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 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 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 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.

OBJECTIVELongitudinal studies in height for school-age children and adolescents mainly focused on the velocity, spurt and peak of growth, and currently no changing growth trajectory or channel around the baseline were reported except the shift of percentiles among infants. This study aimed to analyze general characteristic of the growth trajectory of height among children and adolescents so as to provide scientific evidence for early detecting height deviation and evaluating treatment interventions for pediatric clinical and health care professionals.

METHODHeight measurement data of 4 632 school-aged children and adolescents were retrospectively collected from two middle schools in urban Beijing between 2006 and 2012, with physical examination records varying from 1 to 8 times. Corresponding Z-score curve of the first height data of each study subject was defined as the baseline growth trajectory. Interval censored data were determined by calculating and comparing the amount of up or down floating deviation of those follow-up measurements around the baseline trajectory at different time points, and the LIFEREG procedure was used to fit parametric regression model. Defined 0.67 s as isometric growth channel, proportions of follow-up measurements along the baseline or off-baseline channel were calculated at different baseline Z-score interval channel.

RESULTTotally 3 308 subjects with height examination records of 3 times or more were included in this study. Interval censored data of height abide by the exponential distribution based on parametric regression model. The exponential distribution model with two covariates of sex and baseline Z-score interval channel showed that sex was not statistically significant (P = 0.186 6). After removing factor of sex, the model only with baseline Z-score channel displayed that those Z-score channels over +2.00 s (P = 0.946 7) and -2.00-1.34 s (P = 0.091 1) were not statistically significant with the control of the channel below -2.00 s. Refined exponential distribution model (P < 0.000 1) was constructed after the Z-score channel reduced to six consecutive isometric growth channels. There were district differences in height deviations around the baseline trajectory in different baseline Z-score interval channels, floating downward in upper channel and floating upward in lower channel. Overall, the range of deviation of 4.06 cm was observed around the baseline trajectory in 90% of individuals (from P5 to P95), with the floating down 2.60 cm and the floating up 1.46 cm. The proportions of the individuals growing along the original channel were 43.8%-47.4% in the upper Z interval (0-2.00 s) and 33.0%-37.9% in the lower Z interval (-2.00-0 s); the proportions not shifting ± 1 channel were 94.0%-94.8% in the upper part and 79.1%-91.0% in the lower part.

CONCLUSIONThis study obtained general characteristics of growth trajectory of height among children and adolescents: the deflection range of shifting up and down is about 4 cm around the baseline trajectory for 90% individuals, with the downward float 2.00-3.00 cm and the upward 1.00-2.00 cm; and 30%-50% individuals go along the baseline channel and 80%-90% individuals do not exceed ± 1 channels.

Adolescent ; Adolescent Development ; Body Height ; Child ; Child Development ; Humans ; Longitudinal Studies ; Retrospective Studies

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.

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.

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.