Abstract The health of adolescents is a barometer of social development, adolescents undergo a critical period for the development of competencies related to health and well being, which is also an important stage for laying the foundation for health. This editorial proposes key considerations for the successful system optimization in adolescent health services and relevant policies in China, and presents an indicator and monitoring framework for adolescent health promotion toward Healthy China 2030, through summarizing the health and developmental challenges faced by Chinese adolescents, and embracing innovations in national policy development.

Abstract As the compositional nature of "constant sum" of physical activity, sedentary behavior and sleep are widely recognized, the methodological and result limitations of previous studies that considered physical activity, sedentary behavior, or sleep as independent influences on physical fitness and health have been highlighted. At present,physical activity guidelines of various countries have shifted from local recommendations based on physical activity amount to global recommendations based on 24 h time frame. From the perspective of time use, the content of daily schedule of children and adolescents also has the attribute of "constant sum" of compositional data, and the reduction of students homework burden and extracurricular discipline training after "double reduction" inevitably means an increase in the time allocated to other activities. From the perspective of time use, the paper focuses on physical fitness and health promotion strategies in the context of "double reduction".

Abstract Improving the system of adolescent myopia prevention and control and promoting adolescent healthy development is one of the main directions of healthy China construction in the new era. The paper reviewed national myopia policies and local practices, and proposed reflections on the high burden and complex etiology of myopia among adolescents, as well as unclear role and lack of coordination mandate during the COVID 19 epidemic. Based on the synergy theory, through the analysis of the functional positioning of multiple subjects in the prevention and control of myopia, the paper highlighted the multi party linkage of government, schools, medical institutions, communities, families and markets, profiling the resources and advantages of each subject, as well as dynamic management of adolescent myopia, as well as a multi subject collaborative prevention and control system with national unity, clear rights and responsibilities, and long term cooperation.

Objective: To examine the relationship between 24 hour movement behavior and physical fitness of pupils by using compositional analyses, so as to provide a theoretical basis for physical activity promotion and physical fitness improvement. Methods: By random cluster sampling method, 120 students of grade 4 and 5 from the Second Experimental Primary School of Yingze District of Taiyuan were selected. Physical fitness was evaluated by the indicators of the Protocol of National Physical Training Standard and 20 meter shuttle run. The movement behavior was measured by accelerometer. The relationship between each behavior and physical fitness was analysed by component multiple linear regression, and the effect of replacement of components on physical fitness was discussed. Results: Girls 1minute situps were lower than boys（24.79±7.77，28.21±6.52），and sitting forward flexion was higher than boys[9.00（5.00，14.00），5.20（1.00，9.75）cm]（ t/Z =2.60，-3.15， P ＜0.05）. Boys showed higher light physical activity(LPA), moderate to vigorous physical activity(MVPA) and lower sedentary behavior(SB), while girls showed lower LPA, MVPA and higher SB. MVPA was positively correlated with the performance of 30 second rope skipping and 20 meter shuttle run ( β= 13.19, 7.90, P <0.05). Sleep(SLP), SB, and LPA were not significantly correlated with physical fitness. After re allocating 10 min MVPA to SB and SLP，the performance of 30 second rope skipping and 20 meter shuttle run increased by 2.25，2.28 and 1.28 ,1.34 times，respectively，while significantly decreased after reverse reallocation ( P <0.05). MVPA replaced LPA，the 20 meter shuttle run performance increased 1.46 times，while decreased significantly in reverses ( P <0.05). Conclusion MVPA is positively correlated with the speed and endurance of pupils. There are gender differences in movement behavior patterns and physical fitness. Children, especially girls, should be encouraged to raise exercise awareness and increase PA, especially MVPA.

Objective: To systematically review the associations of physical activity (PA), sedentary behavior (SB) and sleep with obesity, as well as isotemporal substitution effects among behaviors, determined with compositional data analysis methods, to provide a reference for obesity interventions among children and adolescents. Methods: Studies in the CNKI, Wanfang, PubMed, SPORTDiscus, Web of Science and Medline databases were searched from January 1, 2014 to May 1, 2022. Two experienced reviewers independently completed document screening, data extraction and quality assessment. Results: Sixteen articles were included, with a methodological quality score range of 7-12 points. Moderate to vigorous physical activity (MVPA), sleep and obesity were negatively correlated, and substituting other behaviors with MVPA decreased obesity risk. The substitution time ranged from 1.5 min/day to 60 min/day. Light physical activity(LPA) and SB were positively correlated with obesity. Conclusion MVPA is the primary focus of obesity interventions in children and adolescents, and extra 60 min of MVPA per week on the existing level of physical activity may be the minimum necessary to decrease the risk of obesity.

Objective: The method of compositional data analysis was used to explore the relationship between 24 hour movement behavior and obesity indicators, and to examine the difference of quantitative effect on obesity indicators when one behavior replaced another behavior, so as to provide specific movement behavior advice for weight control in children and adolescents. Methods: In June 2021, 231 students from eight classes in a primary school and a middle school in Taiyuan City, Shanxi Province were voluntarily recruited by using random cluster sampling. ActiGraph GT3X+ accelerometer was used to measure 24 hour movement behavior and Inbody J20 body composition analyzer was used to measure body composition. The relationship between each component and obesity indicators was analyzed by compositional multivariate linear regression model. In addition, 30 minutes of one behavior was used to replace another behavior to predict the effect difference of the outcomes. Results: After adjusting for covariates such as height, weight, age, and sex, compared with time spent in sedentary behavior(SB), sleep (SLP) and light physical activity (LPA), time spent on moderate to vigorous physical activity (MVPA) was positively correlated with fat free mass index (FFMI) ( β= 0.40, P ＜0.05), negatively correlated with waist circumference (WC) ( β=-2.50, P ＜0.05) and waist hip ratio (WHR) ( β= -0.04 , P ＜0.05). Compared with SB, SLP and MVPA, time spent on LPA was positively correlated with WHR ( β=0.06, P < 0.05 ). If MVPA of 30 min/d replaces SLP, SB, and LPA respectively, WC and WHR decrease 1.10,1.10,1.34 cm and 0.02, 0.02 ,0.02 respectively, and FFMI increases 0.19,0.19,0.15 kg/m 2 respectively. Conclusion In 24 h movement behavior, with consistent level of sedentary behavior, sleep or low intensity movement behavior, maintaining a high level of MVPA and replacing sedentary with active activities are crucial for optimal abdominal fat and fat free mass in children and adolescents.

Objective: To understand prevalence and trend of drinking behavior among middle school students in Quzhou during 2012 to 2022, and to provide a basis for formulating scientific and effective intervention measures for adolescent drinking. Methods: By using stratified cluster sampling method, a questionnaire survey using Zhejiang adolescent health related behavior questionnaire was conducted anonymously in selected classes in May 2012, 2017 and 2022, respectively. Changes of drinking behavior of middle school students in different years were analyzed. Results: The prevalence of ever drinking, current drinking and drunkenness among middle school students in Quzhou decreased from 58.05%, 22.70% and 21.25% in 2012 to 41.83%, 15.35% and 11.54% in 2022, respectively ( χ 2 trend =82.69, 30.00，58.24, P <0.01). In the past 30 days, 66.67% of students reported drinking 1-2 days, the proportion of drinking for 3-5 days increased from 16.36% in 2012 to 26.19% in 2022, the proportion of drinking for 6-19 days decreased from 13.03% in 2012 to 3.40% in 2022. The proportion of buying alcohol increased from 22.12% in 2012 to 35.03% in 2022. The results of the three surveys showed that, now drinking rates, drinking rates, Male students (27.88%，23.96%，18.75%；24.69%，17.44%，13.75%) was higher than the girls (17.60%，17.25%，11.31%；17.87%，10.61%，8.91%)， non ordinary high schools (33.96%，34.69%，22.77%；33.65%，23.91%，19.49%) were higher than ordinary high schools (25.82%，18.80%， 12.62 %；25.82%，17.35%，9.94%) and junior middle school (16.53%，15.83%，12.22%；13.93%，8.47%，7.35%). Conclusion Progress in adolescent drinking control is being made in Quzhou, with the prevalence of ever drinking, current drinking and drunkenness significantly decreased. It is necessary to strengthen the control of drinking behavior among middle school students from the aspects of school, family and society, especially for boys and students in non ordinary high school students.

Objective: To investigate the status of physical development, vitamin A and vitamin D among primary and middle school students in poor rural areas in Hubei, to evaluate the implementation effectiveness of the Nutrition Improvement Program for Rural Compulsory Education Students (abbreviated to the program) from 2012 to 2021. Methods: In Enshi City, a pilot monitoring county of the program in Hubei, and a total of 2 554 students from one primary school and one junior middle school were randomly selected. During September to October in 2012-2021, height was measured, and fasting venous blood was collected from students, and serum vitamin A and vitamin D were detected. Results: From 2012 to 2021, height, serum vitamin A and serum vitamin D concentration increased by 2.7 cm, 96.7 μg/L and 8.6 ng/mL. Growth retardation rate decreased by 1.0%. The subclinical and clinical deficiency of serum vitamin A decreased by 37.3% and 6.2%. The subclinical and clinical deficiency of serum vitamin D decreased by 45.7% and 8.5%. Height was positively correlated with serum vitamin A status and negatively correlated with serum vitamin D status ( r =0.08,-0.08, P <0.01). Conclusion The pilot counties of the program in Enshi, has witnessed improvement in height, serum vitamin A and vitamin D status among primary and secondary students. However, future efforts remains essential as subclinical deficiency of vitamin A and vitamin D are noted in some students. Serum vitamin A is positively associated with height, and vitamin D is negatively associated with height.Considering the correlation between serum vitamin A and vitamin D status with height, continued efforts should be implemented in poor rural areasto strengthen targeted nutrition intervention for students in Hubei.

Objective: To understand the status of anemia among rural children aged 3-6 in central China and its relationship with dietary behavior, and to provide reference for prevention and intervention of anemia in rural children. Methods: From April to June 2021, stratified cluster sampling was used to select 1 246 preschool children aged 3 to 6 years old in rural areas in central China. Peripheral blood of the ring finger was collected. Dietary behaviors regarding consumption of cereals and potatoes, fruits, vegetables, soy products, milk, animal foods, food diversity, and drinking water were investigated. Logistic regression analysis was used to analyze the association between anemia and dietary behaviors. Results: The detection rate of anemia in rural children aged 3-6 in central China was 13.88%. The anemia detection rate of left behind children (19.00%) was higher than that of non left behind children (11.27%), and the difference was statistically significant ( χ 2=13.93, P <0.01). Logistic regression analysis showed that the proportion of left behind children ( OR=1.28, 95%CI =1.16-1.56) with anemia was higher than that of non left behind children ( P <0.01). Consumption of animal food intake ≥3 times/week ( OR=0.82, 95%CI =0.69-0.91), and ≥2 kinds of vegetables ( OR= 0.86, 95%CI =0.71-0.93) were associated with lower rate of anemia ( P <0.05). Conclusion The detection rate of anemia in rural children aged 3-6 years in central China is relatively high, especially in left behind children. Dietary literacy of caregivers should be further improved regarding increased intake of animal foods and vegetables to reduce the risk for anemia in preschoolers.

Objective: To assess the status of current e cigarette perception and its influencing factors among adolescents in Shanghai, so as to provide reference for the refinement of the prevention and control measures of teenagers e cigarette use. Methods: From May to June 2021, a stratified random cluster sampling was used to investigate 7 456 junior high and high school students in Shanghai. Harm and benefit perception of e cigarette as well as its social environment benefits were collected. Results: The rate of adolescents ever and current e cigarette use was 3.19% and 1.09%, respectively. The top four risk factors for low harm perception of e cigarette were adolescent e cigarette use( OR=2.74, 95%CI =2.10-3.59), high school students ( OR=1.47, 95%CI = 1.32 - 1.64 ), family members ( OR=1.45, 95%CI =1.24-1.70) and friends ( OR=1.36, 95%CI =1.20-1.54) using e cigarette. Adolescent ecigarette use ( OR=2.77, 95%CI =1.97-3.89), high school students( OR=2.11, 95%CI =1.89-2.36), friends ( OR= 1.63, 95%CI =1.42-1.87) and family members using e cigarette( OR=1.39, 95%CI =1.18-1.65) were the top four associated factors for high benefit perception of e cigarette. And, adolescent e cigarette use ( OR=1.95, 95%CI =1.47-2.59), high school students ( OR= 1.73, 95%CI =1.55-1.93), friends ( OR=1.60, 95%CI =1.40-1.82) and pocket money≥200 yuan using e cigarette( OR= 1.29 , 95%CI =1.17-1.43) were the top four risk factors for high social environmental benefit perception of e cigarette. Moreover, perception of e cigarette harm, benefit and social environmental benefit were associated with the risk of future use of e cigarette( OR = 0.78,1.44,1.21, P <0.01). Conclusion Being high school students and using e cigarette by oneself, friends, and family members are the important influencing factors for adolescents e cigarette perception. Both low harm and high benefit perception of e cigarette elevate the risk of future e cigarette use among adolescents, so effective measures should be taken to promote control education about e cigarette and smoke free environment construction.