Reference values and growth curves of length for weight and head circumference for weight among Chinese newborns / 中华儿科杂志

Objective: To establish the reference values and growth curves of length for weight and head circumference for weight among Chinese newborns in order to provide a reference for the assessment of body proportionality at birth. Methods: A cross-sectional design was applied. A total of 24 375 singleton live birth newborns with gestational ages at birth of 24+0 to 42+6 weeks were recruited from June 2015 to November 2018 from 13 cities including Beijing, Harbin, Xi'an, Shanghai, Nanjing, Wuhan, Guangzhou, Fuzhou, Kunming, Tianjin, Shenyang, Changsha, and Shenzhen, excluding those with maternal or newborn conditions that may impact the establishment of the reference values. The generalized additive model for location, scale, and shape was employed to establish reference values in terms of percentile and growth curves of length for weight and head circumference for weight for male and female newborns. The random forest machine learning method was employed to analyze the importance of variables between the established reference values in this study and the previous published weight/length, body mass index (BMI), ponderal index (PI), weight/head circumference, length/head circumference in the assessment of symmetrical and asymmetrical small for gestational age (SGA) newborns. Results: A total of 24 375 newborns with 13 197 male infants (preterm birth 7 042 infants and term birth 6 155 infants) and 11 178 female infants (preterm birth 5 222 infants and term birth 5 956 infants) were included in this study. The reference values in terms of percentile (P3, P10, P25, P50, P75, P90, P97) and growth curves of length for weight and head circumference for weight were obtained for male and female newborns with gestational ages of 24+0 to 42+6 weeks. The median birth lengths corresponding to the birth weights of 1 500, 2 500, 3 000, and 4 000 g were 40.4, 47.0, 49.3 and 52.1 cm for males and 40.4, 47.0, 49.2, and 51.8 cm for females, respectively; the median birth head circumferences were 28.4, 32.0, 33.2 and 35.2 cm for males and 28.4, 32.0, 33.1, and 35.1 cm for females, respectively. The differences of length for weight between males and females were minimum, with the difference range of -0.3 to 0.3 cm at P50; the differences of head circumference for weight between males and females were minimum, with the difference range of 0 to 0.2 cm at P50. Based on the match between birth length and birth weight for classifying symmetrical and asymmetrical SGA, length for weight and PI contributed the most, accounting for 0.32 and 0.25, respectively; based on the match between birth head circumference and birth weight, head circumference for weight and weight/head circumference contributed the most, accounting for 0.55 and 0.12, respectively; based on the match between birth length or head circumference with birth weight, head circumference for weight and length for weight contributed the most, accounting for 0.26 and 0.21, respectively. Conclusion: The establishment of the new standardized growth reference values and growth curves of length for weight and head circumference for weight among Chinese newborns are useful for clinical practice and scientific research.

Risk factors of simple obesity in preschool children in nine cities of China / 中华流行病学杂志

Objective: To examine risk factors of simple obesity and their interaction in preschool children in China. Methods: A total of 63 292 preschool children aged 3-7 years selected by cluster random sampling in 9 cities of China, including Beijing, Harbin, Xi'an, Shanghai, Nanjing, Wuhan, Guangzhou, Fuzhou and Kunming, were investigated from June to November in 2016. Based on the BMI-for-age cut off points of overweight and obesity for Chinese children aged 2-18 years, a total of 1 522 obese children (1 006 boys and 516 girls) were screened. By population-based matched case-control design, a normal weight child was randomly selected to match with an obese child by sex, age (difference ≤6 months) and body height (difference ≤5 cm) from the survey area. Conditional logistic regression model was used to analyze association of risk factors with obesity and the interaction of risk factors. Results: ① Univariate conditional logistic regression model showed that 17 risk factors of simple obesity had statistical significance (P<0.001), including high birth weight, cesarean section, gestational diabetes, gestational hypertension, formula feeding in the first 6 months after birth, strong appetite, fast or slow eating speed, low intensity of outdoor activities, daily outdoor activity time <1 hour, daily screen viewing time < 1 hour or ≥2 hours, daily night sleep time <9 hours, mother overweight, father overweight, mother's low educational level, father's low educational level, non-nuclear family structure, and parents not being the primary caregivers of children. ②Multivariate conditional logistic regression model showed that 12 risk factors had statistical significance, including high birth weight (OR=1.83, 95%CI:1.29-2.61, P<0.001), cesarean section (OR=1.22, 95%CI:1.07-1.39, P=0.003), gestational diabetes (OR=4.57, 95%CI:2.13-9.79, P<0.001), mother's low educational level (OR=1.52, 95%CI:1.11-2.07, P=0.008), single parent family (OR=4.79, 95%CI:1.44-15.88, P=0.010), mother overweight (OR=2.58, 95%CI:1.93-3.46, P<0.001), father overweight (OR=2.40, 95%CI:1.86-3.10, P<0.001), strong appetite (OR=7.78, 95%CI:5.38-11.27, P<0.001), fast eating speed (OR=6.59, 95%CI:4.86-8.94, P<0.001), daily outdoor activity time <1 hour (OR=1.42, 95%CI: 1.09-1.85, P=0.009), daily night sleep time <9 hours (OR=1.59, 95%CI: 1.13-2.23, P=0.007), daily screen viewing time ≥2 hours (OR=1.69, 95%CI:1.27-2.24, P<0.001). ③ Interaction of the four groups of risk factors had statistical significance, including interaction between mother overweight and father overweight (OR=5.53, 95%CI: 3.76-8.13, P<0.001), interaction between strong appetite and fast eating speed (OR=54.48, 95%CI: 32.95-90.06, P<0.001), interaction between low intensity of outdoor activity and daily outdoor activity time <1 hour (OR=2.12, 95%CI: 1.29-3.48, P=0.002), interaction between daily night sleep time <9 hours and daily screen viewing time ≥2 hours (OR=2.83, 95%CI: 1.71-4.68, P<0.001). Conclusions: This study identified 12 risk factors of childhood obesity, including high birth weight, cesarean section, gestational diabetes, mother's low educational level, single parent family, mother overweight, father overweight, strong appetite, fast eating speed, daily short outdoor activity time, daily short night sleep time, daily long screen viewing time, and interaction of the four groups of risk factors had statistical significance, including strong interaction between mother overweight and father overweight, interaction between strong appetite and fast eating speed, interaction between low intensity of outdoor activity and daily short outdoor activity time, interaction between daily short night sleep time and daily long screen viewing time.

Body mass index cut-offs for overweight and obesity in Chinese children and adolescents aged 2-18 years / 中华流行病学杂志

Objective To study the body cut-offs of mass index (BMI) for the purpose of screening overweight and obesity for Chinese children and adolescents aged 2-18 years. Methods Based on the BMI growth reference values for Chinese children aged 0-18, using the common methods to establish the BMI cut-offs for screening overweight and obesity. These methods were having the same empirical percentile or Z scores and the BMI value at 18 years consistent with adults.Three sets of BMI cut-offs, including (BMI24, BMI28) , (P85, P95) and (Z1, Z2) , were initially identified. Differences were compared on different cut-off points and prevalence rates of overweight and obesity with different BMI reference, different values and "prevalence" of overweight and obesity based on "2004 Beijing Child and Adolescent Metabolic Syndrome Study ". Cut-offs standards which recommended by the Chinese Working Group on Obesity for Children (WGOC) and by the International Obesity Task Force (IOTF) were also used. Finally the appropriate cut-offs were defined. Results Three sets of BMI cut-offs for screening overweight and obesity for Chinese children and adolescents aged 2-18 years were obtained according to the above mentioned methods for selection. The prevalence rates of overweight and obesity defined by those cut-offs appeared not to be significantly different. Compared with the WGOC, the BMI cut-off points for screening overweight and obesity for both boys and girls from our study were very close to the WGOC', but cut-off points for screening overweight for girls aged 8.5-15.5 y was 0.3-1.0 kg/m2 lower than the WGOC'. Going through the database on screening of "2004 Beijing Children's Metabolic Syndrome Survey ", the prevalence of overweight for girls was about 3.4% higher than using the cut-offs of WGOC. Conclusion Results from this study suggested that the BMI cut-offs passed through the cut-off point of BMI24 and BMI28 at 18 years was appropriate for screening overweight and obesity in Chinese children from 2 to 18 years, and achieved the continuity in age and consistency in screening standard when using the BMI indicator in children and adolescents.

Height and weight standardized growth charts for Chinese children and adolescents aged 0 to 18 years / 中华儿科杂志

<p><b>OBJECTIVE</b>To construct the height and weight growth charts for Chinese children and adolescents from birth to 18 years for both clinical and preventive health care uses.</p><p><b>METHODS</b>Data from two national representative cross-sectional surveys which were The National Growth Survey of Children under 7 years in the Nine Cities of China in 2005 and The Physical Fitness and Health Surveillance of Chinese School Students in 2005. The data from 94,302 urban healthy children were used to set up the database of length/height (length was measured for children under 3 years) and weight. The LMS method was used to smooth the growth curves, with estimates of L, M, and S parameters, values of percentile and Z-score curves which were required were calculated, and then generated standardized growth charts.</p><p><b>RESULTS</b>The 3rd, 10th, 25th, 50th, 75th, 90th, 97th smoothed percentiles curves and -3, -2, -1, 0, +1, +2, +3 Z-scores curves of weight-for-age, length/height-for-age for boys and girls aged 0-18 years were made out respectively. Comparison with the new WHO growth charts and 2000 CDC growth charts for the United States, the results showed that there was some big difference in weight and height among the three growth charts. For boys under 15 years of age and girls under 13 years of age, the China curves are slightly higher than WHO and CDC curves, but after those ages, the China curves fall behind and the difference became larger as age progresses. At the age of 18 years, the Chinese children are 3.5 cm shorter in boys and 2.5 cm shorter in girls as compared with the U. S. children. The difference in weights are very large for the school children, especially in girls. The weight of Chinese boys was 5.9 kg less than that of the U. S. boys at 18 years, and the difference was much bigger in girls, the weight of U.S. girls between 8 to 18 years was 4.1-20.5 kg more than that of Chinese girls at the same age range.</p><p><b>CONCLUSION</b>The new growth charts of height and weight were based on national survey data and therefore are recommended as the China national growth standards for use in pediatric clinics and public health service. Application of the charts will promote child growth monitoring, discovering early growth disorder, and will be useful to diagnosis of diseases and assessment of therapeutic effects.</p>

Body mass index growth curves for Chinese children and adolescents aged 0 to 18 years / 中华儿科杂志

<p><b>OBJECTIVE</b>To construct the body mass index (BMI) reference data and curves for Chinese children and adolescents from birth to 18 years of age.</p><p><b>METHODS</b>Data from two national representative cross-sectional surveys which were The National Growth Survey of Children under 7 years in the Nine Cities of China in 2005 and The Physical Fitness and Health Surveillance of Chinese School Students in 2005. Height (length was measured for children under 3 years) and weight data of 93,702 urban healthy children from nine cities/provinces used to calculate the BMI. The LMS method was used to smooth the BMI, with estimates of L, M, and S parameters, values of percentile and Z-score curves which were required were calculated, and then standardized growth charts were generated. Adult cut-offs for overweight and obesity at 18 years was used to study the cut-offs for children 2 to 18 years of age.</p><p><b>RESULTS</b>The smoothed percentiles and Z-scores reference data and curves of BMI-for-age for boys and girls aged 0-18 years were made out respectively. BMI cut-off values for overweight and obesity for children from 2 to 18 years of age were also defined. At 18 years, the BMI values are equivalent to the overweight cut-off (> or =24 kg/m2) and obesity cut-off (> or =28 kg/m2) for Chinese adults. Comparison with the reference of the WHO and 2000 CDC for the United States, there were some difference among them, at the 97th percentile curve there was a big difference between Chinese and U. S. adolescents. On the whole, the China BMI curve for boys was higher than the new WHO curve and lower than 2000 CDC at 97 percentile curve, but the China BMI curve for girls was lowest among the three curves. There was also significant difference between China and Japan BMI values at 97 percentile curve.</p><p><b>CONCLUSION</b>BMI growth curves are very useful in child growth monitoring and nutritional surveillance, discovering overweight and obesity. The BMI growth charts are recommended for use in pediatric clinic and public health service.</p>

General growth patterns and simple mathematic models of height and weight of Chinese children / 中华儿科杂志

<p><b>OBJECTIVE</b>To explore the growth patterns and simple mathematic models of height and weight of Chinese children.</p><p><b>METHODS</b>The original data had been obtained from two national representative cross-sectional surveys which were 2005 National Survey of Physical Development of Children (under 7 years of age) and 2005 Chinese National Survey on Students Constitution and Health (6 - 18 years). Reference curves of height and weight of children under 7 years of age was constructed by LMS method, and data of children from 6 to 18 years of age were smoothed by cubic spline function and transformed by modified LMS procedure. Growth velocity was calculated by smoothed values of height and weight. Simple linear model was fitted for children 1 to 10 years of age, for which smoothed height and weight values were used.</p><p><b>RESULTS</b>(1) Birth length of Chinese children was about 50 cm, average length 61 cm, 67 cm, 76 cm and 88 cm at the 3rd, 6th, 12th and 24th month. Height gain was stable from 2 to 10 years of age, average 6 - 7 cm each year. Birth length doubles by 3.5 years, and triples by 12 years. The formula estimating average height of normal children aged 2 - 10 years was, height (cm) = age (yr) x 6.5 + 76 (cm). (2) Birth weight was about 3.3 kg. Growth velocity was at peak about 1.0 - 1.1 kg/mon in the first 3 months, decreased by half and was about 0.5 - 0.6 kg/mon in the second 3 months, and was reduced by a quarter, which was about 0.25 - 0.30 kg/mon, in the last 6 months of the first year. Body mass was up to doubles, triples and quadruple of birth weight at about the 3rd, 12th and 24th month. Average annual gain was about 2 kg and 3 kg from 1 - 6 years and 7 - 10 years, respectively. The estimated formula for children 1 to 6 years of age was weight (kg) = age (yr) x 2 + 8 (kg), but for those 7 - 10 years old, weight (kg) = age (yr) x 3 + 2 (kg).</p><p><b>CONCLUSIONS</b>Growth patterns of height and weight at the different age stages were summarized for Chinese children, and simple reference data of height and weight velocity from 0 to 18 years and approximate estimation formula from 1 - 10 years was presented for clinical practice.</p>