Association of total body fat and fat distribution with bone mineral density among children and adolescents aged 6-17 years from Guangzhou, China.

This study aimed to assess the associations of total body fat and fat distribution with bone mineral density (BMD) among children and adolescents in this cross-sectional study. A total of 1032 boys and 897 girls aged 6-17 years were enrolled between May 2019 and June 2019 in Guangzhou, China. BMD, total body fat (fat mass index [FMI] and body fat percentage [BF%]), and fat distribution (trunk-to-limb and android-to-gynoid ratios) were measured by dual-energy X-ray absorptiometry. Inverse probability of treatment weighting regression was used to explore the association between fat and BMD. Traditional regression of covariate adjustment was applied as sensitivity analysis. Regression with inverse probability weighting suggested BF% and android-to-gynoid ratio were negatively associated with BMD in boys (ß = - 0.12 and - 0.16, respectively; P < 0.05). Android-to-gynoid ratio was also inversely associated with BMD in girls (ß = - 0.08, P < 0.05). When stratified by age, the negative associations were retained in boys aged 12-17 years (ß = - 0.23 and - 0.25, respectively; P < 0.001). But for girls, it showed a positive association of FMI with BMD in the 6-9 years group (ß = 0.33, P < 0.001) and a negative association between the android-to-gynoid ratio and BMD in the 10-17 years group (ß = - 0.10, P < 0.05). Traditional regression supported the robustness of the results.  Conclusion: Total body fat is positively associated with BMD in younger girls but inversely associated in older boys. As for abdominal adipose, it is associated with lower BMD in both older boys and girls. What is Known: • The lean mass has been consistently positively associated with bone mineral density (BMD) among children and adolescents. However, the impact of fat mass on BMD remained controversial. • Beyond total body fat, site-specific fat mass, especially abdominal adiposity, might impede bone formation. What is New: • The associations of total body fat and fat distribution with BMD in children and adolescents were gender- and age-specific. • More attention should be paid to the abdominal fat accumulation to promote bone health in older children.

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.

Comparative analysis of bone mineral content measured by bioelectrical impedance analysis and dual energy X ray absorption among children and adolescents / 中国学校卫生

Objective@#To compare bioelectrical impedance analysis (BIA) and dual energy X ray absorptiometry (DXA) for measuring body mineral content (BMC) of children and adolescents, and to provide a basis for BIA to accurately measure BMC in children and adolescents.@*Methods@#By using the convenience sampling method, among 1 469 children and adolescents aged 7-17 were recruited in Guangzhou from April to May 2019, the BMC was measured by DXA and BIA. The intraclass correlation coefficient ( ICC ) and Bland Altman analysis were used to evaluate the agreement between BIA and DXA. Bland Altman analysis was performed on log transformed data. The BMC was categorized into age and specific tertiles, and the agreement between methods was evaluated based on the kappa coefficients. Treating the BMC with DXA as the dependent variable, a prediction model was constructed for correcting the BIA measure.@*Results@#The ICC s were 0.93 and 0.94 for boys and girls, respectively. In Bland Altman analysis, the limits of agreements for the BIA to DXA ratio were wide in boys and girls, ranging from 0.27-0.76 and 0.17-0.72, respectively. The kappa coefficients for categorized BMC levels were 0.57 and 0.45 for boys and girls, respectively, showing a fair to good degree of agreement. When sub grouped by BMI, the kappa coefficients for all BMI groups of boys and overweight girls were all >0.75 , with an excellent agreement. The prediction models for boys and girls were as follows: BMC DXA =-0.51+0.44× BMC BIA + 0.06× Age +0.02× BMI ; and BMC DXA =-0.55+0.43× BMC BIA +0.06× Age +0.02× BMI , respectively. The R 2 for models of boys and girls were 0.87 and 0.87, respectively.@*Conclusion@#The agreement between BIA and DXA was poor for measuring BMC, but acceptable when evaluating the categorized BMC levels, suggesting the BIA may be applied in assessment of the BMC levels when compared to the age and gender specific population. Additionally, the prediction model for correcting BMC by BIA fis well to the measurement by DXA.

Influence of birthweight and delivery mode on obesity among primary school students in Guangzhou / 中国学校卫生

Objective@#To explore the influence of birthweight and delivery mode on overweight/obesity and abdominal obesity in primary school students, and to provide evidence for childhood obesity prevention.@*Methods@#After physical examination, questionnaire survey was conducted among 3 361 students and their parents from 3 primary schools in Guangzhou selected through stratified clustering sampling. Information about birthweight and delivery mode was collected. Logistic regression model was used to analyze the association of birthweight and delivery mode with overweight/obesity and abdominal obesity. The multiplicative interaction term and the Delta method was used to explore the potential interaction.@*Results@#The prevalence rate of overweight and obesity for primary school students was 21.33%, and the rate of abdominal obesity was 12.08%. Multivariate Logistic regression analysis showed that delivery by cesarean section was associated with 44% increased risk of overweight/obesity(OR=1.44, 95%CI=1.16-1.80), as compared to vaginal delivery. Higher birthweight was linked to increased risk of overweight/obesity(OR=1.62, 95%CI=1.09-2.42). There was no significant association of birth weight and delivery mode with abdominal obesity in multivariate analysis(P>0.05). Additionally, a positive additive interaction was seen between delivery mode and parental obesity for students risk of overweight/obesity(RERI=0.33, 95%CI=0.02-0.65), as well as for the risk of abdominal obesity(RERI=0.39, 95%CI=0.12-0.65).@*Conclusion@#Cesarean section delivery and higher birthweight are linked to increased risk of overweight and obesity in primary school students. The synergistic effect of cesarean section and parental obesity may increase the risk of childhood obesity.

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.

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.

Effects of maternal passive smoking during pregnancy and girls’ overweight / 中国学校卫生

Objective@#To investigate the effect of maternal passive smoking during pregnancy and girls’ overweight /obesity on the age at menarche(AAM), and to provide a reference for improving healthy development of children and adolescents.@*Methods@#Based on the school entrance physical examination in 2016, a cross-section study was conducted by convenient sampling method, in a total of 2 722 students of 7th grade, from 26 middle schools in urban areas of Guangzhou. Multivariate logistic regression model was used to investigate the relationship between maternal passive smoking during pregnancy and girls’ overweight /obesity and AAM. A four-way decomposition method was used to explore the mediated effect of girls’ overweight/obesity on the relationship between maternal passive smoking during pregnancy and AAM.@*Results@#The proportion of girls who had menstruate was 90.82%(2 472/2 722). The median AAM was 12.00 years old, with an early menarche rate of 34.91%(863/2 472). Compared with girls whose mother hadn’t passive smoking during pregnancy, the risk of early AAM in girls with mother passive smoking during pregnancy≤3 days/week increased by 32%(OR=1.32, 95%CI=1.06-1.65), the risk in girls with maternal passive smoking during pregnancy>3 days/week increased by 58%(OR=1.58, 95%CI=1.21-2.07). Multivariate Logistic regression analysis showed that, overweight or obesity girls had a 77% higher risk of early AAM than non-overweight/obesity girls(OR=1.77, 95%CI=1.36-2.31). The four-way decomposition analysis showed 79.60% of early AAM risk could be accounted by maternal passive smoking during pregnancy(P<0.01).@*Conclusion@#Girls’ overweight/obesity and maternal passive smoking during pregnancy were associated with early menarche. The effect on daughters’ age at menarche is mainly in a direct effect manner of maternal passive smoking during pregnancy.