[Physical growth trend of Chinese children under 7 years old, in 1975 - 2005].

Objective: To analyze the physical growth changes in Chinese children aged from 0 to 7 years old during the past 30 years.

Methods: Four national physical growth surveys of the children under 7 years old were undertaken in the same urban and suburban areas of nine main cities in China from 1975 to 2005. The nine cities were Beijing, Harbin and Xi'an in the northern part; Shanghai, Nanjing and Wuhan in the central part; Guangzhou, Fuzhou and Kunming in the southern part of China. Random cluster sampling method was used. The children aged from 0 to 7 years old were classified into 22 groups by age. The sample size was ranged from 150 to 200 persons for each sex-age group in each area (urban/rural) of each city. Totally, 158 400, 152 874, 157 362 and 138 775 healthy children were examined in 1975, 1985, 1995 and 2005 respectively. The data of weight, height, chest and head circumference obtained from these surveys were analyzed.

Results: Average weight and height in most of the age groups for both boys and girls from urban and suburban rural areas has been significantly improved during the past 30 years, the average increments of weight were 0.76 kg to 1.14 kg in 12 - 15 months group and 2.58 kg to 3.26 kg in 6 - 7 years group; and the average increments of height were 2.7 cm to 3.8 cm in 12 - 15 months group and 5.0 cm to 7.6 cm in 6 - 7 years group. Chest circumference did not show an increase in infants younger than 4 months and increased slightly after 4 months. The average increments of head circumference were 0.1 cm to 1.0 cm. From 1975 to 2005, the increments of weight and height per 10 years was in an increasing trend, e.g. weight increments of 5 - 6 years old were 0.58 kg, 1.02 kg and 1.67 kg and the height increments were 1.5 cm, 2.0 cm and 2.6 cm for every 10 years. The urban-rural difference in height has become smaller, the height difference in 6 - 7 years group for boys was decreased from 4.9 cm in 1975 to 2.6 cm in 2005. The weight has become smaller in children under 3 years old but becoming greater after 3 years, such as the difference increased from 1.14 kg in 1975 to 1.72 kg in 2005 for boys aged 6 - 7 years old. The regional difference also showed a decreasing trend.

Conclusion: The physical growth of Chinese children had been much improved during the past 30 years and the secular trend should be still continuing at an accelerated growth stage. The urban-rural difference and regional difference in weight and height had become smaller.