中国7岁以下儿童重量指数的生长规律及参照标准建立

目的 分析中国7岁以下正常儿童重量指数（PI）随年龄增长的变化规律，制定0~2岁儿童PI的参照标准及生长曲线。方法 体重和身高测量值来自2005年“中国九市7岁以下儿童体格发育调查”，根据体重和身高测量值计算PI值［体重(kg)·身长-3(m-3)］，并建立7岁以下正常儿童PI数据库。分析PI在各主要百分位（P3、P50及P97）上的变化规律，比较PI在性别和城郊群体水平上的差异。以3岁以下儿童为参照人群，采用LMS方法建立PI参照值及标准化曲线，模型构建使用LMS Pro软件。选择“转换年龄”模式，具体参数：男性自由度L-M-S=3-11-6，POWER=0.05及OFSET=0.10；女性自由度L-M-S=3-11-4，POWER=0.05及OFSET=0.15。结果 0~7岁儿童总样本量为138 775名，其中城区69 760名（男34 901名，女34 859名），郊区69 015名（男34 650名，女34 365名），男女及城郊样本量各半，各年龄组1 496~1 666名。0~2岁儿童曲线拟合的数据：男23 703名，女23 625名，每年龄组1 512~1 622名。①PI随年龄增长先攀升，2~3月龄达峰值，然后急速下降，2岁以后趋缓，并随年龄增长持续缓慢下降。男女间、城郊间差异均不明显；但在1月龄至3岁，男性略高于女性，1~6月龄及2~3岁时郊区略高于城区。②采用百分位和标准差单位两种表达形式给出0~2岁儿童数值及标准化生长曲线图。结论 本研究分析了中国7岁以下正常儿童PI的生长规律，建立了0~2岁儿童PI的参照标准及生长曲线，为进一步研究和应用PI奠定基础。

Growth patterns and reference growth curves of ponderal index for Chinese children under 7 years of age

Objective To describe the ponderal index (PI) growth patterns of Chinese children younger than 7 years old and establish the standardized PI growth curves for infants younger than 2 years old. Methods Weight and height measurements came from the National Growth Survey of Children under 7 years of age in the Nine Cities of China (NGSCNCC) in 2005, and PI was calculated as weight/(height3) (kg·m-3). The database of PI was established. The PI characteristics in the empirical percentiles (P3, P50 and P97) were analyzed and the differences on PI were compared between genders, urban-rural areas and ages. The PI growth curves were constructed based on urban children younger than 3 years old from the 2005 NGSCNCC using the Cole's LMS method for fitting. The LMS Pro software was employed and the parameters for this study were as follows: degree of freedom in boys was LMS = 3-11-6, POWER = 0.05 and OFSET = 0.10; in girls LMS = 3-11-4, POWER = 0.05 and OFSET = 0.15. Results A total of 138 775 children aged 0 to 7 years were enrolled, including 69 760 in urban area(34 901 boys and 34 859 girls) and 69 015 in rural area(34 650 boys and 34 365 girls). There were 1 496 to 1 666 children in each age group. PI rised with age increased, reached the peak at 2-3 months of age, then rapidly declined and decreased slowly at preschool age in urban-rural areas. For example, PI of boys in urban area at birth was 26.03, reached the peak 28.29 at 2-3 months of age, then declined to 17.38 at 2-2.5 years of age, decreased to 12.99 at 6-7 years of age. Overall, there was no significant difference between sexes or urban-rural areas,but at 1 month to 3 years of age PI was slightly higher in boys than that in girls, at 1-6 months and 2-3 years of age PI was slightly higher in rural than in urban children. PI growth curves were given for Chinese children aged 0 to 2 years by two forms, percentiles and standard deviation scores including 23 703 boys(excluded 18 boys) and 23 625 girls(excluded 17 girls). Conclusions The study described the PI growth patterns of Chinese children and established the standardized PI growth curves which may provide a scientific basis for clinical practice and further explorations on the related issues in this field.