The 5th national survey on the physical growth and development of children in the nine cities of China: Anthropometric measurements of Chinese children under 7 years in 2015
Funding information: The National Health and Family Planning Commission of the People's Republic of China and Beingmate Women and Children Development Research Foundation.
Abstract
Objectives
To describe the physical growth of healthy children under 7 years in China based on the latest national survey and provide more data for revising growth reference and monitoring the impact of social development on children's health and growth.
Methods
In the cross-sectional survey, 161,774 healthy children under 7 years were selected by multistage stratified cluster sampling method in nine cities of China. According to the geographical location, the nine cities were divided into northern, central and southern regions, and each city included urban and suburban areas. Anthropometric measurements were obtained on the spots and other related information was collected with questionnaires.
Results
There were slight urban–suburban difference and obvious regional difference in anthropometric measurements in China. Comparison with the 4th NSPGDC in 2005, measurements increased 0.1–1.1 kg in weight, 0.5–1.8 cm in height in urban areas (except children under 3 years) and 0.1–2.5 kg in weight, 0.2–3.8 cm in height in suburban areas. The urban–suburban difference of those measurements became smaller than 10 years ago, but their regional difference persistently exist. Chinese children were 0.36 SD in weight, 0.43 SD in height in urban areas and 0.30 SD in weight, 0.30 SD in height in suburban areas higher than WHO standards.
Conclusions
Physical growth of children under 7 years old was undergoing a slowly positive secular trend during the latest decade in more economically developed regions of China. Urban–suburban difference of those measurements became smaller, while their regional difference persistently exist. Chinese healthy children under 7 years in nine cities was taller and heavier than WHO standards.
1 Introduction
Childhood growth is a complex biological phenomenon, which can be evaluated by monitoring the basic physical measurements, i.e., mainly body weight and height. They were firstly used to illustrate the law of human physical growth as early as the second half of the 18th century (Tanner, 1987). These measurements were then applied to the burgeoning field of auxological epidemiology, when researchers recognized that differences in these growth measures were inextricably shaped by genetic background, social, and environmental conditions (Tanner, 1992). Moreover, these early researchers revealed positive secular trends in physical growth patterns within and across populations with improved access to medical intervention and improved nutrition. Growth of a population can therefore be used as a “mirror of conditions in society” (Tanner, 1987). Thus, anthropometric measurements have become the important reference data for anthropology, economics, biology, and clinical practices (Cole, 2000; Fogel, Engerman, & Trussell, 1982; Tanner, 1992).
Many large-scale growth surveys have been conducted across global populations (Gökçay, Furman, & Neyzi, 2008; Khadilkar, Khadilkar, Cole, & Sayyad, 2009; Kim et al., 2008; Kulaga et al., 2010, 2013; McDowell, Fryar, Ogden, & Flegal, 2008; Orden & Apezteguía, 2016; Roelants, Hauspie, & Hoppenbrouwers, 2009; Rosario, Schienkiewitz, & Neuhauser, 2011; Schönbeck et al., 2013; Tinggaard et al., 2014; Zsakai & Bodzsar, 2012) and even some countries had carried out some periodic growth surveys at regular intervals. These regular surveys have the potential to reveal patterns of childhood growth across historical periods and provide critical data on secular trends in physical growth. Among some of the most data-rich population surveys available include the national Dutch survey, which began data collection in 1955 and continues to monitor growth in decennial studies (a total of five times survey until 2009) (Schönbeck et al., 2013). Other regular surveys that monitor physical growth are available for US populations since the 1960s (Fryar, Gu, & Ogden, 2012), for Japan from 1960 to 2010 (Ministry of Health, Labour, and Welfare, 2011 2010), for Korea from 1965 to 2005 (Kim et al., 2008), and for the Czech Republic from 1951 to 2010 (Kobzová, Vignerová, Bláha, Krejcovský, & Riedlová, 2004). These data have illustrated not only significant population differences of physical growth between countries, but also the various changing of physical growth over times from country to country. In some developed countries, the positive secular trend that was documented for some anthropometric measures (i.e., height and weight), has decelerated or even plateaued leading to the conclusion that these populations might have reached their full growth potential due to improvement in life standards and health. However, this is not the result in other countries and physical growth continues to exhibit rapid positive secular trends (Komlos & Breitfelder, 2008; Muhardi, Abrahamse-Berkeveld, Acton, & van der Beek, 2016; Natale & Rajagopalan, 2014). These suggest that it is necessary to carry out physical growth survey in more populations over times, especially in developing countries, which would be helpful for comprehensive understanding the laws and characteristics of human physical growth.
In China, early surveys on physical growth, which began in the 1930s, only contained regional data (Qin & Sui, 1956; Wu, 1957), that is, until 1975, when “The National Survey on the Physical Growth and Development of Children in the Nine Cities of China” (NSPGDC) was conducted and it was the first large-scale national survey on children's growth. NSPGDC divided investigation sites into northern, central and southern region according the geographical latitude considering the vast territory with diverse regional characteristics in China, such as latitude, climate, living environment and cultural customs. Meanwhile, the subjects were also stratified sampling by urban and suburban areas of the city because of their disparity of social economic development (Institute of Pediatrics of Chinese Academy of Medical Sciences, 1977a,b). This study obtained the first complete anthropometric data of Chinese children and then it was carried out in 1985, 1995, and 2005 using the same methods in the same sites (Coordinating Study Group of Nine Cities on Physical Growth and Development of Children and Capital Institute of Pediatrics, 1987; Coordinating Study Group of Nine Cities on Physical Growth and Development of Children and Capital Institute of Pediatrics, 1998, 2007; Zhang & Huang, 1988). The data of the previous four surveys had illustrated the significant positive secular trend in height, weight, and head circumference in Chinese children and the gradually narrowing trend of their urban–suburban difference with the rapid socioeconomic development since Chinese economic reform and opening, especially in recent several decades (National Bureau of Statistics of China and UNFPA, 2014; National Bureau of Statistics of China, 2015; Zong, Li, & Zhu, 2011). However, we also have many questions on children's growth in the context of sustained and rapid social development of China. For example, what do growth patterns among present-day Chinese children look like? Are positive secular trends in growth still evident? Will the urban–suburban difference in growth diminish with the improvement of suburban living environment? Will the regional difference in growth become narrow? Based on these questions, the 5th NSPGDC was conducted in 2015 using the same methods in the same sites with the previous NSPGDC. The aim of this paper is to present the data on anthropometric measurements in this survey and their comparison to the 4th NSPGDC data in 2005 as well as WHO standards in 2006. It would be valuable to understand the children's growth and its changes in Asian developing countries during the process of rapid social development and supply more data for anthropological research.
2 Methods
2.1 Data source
All data were collected in the 5th NSPGDC. This investigation was conducted across nine cities between June and October, 2015. The nine cities included Beijing (Municipality), Harbin (Heilongjiang's provincial capital), Xi'an (Shanxi's provincial capital), Shanghai (Municipality), Nanjing (Jiangsu's provincial capital), Wuhan (Hubei's provincial capital), Guangzhou (Guangdong's provincial capital), Fuzhou (Fujian's provincial capital), and Kunming (Yunnan's provincial capital). All of these cities were also the study sites in the previous four NSPGDC. Among them, the first three cities, the middle three and the last three were respectively considered as northern, central, and southern regions according to their latitude (Figure 1).
The nine cities of the NSPGDC
2.2 Sample methods and subjects
Multistage stratified cluster sampling method was used according to urban/suburban areas and administrative districts in each city. The hospitals, communities and kindergartens in each selected administrative district were considered as the cluster sample unit. Newborns came from hospital, children aged 1 month to 3 years came from community, and children over 3 years (including 3 years) came from kindergarten. Children under 7 years, who are local residences in the selected region or those lived in this region for longer than 2/3 of their time of life, were included. Exclusion criteria: gestational age at birth <37 weeks or birth weight <2.5 kg, twins or multiple births, participants suffering from chronic systemic disease, congenital diseases, endocrine diseases, diseases of the nervous system, and those presenting with fever for more than 7 days in the past 2 weeks or continuous diarrhea more than five times every day for 5 days or longer. All children were divided into 22 age groups: birth, 1m-, 2m-, 3m-, 4m-, 5m-, 6m-, 8m-, 10m-, 12m-, 15m-, 18m-, 21m-, 2y-, 2.5y-, 3y-, 3.5y-, 4y-, 4.5y-, 5y-, 5.5y-, and 6-7y. The sample size for each sex–age subgroup in urban/suburban areas in each city was 150–200. In total, 161,774 children were included in the study, of which 83,628 from urban areas (41,990 boys and 41,638 girls), 78,146 from suburban areas (39,161 boys and 38,985 girls).
2.3 Measurements
Children were barefoot and wore the lightest vest, shorts or underwear, then their weight, height/length, head circumference (HC), sitting height (SH), chest circumference (CC), and waist circumference (WC) were measured and each indicator was completed by two investigators.
Weight was measured by Newborn scale (maximum range 20 kg and accurate to 10 g) for newborns and by Electronic Scale (T-Scale M303, maximum range 250 kg and accurate to 50 g, with “Tare” function) for children aged 1 month or older. Newborns' weight was recorded in grams to the nearest 10 g after putting them on the scale. Children aged 1 month or older were weighed by their parents holding them or sitting/standing alone in the middle of the scale and then the readings were recorded in kilograms to the nearest 0.01 kg. Recumbent length of children under 3 years of age and standing height of children aged 3 years or older were measured respectively using Infantometer (maximum range 110 cm, and accurate to 0.1 cm) and Height-Sitheight Stadiometer (maximum range 150 cm, and accurate to 0.1 cm) and then the readings were recorded to the nearest to 0.1 cm. HC of children under 3 years were measured using a flexible, nonstretchable plastic tape (0.7 cm wide, maximum range 110 cm, and accurate to 0.1 cm) and the readings were recorded to the nearest 0.1 cm. The specific measuring methods of weight, length/height and HC followed the standard procedures outlined elsewhere (de Onis, Onyango, Van den Broeck, Chumlea, & Martorell, 2004; WHO, 2004). SH of children aged 3 years or older were measured using the same equipment with height and the corresponding number of SH in vertical board were read to nearest 0.1 cm and its measuring details had been outlined previously (Zhang & Li, 2015). CC and WC of children aged 3 years or older were measured using the same tape with HC. The investigators recorded CC to the nearest 0.1 cm after positioning the tape on the lower edge of the breast nipple and around the lower edge of two shoulder blades of children at the end of normal expiration, making sure to keep the measuring tape snug but not tight enough to cause compression of the skin. The measuring details of WC followed the standard procedure (WHO STEPS Surveillance, 2008) and WC was measured twice, then the means of two readings were recorded to the nearest 0.1 cm. Body mass index (BMI) was calculated by the formula: weight (kg)/(height × height) (m2). The ratio of sitting height to height (SH/H) was calculated by the formula: SH/H *100.
In addition, questionnaires were used to find out about some social–economic characteristics of the child's family (including education of parents and the total family income of the previous year of this survey), the parents' body measurements (height and weight), birth information (birth weight and delivery modes), and the feeding or eating information (child's breast feeding and complementary food for children under 2 years and eating behavior for children older than 3 years). The trained investigators filled the questionnaires by asking the parents or the main caregivers of the child on the spot.
2.4 Quality control
Measuring equipments in all sites were uniform and were calibrated daily using standard weights for Electronic Scale (the error less than 50 g) and steel rule with length of 2 m for Infantometer, Height-Sitheight Stadiometer, and nonstretchable plastic tape (the error less than 0.5 cm). All investigators had participated in rigorous specialized training and passed an examination before the survey. Measurement errors were no more than 50 g in weight or 0.5 cm in length within intraobserver and interobserver measurements. The 5% of total subjects in each site were repeat measured randomly per day, and the proportion of subjects beyond allowable errors of the two measurements was no more than 10%.
2.5 Ethics statement
The 5th NSPGDC was approved by the Ethics Committee of the Capital Institute of Pediatrics, and informed consent was verbal. Members of the survey's staff explained to the parents of children the purpose of the survey and all participations were voluntary.
2.6 Statistic methods
SPSS 21.0 for Windows was used to clean and analyze the data. The gender difference, urban–suburban difference and the difference between the 4th and 5th NSPGDC were analyzed by the independent-samples t test. Analysis of Variance and the Student–Newman–Keuls method tested the region difference among northern, central, and southern regions. The Z scores of weight, height/length, HC, and BMI were calculated by LMS method using the WHO standards and the difference between Chinese children and WHO standards was analyzed by one-sample t test of Z scores. The proportions of parental education or family income per year were calculated and their differences between urban and suburban areas were analyzed by
test. A value of p < 0.05 was considered statistically significant.
3 Results
3.1 Parental educational and family economical background
Table 1 shows the parental education and family income per year to characterize family socioeconomic status (SES) of the subjects. We can see that the parental education and family income in urban areas was higher than that of suburban areas, 67.8 vs. 35.8% for the proportion of college degree and above of mother and 70.4 vs. 58.0% for the proportion of 50–100 thousand yuan of family income per year in urban and suburban areas.
| Urban | Suburban | χ2 | |||
|---|---|---|---|---|---|
| Education | Father | College degree and abovea | 58,187 (69.6%) | 29,090 (37.3%) | 19,268.668* |
| Senior school/technical secondary schoolb | 17,219 (20.6%) | 24,136 (30.9%) | |||
| Junior high school and below c | 8064 (9.6%) | 24,861 (31.7%) | |||
| Unknown | 158 (0.2%) | 59 (0.1%) | |||
| Mother | College degree and abovea | 56,761 (67.8%) | 27,976 (35.8%) | 19,203.412* | |
| Senior school/technical secondary schoolb | 17,738 (21.3%) | 23,568 (30.1%) | |||
| Junior high school and belowc | 8917 (10.6%) | 26,538 (34.0%) | |||
| Unknown | 212 (0.3%) | 64 (0.1%) | |||
| Family incomed | ≤¥30,000 | 3970 (4.7%) | 7813 (10.0%) | 7894.413* | |
| ¥30,000–49,999 | 14,136 (16.9%) | 22,183 (28.4%) | |||
| ¥50,000–99,999 | 30,080 (36.0%) | 29,019 (37.1%) | |||
| ¥100,000–299,999 | 28,747 (34.4%) | 16,310 (20.9%) | |||
| ≥¥300,000 | 6184 (7.4%) | 2491 (3.2%) | |||
| Unknown | 511 (0.6%) | 330 (0.4%) | |||
- Note: χ2 was the statistic of comparison between urban and suburban. *: p < 0.01.
- a refers to the years of education less than or equal to 9 years.
- bRefers to the years of education between 10 and 12 years.
- cRefers to the years of education longer than or equal to 13 years.
- dRefers to the total family income of the previous year of this survey.
3.2 Anthropometric measurements in 2015
3.2.1 Anthropometric measurements characteristics with age
Anthropometric indicators were given in Tables 2 and 3. The mean weight, height/length, HC, SH, CC, and WC of children under 7 years increased with chronological age and the younger the age, the more rapid the growth. For example, the increments of weight and height of boys were about 6.6 kg, 25.6 cm during the first year of life and 2.6 kg, 12.2 cm during the second year. Then the average increments at the age 3–7 years were about 2.4 kg/year in weight and 7.0 cm/year in height. HC of boys increased about 11.9 and 2.3 cm during the first and second year of life. The average increments of SH, CC, and WC of boys were about 3.0 cm/year, 2.1 cm/year, 1.9 cm/year over the age range 3–7 years. The means of BMI increased sharply from birth to 10–12 months, then gradually decreased until the age of 3 years. BMI basically remained stable during 3–5 years and slightly increased at age of 6–7 years. SH/H gradually decreased with age from 3 to 7 years.
| Boys | |||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Weight (kg) | Length/height (cm) | HC (cm) | SH (cm) | CC (cm) | WC (cm) | BMI (kg/m2) | SH/H | ||||||||||
| Age group | N | Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD |
| Birth | 2264 | 3.38 | 0.40 | 50.4 | 1.6 | 34.0 | 1.4 | – | – | – | – | – | – | 13.28 | 1.19 | – | – |
| 1m∼ | 3715 | 4.98 | 0.62 | 56.3 | 2.1 | 37.8 | 1.2 | – | – | – | – | – | – | 15.69 | 1.35 | – | – |
| 2m∼ | 3664 | 6.24 | 0.74 | 60.3 | 2.3 | 39.6 | 1.2 | – | – | – | – | – | – | 17.11 | 1.51 | – | – |
| 3m∼ | 3720 | 7.12 | 0.81 | 63.4 | 2.2 | 40.9 | 1.3 | – | – | – | – | – | – | 17.71 | 1.58 | – | – |
| 4m∼ | 3627 | 7.77 | 0.90 | 65.7 | 2.3 | 42.0 | 1.3 | – | – | – | – | – | – | 17.97 | 1.61 | – | – |
| 5m∼ | 3614 | 8.24 | 0.96 | 67.6 | 2.3 | 42.9 | 1.3 | – | – | – | – | – | – | 17.97 | 1.63 | – | – |
| 6m∼ | 3797 | 8.69 | 1.00 | 69.5 | 2.4 | 43.8 | 1.3 | – | – | – | – | – | – | 17.97 | 1.57 | – | – |
| 8m∼ | 3768 | 9.29 | 1.05 | 72.3 | 2.5 | 45.0 | 1.3 | – | – | – | – | – | – | 17.73 | 1.50 | – | – |
| 10m∼ | 3736 | 9.83 | 1.11 | 75.0 | 2.6 | 45.7 | 1.4 | – | – | – | – | – | – | 17.47 | 1.48 | – | – |
| 12m∼ | 3780 | 10.26 | 1.13 | 77.5 | 2.7 | 46.3 | 1.3 | – | – | – | – | – | – | 17.04 | 1.41 | – | – |
| 15m∼ | 3715 | 10.97 | 1.19 | 81.2 | 2.9 | 47.0 | 1.3 | – | – | – | – | – | – | 16.61 | 1.35 | – | – |
| 18m∼ | 3766 | 11.48 | 1.29 | 83.8 | 3.1 | 47.5 | 1.3 | – | – | – | – | – | – | 16.32 | 1.29 | – | – |
| 21m∼ | 3724 | 12.34 | 1.35 | 87.0 | 3.2 | 48.1 | 1.3 | – | – | – | – | – | – | 16.27 | 1.32 | – | – |
| 2.0y∼ | 3828 | 12.98 | 1.51 | 90.6 | 3.6 | 48.5 | 1.4 | – | – | – | – | – | – | 15.79 | 1.26 | – | – |
| 2.5y∼ | 3762 | 14.20 | 1.72 | 95.4 | 3.8 | 49.1 | 1.4 | – | – | – | – | – | – | 15.57 | 1.27 | – | – |
| 3.0y∼ | 3799 | 15.43 | 1.98 | 99.2 | 4.0 | – | – | 57.9 | 2.5 | 51.2 | 2.7 | 48.5 | 3.3 | 15.63 | 1.32 | 58.4 | 1.5 |
| 3.5y∼ | 3837 | 16.54 | 2.12 | 102.9 | 4.1 | – | – | 59.5 | 2.5 | 52.3 | 2.7 | 49.5 | 3.3 | 15.57 | 1.32 | 57.8 | 1.4 |
| 4.0y∼ | 3812 | 17.66 | 2.41 | 106.5 | 4.2 | – | – | 61.0 | 2.5 | 53.3 | 3.0 | 50.5 | 3.7 | 15.53 | 1.45 | 57.3 | 1.4 |
| 4.5y∼ | 3831 | 18.86 | 2.77 | 109.8 | 4.5 | – | – | 62.5 | 2.6 | 54.4 | 3.2 | 51.3 | 4.1 | 15.59 | 1.54 | 56.9 | 1.3 |
| 5.0y∼ | 3804 | 20.17 | 3.12 | 113.6 | 4.7 | – | – | 64.0 | 2.7 | 55.4 | 3.5 | 52.1 | 4.5 | 15.58 | 1.68 | 56.4 | 1.3 |
| 5.5y∼ | 3779 | 21.49 | 3.43 | 116.7 | 4.7 | – | – | 65.4 | 2.7 | 56.5 | 3.7 | 53.1 | 4.8 | 15.73 | 1.80 | 56.1 | 1.3 |
| 6∼7y | 3809 | 23.50 | 4.00 | 121.5 | 5.0 | – | – | 67.3 | 2.8 | 58.1 | 4.2 | 54.5 | 5.3 | 15.86 | 1.97 | 55.4 | 1.4 |
| Girls | |||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Weight (kg) | Length/height (cm) | HC (cm) | SH (cm) | CC (cm) | WC (cm) | BMI (kg/m2) | SH/H | ||||||||||
| Age group | N | Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD |
| Birth | 2147 | 3.26 | 0.40 | 49.8 | 1.6 | 33.7 | 1.3 | – | – | – | – | – | – | 13.10 | 1.14 | – | – |
| 1m∼ | 3703 | 4.67 | 0.59 | 55.2 | 2.1 | 37.1 | 1.2 | – | – | – | – | – | – | 15.25 | 1.35 | – | – |
| 2m∼ | 3605 | 5.74 | 0.66 | 58.9 | 2.2 | 38.7 | 1.2 | – | – | – | – | – | – | 16.48 | 1.42 | – | – |
| 3m∼ | 3732 | 6.51 | 0.74 | 61.8 | 2.2 | 39.9 | 1.2 | – | – | – | – | – | – | 17.01 | 1.53 | – | – |
| 4m∼ | 3594 | 7.11 | 0.81 | 64.0 | 2.1 | 41.0 | 1.2 | – | – | – | – | – | – | 17.31 | 1.55 | – | – |
| 5m∼ | 3626 | 7.60 | 0.88 | 66.0 | 2.3 | 41.9 | 1.3 | – | – | – | – | – | – | 17.41 | 1.57 | – | – |
| 6m∼ | 3753 | 8.05 | 0.94 | 67.8 | 2.4 | 42.7 | 1.3 | – | – | – | – | – | – | 17.47 | 1.56 | – | – |
| 8m∼ | 3763 | 8.66 | 1.03 | 70.8 | 2.6 | 43.8 | 1.3 | – | – | – | – | – | – | 17.24 | 1.51 | – | – |
| 10m∼ | 3763 | 9.17 | 1.05 | 73.5 | 2.6 | 44.6 | 1.3 | – | – | – | – | – | – | 16.94 | 1.42 | – | – |
| 12m∼ | 3743 | 9.66 | 1.08 | 76.2 | 2.7 | 45.2 | 1.3 | – | – | – | – | – | – | 16.62 | 1.36 | – | – |
| 15m∼ | 3733 | 10.38 | 1.17 | 79.9 | 3.0 | 46.0 | 1.3 | – | – | – | – | – | – | 16.23 | 1.34 | – | – |
| 18m∼ | 3750 | 10.84 | 1.23 | 82.5 | 3.1 | 46.5 | 1.3 | – | – | – | – | – | – | 15.88 | 1.26 | – | – |
| 21m∼ | 3636 | 11.69 | 1.27 | 85.8 | 3.1 | 47.1 | 1.3 | – | – | – | – | – | – | 15.85 | 1.27 | – | – |
| 2.0y∼ | 3774 | 12.34 | 1.46 | 89.2 | 3.5 | 47.5 | 1.4 | – | – | – | – | – | – | 15.48 | 1.26 | – | – |
| 2.5y∼ | 3756 | 13.58 | 1.66 | 94.1 | 3.8 | 48.1 | 1.4 | – | – | – | – | – | – | 15.29 | 1.26 | – | – |
| 3.0y∼ | 3807 | 14.83 | 1.85 | 98.1 | 3.9 | – | – | 56.9 | 2.4 | 50.0 | 2.5 | 47.7 | 3.1 | 15.38 | 1.29 | 58.1 | 1.5 |
| 3.5y∼ | 3800 | 15.89 | 1.97 | 101.8 | 4.1 | – | – | 58.6 | 2.4 | 51.0 | 2.6 | 48.5 | 3.3 | 15.31 | 1.30 | 57.6 | 1.4 |
| 4.0y∼ | 3756 | 16.91 | 2.24 | 105.2 | 4.2 | – | – | 60.1 | 2.5 | 51.8 | 2.8 | 49.3 | 3.5 | 15.22 | 1.37 | 57.1 | 1.4 |
| 4.5y∼ | 3772 | 18.03 | 2.43 | 108.7 | 4.3 | – | – | 61.7 | 2.5 | 52.7 | 2.9 | 49.9 | 3.7 | 15.22 | 1.44 | 56.8 | 1.4 |
| 5.0y∼ | 3788 | 19.29 | 2.79 | 112.5 | 4.5 | – | – | 63.3 | 2.5 | 53.8 | 3.2 | 50.8 | 4.1 | 15.21 | 1.57 | 56.3 | 1.4 |
| 5.5y∼ | 3804 | 20.50 | 3.20 | 115.5 | 4.7 | – | – | 64.6 | 2.6 | 54.7 | 3.6 | 51.4 | 4.4 | 15.30 | 1.71 | 55.9 | 1.4 |
| 6∼7y | 3818 | 22.15 | 3.56 | 120.0 | 5.0 | – | – | 66.4 | 2.7 | 56.0 | 3.8 | 52.3 | 4.7 | 15.31 | 1.78 | 55.4 | 1.3 |
3.2.2 Gender difference
Tables 2 and 3 illustrate that anthropometric measurements of boys were higher than those of girls, and the differences were 0.3–1.3 kg in weight (p < 0.001), 0.6–1.6 cm in height (p < 0.001), 0.7–1.0 cm in HC (p < 0.001), 0.7–1.0 cm in SH (p < 0.001), 1.1–2.2 cm in CC (p < 0.001), 0.8–2.2 cm in WC (p < 0.001), 0.18–0.71 kg/m2 in BMI (p < 0.001), and 0.1–0.3 in SH/H (p = 0.000–0.003) for children under 7 years.
3.2.3 Urban–suburban difference
There were slight urban–suburban differences in weight and height. Urban children were 0.1–0.4 kg heavier and 0.2–1.0 cm taller than suburban children in most age groups (Table 4). The similar results were observed in SH, CC, and WC, and their urban–suburban difference were respectively 0.1–0.4, 0.1–0.5, and 0.1–0.6 cm (p = 0.000–0.0036), while the difference of HC was not significant (0.0–0.2 cm, p = 0.050–0.886). Urban–suburban difference of BMI was not significant in all age group except for children aged under 2 months (0.0–0.1 kg/m2, p = 0.053–0.924). SH/H of urban children was slightly lower than that of suburban children (0.1–0.2, p = 0.000–0.038).
| Weight (kg) | Height (cm) | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Boys | Girls | Boys | Girls | |||||||||||||
| 2005 | 2015 | 2005 | 2015 | 2005 | 2015 | 2005 | 2015 | |||||||||
| Differencea | pb | Differencea | pb | Differencea | pb | Differencea | pb | Differencea | pb | Differencea | pb | Differencea | pb | Differencea | pb | |
| 1m∼ | −0.02 | 0.568 | −0.09 | 0.000 | −0.03 | 0.238 | −0.11 | 0.000 | 0.1 | 0.049 | −0.2 | 0.048 | 0.1 | 0.367 | −0.1 | 0.083 |
| 3m∼ | 0.13 | 0.000 | 0.01 | 0.644 | 0.08 | 0.000 | 0.01 | 0.579 | 0.6 | 0.000 | 0.2 | 0.029 | 0.5 | 0.000 | 0.1 | 0.005 |
| 6m∼ | 0.21 | 0.000 | 0.06 | 0.004 | 0.21 | 0.000 | 0.06 | 0.006 | 0.6 | 0.000 | 0.2 | 0.000 | 0.6 | 0.000 | 0.2 | 0.001 |
| 12m∼ | 0.46 | 0.000 | 0.09 | 0.000 | 0.44 | 0.000 | 0.09 | 0.000 | 1.2 | 0.000 | 0.4 | 0.000 | 1.3 | 0.000 | 0.4 | 0.000 |
| 24m ∼ | 0.51 | 0.000 | 0.08 | 0.091 | 0.56 | 0.000 | 0.01 | 0.804 | 1.7 | 0.000 | 0.3 | 0.035 | 1.8 | 0.000 | 0.2 | 0.056 |
| 3.0y∼ | 0.74 | 0.000 | 0.11 | 0.017 | 0.67 | 0.000 | 0.08 | 0.046 | 1.8 | 0.000 | 0.5 | 0.000 | 1.6 | 0.000 | 0.5 | 0.000 |
| 4.0y∼ | 0.99 | 0.000 | 0.27 | 0.000 | 1.01 | 0.000 | 0.11 | 0.047 | 2.1 | 0.000 | 0.6 | 0.000 | 2.2 | 0.000 | 0.4 | 0.001 |
| 5.0y∼ | 1.51 | 0.000 | 0.41 | 0.000 | 1.26 | 0.000 | 0.42 | 0.000 | 2.6 | 0.000 | 1.0 | 0.000 | 2.4 | 0.000 | 0.8 | 0.000 |
| 6∼7y | 1.72 | 0.000 | 0.39 | 0.003 | 1.44 | 0.000 | 0.38 | 0.001 | 2.6 | 0.000 | 0.6 | 0.000 | 2.4 | 0.000 | 0.4 | 0.007 |
- Note: aThe urban–suburban difference is equal to measurements means of urban children minus of those of suburban children.
- bThe p value of t test between urban and suburban areas in the two surveys.
3.2.4 Regional difference
Figure 2 illustrates that weight and height of northern and central children were significantly higher than those of southern children (from birth to 7 years heavier 0.3–1.5 kg and taller 0.6–2.0 cm, p < 0.001), while there were no significant differences between northern and central children (0.0–0.5 kg in weight and 0.0–0.5 cm in height, p = 0.065–0.976). The similar results were observed in other indicators (HC, SH, CC, WC, and BMI of northern and central children were respectively higher than that of southern children 0.1–0.6, 0.8–1.3, 0.6–1.2, 0.9–2.2, and 0.15–0.80 kg/m2 from birth to 7 years (p < 0.001). Regional difference of SH/H was no statistical significance (0.0–0.1, p = 0.066–0.823). Based on the comparison of height among the nine cities, we demonstrate that the tallest children were from Nanjing, Shanghai, Beijing, and Harbin. Guangzhou and Kunming children were significantly shorter than other seven cities. The height differences between minimum and maximum in the nine cities were 1.0–3.4 cm from birth to 7 years. Taking the mean height of urban children 5–5.5 years as an example, the tallest were Nanjing boys and girls (115.6 and 114.0 cm) and the smallest were Guangzhou (112.2 and 110.8 cm).
Regional difference of weight and height in the 5th NSPGDC. (A) Boys and (B) girls
3.3 Comparison with the 4th NSPGDC (2005)
A comparison with the 4th NSPGDC in 2005 found that there was no significant change in weight and height before 3 years of age (0.0–0.2 kg and 0.0–0.5 cm, p = 0.060–0.974), after that weight increases 0.1–1.1 kg and height increases 0.5–1.8 cm in urban children (p = 0.000–0.050) (Figure 3). In contrast, weight and height had increased 0.1–2.5 kg and 0.2–3.8 cm in suburban children, especially the increments were dramatic for children older than 1 years (p < 0.001) (Figure 4). The changes of HC in urban and suburban children aged 0–3 years were 0.0–0.4 cm and there were no statistical significance in most age groups (p = 0.066–0.974). The increments of SH were 0.2–0.9 cm in urban areas and 0.7–1.8 cm in suburban areas for 3–7 years old children (p < 0.001). The increments of CC were −0.3 to 0.7 cm in urban areas (p > 0.05 except for 6–7 years children) and 0.2–1.9 cm in suburban areas (p = 0.000–0.006). The changes of BMI were not apparent in most age groups (0.0–0.3 kg/m2, p > 0.05), except for the suburban children aged 3–7 years (0.2–0.8 kg/m2 and p = 0.000–0.005). SH/H had slightly decreased 0.1–0.3 during this decade (p = 0.000–0.050). In addition, Tables 4 and 5 demonstrated a narrowing trend of urban–suburban difference and a persistent existence of regional difference in height and weight.
Comparison of weight and height of urban children between the 4th and 5th NSPGDC. (A) Boys and (B) girls
Comparison of weight and height of suburban children between the 4th and 5th NSPGDC. (A) Boys and (B) girls
| Weight (kg) | Height (cm) | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Boys | Girls | Boys | Girls | |||||||||||||
| 2005 | 2015 | 2005 | 2015 | 2005 | 2015 | 2005 | 2015 | |||||||||
| Differencea | pb | Differencea | pb | Differencea | pb | Differencea | pb | Differencea | pb | Differencea | pb | Differencea | pb | Differencea | pb | |
| 1m∼ | 0.25 | 0.000 | 0.20 | 0.000 | 0.26 | 0.000 | 0.23 | 0.000 | 0.8 | 0.000 | 0.8 | 0.000 | 0.9 | 0.000 | 1.0 | 0.000 |
| 3m∼ | 0.45 | 0.000 | 0.46 | 0.000 | 0.40 | 0.000 | 0.43 | 0.000 | 0.9 | 0.000 | 1.0 | 0.000 | 0.9 | 0.000 | 1.1 | 0.000 |
| 6m∼ | 0.66 | 0.000 | 0.60 | 0.000 | 0.58 | 0.000 | 0.63 | 0.000 | 1.2 | 0.000 | 1.2 | 0.000 | 1.1 | 0.000 | 1.3 | 0.000 |
| 12m∼ | 0.71 | 0.000 | 0.77 | 0.000 | 0.65 | 0.000 | 0.68 | 0.000 | 1.5 | 0.000 | 1.5 | 0.000 | 1.5 | 0.000 | 1.4 | 0.000 |
| 24m ∼ | 0.86 | 0.000 | 0.83 | 0.000 | 0.60 | 0.000 | 0.78 | 0.000 | 2.1 | 0.000 | 1.9 | 0.000 | 1.6 | 0.000 | 1.8 | 0.000 |
| 3.0y∼ | 0.71 | 0.000 | 1.00 | 0.000 | 0.61 | 0.000 | 0.86 | 0.000 | 1.5 | 0.000 | 1.9 | 0.000 | 1.3 | 0.000 | 1.7 | 0.000 |
| 4.0y∼ | 0.64 | 0.000 | 1.00 | 0.000 | 0.62 | 0.000 | 0.89 | 0.000 | 1.2 | 0.000 | 1.9 | 0.000 | 1.0 | 0.000 | 1.7 | 0.000 |
| 5.0y∼ | 0.70 | 0.000 | 1.14 | 0.000 | 0.58 | 0.000 | 0.91 | 0.000 | 1.2 | 0.000 | 2.0 | 0.000 | 1.1 | 0.000 | 1.5 | 0.000 |
| 6∼7y | 0.73 | 0.000 | 1.51 | 0.000 | 0.34 | 0.000 | 1.30 | 0.000 | 1.0 | 0.000 | 2.0 | 0.000 | 0.6 | 0.000 | 1.5 | 0.000 |
- Note: a The regional difference is equal to maximum minus minimum means of measurements among the northern, central, and southern regions.
- bThe p value of ANOVA among the three regions in the two surveys.
3.4 Comparison with the WHO standards
Using WHO standard, we calculated the Z scores of weight (WAZ), height (HAZ/LAZ), HC (HCAZ), and BMI (BMIZ). The mean Z scores have shown in Table 6. Weight and height of 0–7 years children in China, both urban and suburban areas, are all higher than the WHO standards. The differences of HC between Chinese and WHO sample were not significant. The prevalence rates of underweight, stunting and obesity of Chinese children aged under 7 years according WHO standards were 0.5, 0.7, 0.6% in urban areas and 0.7, 1.1, 0.7% in suburban areas, respectively (Table 7).
| Urban | Suburban | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| WAZ | HAZ/LAZ | HCAZ | BMIZ | WAZ | HAZ/LAZ | HCAZ | BMIZ | |||||||||
| Age group | Means | SD | Means | SD | Means | SD | Means | SD | Means | SD | Means | SD | Means | SD | Means | SD |
| 1m∼ | 0.35* | 0.85 | 0.37* | 0.99 | −0.04 | 0.94 | 0.20* | 0.92 | 0.38* | 0.88 | 0.31* | 1.00 | −0.02 | 0.96 | 0.29* | 0.95 |
| 3m∼ | 0.58* | 0.94 | 0.56* | 1.01 | 0.00 | 1.01 | 0.36* | 1.00 | 0.54* | 0.99 | 0.46* | 1.04 | 0.03 | 1.01 | 0.38* | 1.04 |
| 6m∼ | 0.48* | 0.95 | 0.46* | 1.02 | 0.08 | 0.99 | 0.31* | 0.98 | 0.40* | 1.00 | 0.30* | 1.07 | 0.05 | 1.01 | 0.31* | 1.01 |
| 12m∼ | 0.35* | 0.91 | 0.38* | 1.02 | 0.08 | 0.97 | 0.19* | 0.93 | 0.26* | 0.94 | 0.20* | 1.03 | −0.03 | 0.97 | 0.20* | 0.97 |
| 24m ∼ | 0.25* | 0.93 | 0.38* | 1.02 | 0.03 | 0.99 | 0.00 | 0.96 | 0.17* | 0.95 | 0.22* | 1.00 | −0.08 | 1.00 | 0.02 | 0.98 |
| 3y∼ | 0.22* | 0.94 | 0.34* | 0.96 | – | – | −0.01 | 0.98 | 0.17* | 0.94 | 0.23* | 0.97 | – | – | 0.03* | 0.97 |
| 4y∼ | 0.22* | 0.97 | 0.32* | 0.94 | – | – | 0.04* | 1.03 | 0.15* | 0.95 | 0.21* | 0.94 | – | – | 0.02 | 0.99 |
| 5y∼ | 0.40* | 1.04 | 0.56* | 0.94 | – | – | 0.05* | 1.13 | 0.26* | 1.04 | 0.38* | 0.96 | – | – | 0.01 | 1.11 |
| 6∼ 7y | 0.44* | 1.08 | 0.62* | 0.93 | – | – | 0.07* | 1.18 | 0.31* | 1.08 | 0.49* | 0.95 | – | – | −0.02 | 1.16 |
| Total | 0.36* | 0.95 | 0.43* | 0.99 | 0.02 | 0.99 | 0.14* | 1.01 | 0.30* | 0.98 | 0.30* | 1.01 | −0.01 | 0.99 | 0.17* | 1.02 |
- Note: * p < 0.05.
| Urban | Suburban | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Underweight (WAZ ≤ 2) | Stunting (HAZ ≤ 2) | Obesity (BMZ > 3) | Underweight (WAZ ≤ 2) | Stunting (HAZ ≤ 2) | Obesity (BMZ > 3) | |||||||
| Age group | N | % | N | N | % | N | % | N | % | SD | Mean | SD |
| 1m∼ | 36 | 0.5% | 53 | 0.7% | 22 | 0.3% | 35 | 0.5% | 74 | 1.0% | 27 | 0.4% |
| 3m∼ | 33 | 0.3% | 68 | 0.6% | 76 | 0.7% | 57 | 0.5% | 108 | 1.0% | 95 | 0.9% |
| 6m∼ | 50 | 0.4% | 82 | 0.7% | 57 | 0.5% | 87 | 0.8% | 151 | 1.3% | 81 | 0.7% |
| 12m∼ | 79 | 0.5% | 149 | 1.0% | 69 | 0.5% | 106 | 0.7% | 227 | 1.5% | 89 | 0.6% |
| 24m ∼ | 40 | 0.5% | 70 | 0.9% | 36 | 0.5% | 75 | 1.0% | 104 | 1.4% | 42 | 0.6% |
| 3y∼ | 34 | 0.4% | 39 | 0.5% | 55 | 0.7% | 56 | 0.7% | 69 | 0.9% | 44 | 0.6% |
| 4y∼ | 40 | 0.5% | 46 | 0.6% | 67 | 0.9% | 44 | 0.6% | 53 | 0.7% | 52 | 0.7% |
| 5y∼ | 40 | 0.5% | 22 | 0.3% | 88 | 1.2% | 55 | 0.7% | 55 | 0.7% | 89 | 1.2% |
| 6∼7y | 30 | 0.8% | 7 | 0.2% | 43 | 1.1% | 30 | 0.8% | 15 | 0.4% | 41 | 1.1% |
| Total | 436 | 0.5% | 593 | 0.7% | 519 | 0.6% | 545 | 0.7% | 856 | 1.1% | 560 | 0.7% |
4 Discussion
The nine cities that were the focus of this study are located in different geographical areas across China. Two of the nine are municipalities, and the other seven are provincial capitals and their economies are in the middle or upper level of China (National Bureau of Statistics of China, 2015). These results indicate that growth in height, weight, and sitting height in most of age groups of children under 7 years has demonstrated a positive secular change compared to the 2005 dataset. The changes illustrate that the growth potential of Chinese children continued to be well realized within the context of the social stability, sustained economic development, health care, and living standards' improvement, and the extensive popularization of the information or knowledge of target child rearing techniques during the last 10 years in China (National Bureau of Statistics of China, 2015).
However, we can also find that the increments of height and weight in latest decade were shrinking when compared with that of the first three decades (1975–1985, 1985–1995, and 1995–2005) reported in elsewhere, especially in urban areas (Zong et al., 2011). Taking the increments of urban boys aged 5–6 years as an example, the increment of weight was 0.50 kg during 2005–2015, which was obviously smaller than the corresponding values 0.58, 1.02, and 1.67 kg during 1975–1985, 1985–1995, and 1995–2005, respectively. The increment of height was 0.9 cm during 2005–2015, also smaller than the corresponding values 1.5, 2.0, and 2.6 cm during 1975–1985, 1985–1995, and 1995–2005. The growth of children, indicated by height and weight, is undergoing a slowly positive secular trend in more economically developed regions of China. That is, the positive secular trend will decelerate or even gradually reaching a plateau when there is significant improvement in those factors known to negatively influence growth with rapidly developing of socioeconomic, and the full genetic potential in height and weight will be realized. Similar trends of physical growth has been reported in some developed countries (Krawczynski, Walkowiak, & Krzyzaniak, 2003; Schönbeck et al., 2013), which indicate that the secular trend in growth was coincident in various population, but their progresses are different because of the speed and degree of social development.
In the NSPGDC, urban areas refer to the center of the city and suburban areas refer to the peripheral regions that surround the center of the city. Results of the 1st–4th NSPGDC (1975–2005) had shown that the physical growth of urban children were better than that of suburban children. Thus, we can see that the urban–suburban difference in growth has existed for a long time, which was the results of uneven economic and social development between urban and suburban areas (Zhang & Huang, 1988; Zong et al., 2011). In past decades, especially the last 10 years, however, rapidly urbanization in suburban areas in China, has narrowed the urban–suburban differences in socioeconomic, living environment, various nutritional bases, accessibility of health care services, parental education, and health awareness. Consequently, the growth in height and weight of suburban children exhibited a significant improvement. Alternatively, growth-promoting environmental factors may have gradually stabilized, so the increasing tendency of growth in urban children has decelerated and their growth potential was well realized. These two aspects could explain why the urban–suburban difference in physical growth became smaller and smaller, though the growth level of urban children was still slightly better than that of suburban children in this survey. We can also find the urban–suburban difference in growth has been significantly smaller than the gender difference and region difference in growth in the survey. The urban–suburban difference could well embody the effect of social environment factors on physical growth because of the same genetic background and local customs in urban and suburban areas. The narrowing of urban–suburban difference of physical growth reveals the positive effects of even economic development and environment improvement on children's growth, which could provide important reference data to improve growth status of children in undeveloped areas.
China is a country with a vast territory, and there are great differences in climate, geographical environment, economy and living habits among different regions. Consequently, we divided the investigated sites into northern, central and southern regions. Our results illustrated that southern children are lighter and shorter than northern and central children. The similar results were observed in the previous four NSPGDC (Coordinating Study Group of Nine Cities on Physical Growth and Development of Children and Capital Institute of Pediatrics, 1987; Coordinating Study Group of Nine Cities on Physical Growth and Development of Children and Capital Institute of Pediatrics, 2007; Institute of Pediatrics of Chinese Academy of Medical Sciences, 1977a,b; Li & Zhang, 1998; Zhang & Huang, 1988;), which reveal that the region difference are significant and consistent. From the comparison of the nine cities, we can see that physical growth of Guangzhou children are significantly lower than those of other cities, though its socioeconomic development level is relatively higher in China (the latest GDP per capita and per capita disposable income of Guangdong province was respectively¥63469 and ¥32148, which higher than other province except for Beijing, Shanghai and Jiangsu province in 2014 (National Bureau of Statistics of China, 2015). Leung et al. also reported similar results in Hong Kong population when comparing with data of Beijing (Leung, Chan, Lui, Lee, & Davies, 2000). Meanwhile, other surveys had shown that southern adults height were significantly shorter than that of northern and central adults in China (Cai, Dong, & Ma, 2012), which indicate a regional difference in height among adults as well. Accordingly, we speculate that the regional difference of physical growth in children may not only correlate with the socioeconomic situation (GDP per capita of northern, central and southern region were respectively ¥62050, ¥75463, and¥51402 (National Bureau of Statistics of China, 2015), but also related to climate, geographical environment, local customs or their interaction of these factors. Regional difference may be not disappear along with the times change and social economic improvement.
Our sample were from relatively developed major cities located in different region of China, which would represent the healthy children in the middle and upper economic level region of China. From the comparison of the 4th NSPGDC (2005) to WHO standards, we demonstrated that weight and height of urban children (<7 years old) were higher than the WHO standard (World Health Organization and Multicentre Growth Reference Study Group, 2006), and that of suburban children were slightly lower or close to the WHO standards. In the 2015 dataset, results indicate that weight and height of children (<7 years old) in nine cities, both in urban and suburban areas, have been higher than the WHO standards. In addition, the prevalence of underweight, stunting and obesity were lower than 2%, which reveal that the data of this survey came from well-nourished healthy population according WHO standards. Consistent results were observed in Chinese national physique monitoring in 2014, for example, height and weight of children aged 3–4 years were higher than the WHO standards 0.48SD, 0.56SD in boys and 0.34SD, 0.38SD in girls (General Administration of Sport of China, 2015). Some differences were also reported comparing Taiwan and Hongkong children with WHO standards (Li, Lin, Lin, & Chiang, 2016; Schooling, Hui, Cowling, Ho, & Leung, 2013). Similarly, the population differences are also confirmed by other countries data when comparing to WHO standards (Tanaka et al., 2013; Vignerová et al., 2015).
5 Conclusions
Physical growth of children under 7 years old was undergoing a slowly positive secular trend during the last decade in more economically developed regions of China. Urban children were slightly taller and heavier than suburban children, but those differences became smaller and smaller. The regional difference of physical growth persistently exist. Weight and height of healthy children aged under 7 years in nine cities of China were higher than WHO standards.
Acknowledgments
We express our sincere gratitude to the National Health and Family Planning Commission of the People's Republic of China and the nine provinces and cities Health and Family Planning Commission for their supports and organization in the process of starting and implementing the project. We thanks to all members of the Coordinating Study Group of Nine Cities on the Physical Growth and Development of Children for their excellent fieldwork, especially their careful measurements. We also thank all the children and their parents involved in the survey for their support and participation.
Conflict of interests
The authors report no conflicts of interest. The authors are responsible for the content and writing of the paper.
