Objective Longitudinal 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.Method Height 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.Result Totally 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.Conclusion This 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.%目的 通过体检检测数据,分析儿童青少年身高生长轨迹的变化规律,为儿科临床及保健医生早期识别生长偏离及评估干预治疗提供科学依据.方法 回顾性收集2006至2012年北京市东城区某两所普通学校4 632名中小学生体检监测数据,监测记录为1～8次.将每个对象第一次身高记录对应的Z分曲线定义为基线生长轨迹,计算不同时点身高随访测量围绕基线轨迹向上或向下的偏离量确定上下浮动区间数据,采用LIFEREG程序拟合参数回归模型.构建等距为0.67标准差(s)的生长轨道,计算处在不同基线Z区间轨道内身高随访测量沿基线轨道或偏离基线轨道运行的构成比.结果 将身高监测记录≥3次者3 308人纳入进行统计分析.本组资料身高浮动区间数据服从指数分布,拟合含性别和基线Z区间轨道两协变量的指数分布模型显示性别差异无统计学意义(P =0.186 6).将性别因素剔除后拟合只含有基线Z区间轨道的模型显示Z区间在＞2.00s和-2.00～-1.34 s差异均无统计学意义(P=0.946 7、0.091 1).将基线Z区间缩减为6个连续的轨道后,拟合出了精练的、差异有统计学意义的指数模型(P ＜0.000 1).处在不同轨道的个体,身高随基线轨迹上下浮动的偏离量有明显差异,高轨道向下浮动,低轨道向上浮动.总体上,90％的个体(P5～ P95)围绕基线轨迹上下浮动的偏离量范围为4.06 cm,其中向下浮动2.60 cm,向上浮动1.46 cm.个体在Z区间上半部(0～2.00 s)沿原生长轨道运行的比例为43.8％～47.4％,在下半部(-2.00 s～0)为33.0％ ～ 37.9％;在上半部运行不跨越±1个轨道的比例为94.0％～94.8％,在下半部为79.1％ ～91.0％.结论 儿童青少年身高生长轨迹的一般规律:90％的个体围绕基线轨迹上下浮动的偏离量范围约为4.00 cm,其中向下浮动2.00 ～3.00 cm,向上浮动1.00～2.00 cm;30％～50％的个体沿原生长轨道前进,80％ ～ 90％的个体运行不跨越±1个轨道.
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