To investigate the association of moderate to vigorous intensity physical activity (MVPA) and screen time (ST) with emotional and behavioral problems in middle school students, so as to provide a basis for improving the mental health level of adolescents.

Four public junior high schools in Jinshan District, Shanghai were selected by random cluster method from September 19 to October 18, 2023, with 779 first-grade students included. Strengths and Difficulties Questionnaire (SDQ), as well as physical activity and screen time were collected. Binary Logistic regression analysis was used to investigate the association between MVPA, ST and different dimensions of emotional and behavioral problems.

Students with MVPA < 60 min/d accounted for 82.4%, and with ST>2 h/d accounted for 29.5%. The abnormal rate of SDQ dimensions among students ranged from 6.8% to 19.3%, with the highest abnormal rate observed in behavioral problems. The results of binary Logistic regression analysis showed that, compared with high level of MVPA, students with low level of MVPA had a significantly increased risk of developing problems in prosocial behavior [OR(95%CI)=2.16(1.37-3.41), P < 0.05]. Compared with low-level ST, students with high-level had an increased risk of experiencing emotional symptoms, behavioral problems and peer interaction problems [OR(95%CI)=2.00(1.25-3.22), 2.00(1.41-2.84), and 1.69(1.22-2.33), P < 0.05]. Compared with high MVPA and low ST, students with low MVPA and high ST had an increased risk of developing problems in the dimensions of conduct problems, prosocial behavior, and overall difficulty score [OR(95%CI)=1.92(1.13-3.23), 2.73(1.56-4.77), and 2.07(1.19-3.60), P < 0.05].

Physical activity and screen time are related to emotional and behavioral problems in middle school students. Insufficient physical activity time and excessive screen time might increase the risk of emotional and behavioral problems. Interventions can be administered on physical activity and screen time among adolescents to promote their mental health.

To explore the association of latent profiles of mobile phone dependence and self-control with physical exercise among junior high school students, so as to provide references for the prevention of mobile phone dependence and the improvement of self-control among junior high school students.

From April to May 2024, a stratified random cluster sampling method was used to select a total of 2 311 students from grade 7 to grade 9 in three public junior high schools in Xiangxi Autonomous Prefecture, Hunan Province. Latent profile analysis was conducted to identify the latent profiles of mobile phone dependence and self-control among junior high school students. Pearson correlation analysis was used to examine the correlation between mobile phone dependence and self-control, and Chi-square test was used to analyze the distribution differences of latent profiles of adolescents across different demographic characteristics. Multiple Logistic regression analysis was applied to explore the association between mobile phone dependence, self-control, and physical exercise.

Four latent profiles of mobile phone dependence and self-control were identified: low dependence-moderate self-control group (n=885, 38.3%), moderate dependence-low self-control group (n=910, 39.4%), high dependence-no self-control group (n=232, 10.0%), and no dependence-high self-control group (n=284, 12.3%). Significant differences were observed in the distribution of latent profiles across gender, grade and only-child status (χ²=10.85, 35.72, 13.85, P < 0.05). Logistic regression analysis showed that, after controlling for demographic variables, compared with the low dependence-moderate self-control group, physical exercise was negatively associated with the moderate dependence-low self-control group (OR=0.79) and the high dependence-no self-control group (OR=0.81), while positively associated with the no dependence-high self-control group (OR=1.58) (P < 0.01).

The influence of physical exercise on junior high school students' different potential profile types of mobile phone dependence and self-control is different. Schools and families should adopt targeted physical exercise interventions based on the characteristics of different profiles to promote the physical and mental health of junior high school students.

To systematically evaluate the effects of postnatal cadmium exposure on children's pubertal and physical development, so as to provide reference for the latter research on cadmium exposure.

A computer search of PubMed, EBSCO, Web of Science, OVID, CNKI, WanFang, VIP and CBM database were conducted to collect relevant studies, and the search period was from the time of database construction to 27 February 2024. Two reviewers independently screened the literature, extracted data and evaluated the risk of bias of the included studies, and used GRADE to assess the certainty of the evidence for each outcome. Meta-analysis of the risk ratio (HR) for the occurrence of menarche was performed using Stata 17.0 software, and the results were summarized qualitatively for other indicators.

A total of 6 cohort studies were included, comprising four pubertal development and two physical development studies with a total of 2 899 children. Studies of cadmium exposure and menarche in girls all found that late menarche in children with higher urinary cadmium concentrations (HR=0.86, 95%CI=0.74-0.99, P < 0.05; 3 studies; moderate-certainty evidence), and one of these studies found no statistically significant effect of cadmium exposure on breast and pubic hair development in children (aOR=0.90, 95%CI=0.72-1.14; aOR=0.85, 95%CI=0.64-1.13, P>0.05; low-quality evidence); the only study testicular volume, external genitalia and pubic hair development in boys found on effects of urinary cadmium exposure on pubertal development (aOR=0.76, 95%CI=0.50-1.15; aOR=1.07, 95%CI=0.79-1.45; aOR=0.79, 95%CI=0.51-1.23, P>0.05; low-certainty evidence). Regarding the effects of cadmium exposure on children's height and weight (2 studies, low-certainty evidence), the results of one study showed that cadmium exposure was negatively associated with children's physical growth (multivariable-adjusted attributable differences in height and weight study, being -1.60 cm, 95%CI=-2.40 to -0.77 cm; and -0.57 kg, 95%CI=-0.88 to -0.26 kg, P < 0.05), while the other showed no effect of cadmium exposure on children's height and weight (F=1.35, 1.76, P>0.05), but a negative effect on head and chest circumference (F=3.43, 4.50, P < 0.05; low-certainty evidence).

Cadmium exposure in childhood causes delayed menarche in girls and affects physical growth to some extent.

To analyze factors impacting mental health status of medical students based on ecological systems theory, so as to provide reference for the mental health promotion system for medical students.

In June 2024, 1 760 medical school students randomly selected from 19 different kinds of medical colleges in eastern China by stratified cluster were surveyed using questionnaires and expert interviews. Descriptive statistics, cross-analysis, hierarchical linear regression analysis, structural equation models were used for data analysis.

Medical school students had higher satisfaction with the school (65.85%) and a great sense of perceived social support (57.16%). Furthermore, 91.14% of the students had normal interpersonal relationships. However, 44.89% reported that their mental health was impacted by high level of depression. The hierarchical linear regression analysis showed that the mental health outcomes of the medical students were positively predicted by higher perceived social support scores (β=-11.40), institutional satisfaction (β=-4.85), and lower help-seeking stigma scores (β=9.31) (P < 0.05). The structural equation modeling showed that the status of both perceived social support and self-help-seeking stigma had significant impacts on depression severity (β=-0.32, -0.53) and interpersonal relationship sensitivity (β=-0.31, 0.58) among medical students (P < 0.01).Through expert interviews, collaborations between the school and the tripartite organization (families, universities and society) was of growing importance.

Perceived social support and self-stigma have a significant impact on the mental health status of medical students. The problem of self-stigma of medical students should be paid attention to. Therefore, families, universities and society should work together to improve the mental health of medical students.

To evaluate the prevalence and future trend of change of the disease burden of injuries in Chinese children and adolescents from 1990 to 2021, so as to provide reference for injury prevention and control in this population.

Using data from the Global Burden of Diseases, Injuries, and Risk Factors Study 2021 (GBD 2021), the trend of change in the disease burden of injuries in children and adolescents in China from 1990 to 2021 was analyzed by the Joinpoint regression model. The Bayesian age period cohort model (BAPC) was used to predict the disease burden of injuries among children and adolescents in China from 2022 to 2031.

From 1990 to 2021, the standardized incidence rate, standardized prevalence rate, standardized mortality rate, and standardized disability-adjusted life years (DALYs) rate of injuries among children and adolescents in China showed an overall downward trend (AAPC=-1.14%, -0.76%, -5.41%, -5.03%, P < 0.05). For different genders, the standardized incidence rate (7 106.00/100 000, 5 388.00/100 000), standardized mortality rate (92.00/100 000, 19.00/100 000), and standardized DALYs rate (7 834.00/100 000, 1 673.00/100 000) of injuries in boys were higher than the rate of injuries in girls in 1990 and 2021 (5 188.00/100 000, 3 874.00/100 000; 61.00/100 000, 10.00/100 000; 5 398.00/100 000, 945.00/100 000). Compared with Asia and globally, China had the fastest decline in the standardized mortality rate (AAPC=-5.41) and the slowest decline in the standardized prevalence rate (AAPC=-0.76) among children and adolescents. The results of the Joinpoint burden trend analysis demonstrated that the standardized incidence rate of injuries showed an increasing trend from 2005 to 2021, and the standardized prevalence rate of injuries showed an increasing trend from 2006 to 2021. Among the different age groups, the disease burden of injuries was highest in the 15-19-year-old group in 2021. For different types of injuries, the standardized incidence rate, standardized mortality rate, and standardized DALYs rate of unintentional injury were higher than those of transport injury, and self-harm and interpersonal violence from 1990 to 2021. The BAPC prediction model showed that the standardized incidence rate (4 833.05/100 000-5 313.70/100 000) and standardized prevalence rate (5 433.90/100 000-5 821.88/100 000) of injury showed an increasing trend, and the standardized mortality rate (13.69/100 000-5.52/100 000) and the standardized DALYs rate (1 226.37/100 000-510.14/100 000) showed a decreasing trend during 2022-2031. The analysis of influencing factors found that children and adolescents who drank alcohol were at high risk of injury burden.

From 1990 to 2021, the injury burden of children and adolescents in China generally showed a downward trend. The standardized incidence rate and standardized prevalence rate of injuries are predicted to increase from 2022 to 2031. More targeted and individualized intervention measures should be developed to reduce the injury burden in children and adolescents.

To understand the growth and development levels of four physical measurements in children aged 3-6 years in China, so as to provide a reference for child nutrition improvement and health promotion.

A stratified random sampling method was used to collect physical measurement data from 120 kindergartens 25 842 children aged 3-6 years across 24 provinces and cities in seven natural geographical regions of North China, Northeast China, East China, Central China, South China, Southwest China and Northwest China from 2020 to 2023. The development levels of head circumference, chest circumference, waist circumference, and hip circumference were evaluated using a grading method. The analysis of gender and age differences was conducted using Mann-Whitney U test and Kruskal-Wallis test, and the comparison of abnormal detection rates for different genders was conducted using Chi-square test.

The distribution range of children aged 3-6 was 51.74(50.08, 53.33) cm in terms of head circumference, 55.73(52.09, 59.04) cm in terms of chest circumference, 53.04(48.92, 56.40) cm in terms of waist circumference, and 59.36(56.30, 62.32) cm in terms of hip circumference. The detection rate of abnormal head circumference in boys and girls aged 3-6 years old was relatively high (19.71%-42.02%), and the detection rate of abnormal physical circumference development levels in boys was higher than that in girls of all ages (χ²=5.63-83.35, P < 0.05). The detection rate of abnormal hip circumference (4.89%-6.53%) and chest circumference (4.51%-6.38%) in boys and girls aged 3-6 was relatively low, and there was no statistically significant difference in the abnormal rate between different ages and genders (χ²=0.00-1.61, 0.00-3.71, P>0.05). The detection rate of abnormal waist circumference in boys and girls aged 3-6 was relatively high (13.70%-42.45%), and the detection rate of abnormal waist circumference in girls was higher than that in boys aged 4-6 groups (χ²=10.49-58.18, P < 0.05).

The overall physical development of children aged 3-6 years in China is improving, but the abnormal detection rates for head circumference and waist circumference are relatively high. Child healthcare should focus on preventing and treating abdominal obesity, with differentiated health intervention strategies based on different age groups and genders.

To analyze the time-varying characteristics of weight among Han primary and secondary school students in Xinjiang from 1985 to 2019, so as to provide a scientific basis for formulating nutrition policies for adolescents in ethnic minority areas.

Weight data of Han primary and secondary school students aged 7-18 in Xinjiang from the National Student Physical Fitness and Health Survey from 1985 to 2019 were selected. Statistical analysis was conducted by using general linear model test, one-way ANOVA and t-test. The weight development trends in 2025 and 2030 were predicted through time-series analysis.

From 1985 to 2019, the weight of Han Chinese boys and girls from primary and secondary schools in Xinjiang showed a continuous upward trend (boys: B=0.25, girls: B=0.16, P < 0.01). There were statistically significant differences in weight between boys and girls aged 7-18 in different years (boys: F=102.35-142.05, girls: F=98.03-140.59, P < 0.01). Compared with 1985, the weight of urban boys and girls increased by 11.92 and 7.95 kg in 2019, as well as rural boys and girls by 11.36 and 5.61 kg, and the average weight gain of urban students was greater than that of rural students. From 1985 to 2019, the weight of urban boys and girls were higher than that of rural boys and girls (boys: t=30.12-37.55, girls: t=30.12-38.64, P < 0.01). In 2005, the weight difference between urban and rural boys and girls was the largest, at 4.23 and 2.32 kg. The average weight of boys and girls in the age groups of 7-18 would continue to increase in 2025 and 2030; compared with 2019, the 7-year-old age group for boys and the 17-year-old age group for girls would have the largest growth in 2030 by 2.29 and 3.75 kg.

From 1985 to 2019, the weight of students aged 7-18 in Xinjiang showed an upward trend, and the weights of both boys and girls would gradually increase in 2025 and 2030. Attention should be paid to students' physical health and adopt comprehensive measures to prevente overweight and obesity.

To evaluate the accuracy of body mass index (BMI), waist circumference (WC) and waist-to-height ratio (WHtR) in screening true obesity among children, so as to provide a scientific basis for precise screening and early prevention and control of childhood obesity.

A total of 1 322 children aged 10-15 years old were surveyed by the Huantai Children Cardiovascular Health Cohort in 2021. Fat mass percentage (FMP) and fat mass index (FMI) were measured by bioelectrical impedance analysis, with FMP or FMI values at or above the age- and sex-specific 70th percentiles as the criteria for defining true obesity. BMI, WC and WHtR were used to define general obesity and central obesity. The accuracy of these measures in screening for true obesity was evaluated by calculating the missed diagnosis rate, misdiagnosis rate, area under the curve(AUC) for receiver operating characteristic and Kappa coefficient.

Boys had higher BMI [(21.79±4.56) kg/m²], WC [(76.41±12.53) cm] and WHtR (0.47±0.07) than girls [(20.83±4.13) kg/m², (70.69±10.06) cm, (0.45±0.06)] (t=4.02, 9.19, 6.63), while boys had lower FMP [(18.29±8.35)%] and FMI [(4.35±2.79) kg/m²] than girls [(24.87±6.51)%, (5.44±2.53) kg/m²] (t=-16.10, -7.42) (P < 0.01). Using FMP as a reference standard, the diagnosis error rates of screening for true obesity based on BMI, WC and WHtR were 12.24%, 2.11% and 2.11%, respectively; the diagnosis error rates were 10.88%, 27.28% and 24.33%; the AUC values were 0.88, 0.85 and 0.87; the Kappa coefficients were 0.67, 0.48 and 0.52. Using FMI as a reference standard, rates of BMI, WC and WHtR screening for true obesity were 14.20%, 1.23% and 2.78%; the diagnosis error rates were 4.81%, 20.84% and 18.14%; the AUC values were 0.90, 0.89 and 0.90; the Kappa coefficients were 0.81, 0.64 and 0.67.

BMI has a higher diagnosis error rate in screening for true obesity in children, while WC and WHtR have higher diagnosis error rates. It is recommended to promote body fat assessment in clinical practice, so as to achieve more accurate prevention and control of chronic diseases.

To analyze the temporal variation patterns of sickness absenteeism among primary and secondary school students in Shanghai, so as to explore models suitable for predicting peaks and intensity of absenteeism rates.

The seasonal and trend decomposition using loess (STL) method was used to analyze the seasonal and long-term trend changes in sickness absenteeism among primary and secondary school students from September 1 in 2010 to June 30 in 2018, in Shanghai. A hierarchical clustering method based on Dynamic Time Warping (DTW) was employed to classify absenteeism symptoms with similar temporal patterns. Based on historical data, the study constructed and evaluated different time series algorithms and machine learning models to optimize the accuracy of predicting the trend of sickness absenteeism.

During the research period, the average new absenteeism rate due to illness was 16.86 per 10 000 person-day for every academic year, and the trend of sickness absenteeism exhibited both seasonality and a long-term upward trend, reaching its highest point in the 2017 academic year (22.47 per 10 000 person-day). The symptoms of absenteeism were divided into three categories: high incidence in winter and spring (respiratory symptoms, fever and general discomfort, etc.), high incidence in summer (eye symptoms, nosebleeds, etc.) and those without obvious seasonality (skin symptoms, accidental injuries, etc.).The constructed time series models effectively predicted the trend of absenteeism due to illness, although the accuracy of predicting peak intensity was relatively low. Among them, the multi-layer perceptron (MLP) model performed the best, with an root mean squared error (RMSE) of 8.96 and an mean absolute error (MAE) of 4.37, reducing 36.51% and 39.02% compared to the baseline model.

Time series models and machine learning algorithms could effectively predict the trend of sickness absenteeism, and corresponding prevention and control measures can be taken for absenteeism caused by different symptoms during peak periods.

To explore the relationship between visual acuity and physical fitness of university freshmen, so as to provide reference for myopia prevention and control for freshmen.

From October to November 2022, 2 160 college freshman without majoring in public safety administration, selected from Guangxi Police College in 2022 by using the stratified cluster random sampling method, were reviewed for the results of visual acuity test and physical fitness scores. The physical fitness indices were evaluated by using the Z-scores of physical fitness test scores, and the strength of association between the level of physical fitness index and myopia was analyzed by using Logistic regression model.

Among 2 160 college freshman without majoring in public safety administration, 917 (42.5%) students were diagnosed screening myopia, including 66 (3.1%) cases of high myopia, 383 (17.7%) cases of moderate myopia and 468 (21.7%) cases of mild myopia. The differences in the distribution of visual acuity tests among students with different physical fitness indices, body mass index, and gender were statistically significant (Z/H=54.50, 49.53, 15.51, P < 0.01). Low-level and low-middle-level physical fitness indices were associated with screening myopia among freshmen[OR(95%CI)=2.81(1.93-4.08), 1.87(1.38-2.54)], and low-level physical fitness indexes were associated with high myopia [OR(95%CI)=7.22(2.33-22.32)] (P < 0.01).

Screening myopia among college freshman without majoring in public safety administration is related to physical fitness, and low-level and low-middle-level physical fitness index are risk factors for myopia. Improving the level of physical fitness might be effective in preventing myopia.