (95%CI: 11.9–14.5), higher among boys than girls (15.7% vs. 10.5%), and among rural students than urban students (13.9% vs. 11.6%). After adjustment for socio-demographic status, lifestyle factors, academic performance, self-reported health and mental health, the odds ratios for suicidal ideation and attempt among students who reported being threatened or injured with a weapon were 1.46 (1.31–1.61) and 1.68 (1.31–2.13) respectively, as compared with those who did not report being threatened or injured. Preventive measures for physical bullying in school need to be reinforced in China. Being threatened or injured with a weapon is associated with both suicidal ideation and attempt among middle and high school students. Suicide prevention should be an important component of psychological interventions for threatened or injured students.

Background: Existing literature on the association between the frequency of muscle-strengthening exercise (MSE) and depression among adolescents is limited and contradictory. Objective: This study aimed to elucidate the association of MSE frequency with depression symptoms among middle and high school students in China. Methods: A total of 27,070 students in grades 7-12 from 376 middle and high schools were surveyed using an anonymous self-administered questionnaire between April and June 2022. Information on engaging in MSE was self-reported, and depression symptoms were assessed using the Patient Health Questionnaire-9 (PHQ-9). Poisson regression was used to examine the association between MSE frequency and depression symptoms. Results: Among the 27,006 eligible students, 51.6% (n=13,933) were boys, and the mean age was 15.6 (SD 1.7) years. The overall prevalence of meeting MSE recommendations (ie, engaging in MSE ≥3 days/week) was 34.6% (95% CI 32.6%-36.6%; n=9145); the prevalence was higher in boys (43.8%, 95% CI 41.8%-45.8%; 6067/13,933) than in girls (24.3%, 95% CI 22%-26.6%; 3078/13,073; P<.001). A total of 5882 (21.8%) students reported having depression symptoms. After adjustment for sociodemographic status, lifestyle factors, academic performance, and experience of physical fighting, compared to students who did not engage in MSE, the prevalence ratios (PRs) for depression symptoms were 0.98 (95% CI 0.97-0.99) for those engaging in MSE once a week, 0.95 (95% CI 0.93-0.97) for 2 days/week, 0.93 (95% CI 0.90-0.96) for 3 days/week, 0.90 (95% CI 0.87-0.94) for 4 days/week, 0.88 (95% CI 0.84-0.93) for 5 days/week, 0.86 (95% CI 0.81-0.92) for 6 days/week, and 0.84 (95% CI 0.78-0.90) for 7 days/week, respectively. Conclusions: The overall prevalence of meeting MSE recommendations among Chinese adolescents is low. The frequency of MSE was inversely associated with depression symptoms.

Objectives To ascertain the prevalence and associated factors of anxiety symptoms among middle and high school students in Zhejiang after 2 years of the COVID-19 pandemic. Design A school-based cross-sectional study. Setting 30 counties/districts in Zhejiang Province, China. Participants 27 019 students attending middle and high schools. Outcome measures Anxiety symptoms were assessed using the Generalised Anxiety Disorder 7-item scale (GAD-7). A total score of 10 or more is considered indicative of anxiety symptoms. Results The overall prevalence (95% CI) of anxiety symptoms was 14.2% (13.4 to 15.0), higher among girls (18.6%, 95% CI: 17.5 to 19.7) than boys (10.2%, 95% CI: 9.5 to 10.9) (p<0.001), higher among rural students (15.1%, 95% CI: 14.1 to 16.2) than urban students (12.5%, 95% CI: 11.6 to 13.4) (p<0.001). Older age (14–15 years, OR=1.25, 95% CI: 1.09 to 1.44; ≥16 years, OR=1.32, 95% CI: 1.07 to 1.63), being girls (OR=1.76, 95% CI: 1.58 to 1.96), living in rural areas (OR=1.14, 95%CI: 1.01 to 1.29), poor academic performance (OR=1.20, 95% CI: 1.03 to 1.41), alcohol drinking (OR=1.15, 95% CI: 1.01 to 1.30), inadequate fruits (OR=1.31, 95% CI: 1.19 to 1.45) and vegetables intake (OR=1.32, 95% CI: 1.10 to 1.57), insomnia (sometimes, OR=2.14, 95% CI: 1.93 to 2.38; often/always, OR=4.73, 95% CI: 4.03 to 5.56), loneliness (sometimes, OR=2.97, 95%CI: 2.59 to 3.41; often/always, OR=8.35, 95% CI: 7.20 to 9.69), sadness (OR=2.51, 95% CI: 2.25 to 2.79) and physical fight (OR=1.29, 95% CI: 1.13 to 1.48) were positively associated with anxiety symptoms, while studying at vocational high school (OR=0.61, 95% CI: 0.49 to 0.75), coming from family with middle income (OR=0.76, 95% CI: 0.64 to 0.89), being physically active 3–7 days weekly (OR=0.85, 95% CI: 0.75 to 0.95) were negatively associated with anxiety symptoms. Conclusion Anxiety symptoms prevailed among middle and high school students in China. A variety of factors, containing sociodemographic factors, lifestyle behaviours, mental health, academic performance and physical fight should be taken in consideration in addressing prevention and intervention of anxiety symptoms.