[A national survey on physical growth and development of children under seven years of age in nine cities of China in 2015].

Objective: To investigate and analyze the status of physical growth and its change in children under 7 years of age in 9 cities of China, and to provide scientific data for renewing and developing the new growth reference of Chinese children. Methods: Data of healthy children under 7 years of age were collected by stratified cluster sampling method in Beijing, Harbin, Xi'an, Shanghai, Nanjing, Wuhan, Guangzhou, Fuzhou and Kunming during the period from June to November in 2015. They were divided into 22 age groups. The sample size of boys or girls, urban or suburban was 150-200 in each age group in each city, and the total sample size in the 9 cities was 161 774. Weight, length/height, head circumference, sitting height, chest circumference and waist circumference were measured by the trained investigators using standard methods. There were strict quality control measures during investigation process. The t test was used to compare the difference of physical growth between two groups and one-way ANOVA was used to compare the difference of physical growth among three groups. Results: (1) The level of physical growth of children under 7 years were different between boys and girls, urban and suburban, as well as different regions of China in 2015. The urban-suburban difference was more significant in children older than 8 months, that is, the weight and height of urban children were greater than those of suburban children (0.01-0.48 kg and 0.1-1.1 cm respectively). (2) Weight and height of children in the 9 cities, whether urban or suburban areas, had been greater than WHO growth standards, for example, the Z-scores of height values of urban and suburban children were 0.43 ±0.99 (t=130.551, P<0.05) and 0.30 ±1.01 (t=87.407, P<0.05) higher than the WHO standards. (3) The physical growth of children in the 9 cities was improved in varying degrees during the past 10 years. For example, the changes of weight and height in urban children under 3 years were not significant, while there was significant improvement among children older than 3 years and the increasing trend became apparent along with the increasing of age (0.05-1.18 kg in weight and 0.5-1.8 cm in height). The urban-suburban difference of physical growth in each age group of boys and girls narrowed significantly during the past 10 years, which was clearly shown from the narrowing urban-suburban differences of weight and height in boys aged 5.5-<6.0 years (1.58 kg in 2005 vs. 0.44 kg in 2015 and 2.8 cm in 2005 vs. 0.9 cm in 2015) . (4) From the increments of each decade during 1975-2015, a rapid increments of physical growth during 1975-2005 were found, while the increments after 2005 had slowed comparing with that of the previous period in urban areas, for example, the increments of height in boys aged 5.5-<6.0 years were 1.5, 2.1, 2.7, 0.7 cm respectively in the 1(st), 2(nd), 3(rd) and 4(th) decade (1975-1985, 1985-1995, 1995-2005, 2005-2015) . In suburban areas, the trends of the previous 3 decades were similar with that of urban children, while the increments of the 4(th) decade were still bigger though they were slightly smaller than those of the 3(rd) decade, for example, the increments of height in boys aged 5.5-<6.0 years were 2.4, 2.3, 3.2, 2.6 cm in the 1(st), 2(nd), 3(rd) and 4(th) decade respectively. Conclusions: Physical growth of children under 7 years of age showed a slow positive secular trend during the last decade after a rapid increase. The increments of suburban children's physical growth were greater than those of urban children. The physical growth of children under 7 years in 9 Chinese cities exceeded the WHO standards.目的： 了解和掌握我国7岁以下儿童体格发育现状及变化趋势，并为进一步更新和制定新的儿童生长标准提供科学数据。 方法： 于2015年6—11月应用分层随机整群抽样的方法，调查北京、哈尔滨、西安、上海、南京、武汉、广州、福州、昆明9个城市（简称九市）及其郊区7岁以下健康儿童体格发育现状，分22个年龄组，每市每个年龄组城区和郊区男、女各150~200名，共计161 774名。测量指标包括体重、身高（长）、坐高、头围、胸围和腰围；测量工具统一配备，测量方法、测量人员统一培训，实施过程进行严格质量控制。组间比较采用t检验或单因素方差分析。 结果： （1）2015年九市儿童体格发育水平存在性别、城郊、地区差异，其中城郊差异在8月龄后较为明显，主要表现为城区儿童比郊区儿童重0.01~0.48 kg、高0.1~1.1 cm。（2）2015年九市城区和郊区各年龄组儿童体重、身高均明显高于世界卫生组织（WHO）标准，如城、郊区儿童身高Z分值分别高0.43±0.99（t=130.551，P<0.05）和0.30±1.01（t=87.407，P<0.05）。（3）九市儿童以身高和体重为主要指标的生长水平在2005—2015年的10年间又有不同程度增长，其中城区<3岁时变化不大，3岁以后增幅随年龄增长而逐渐增大，体重增长0.05~1.18 kg，身高增幅0.5~1.8 cm。各年龄组身高、体重的城郊差异明显缩小，如5.5~<6.0岁男童体重城郊差值从2005年的1.58 kg降至2015年的0.44 kg，身高城郊差值从2005年的2.8 cm降至2015年的0.9 cm。（4）1975—2015年的40年间，城区儿童体重、身高的增幅在前3个10年呈递增趋势，但是第4个10年（即2005—2015年）明显降低，如5.5~<6.0岁男童身高4个10年的增幅依次为：1.5、2.1、2.7、0.7 cm；郊区儿童前3个10年的变化趋势与城区一致，第4个10年虽然较第3个10年增幅略有下降，但依然保持着较大幅度的增长，如5.5~<6.0岁男童身高4个10年的增幅依次为：2.4、2.3、3.2、2.6 cm。 结论： 近10年我国儿童的生长发育水平已从快速增长期进入到缓慢增长期；郊区儿童的增长幅度明显大于城区，城郊差异明显缩小；九市儿童的生长水平已超过WHO标准。.