Objective:To investigate the influence and mechanisms of metformin on the proliferation and apoptosis of human keloid fibroblasts (Fbs).Methods:This study was an experimental research. The keloid tissue was collected from 7 keloid patients (2 males and 5 females, aged 20-65 years, with a disease course of more than 1 year) who underwent keloid excision surgery at the Department of Plastic, Cosmetic and Maxillofacial Surgery of the First Affiliated Hospital of Xi'an Jiaotong University from September 2020 to September 2023. The primary Fbs were isolated and cultured, and cells from passages 3 to 6 were used for experiments. The cells were divided into control group and metformin group, and were cultured in complete medium. The medium for metformin group was supplemented with metformin at a final molarity of 60 mmol/L. The cell counting kit-8 was used to assess the proliferation activity of cells in two groups after 12 and 24 hours of culture, and the proliferation inhibition rate of cells in metformin group after 12 and 24 hours of culture was calculated, with a sample size of 6. The apoptosis detection kit was used to detect the apoptotic distribution of cells in control group after 0 hour (immediately) of culture and in metformin group after 12 and 24 hours of culture, with a sample size of 3. The cell cycle detection kit was used to detect the cycle distribution of cells in two groups after 12 and 24 hours of culture, with a sample size of 3. The eukaryotic mRNA sequencing was performed on suitable number of cells of two groups after 24 hours of culture, and the Kyoto encyclopedia of genes and genomes functional annotation analysis and functional enrichment analysis were performed after screening for differentially expressed genes (DEGs) with significantly differential expression between two groups. Western blotting was conducted to detect the protein expressions of phosphatidylinositol 3-kinase (PI3K), phosphorylated protein kinase B (p-Akt), and phosphorylated mammalian target of rapamycin (p-mTOR) in the PI3K/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway of cells in two groups after 24 hours of culture, with a sample size of 3.Results:After 12 and 24 hours of culture, the proliferation activity of cells in metformin group was significantly lower than that in control group (with t values of 4.70 and 24.02, respectively, P<0.05); the proliferation activity of cells in metformin group after 24 hours of culture was significantly lower than that after 12 hours of culture within the group ( t=4.73, P<0.05). Compared with that after 12 hours of culture within the group, the proliferation inhibition rate of cells in metformin group was significantly increased after 24 hours of culture ( t=5.29, P<0.05). Compared with that in control group after 0 hour of culture, the proportion of early apoptotic cells in metformin group was significantly increased (with t values of 6.62 and 4.58, respectively, P<0.05), and the proportion of early and late apoptotic cells was significantly increased after 12 and 24 hours of culture (with t values of 4.84 and 3.75, respectively, P<0.05). After 24 hours of culture, the proportion of late apoptotic cells in metformin group was significantly higher than that after 12 hours of culture within the group ( t=4.55, P<0.05). After 12 hours of culture, the proportion of S-phase cells in metformin group was significantly lower than that in control group ( t=5.90, P<0.05). After 24 hours of culture, compared with that in control group, the proportion of G0/G1-phase cells in metformin group was significantly increased ( t=5.36, P<0.05), while the proportion of G2/M-phase cells was significantly decreased ( t=17.63, P<0.05). The proportion of S-phase cells in metformin group after 24 hours of culture was significantly higher than that after 12 hours of culture within the group ( t=7.60, P<0.05). After 24 hours of culture, 4 814 DEGs with significantly differential expression were detected in the cells of metformin group compared with control group. The significantly upregulated and downregulated DEGs were mainly involved in biological functions related to signal transduction, cell growth and death, transport and catabolism, the endocrine system, the immune system, and cancer. The pathways that were significantly enriched with DEGs with significantly differential expression included the cell cycle and DNA replication, with the highest number of genes in the PI3K/Akt signaling pathway. After 24 hours of culture, the protein expressions of PI3K, p-Akt, and p-mTOR of cells in metformin group were 0.190±0.017, 0.170±0.017, and 0.247±0.005, respectively, which were significantly lower than 0.440±0.026, 0.300±0.060, and 0.547±0.025 in control group (with t values of 13.69, 3.61, and 20.12, respectively, P values all <0.05). Conclusions:Metformin can significantly inhibit the proliferation of human keloid Fbs through the PI3K/Akt/mTOR signaling pathway and effectively induce its apoptotic process, thereby exerting antifibrotic effects.

Objective:To explore the effect of continuous improvement model with Definition,Measure,Analyze,Improve,and Control(DMAIC)on the management for equipment of diagnosing and treating chronic respiratory diseases.Method:To address the management issues of diagnosis and treatment equipment for chronic respiratory diseases,multiple management strategies were formulated on the basis of definition,measurement,analysis,improvement and control stages of the DMAIC continuous improvement model.Selected 80 diagnostic and therapeutic equipment used at the department of respiratory in People's Hospital of Xinjiang Uygur Autonomous Region from August 2021 to July 2023.The conventional management method was used to manage them during August 2021 to July 2022,and the management method of DMAIC continuous improvement management model(continuous improvement management method)for chronic respiratory diseases was adopted to manage them during August 2022 to July 2023.The ratio of failure equipment,score of risk assessment,qualified rate of examination,and satisfaction score of users who operated equipment by using the two kinds of management methods were compared.Result:The average failure ratios of shutdown due to failure,injury that caused external environment,abnormal self-examination at power on,unqualified quality inspection,and poorly operational quality in treatment in equipment of diagnosing and treating respiratory disease by using continuous improvement management method were respectively(1.58±0.51)%,(0.34±0.10)%,(0.65±0.20)%,(2.08±0.53)%and(1.61±0.52)%,which were all lower than those by using conventional management method,and the differences of them were significant(t=14.512,11.205,24.354,17.169,17.663,P<0.05).The degree of detectability,severity,and probability scores of occurrence of the equipment by using continuous improvement management method were lower than those of conventional management method,and the differences were statistically significant(t=10.478,6.930,9.407,P<0.05).The qualified rate of equipment inspection of continuous improvement management method was higher than that of conventional management method,and the difference was statistically significant(x2=9.642,P<0.05).The performance,cleanliness of equipment,and timeliness scores of operators,who used equipment,for diagnosis and treatment equipment that were managed by using continuous improvement management method were all higher than those by using conventional management method,and the differences were statistically significant(t=2.204,2.268,2.604,P<0.05).Conclusion:The DMAIC continuous improvement management model method for equipment of diagnosing and treating chronic respiratory disease can significantly improve management level for equipment,and reduce failure risk of equipment,and increase the utilization efficiency of equipment and the users'satisfaction.

Objective:To explore the effect of continuous improvement model with Definition,Measure,Analyze,Improve,and Control(DMAIC)on the management for equipment of diagnosing and treating chronic respiratory diseases.Method:To address the management issues of diagnosis and treatment equipment for chronic respiratory diseases,multiple management strategies were formulated on the basis of definition,measurement,analysis,improvement and control stages of the DMAIC continuous improvement model.Selected 80 diagnostic and therapeutic equipment used at the department of respiratory in People's Hospital of Xinjiang Uygur Autonomous Region from August 2021 to July 2023.The conventional management method was used to manage them during August 2021 to July 2022,and the management method of DMAIC continuous improvement management model(continuous improvement management method)for chronic respiratory diseases was adopted to manage them during August 2022 to July 2023.The ratio of failure equipment,score of risk assessment,qualified rate of examination,and satisfaction score of users who operated equipment by using the two kinds of management methods were compared.Result:The average failure ratios of shutdown due to failure,injury that caused external environment,abnormal self-examination at power on,unqualified quality inspection,and poorly operational quality in treatment in equipment of diagnosing and treating respiratory disease by using continuous improvement management method were respectively(1.58±0.51)%,(0.34±0.10)%,(0.65±0.20)%,(2.08±0.53)%and(1.61±0.52)%,which were all lower than those by using conventional management method,and the differences of them were significant(t=14.512,11.205,24.354,17.169,17.663,P<0.05).The degree of detectability,severity,and probability scores of occurrence of the equipment by using continuous improvement management method were lower than those of conventional management method,and the differences were statistically significant(t=10.478,6.930,9.407,P<0.05).The qualified rate of equipment inspection of continuous improvement management method was higher than that of conventional management method,and the difference was statistically significant(x2=9.642,P<0.05).The performance,cleanliness of equipment,and timeliness scores of operators,who used equipment,for diagnosis and treatment equipment that were managed by using continuous improvement management method were all higher than those by using conventional management method,and the differences were statistically significant(t=2.204,2.268,2.604,P<0.05).Conclusion:The DMAIC continuous improvement management model method for equipment of diagnosing and treating chronic respiratory disease can significantly improve management level for equipment,and reduce failure risk of equipment,and increase the utilization efficiency of equipment and the users'satisfaction.

Objective:To investigate the influence and mechanisms of metformin on the proliferation and apoptosis of human keloid fibroblasts (Fbs).Methods:This study was an experimental research. The keloid tissue was collected from 7 keloid patients (2 males and 5 females, aged 20-65 years, with a disease course of more than 1 year) who underwent keloid excision surgery at the Department of Plastic, Cosmetic and Maxillofacial Surgery of the First Affiliated Hospital of Xi'an Jiaotong University from September 2020 to September 2023. The primary Fbs were isolated and cultured, and cells from passages 3 to 6 were used for experiments. The cells were divided into control group and metformin group, and were cultured in complete medium. The medium for metformin group was supplemented with metformin at a final molarity of 60 mmol/L. The cell counting kit-8 was used to assess the proliferation activity of cells in two groups after 12 and 24 hours of culture, and the proliferation inhibition rate of cells in metformin group after 12 and 24 hours of culture was calculated, with a sample size of 6. The apoptosis detection kit was used to detect the apoptotic distribution of cells in control group after 0 hour (immediately) of culture and in metformin group after 12 and 24 hours of culture, with a sample size of 3. The cell cycle detection kit was used to detect the cycle distribution of cells in two groups after 12 and 24 hours of culture, with a sample size of 3. The eukaryotic mRNA sequencing was performed on suitable number of cells of two groups after 24 hours of culture, and the Kyoto encyclopedia of genes and genomes functional annotation analysis and functional enrichment analysis were performed after screening for differentially expressed genes (DEGs) with significantly differential expression between two groups. Western blotting was conducted to detect the protein expressions of phosphatidylinositol 3-kinase (PI3K), phosphorylated protein kinase B (p-Akt), and phosphorylated mammalian target of rapamycin (p-mTOR) in the PI3K/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway of cells in two groups after 24 hours of culture, with a sample size of 3.Results:After 12 and 24 hours of culture, the proliferation activity of cells in metformin group was significantly lower than that in control group (with t values of 4.70 and 24.02, respectively, P<0.05); the proliferation activity of cells in metformin group after 24 hours of culture was significantly lower than that after 12 hours of culture within the group ( t=4.73, P<0.05). Compared with that after 12 hours of culture within the group, the proliferation inhibition rate of cells in metformin group was significantly increased after 24 hours of culture ( t=5.29, P<0.05). Compared with that in control group after 0 hour of culture, the proportion of early apoptotic cells in metformin group was significantly increased (with t values of 6.62 and 4.58, respectively, P<0.05), and the proportion of early and late apoptotic cells was significantly increased after 12 and 24 hours of culture (with t values of 4.84 and 3.75, respectively, P<0.05). After 24 hours of culture, the proportion of late apoptotic cells in metformin group was significantly higher than that after 12 hours of culture within the group ( t=4.55, P<0.05). After 12 hours of culture, the proportion of S-phase cells in metformin group was significantly lower than that in control group ( t=5.90, P<0.05). After 24 hours of culture, compared with that in control group, the proportion of G0/G1-phase cells in metformin group was significantly increased ( t=5.36, P<0.05), while the proportion of G2/M-phase cells was significantly decreased ( t=17.63, P<0.05). The proportion of S-phase cells in metformin group after 24 hours of culture was significantly higher than that after 12 hours of culture within the group ( t=7.60, P<0.05). After 24 hours of culture, 4 814 DEGs with significantly differential expression were detected in the cells of metformin group compared with control group. The significantly upregulated and downregulated DEGs were mainly involved in biological functions related to signal transduction, cell growth and death, transport and catabolism, the endocrine system, the immune system, and cancer. The pathways that were significantly enriched with DEGs with significantly differential expression included the cell cycle and DNA replication, with the highest number of genes in the PI3K/Akt signaling pathway. After 24 hours of culture, the protein expressions of PI3K, p-Akt, and p-mTOR of cells in metformin group were 0.190±0.017, 0.170±0.017, and 0.247±0.005, respectively, which were significantly lower than 0.440±0.026, 0.300±0.060, and 0.547±0.025 in control group (with t values of 13.69, 3.61, and 20.12, respectively, P values all <0.05). Conclusions:Metformin can significantly inhibit the proliferation of human keloid Fbs through the PI3K/Akt/mTOR signaling pathway and effectively induce its apoptotic process, thereby exerting antifibrotic effects.

Objective:To understand the current status of pubertal sexual characteristics development of girls aged 6-18 years in Tongzhou District of Beijing and to compare the differences in sexual characteristics development among girls characterized as thin, normal, overweight, and obese.Methods:A cross-sectional survey was conducted among 2 844 girls aged 6-18 years in Tongzhou District of Beijing from September 2022 to July 2023. The developmental stages of breast and pubic hair were assessed on site, and menarche status was inquired. Weight and height were measured. The girls were subsequently characterized into thin, normal, overweight and obese groups. Basic information (including family and personal history) was obtained through questionnaires. Probit probability unit regression was applied to calculate the age of each Tanner stage of sexual characteristics development and the age of menarche. The χ 2 test was applied to compare the counting data between two or multiple groups. Results:A total of 2 844 girls were surveyed and 2 704 girls met the inclusion criteria, resulting in a valid response rate of 95.1%. Among these girls, 1 105 (40.9%) were aged 6-9 years, 1 053 (38.9%) were aged 10-13 years, and 546 (20.2%) were aged 14-18 years. The of height-for-age Z-score (HAZ), weight-for-age Z-score (WAZ), and body mass index-for-age Z-score (BAZ) were 0.46(-0.23,1.16), 0.69(-0.16,1.67), and 0.67(-0.27,1.73) respectively. The prevalences of thin, overweight, and obesity were respectively 1.7% (45/2 704), 17.3% (467/2 704), and 19.9% (538/2 704), respectively. There were 45 girls in the thin group, 1 654 girls in the normal weight group, 1 005 girls in the overweight and obesity group. The age of Tanner stage breast 2 (B2), Tanner stage pubic hair 2 (P2), and menarche was 9.0 (95% CI 8.9-9.1), 10.5 (95% CI 10.4-10.6), and 11.4 (95% CI 11.3-1.5) years, respectively. The current status of breast and pubic hair maturity in girls with pubertal development shows that 64.6% (1 211/1 874) of these girls had breast development preceding pubic hair development, 32.4% (607/1 874) had concurrent breast and pubic hair development, and 3.0% (56/1 874) had pubic hairs development preceding breast development. The interval age between B2 and B5 was 4.7 (95% CI 4.6-4.8) years, between P2 and P5 was 4.5 (95% CI 4.4-4.6) years, and between B2 and menarche was 2.4 (95% CI 2.3-2.5) years. The ages of sexual characteristics development in overweight and obese groups were earlier than that in normal and thin groups. The ages of B2 in thin, normal, overweight, and obese groups were 10.0 (95% CI 9.5-10.6), 9.3 (95% CI 9.2-9.4), and 8.6 (95% CI 8.4-8.7) years, respectively. The age of menarche in thin, normal, overweight, and obese groups were 13.1 (95% CI 12.4-13.7), 11.6 (95% CI 11.4-11.7), and 11.1 (95% CI 11.0-11.2) years, respectively. The interval ages between B2 and B5 and between P2 and P5 was 4.5 and 4.1 years, respectively in the overweight and obese groups, and those in normal group and thin group was 4.7 and 4.5 years, 4.6 and 4.7 years, respectively. Conclusions:The ages of sexual characteristics development and menarche tend in Tongzhou District of Beijing to be earlier than that being reported of Beijing's survey 20 years ago. Girls characterized as overweight and obese not only start puberty at an earlier age than girls of normal weight, but also have a shorter developmental process.

Bibenzyls, a kind of important plant polyphenols, have attracted growing attention for their broad and remarkable pharmacological activities. However, due to the low abundance in nature, uncontrollable and environmentally unfriendly chemical synthesis processes, these compounds are not readily accessible. Herein, one high-yield bibenzyl backbone-producing Escherichia coli strain was constructed by using a highly active and substrate-promiscuous bibenzyl synthase identified from Dendrobium officinale in combination with starter and extender biosynthetic enzymes. Three types of efficiently post-modifying modular strains were engineered by employing methyltransferases, prenyltransferase, and glycosyltransferase with high activity and substrate tolerance together with their corresponding donor biosynthetic modules. Structurally different bibenzyl derivatives were tandemly and/or divergently synthesized by co-culture engineering in various combination modes. Especially, a prenylated bibenzyl derivative ( 12) was found to be an antioxidant that exhibited potent neuroprotective activity in the cellular and rat models of ischemia stroke. RNA-seq, quantitative RT-PCR, and Western-blot analysis demonstrated that 12 could up-regulate the expression level of an apoptosis-inducing factor, mitochondria associated 3 (Aifm3), suggesting that Aifm3 might be a new target in ischemic stroke therapy. This study provides a flexible plug-and-play strategy for the easy-to-implement synthesis of structurally diverse bibenzyls through a modular co-culture engineering pipeline for drug discovery.

Objective:To establish the reference values and growth curves of weight/length, body mass index, and ponderal index for Chinese newborns with gestational ages of 24 to 42 weeks, in order to provide a reference for the assessment of body proportionality and nutritional status at birth.Methods:Cross-sectional study design was applied. From June 2015 to November 2018, a total of 24 375 singleton live birth newborns with gestational ages of 24 to 42 weeks from 13 cities including Beijing, Harbin, Xi′an, Shanghai, Nanjing, Wuhan, Guangzhou, Fuzhou, Kunming, Tianjin, Shenyang, Changsha, and Shenzhen were selected, excluding those impacting the establishment of the reference values. The generalized additive model for location, scale, and shape (GAMLSS) was employed to establish percentile (P 3, P 10, P 25, P 50, P 75, P 90, P 97) reference values and growth curves of weight/length, body mass index, and ponderal index for male and female newborns with gestational ages of 24 to 42 weeks. The established growth standards in this study were compared with the standards from the 1988 Chinese data, the INTERGROWTH project, and the USA reference values. Results:A total of 24 375 newborns with 12 264 preterm newborns (7 042 males and 5 222 females) and 12 111 full-term newborns (6 155 males and 5 956 females) were included in this study. The percentile reference values and growth curves of weight/length, body mass index, and ponderal index were obtained for male and female newborns with gestational ages of 24 to 42 weeks. Weight/length of males in all gestational ages at P 10, P 50 and P 90 was 0 to 0.2 kg/m higher than that of females, and body mass index of males in all gestational ages at the P 10, P 50 and P 90 was 0.1 to 0.3 kg/m 2 higher than that of females. The established growth curves of weight/length and body mass index at the upper percentile and ponderal index at both upper and lower percentiles were greatly different from those of the 1988 Chinese data, which, for example, reported the difference ranges at P 90 as -1.09 to 0.40 kg/m for weight/length, -1.19 to 0.92 kg/m 2 for body mass index, and -0.64 to 0.81 kg/m 3 for ponderal index. The established weight/length curves were generally consistent with the reference values from the INTERGROWTH project with a difference of -0.17 to 0.20 kg/m at P 50, while being 0.02 to 0.40 kg/m lower at P 90 and 0.13 to 0.41 kg/m higher at P 10 than that of the INTERGROWTH reference values at gestational ages of ≤32 weeks. The established body mass index curves differed from that of the USA reference values with a difference of -0.47 to 0.17 kg/m 2 at P 50, while being 0.53 to 1.10 kg/m 2 lower at gestational ages of ≥37 weeks but 0.17 to 0.45 kg/m 2 higher at gestational ages of ≤28 weeks than that of the USA reference values at P 90. Conclusion:The establishment of the new standardized growth reference values of weight/length, body mass index, and ponderal index for Chinese newborns by different gestational ages are useful for clinical practice and scientific research.

Objective:To analyze the influential factors of stunting among children under 7 years of age in nine cities of China in order to provide empirical data for early prevention and intervention for stunting.Methods:The survey was carried out with 1∶1 case-control study design in the communities and kindergartens of nine cities (Beijing, Harbin, Xi′an, Shanghai, Nanjing, Wuhan, Guangzhou, Fuzhou, and Kunming) from June to November in 2016. Children of heights lower than the 3 rd percentile according to the 2009 children′s height standard in China were included as the stunting case group ( n=1 281), and those with normal height matched for geolocation, gender, and age were recruited as the control group ( n=1 281). The height and weight were measured on site, and the information related to family, perinatal status, diet and feeding, lifestyle, and medical history was collected by questionnaire. Continuous variables were compared by paired samples t test and Wilcoxon matched-pair signed ranks test, and proportions were compared by paired Chi square test. Multivariate analysis were carried out using conditional Logistic regression model. Results:Among 1 281 pairs of stunting and control group, there were 677 pairs of boys and 604 pairs of girls, with 238 pairs of children under age 3 years and 1 043 pairs of children aged 3 to 7 years. The Z scores for height and weight of stunting group were lower than that of control group (-2.27 (-2.54, -2.08) vs. -0.59 (-1.04, -0.10), -1.85 (-2.35, -1.38) vs. -0.69 (-1.20, -0.21), Z=30.982, 25.580, both P<0.01). Among family related factors, parental education level, height, weight, and height of grandparents in stunting children were all lower than those in control group (all P<0.05). Among individual related factors, proportion of preterm birth, low birth weight, shorter birth length, mother's pregnancy complications, difficulties adding milk or complementary feeding, poor appetite, slow eating, picky and partial eating, passive eating, more snack intake, shorter sleep duration, difficulty falling asleep, disturbed sleep, and recurrent infectious diseases in infant in stunting children were all higher than those in control group (all P<0.05). Multivariate Logistic regression analysis results illustrate that the lower the parental education level and the parental height, the higher the risk of stunting. For example, the risk of stunting in children whose fathers had short stature was 6.46 times (95% CI: 2.73-15.30) of those children whose fathers′ height were medium and the risk of stunting in children whose mothers were short stature was 10.56 times (95% CI: 4.92-22.69) of those children whose mothers′ height were medium. The risks of stunting increase significantly among preterm children or those with low birth weight ( OR=2.27, 95% CI: 1.33-3.88), birth length<45 cm ( OR=3.56, 95% CI: 1.41-8.98), difficulties adding milk or complementary feeding ( OR=2.04, 95% CI: 1.32-3.15), poor appetite ( OR=3.20, 95% CI: 1.74-5.89), slow eating ( OR=1.85, 95% CI: 1.31-2.63), and food allergy ( OR=1.80, 95% CI: 1.02-3.16). Conclusion:Parental short stature, preterm birth or low birth weight, shorter birth length, feeding difficulty in infant, poor appetite, slow eating, and food allergy are the main risk factors for stunting in infants and children.

Objective: To survey the children under 7 years of age in nine cities of China for a better understanding of the current situation of childhood stunting. Methods: According to a stratified cluster sampling design, a cross-sectional survey on children under 7 years of age was carried out in 9 cities (Beijing, Harbin and Xi′an in northern China; Shanghai, Nanjing and Wuhan in central China; and Guangzhou, Fuzhou and Kunming in southern China) from June to November in 2016. A total of 110 499 children were recruited. Height of children was evaluated using the growth standards for Chinese children (2009 edition) .Children with height less than the 3rd percentile of the growth standards were considered as stunting, and children with height between the 3rd and 10th percentiles of the growth standards were considered as relatively short stature. Chi-square test was used for comparison between data of boys and girls, urban and suburban, as well as among different ages and regions. Results: Totally 113 084 children under 7 years of age should be investigated and actually 110 499 children were investigated, with a rate of 97.7%. The prevalence of stunting was 1.9% (2 141/110 499) among all the children. The prevalence of stunting in urban children (1.6%, 904/55 524) was lower than that in suburban children (2.3%, 1 237/54 975, χ²=56.246, P<0.01). The gender difference in stunting prevalence was not statistically significant (1.9% (1 121/57 921) in boys and 1.9% (1 020/52 578) in girls, χ²=0.003, P=0.965). The prevalence of stunting decreased with age for children younger than 3 years, from 1.8% (312/17 080) in 0-<1 year of age group to 1.2% (168/13 740) in 2-<3 years of age group, but increased to 2.2% (240/11 073) at 6-<7 years group. Comparison among different regions showed that the stunting prevalence in southern region was higher than those in the central and northern regions (0.9% (193/20 374) in northern urban, 0.8% (154/18 486) in central urban, and 3.3% (557/16 664) in southern urban children), showing a statistical significance (χ²=437.736, P<0.01); 1.1% (241/21 924) in northern suburban, 1.4% (227/16 775) in central suburban and 4.7% (769/16 276) in southern suburban children, showing a statistical significance (χ²=646.533, P<0.01). In urban areas, the difference between the central and northern regions showed no statistical significance (χ²=1.429, P=0.232) and the stunting prevalence of central Chinese children was slightly higher than that of northern Chinese children in suburban areas (χ²=5.130, P=0.024). Among the nine cities, the stunting prevalence of Guangzhou (6.1%, 613/10 019) was higher than those of other cities (χ²=1 559.64, P<0.01). Among the stunting children, 78.4% (1 679/2 141) were classified as borderline or mild and only 7.2% (154/2 141) were classified as severe. The prevalence of relatively short stature was 5.2% (5 721/110 499). Conclusions The prevalence of stunting among children under 7 years of age in nine cities of China is low and most of the stunting children were classified as mild; the prevalence of stunting in suburban children is higher than that in urban children; the gender difference show no statistical significance; and the prevalence of stunting in southern Chinese children is higher than those in central and northern Chinese children.

Objective: To investigate the timing of permanent tooth emergence and its association with physical growth among children aged 4-7 years in 9 cities of China, and to analyze the trend of permanent teeth development. Methods: According to a stratified cluster sampling design, a cross-sectional survey on the timing of permanent tooth emergence children aged 4-7 years was carried out in 9 cities (Beijing, Harbin and Xi′an in northern China; Shanghai, Nanjing and Wuhan in central China; Guangzhou, Fuzhou and Kunming in southern China) from June to October in 2015. A total of 37 973 children (19 035 boys and 18 938 girls) were recruited and were divided into different age groups (4.0-<4.5, 4.5-5.0, 5.0-5.5 and 6.0-<7.0 years of age). The situation of the exfoliation of primary teeth and the eruption of permanent teeth were investigated. Height and weight were measured using the standardized methods. Z-scores of physical growth indicators were calculated using the growth standards for Chinese children in 2009. Probit regression analysis was used to determine the median and percentile age of transition from deciduous to permanent teeth. Chi-square test was used for comparison of categorical data and t test was used for comparison of measurement data between boys and girls, urban and suburban as well as among different ages and regions. Meanwhile, the data from the national survey on physical growth and development of children under 7 years of age in 9 cities of China in 1995 were used to analyze the trends of the permanent teeth development. Results: The rate of transition from deciduous to permanent teeth in 37 973 children aged 4-7 years was higher with age, which was 0.6% (42/7 568) in 4.0-<4.5 years of age group, 30.3% (2 295/7 583) in 5.5-<6.0 years of age group, and 74.5% (5 680/7 627) in 6.0-<7.0 years of age group. The rates of transition from deciduous to permanent teeth in boys were all lower than those of girls except for children aged 4.0-<4.5 years (all P<0.01). The rate of transition from deciduous to permanent teeth in urban children was higher than that in suburban children for older than 5.5-6.0 years of age group in boys and older than 4.5-5.0 years of age group in girls, which was 74.2% (1 427/1 924) in urban boys aged 6.0-<7.0 years and 69.2% (1 305/1 885) in suburban boys aged 6.0-<7.0 years (χ²=11.446, P<0.01). The age of transition from deciduous to permanent teeth was 6.00 (95%CI: 5.98-6.01) years and the range of the 3-97 percentile was 4.88-7.11 years of age. The median permanent tooth emergence age of girls was lower than that of boys (5.94 vs. 6.06 years) and the median age of urban children was lower than that of suburban children (5.94 vs. 6.05 years). The median permanent tooth emergence age of southern Chinese children (6.05 years) was higher than that of northern (5.97 years) and central Chinese children (5.97 years). The weight for age Z-scores (WAZ), height for age Z-scores (HAZ) and body mass index for age Z-scores (BMIZ) of children with transition from deciduous to permanent teeth (0.35±1.17, 0.32±1.00, 0.23±1.16) were significantly higher than those of children without transition from deciduous to permanent teeth (0.03±1.13, 0.03±1.02, 0.04±1.13, t=20.81,21.67,12.09, all P<0.05). In comparison with the data in 1995, data in 2015 showed that the rate of transition from deciduous to permanent teeth was higher, for example, the rate of urban boys aged 6.0-<7.0 years group was 63.8% (1 146/1 796) in 1995, and increased to 74.2% (1 427/1 924) in 2015 (χ²=46.748, P<0.01). The median permanent tooth emergence age decreased by 0.24 years in 2015 as compared with that in 1995. Conclusions The development of permanent teeth is earlier in girls than in boys, earlier in urban children than in suburban children and slightly delay in southern children than in central and northern Chinese children. In addition, the development of permanent teeth, which is related to the physical growth, slightly accelerate in China during the past 20 years.