OBJECTIVETo describe secular trends on physical growth of children in China during the year of 1985-2005 and to analyze the urban-suburban-rural difference and its change.

METHODSThe measurements of height, weight and chest circumference obtained from two serial national cross-sectional surveys for children aged 0 to 7 years in China were used to analyze the secular trends, and the growth differences among urban, suburban and rural children were compared.

RESULTSThe average weight and height for both boys and girls from urban, suburban and rural areas have significantly increased in most age groups during the past 20 years; The average chest circumference increased slightly, ranging from 0.0 to 2.0 cm. From 1985 to 2005, the urban-suburban difference in height had become smaller, and that in weight showed similar trend for children under 3 years old but became larger after 3 years old; the suburban-rural difference both in height and weight became larger after 6 months old. The increment per decade in height was the greatest in the suburban group while the greatest increment in weight was the urban group.

CONCLUSIONPositive secular trends were observed among urban, suburban and rural areas in Chinese children under 7 years old during the 1980s and the 2000s, reflecting a rapid socio-economic development in China.

Adolescent ; Adult ; Anthropometry ; Child ; Child, Preschool ; China ; Female ; Growth ; Humans ; Infant ; Male ; Rural Population ; Suburban Population ; Urban Population

Objective: To investigate the status of the development of primary teeth and to identify the development patterns among infants and toddlers in nine cities of China in 2015. Methods: Healthy children aged 1-<36 months were investigated by across-sectional survey and retrospective studies, which 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 October in 2015. Subjects (n=103 995) were divided into 14 age groups (1-<2, 2-<3, 3-<4, 4-<5, 5-<6, 6-<8, 8-<10, 10-<12, 12-<15, 15-<18, 18-<21, 21-<24, 24-<30, 30-<36 months). There were 150-200 boys and girls respectively in each group of urban and suburb areas in each city. The eruption status and the number of primary teeth were examined by the trained child health care physician or pediatrician on the spot. The timing of primary teeth eruption of children was retrospectively surveyed using a questionnaire. The prevalence of primary teeth was calculated and χ² test was used for comparison of categorical data. Probit regression analysis was used to determine the median and percentile age of eruption of primary teeth. Results: Totally 103 995 children aged 1-<36 months were investigated. There were 52 346 children in urban areas (boys 26 228, girls 26 118) and 51 649 children in suburb areas (boys 25 912, girls 25 737). The eruption rate of primary teeth in children under 2 years became higher with age and the difference among each age group was statistically significant (χ²=85 913.868, P<0.01), which was 0.3% (22/7 450) in 3-<4 months group, 43.0% (3 227/7 503) in 6-<8 months group and 99.9% (7 441/7 446) in 15-<18 months group. The eruption age of primary teeth was 6.6 months (95%CI: 6.5-6.7 months), and the range of the 3rd to 97th percentile was 4.1-10.6 months. The eruption ages of primary teeth in urban and suburb areas children were 6.6 months (95%CI: 6.5-6.7 months) and 6.6 months (95%CI: 6.5-6.7 months) respectively. The eruption age of primary teeth was earlier in boys (6.4 months, 95%CI: 6.3-6.5 months) than that in girls (6.7 months, 95%CI: 6.6-6.8 months). The median eruption age of primary teeth was earlier in northern China (6.2 months) than that in central (6.7 months) and southern China (6.9 months). The eruption rate of primary teeth became higher with age, showing that the median number of primary teeth was 2 in 8-<10 months group, 8 in 12-<15 months group and 20 in 30-<36 months group. Conclusions The timing of eruption of primary teeth was similar between urban and suburb areas children and that of the boys was slightly earlier than that of the girls. There were slight differences among different regions in the eruption timing of primary teeth. The range of the 3rd to 97th percentile in the eruption age of primary teeth was 4.1-10.6 months and the number of primary teeth followed the regular development pattern with age.

Objective: To observe the development of the anterior fontanel (AF) in healthy Chinese children from 1 to 36 months, and to assess the relationship between the closure of the AF and physical development in Chinese children. Method: This was a cross-sectional evaluation of the AF in a series of 104 147 healthy children between June 2015 and October 2015 from nine cities in China. The size and closure of AF of the children were measured and recorded, and the age for the closure of AF was calculated using probit analysis. The data in 2015 were compared with the data from the same surveys in 1985, 1995 and 2005 respectively. Result: (1) Totally, 104 147 healthy children (52 216 boys and 51 931 girls; range 1 month to 36 months) from nine cities enrolled in this cross-sectional study. (2)The size of AF gradually decreased with age, and the mean size of AF was 2.0(95% confidence interval (CI)2.0-2.1) cm at the age of 1 month, 0.6(95% CI 0.5-0.6) cm at the ages of 12-14 months, and 0.0(95% CI 0.0-0.0) cm at the ages of 21-23 months, respectively. (3) The percentage for the closure of AF was 0.1% at the age of 3 months, 67.5% at the ages of 15-17 months. The oldestt age for closure was 35 months. The mean age for the closure of AF was 14.5 months (95% CI 14.4-14.6), and the 3rd and 97th centiles of the age for the closure of AF were 6.6 and 22.4 months. (4) Over the past 30 years from 1985 to 2015, no significant change was found regarding the mean age for the closure of AF in children from urban area, contrarily, the mean age was 1.1 months earlier in suburban area. (5) The height and weight of children in the closed AF group were significantly higher than those of children in unclosed AF group(all P<0.01), but no significant difference was found regarding the head circumference between the two groups. Conclusion The size of AF at 1 month was maximum, then decreases gradually with age, and the mean age for the closure of AF was 14.5 (95% CI 14.4-14.6) months. No significant correlation was found between the development of AF and the head circumference, but there was a positive correlation between the development of AF and the height and weight. There was no significant change regarding the secular trend of the age for the closure of AF.

Objective: To analyze the current situation of gross motor development of infants in nine cities of China and their relationship with physical growth. Methods: Healthy full-term infants aged 1-24 months were investigated by cross-sectional survey, which was carried out in nine cities (Beijing, Harbin, Xi'an in northern, Shanghai, Nanjing, Wuhan in central, and Guangzhou, Fuzhou, Kunming in southern regions of China) from June to October in 2015. Subjects were grouped into 12 age groups (1-<2, 2-<3, 3-<4, 4-<5, 5-<6, 6-<8, 8-<10, 10-<12, 12-<15, 15-<18, 18-<21, 21-<24 months). Gross motor development of infants was examined by fieldworkers and the information on parental education, family income and birth status were obtained by questionnaire. Weight, length and head circumference was measured by fieldworkers according to standard methods in the fields and their Z scores were calculated by using WHO growth standard. Z scores of weight (WZ), length (LZ) and head circumference (HCZ) <-2 s was considered as lower group, -2 s-<-1 s as medium-lower group, -1 s-1 s as medium group, 1 s-<2 s as medium-higher group and ≥2 s as higher group. The age of gross motor development was calculated by Probit regression analysis and χ² test was used for comparison of categorical data. Results: (1) The number of infants whose gross motor development was examined were 88 968 in the nine cities. The proportion of achievement of motor development became larger with the chronological age, i.e. it was 11.1% (800/7 236) at 5-<6 months, 65.2% (4 921/7 545) at 6-<8 months and 98.5% (7 417/7 531) at 8-<10 months for sitting alone without support. There was no gender difference in the proportion of achievement of sitting alone without support, hand-knee crawl, stand alone and walk alone (χ²=2.873, 0.275, 0.250, 0.576, all P>0.05). (2) The median age of achievement of sitting alone without support, hand-knee crawl, stand alone, walk alone was respectively 5.9, 7.8, 10.8, 13.0 months, and their ranges from 1^st to 99^th percentile were respectively 4.2-8.3 months, 4.9-12.6 months, 7.6-15.4 months, 9.8-17.4 months. The gender difference of median age of gross motor development was 0.0-0.1 months and their regional difference was 0.0-0.7 months. (3) In the lower weight group, their median age of sitting alone without support and walk alone were 0.2-0.6 months later than the medium weight group, while their median age of hand-knee crawl and stand alone were similar to those of the medium weight group. In higher weight group, the median age of sitting alone without support and stand alone were similar to that of the medium weight group, while their median age of hand-knee crawl was 0.3 later months and their median age of walk alone was 0.3 months earlier than that of the medium weight group. There was no significant relationship between length and the age of sitting alone or standing alone (the difference was 0.0-0.2 months in each group). The median age of hand-knee crawl and walk alone was 0.4-0.7 months later in lower length group than in other length groups. The median age of gross motor development was similar among different head circumference groups (0.0-0.2 months). The relationship between weight/length and motor development was similar to that between weight and motor development. Conclusions There were no gender difference and slightly regional difference in the age of achievement of gross motor skills. The percentile age of gross motor skills helps to understand the population variation in healthy infants. The gross motor development is related with weight, length and body proportion.

Objective To analyze the breastfeeding rate of children under two years of age in nine cities of China in 2015 and variations in breastfeeding patterns from 1985 to 2015. Methods All data were collected from a series of national cross-sectional surveys "National Growth Survey of Children under Seven Years Old in Nine Cities of China" (urban and suburban areas of Beijing, Haerbin, Xi'an, Wuhan, Nanjing, Shanghai, Guangzhou, Fuzhou and Kunming) conducted from each May to October in 1985, 1995, 2005 and 2015. Stratified cluster sampling was used to select healthy children at least 150 in each subpopulation. Feeding patterns within 24 h prior to investigation were analyzed through face-to-face interviews using a self-made questionnaire. The rates of exclusive breastfeeding, mixed feeding and formula feeding were described as composition ratios. The difference between urban and suburban areas was analyzed by Chi-square test and the weaning age was calculated with a Probit model. Results (1) In 2015, the exclusive breastfeeding rate for infants under six months of age was 48.8% (9 143/18 722) in urban areas and 48.4% (8 652/17 878) in suburban areas, and the breastfeeding rates at one and two years old were 36.1% (1 351/3 746) and 5.8% (211/3 668) in urban areas and 29.9% (1 128/3 776) and 4.3% (157/3 683) in suburbs. The differences of breastfeeding patterns in ≥1-<2, ≥2-<3, ≥ 3-<4, ≥ 5-<6, ≥ 10-<12, ≥ 12-<15, ≥ 18-<21 and ≥ 21-<24 months of age were all significantly between suburbs and urban areas (χ2=8.575-36.299, all P<0.01). The age at weaning age was 9.4 months and 9.3 months in urban and suburban areas, respectively. (2) From 1985 to 2005, breastfeeding rates showed a decreasing trend, especially in suburban areas where the exclusive breastfeeding rate for infants under six months of age decreased from 60.2% (8 898/14 780) to 42.5% (6 487/15 261) and the continuous breastfeeding rate decreased from 60.1% (2 164/3 600) to 27.6% (783/2 838) at the age of one and from 8.9% (320/3 600) (in 1995) to 3.0% (85/2 850) in 2015 at the age of two. However, from 2005 to 2015, breastfeeding rates were on the rise, especially in urban areas in which the exclusive breastfeeding rate for infants under six months of age increased from 32.8% (5 176/15 782) to 48.8% (9 143/18 722) and the continuous breastfeeding rates at one and two years old respectively increased from 17.0% (499/2 940) to 36.1% (1 351/3 746) and from 1.2% (34/2 856) to 5.8% (211/3 668). Conclusions There are great changes in breastfeeding patterns for Chinese children in the nine cities from 1985 to 2015. In the first two decades, breastfeeding rates decreased and the duration of breastfeeding was shortened, while the last decade have seen increased breastfeeding rates and longer breastfeeding duration. The exclusive breastfeeding rate for infants under six months of age is similar in urban and suburban areas and both have reached about to 50% in 2015, which indicates fruitful results have achieved through the implementation of infant feeding strategies and related measures in China.

Objective:To study and establish the percentile reference values of waist circumference (WC) for Chinese children aged 3-7 years.Methods:A total of 26 480 children aged 3-7 years were collected as part of the National Survey on Physical Growth and Development of Children in nine cities (Beijing, Harbin, Xi’an, Shanghai, Nanjing, Wuhan, Guangzhou, Fuzhou and Kunming) in China from June to November 2015. Sex- and age-specific smoothed percentile reference values of WC were established using the Lambda Mu Sigma method. The P 75 and P 90 curves of WC for children aged 3-7 years in this study were linked with the published P 75 and P 90 cut-off points for Chinese children and adolescents aged 7-18 years. The P 50 percentile of WC in this study was compared with the corresponding percentiles of several foreign studies. Results:The P 5, P 10, P 15, P 20, P 25, P 50, P 75, P 80, P 85, P 90 and P 95 reference values of WC were obtained for boys and girls aged 3-7 years biannually, at the interval of every six months. Results showed that WC at the P 50 had significantly increased from 47.5 cm at the age of 3 to 54.2 cm at the age of 7 for boys and from 47.0 cm at the age of 3 to 52.2 cm for girls at the age of 7. The corresponding WC percentile values appeared a bit higher in boys than those in girls at the same age, with the differences from 0.4 to 3.6 cm. The differences between measured and fitted WC at each empirical percentile ranged from -0.3 to 0.5 cm for both boys and girls aged 3-7 years. The P 75 and P 90 values of WC for boys and girls aged 3-7 years in this study presented a consistent, continuous tendency on age with the published WC cut-off points ( P 75 and P 90) for Chinese children and adolescent aged 7-18. The increasing trend of WC by age in Chinese children aged 3-7 years was consistent with those of foreign studies, at the middle level for boys and lower middle level for girls. Conclusions:Through this study, we established the WC percentile values for Chinese children aged 3-7 years and achieved the continuity in age with the published WC cut-off points for Chinese children and adolescents aged 7-18. These established WC percentile values can be used as reference for clinical practice, health care and scientific research.

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 develop the reference values of carotid intima?media thickness (cIMT) in Chinese children aged 6-11 years. Methods A convenient cluster sampling method was used to conduct a cross?sectional survey from November 2017 to January 2018 in a primary school in Huantai County, Zibo City, Shandong Province. A total of 1 033 children aged 6-11 years (excluding children with obesity or hypertension) were included. Percentile curves for cIMT were drawn using the lambda, mu and sigma (LMS) method. Results This study developed the cIMT reference values (P90 and P95) for sex and age aged 6-11 years, including P90 and P95 reference values of mean cIMT, left cIMT and right cIMT, respectively. With the increase of age, the cIMT percentile values also increased. For the same age and the same percentile, the cIMT values of boys were higher than those of girls. Conclusion This study developed sex?specific and age?specific cIMT percentile reference values in children aged 6-11 years.

Objective To develop and validate a simplified height?specific blood pressure cutoffs table for screening hypertension in Chinese children and adolescents. Methods We developed a simplified height?specific blood pressure cut offs table according to Chinese Blood Pressure Reference for Children and Adolescents aged 7-18 years (WS/T 610?2018) (hereafter referred to as "complex definition"). Populations from Early Warning, Diagnosis and Treatment of Children Cardiovascular Disease Project ("Ji′nan sample") and Shandong Children Cardiovascular Cohort Study Project ("Zibo sample") were used as validation populations for evaluating the screening effect of the simplified table for elevated blood pressure and hypertension in children and adolescents. Results We developed simplified height?specific blood pressure cutoffs table including 7 height groups and 28 cutoffs. Both Ji′nan and Zibo samples were selected by convenient sampling method, and the former included 7 233 participants aged 7 to 17 years, among whom 3 790 (52.4%) were boys. Latter population included 1 277 participants aged 7 to 11 years, among whom 681 (53.3%) were boys. The simplified table performed well for identifying elevated blood pressure in Ji′nan sample, with values of area under the receiver operating curve (AUC) (95%CI), sensitivity, specificity, and Kappa statistic as 0.96 (0.95-0.97), 93.0%, 98.5% and 0.91, respectively, which were similar with results in Zibo sample [the values were 0.92 (0.90-0.95), 87.0%, 98.0% and 0.85, respectively]. The simplified table also performed well for identifying hypertension in Ji′nan sample with values of AUC (95%CI), sensitivity, specificity, and Kappa statistic as 0.92 (0.91-0.94), 86.9%, 98.1% and 0.85, respectively, which were similar with results in Zibo sample [the values were 0.94 (0.91-0.96), 88.2%, 98.9% and 0.88, respectively]. Conclusion Screening for elevated and high blood pressure based on simplified height?specific blood pressure cutoffs table is easy to use and it shows satisfying effect.