Postural habits and lifestyle factors associated with adolescent idiopathic scoliosis (AIS) in China: results from a big case-control study.

BACKGROUND: Adolescent idiopathic scoliosis (AIS) is the most prevalent type of scoliosis affecting children between the ages of 10-16 years. However, risk factors for AIS, particularly the modifiable ones, are still largely unknown. This study aims to investigate the associations of lifestyle and social environment factors with AIS in Chinese schoolchildren. METHODS: This is a matched case-control study based on survey data collected from school-based scoliosis screening program. We used conditional logistic regression models to describe the relative risk of AIS incidence for each variable in the analyses. To examine the independent effect of each factor on developing AIS, a multivariate conditional logistic regression was conducted and odds ratios (ORs) were adjusted for age and other significant variables. RESULTS: Overall, 2538 participants from 49 schools were included in this study, comprising 1269 AIS cases and 1269 controls. Mean age of the study population was 13.4 years ± 1.06 (range 10-18). One thousand five hundred and fifty (61.1%) of the study subjects were girls. After adjusting for other significant factors, inappropriate desk heights, either too low (OR = 1.40, 95% CI 1.04-1.90) or too high (OR = 1.61, 95% CI 1.09-2.38), standing with anterior pelvic tilt (OR = 2.73, 95% CI 1.41-5.28), and sleeping on the right side (OR = 1.38, 95% CI 1.00-1.91), remained associated with elevated AIS risks. In contrast, sitting normally and classroom sitting positions change regularly were associated with lower odds of AIS. The adjusted ORs were 0.69 (95% CI 0.50-0.96) for sitting normally, and 0.72 (95% CI 0.53-0.98) for sitting positions change. CONCLUSIONS: This is the first study to address the associations between desk heights and AIS and showed inappropriate desk heights were related to increased AIS risks. To protect school children from developing AIS, stakeholders are advised to consider introducing height-adjustable desks in the class, changing students' sitting positions in the classroom on a regular basis, and implementing educational programs to help students maintain correct sitting postures.

Association of body composition with pubertal timing in children and adolescents from Guangzhou, China.

Objective: An ongoing debate surrounds the relationship between body composition and pubertal timing, in particular for boys. This cross-sectional study aimed to investigate the association of body composition with pubertal timing among children and adolescents. Methods: A total of 1,493 boys and 1,261 girls who entered puberty were enrolled in Guangzhou, China. Tanner stages were evaluated by examination of breast development for girls and testicular volume for boys. Fat mass (FM) and fat-free mass (FFM) were determined by bioelectrical impedance analysis. Parameters for body composition were transformed into age-and gender-specific Z-scores. The association of body composition with pubertal timing was examined using multinomial logistic regression with inverse probability weighting (IPW) based on the propensity score. Results: For boys, IPW analysis showed Z-scores of body fat percentage (BF%) and FM index (FMI) were negatively associated with early puberty (OR = 0.75, 95% CI = 0.64-0.87; OR = 0.74, 95% CI = 0.63-0.88). As for girls, in contrast to boys, positive associations were seen between BF% and FMI with early puberty (OR = 1.39, 95% CI = 1.19-1.64; OR = 1.59, 95% CI = 1.33-1.90). With respect to appendicular skeletal muscle mass index (ASMI), there was a positive association with early puberty and a negative one with late puberty in boys (OR = 1.26, 95% CI = 1.07-1.49; OR = 0.82, 95% CI = 0.69-0.99). Conclusion: There is a positive association of FM with early puberty for girls while negative for boys. FFM yields a positive association with early puberty and a negative one with late puberty in boys, but not in girls. Our findings highlight the gender differences in the connection between body composition and pubertal onset.

Association between the 24-hour movement guidelines and executive function among Chinese children.

OBJECTIVE: Childhood is a critical period for brain development. However, it remains unknown whether the behaviors in a typical 24-h day are related to children's executive function (EF). This study aimed to investigate the relationship between the 24-h movement guidelines and children's EF. METHOD: Children aged 7-12 years (n = 376) were studied in 2017 in China. Physical activity (PA) was accelerometer-derived, while screen time (ST) and sleep duration were self-reported. Meeting the 24-h movement guidelines was defined as: 1) ≥ 60 min/day of moderate-to-vigorous PA; 2) ≤ 2 h/day of recreational ST; 3) 9-11 h/night of sleep. EF was assessed by the Wisconsin Card Sorting Test (WCST). Number of completed categories (CC), shifting efficiency (SE), non-perseverative errors (NPE), and failure to maintain set (FMS) were used to measure four processes of EF, respectively represented global performance, cognitive flexibility, efficiency in rule discovery, and sustained attention. Generalized linear mixed models (GLMM) were completed to explore the associations of meeting the PA, ST, and sleep duration recommendations with four processes of EF. RESULTS: Statistically significant positive associations were observed between the number of guidelines met, regarded as a continuous variable, with CC [ß = 0.343 (95% confidence interval [CI]: 0.125, 0.561)] and SE [ß = 4.028 (95% CI: 0.328, 7.727)], while number of guidelines met negatively related to NPE [ß = - 4.377 (95% CI:-7.952,-0.802)]. Participants not meeting the two recommendations for PA and sleep duration had lower scores in CC [ß = -0.636(95% CI:-1.125,-0.147)] and SE [ß = -10.610 (95% CI:-18.794,-2.425)] compared with those meeting the two, suggesting inferior global performance and worse efficiency in rule discovery. However, ST recommendation had no significant association with any processes of EF. CONCLUSION: Meeting more recommendations of the 24-h movement guidelines was associated with superior EF in children. Specifically, more PA and healthy sleep duration should be encouraged to promote children's EF.

Association of Sedentary Time and Physical Activity With Executive Function Among Children.

BACKGROUND: This study aimed to examine individual and combined associations between after-school sedentary time (ST) and daily physical activity (PA) with executive function development in children. METHODS: The study included 4304 children aged 6 to 12 years. ST and PA were assessed using the International Physical Activity Questionnaire Short Form, and executive function was assessed using the Behavior Rating Inventory of Executive Function (Parent Version). Participants were classified as low (<2 h per day) or high (≥2 h per day) ST and low (not meeting guidelines) or high (meeting guidelines) PA. Resulting groups were defined as 1) low ST/high PA, 2) low ST/low PA, 3) high ST/high PA, and 4) high ST/low PA. RESULTS: Children in group 4 had the highest mean T-scores for BRIEF indices (48.23 ± 8.44, indicating increased symptoms of executive function dysfunction), followed by those in group 3 (47.10 ± 8.05), group 2 (45.81 ± 7.78), and group 1 (44.41 ± 7.31). ST was positively related to the T-score of all indices, independent of moderate-to-vigorous physical activity (MVPA). Significantly negative associations were observed between MVPA and Metacognition Index only in the high ST subgroup. CONCLUSIONS: Low ST and high PA were positively associated with executive function development in children. Notably, children with high ST and high PA demonstrated more significant deficits in executive function than those with low ST and low PA, suggesting that intervention efforts should focus on ST reduction in addition to promoting PA.

Lifestyle pattern of middle school students in Guangzhou / 中国学校卫生

Objective@#To identify the lifestyle pattern of adolescents in Guangzhou and to provide a scientific basis for targeted and individualized interventions for adolescents with different lifestyle pattern.@*Methods@#A survey was conducted by questionnaire among 12 540 students from 27 middle schools in the urban area of Guangzhou using a convenient sampling method. The latent class model (LCM) was used to identify lifestyle patterns of adolescents, and further analyses were conducted to compare differences in dietary habits and willingness to exercise among the different classes.@*Results@#Three lifestyle patterns were identified based on the latent class model: "high sweet snacks/excessive screen time, sleep and exercise deficiency group", 3 797 people, accounting for 30.3%; "low nutrition diet/severe sleep and exercise deficiency group", 2 745 people, accounting for 21.9%; "general diet/sleep and exercise deficiency group", 5 998 people, accounting for 47.8%. Adolescents of different classes had different perceptions of their eating habits and different degrees of willingness to participate in physical exercise, these differences were statistically significant(χ 2=671.54, Z=153.16, P<0.05).@*Conclusion@#The results of the latent class model showed that the three classes of adolescents had their own unique characteristics. It is necessary to inform them of their needs, provide guidance and implement targeted interventions according to the unique characteristics of the different lifestyle patterns in empirical work.

Adiposity Mediates the Association of Objectively Measured Physical Activity with Cardiorespiratory Fitness in Children.

Background: The relationship of physical activity (PA) to cardiorespiratory fitness (CRF) is well established in children. However, the extent to which adiposity affects this association remains unclear. Objective: The study aimed to explore whether the relationships of different PA intensities to CRF are explained by adiposity. Methods: Cross-sectional data were collected from 374 children (51.87% boys) aged 7-12 years. The time spent (min/day) in vigorous PA (VPA), moderate PA (MPA), light PA (LPA), and sedentary behavior was objectively measured using triaxial accelerometry. Height, weight, and waist circumference (WC) were objectively measured, from which the BMI was derived. The 20-meter shuttle run test was conducted to estimate maximal oxygen consumption [VO2max, mL/(kg·min)]. Linear mixed models and mediation analysis with bootstrapping were used to analyze data. Results: VO2max was positively associated with VPA [ß = 0.143, 95% confidence interval (95% CI): 0.091 to 0.194], MPA (ß = 0.051, 95% CI: 0.016 to 0.086), and moderate-to-vigorous PA (MVPA) (ß = 0.052, 95% CI: 0.029 to 0.075), but not LPA or sedentary time. Both BMI and WC partially mediated the relationships of VPA and MVPA to VO2max, with the percentage of the total effect mediated by adiposity ranging from 18.0% to 19.6%. Similar results were also observed among boys but not among girls. Conclusions: Only moderate or vigorous intensity of PA is favorably correlated with CRF in children. BMI and WC play a pivotal mediating role in these associations, especially in boys, suggesting that promoting higher intensity of PA might benefit children's CRF through reducing adiposity.

Association between weekend catch-up sleep and executive functions in Chinese school-aged children.

STUDY OBJECTIVES: Although weekend catch-up sleep is common among children, the association between weekend catch-up sleep and executive functions remains unclear. We aimed to determine whether weekend catch-up sleep was related to executive functions in school-aged children. METHODS: We analyzed data for 4,699 children (9.00 years ± 1.73 years old, 52.9% boys) from 5 primary schools in Guangzhou, China. Executive functions performance was examined by the Behavior Rating Inventory of Executive Function Parent Form. Validated self-report questionnaires were used to assess sleep status, socioeconomic status, and health behaviors. Multiple linear regression analyses were used to assess the association of weekend catch-up sleep duration with executive functions. RESULTS: Weekday sleep was negatively associated with scores on three composite indices (Behavioral Regulation Index, Metacognition Index, Global Executive Composite), while weekend catch-up sleep was positively associated with them. Children with < 9 hours weekday sleep duration had higher scores in all indices, and there was no correlation between weekend catch-up sleep and scores of all indices (P > .05). For children who slept ≥ 9 hours on weekdays, weekend catch-up sleep of more than 1 hour was associated with increased scores of Behavioral Regulation Index, Metacognition Index, and Global Executive Composite (P < .05). There was no interaction between sex, age, and weekend catch-up sleep and executive functions (P > .05). CONCLUSIONS: Weekend catch-up sleep could not restore the executive functions deficits related to short weekday sleep. Weekend catch-up sleep over 1 hour may have adverse effects on executive functions in school-aged children. CLINICAL TRIAL REGISTRATION: Registry: ClinicalTrials.gov; Title: Prospective Cohort Study on Cognition and Cardiovascular Disease of Sedentary Behaviors in Children; URL: https://clinicaltrials.gov/ct2/show/NCT03582709; Identifier: NCT03582709.

Association between Physician-Diagnosed Asthma and Weight Status among Chinese Children: The Roles of Lifestyle Factors.

Childhood asthma and obesity have posed a parallel epidemic over the past few decades. However, whether asthma diagnosis is associated with obesity, and what the roles of lifestyle factors play in this relationship, remained unclarified. This study aimed to investigate the association between asthma and weight status in Chinese children and explore the potential mediating and/or modifying roles of lifestyle factors in the association. In this cross-sectional study, 16,837 children aged 6-12 years were recruited from Guangzhou, China. Participants' information on physician-diagnosed asthma was collected from parents, and data on physical activity, screen time, and sleeping were reported in a validated questionnaire. Height and weight were objectively measured, and weight status was classified by body mass index (BMI). Multiple logistic regression analysis and mediation analysis were used. Results showed that asthmatic children were at significantly higher risk of obesity (odds ratio (OR) 1.51, 95% confidence interval (CI) 1.03, 2.21) compared with non-asthmatic children. More importantly, this increased risk was even greater in children with moderate-to-vigorous physical activity <60 min/d and children with screen time >2 h/d (both Pinteraction < 0.05). Also, a positive relationship of asthma with overweight was found in children with screen time >2 h/d (OR 3.92, 95% CI 1.56, 9.88), while a negative association was observed between asthma and underweight in children aged 9-12 years (OR 0.23, 95% CI 0.06, 0.92). Mediation analysis indicated that these associations were not mediated by physical activity, screen time, or sleeping. The findings suggested that physician-diagnosed asthma was associated with higher risks of overweight and obesity, and these risks might be exacerbated by insufficient physical activity and prolonged screen time.

High birth weight and its interaction with physical activity influence the risk of obesity in early school-aged children.

BACKGROUND: High birth weight (HBW) is associated with childhood obesity, but with inconsistent results. This study investigated the relationship between HBW and childhood obesity, and further explored the interaction of HBW with behavioral and socio-economic determinants of obesity. METHODS: This cross-sectional study enrolled 1906 grade-two children of Guangzhou, China, from June to November, 2016. Overweight/obesity corresponded to a body mass index higher than the sex-age-specific criteria. Abdominal obesity was assessed using the sex-specific waist-height ratio cutoffs. The association of HBW with obesity was evaluated in multivariable logistic regression model. The relative excess risk due to interaction (RERI) and the attributable proportion of interaction (AP) indices were used to measure additive interaction, while applying the interaction of OR index for multiplicative interaction assessment. RESULTS: Children with HBW had an increased risk of overweight/obesity [odds ratio (OR) = 2.42, 95% confidence interval (CI) = 1.56-3.76] compared with those without HBW. Significant additive interaction of HBW with physical activity was found for overweight/obesity [relative excess risk due to interaction (RERI) = 2.69, 95% CI = 0.62-4.75; attributable proportion of interaction (AP) = 0.72, 95% CI = 0.42-1.02]. The HBW children with insufficient activity had higher odds of overweight/obesity compared to the non-HBW children with sufficient activity (OR = 3.75, 95% CI = 2.06-6.83). In addition, we identified a significant interaction of HBW with household income for abdominal obesity (RERI = 1.20, 95% CI = 0.02-2.37; AP = 0.76, 95% CI = 0.16-1.36). CONCLUSIONS: HBW confers an increased risk for childhood overweight/obesity. Physical activity attenuates the effect of HBW on overweight/obesity, and HBW possibly synergistically interacts with high household income to promote abdominal obesity in childhood.

Anaemia, iron deficiency, iron-deficiency anaemia and their associations with obesity among schoolchildren in Guangzhou, China.

OBJECTIVE: The association of Fe metabolism with obesity in children remains unclear. The present study aimed to assess the status of Fe metabolism parameters, the prevalence of anaemia, Fe deficiency (ID) and Fe-deficiency anaemia (IDA), and the associations of these variables with obesity in Chinese schoolchildren. DESIGN: A cross-sectional study conducted in 5295 schoolchildren aged 7-11 years in Guangzhou, China, 2014-2015. Full data of anthropometric and Fe metabolic parameters were collected to assess obesity, anaemia, ID and IDA. Logistic regression models were established to determine the possible associations of anaemia, ID and IDA with obesity. Two-tailed P values of <0·05 was considered statistically significant. SETTING: Guangzhou City, China. PARTICIPANTS: Schoolchildren aged 7-11 years (n 5295). RESULTS: In this sample, mean Hb concentration was 128·1 g/l and the prevalence of anaemia, ID and IDA was 6·6, 6·2 and 0·6 %, respectively. Of the participants, 14·0 % were overweight and 8·8 % were obese. Importantly, obesity was associated with lower anaemia risk (adjusted OR = 0·553; 95 % CI 0·316, 0·968) but higher ID risk (adjusted OR = 1·808; 95 % CI 1·146, 2·853) after adjustment for confounders. No significant relationship was found between obesity and IDA. CONCLUSIONS: Our results confirmed that anaemia and ID remain public health concerns among schoolchildren in Guangzhou, while IDA is remarkably less prevalent. Furthermore, obesity was associated with lower anaemia risk, but higher ID risk. More efforts should be made to prevent the onset of ID and obesity in the same individual, thus improving the health and fitness of children.

Consumption of milk and dairy product and its influencing factors in primary and middle school students in urban areas of Guangzhou / 中国学校卫生

@#To investigate the current status of milk and dairy product intake of primary and middle school students in Guangzhou and to explore the influencing factors, to provide the basis for promoting the consumption of milk and dairy products for students.@*Methods@#Questionnaire survey was conducted among 7 948 students selected from 3 primary schools and 3 middle schools in Guangzhou. The contents included general information, average amount of the intake of milk and dairy products (including pure milk, yoghurt, milk powder, cheese and other dairy products). Using χ2 test and multivariate Logistic regression to analyze the influencing factors of students’ milk and dairy product intake.@*Results@#About 76.12% of all participants reported milk and dairy products intake<7 times/week, 78.88% reported milk and dairy products intake<300 g/d and the median of milk and dairy products was 178.57 g/d. In the multiple Logistic regression model, girls and high school students were more likely to consume milk and dairy products insufficiently, with the OR of 1.42 (95%CI=1.26-1.60), 1.86 (95%CI=1.51-2.28) respectively. The students with father’s education level being college degree or above (OR= 0.75, 95%CI=0.59-0.94), mother’s education level being high school or above (high school:OR=0.75, 95%CI=0.61-0.93, college degree or above:OR=0.58, 95%CI=0.46-0.72) and annual household income ≥200 000 (OR=0.77,95%CI=0.64-0.92) were more likely to consume sufficient milk and dairy products.@*Conclusion@#Consumption of milk and dairy products among primary and middle school students in Guangzhou was high but not meet the recommended amount,should be strengthened. Health and nutritional education for students and their parents,especially girls and senior students,should be strengthened to promote the milk and dairy products consumption.

Association between screen time and dietary behaviors among urban middle school students in Guangzhou / 中国学校卫生

Objective@#To understand the relationship between screen time and dietary behaviors among urban middle school students in Guangzhou, and to provide scientific evidence for improving students’ health.@*Methods@#Based on the regular medical examinations for elementary and middle school students in Guangzhou, a total of 12 357 middle school students (grade 7 and grade 10) were investigated by using a cross-sectional study. The physical indicators and daily routine were collected by physical examination and questionnaire survey. Multiple Logistic regression analysis was used to explore the association between screen time and dietary behaviors among students.@*Results@#The proportion of excessive screen time was 18.80% (2 323). There was no significant difference between boys (18.52%, 1 165/6 292) and girls (19.09%, 1 158/6 065) (χ2=0.67, P>0.05). Logistic regression results showed that excessive screen time was negatively associated with consumption of vegetables and fruits, with the aORs of 0.50 (95%CI=0.42-0.58) and 0.64 (95%CI=0.58-0.70) respectively, and positively associated with consumption of fried food (OR=1.90, 95%CI=1.70-2.09), western fast food (OR=1.90, 95%CI=1.65-2.19), sweets (OR=1.36, 95%CI=1.25-1.49) and sugar-sweetened beverage (OR=1.70, 95%CI=1.57-1.84).@*Conclusion@#Excessive screen time was associated with unhealthy dietary behaviors among middle school students in Guangzhou. Intervention should be tailored to screen time as well as dietary behaviors.

Effects of physical activity and sedentary behaviour on cardiometabolic risk factors and cognitive function in children: protocol for a cohort study.

INTRODUCTION: Although studies showed that physical activity (PA) and sedentary behaviour (SB) were associated with cardiometabolic risk factors and cognitive function, both independent and combined associations among them are inconsistent. Cardiometabolic risk factors are also associated with cognitive function, but research of children is limited. Additionally, the brain level mechanisms have not been fully established. The proposed study aims to explore the associations and mechanisms of PA and SB on cognitive function and cardiometabolic risk factors in children. METHODS AND ANALYSIS: This is a school-based prospective cohort study. A total of 8324 participants of this study are primary school students aged 7-12 years old who are followed up every 2 years from January 2017 to December 2026. We used a stratified cluster random sampling to select five primary schools in Guangzhou, China. There are three phases at baseline. At phase I, we collect PA, SB and cognitive function by questionnaires and also conduct anthropometric and biochemical measurements in all participants. At phase II, PA, SB and cognitive function are measured respectively by accelerometers and cognitive tasks among participants randomly selected from four subgroups with different SB and PA levels. At phase III, event-related potentials are recorded using electroencephalogram during a cognitive task among participants randomly selected from phase II. We plan to follow-up all participants until they graduate from high school. The process applied at baseline and follow-up are approximately identical. ETHICS AND DISSEMINATION: Procedures described in this manuscript have been approved by the Ethical Review Committee for Biomedical Research, School of Public Health, Sun Yat-sen University (L2016-010). All parents or guardians of participants signed the informed consent form voluntarily before participating in the study. The findings of the study will be published in peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT03582709.

Development and validation of deep learning algorithms for scoliosis screening using back images.

Adolescent idiopathic scoliosis is the most common spinal disorder in adolescents with a prevalence of 0.5-5.2% worldwide. The traditional methods for scoliosis screening are easily accessible but require unnecessary referrals and radiography exposure due to their low positive predictive values. The application of deep learning algorithms has the potential to reduce unnecessary referrals and costs in scoliosis screening. Here, we developed and validated deep learning algorithms for automated scoliosis screening using unclothed back images. The accuracies of the algorithms were superior to those of human specialists in detecting scoliosis, detecting cases with a curve ≥20°, and severity grading for both binary classifications and the four-class classification. Our approach can be potentially applied in routine scoliosis screening and periodic follow-ups of pretreatment cases without radiation exposure.

Associations of Circulating Irisin Concentrations With Cardiometabolic Risk Factors Among Children Vary by Physical Activity or Sedentary Time Levels.

Whether irisin concentrations are associated with physical activity (PA) and sedentary time (ST) remains unknown. The role of irisin on cardiometabolic health among children has been contradictory and scarce. This study aimed to examine associations of PA and ST with irisin concentrations and relationships between irisin concentrations and cardiometabolic parameters among children. Additionally, we assessed the interaction between PA or ST and irisin concentrations on cardiometabolic parameters. Basing on a cross-sectional survey of 3,651 general children aged 7-12 years, 575 with different self-reported PA (moderate-vigorous intensity PA ≥ 60 min/day or <150 min/week) and ST (gender-, age-specific ST ≥ 75% or <25% percentile) levels were selected. PA and ST were assessed by the validated international physical activity questionnaires. Fasting blood glucose and lipid profile levels were measured with standard methods by biochemistry analyzer. Plasma irisin concentrations were measured by ELISA. The associations of PA and ST with circulating irisin concentrations were examined by linear regression. Linear regression analysis was also used to estimate associations of circulating irisin concentrations with cardiometabolic variables. Interactions between PA or ST and irisin concentrations on cardiometabolic parameters were calculated using multiple linear regression models with dichotomized factors (low PA and high PA; low ST and high ST). No significant association was observed between circulating irisin concentrations and habitual PA or ST. Irisin concentrations were negatively associated with body mass index (BMI) (ß = -0.220), BMI z-score (ß = -0.098), waist circumference (ß = -0.621), diastolic blood pressure (DBP) (ß = -0.561), and triglyceride (ß = -0.019) in low PA subgroup, and negatively related to fasting blood glucose (ß = -0.040) among high PA subgroup. Moreover, irisin concentrations were negatively associated with BMI (ß = -0.157) and fasting blood glucose (ß = -0.026) only in high ST subgroup (all P < 0.05). We also observed a significant interaction between PA and irisin concentrations on BMI (P interaction = 0.0350), BMI z-score (P interaction = 0.0173), and DBP (P interaction = 0.0068). In summary, irisin concentrations were not associated with habitual PA or ST in children. The negative associations of irisin concentrations with BMI, BMI z-score, and DBP were found only among children being inactive, implying that irisin may contribute to an improvement in health, especially among children with unhealthy lifestyles.

Levels and correlates of 24-hour movement behaviors in Chinese children aged 6-13 years / 中国学校卫生

Objective@#To investigate the different patterns of 24-h movement behaviors, and their associations with sociodemographic factors in a nationally representative sample of Chinese children aged 6-13 years.@*Methods@#This study was based on a national multi-centered cluster intervention study involving 31 362 children aged 6-13 years from 7 provinces in China. Questionnaires were used to collect moderate to vigorous physical activity (MVPA), screen time (ST) and sleep duration, as well as sociodemographic variables including age, gender, area of residence, parents’ education level and family income. Generalized linear mixed model (GLMM) analyses were conducted for the 24-hour movement behaviors according to sociodemographic variables.@*Results@#The proportions of individuals meeting the MVPA, ST, and sleep guidelines were 32.2%, 78.5%, 30.1%, respectively. The proportion that meet 0, 1, 2 and 3 recommended items was 9.6%, 47.7%, 35.0% and 7.7%, respectively. Age, gender, parents’ education levels and family income showed associations with PA, ST and sleep. Compared with low parents’ education group, the risk for unhealthy behavioral patterns was lower in those with high parents’ education level(P<0.05).@*Conclusion@#The current status of 24-hour physical activity for children aged 6-13 in China is not ideal, and social demographics should be considered when designing targeted interventions to promote children’s health.

Nonlinear association study of sleep duration with behavioral problems in school-age children / 中国学校卫生

Objective@#To evaluate the association between nocturnal sleep duration and behavioral problems in Chinese school-age Children, and to provide reference for the development of recommended nocturnal sleep duration for school-age children.@*Methods@#A total of 4 160 school-age children selected through cluster random sampling in Guangzhou urban areas. Caregivers reported children’s behavioral problems and sleep habits using parent version of the Strengths and Difficulties Questionnaire (SDQ) and sleep quality questionnaires.@*Results@#The average nocturnal sleep duration per day of school-age children is (9.07±0.76)h, the proportion of children having slept less than 9 h/d was 46%(1 912). There were statistically significant differences in the distribution of sleep duration among children with different chronotype and maternal education levels(P<0.05). There were statistically significant differences in children’s sedentary behavior duration and nap duration at different sleep duration(P<0.05). The association between children’s nocturnal sleep duration and behavioral problems was typically nonlinear and U-shaped(P<0.05). The inflection points of nocturnal sleep duration for total difficulties, emotional problems, conduct problems and peer problems were 9.65, 9.25, 9.42 and 9.30 h, respectively.@*Conclusion@#Nocturnal sleep duration shows a nonlinear association with behavioral problems in school-age children. The optimal range of nocturnal sleep duration for mental health is between 9 to 10 hours and the problems of psychological behavior were the least among school-age children.

Association between screen time and metabolic syndrome among 6-13 years old children in Guangzhou / 中国学校卫生

Objective@#To investigate the prevalence of metabolic syndrome (MS) and to explore the relationship of MS with screen time (ST) among children aged 6-13 years in Guangzhou, China.@*Methods@#A total of 4 523 children aged 6-13 from 5 primary schools in Guangzhou were selected using stratified random cluster sampling method. Questionnaire was used to assess children’s basic demographic characteristics and ST. Children’s height, weight, waist circumference and blood pressure were measured objectively, and their blood glucose, triglyceride and high-density lipoprotein-cholesterol were tested. -Chi-square test was performed to compare the prevalence of MS in children among different ST levels. Logistic regression model was used to explore the association between ST and MS.@*Results@#The prevalence of MS in children was 2.4%, and that among boys (3.0%) was higher than in girls (1.7%, P=0.01). children were classified into three groups according to duration of ST: low ST (less than 1 h), moderate ST (1-2 h), high ST (higher than 2 h, 9.0% of total participants). Prevalence of central obesity, triacylglycerol and MS in high ST group was significantly higher than children with low ST(P<0.05). Children with high level of ST showed higher risks of central obesity (OR=1.43, 95%CI=1.04-1.96) and MS (OR=1.94, 95%CI=1.11-3.40) compared with low-level ST group.@*Conclusion@#Higher level of screen time associates with an increased risk of MS in children, which suggest the importance of effective early intervention.

Association of different activity behaviors with body composition among children aged 6 to 12 years in Guangzhou / 中国学校卫生

Objective@#To investigate the associations of reallocating sedentary time to different activity behaviors with body composition, and to provide a reference for prevention and control of childhood obesity.@*Methods@#By using cluster random sampling, 1 621 students from 5 urban primary school in Guangzhou were selected in 2017. Vigorous intensity physical activity (VPA), moderate intensity physical activity (MPA), walking, sedentary behavior, and sleeping were measured by self-reported questionnaire. Inbody 230 was used to assess body composition. Multiple linear regression models were applied to examine isotemporal substitution effect of activity behaviors.@*Results@#In younger children group (aged 6-9 years), replacing 30 min/day sedentary with VPA was associated with a 0.9% lower fat-free mass index(FFMI)(β=0.11, P=0.00). In older children group (aged 10-12 years), replacing 30 min/day sedentary with VPA was associated with a 1.0% lower FFMI(β=0.13, P=0.04); replacing 30 min/day sedentary to walking was associated with both a 2.9% lower percentage of body fat(PBF)(β=-0.65, P<0.01) and a 4.0% lower fat mass index(FMI)(β=-0.18, P=0.00).@*Conclusion@#Replacing sedentary with other intensities of physical activity is crucial for improving fatness status among children aged 6 to 12 years, especially among children aged 10 to 12 years. This current study suggests that children should increase physical activity while reducing sedentary for reducing risk of childhood obesity.

Association of physical activity and sedentary behavior with 20 m shuttle run test performance among children / 中国学校卫生

Objective@#To investigate the independent and joint associations of physical activity and sedentary behavior with 20 m shuttle run test (20 m SRT) performance among children.@*Methods@#Using cluster random sampling method, a total of 1 144 children aged 6-12 years from 1 urban primary school in Guangzhou were selected and completed the questionnaire survey, physical examination, and 20 m SRT. Physical activity and sedentary behavior were collected through questionnaire. Poor performance on 20 m SRT run test was defined as standard Z score ≤0, which was calculated according to gender, age-specific mean and standard deviation. Based on moderate-to-vigorous physical activity (MVPA) (≥60 min/d, 30-<60 min/d, or <30 min/d) and sedentary behavior levels (cut-off point: the gender, age-specific 50th percentile value), all participants were divided into six subgroups. Multiple linear regression and Logistic regression were used to analyze the independent and joint associations of physical activity and sedentary behavior with 20 m SRT performance, respectively.@*Results@#Low level of physical activity (β=-2.99, P<0.05) and high sedentary behavior (β=-1.75, P<0.05) were independently correlated with lower 20 m SRT performance. Compared with the reference group (MVPA≥60 min/d and low sedentary behavior), the risk for low performance on 20 m SRT was higher in those with MVPA<30 min/d, or those with high sedentary behavior. The risk for poor performance on 20 m SRT was gradually elevated with decreased physical activity levels in combination with higher level of sedentary behavior(P<0.05).@*Conclusion@#Physical activity and sedentary behavior were independently related to 20 m SRT performance among children. There is a clear does-response association, with elevated risks for poor performance on 20 m SRT with decreased physical activity levels in combination with higher level of sedentary behavior.