Secular change in height among Mongolian students aged 7-18 years,1985-2010

Objective To observe the height change among Mongolian children and adolescents aged 7-18 years from 1985 to 2010 and to analyze its secular trend. Methods The data were collected from the physical investigation of students nationwide in Mongolian of Tongliao in the year 1985,2000 and 2010.We divided the Mongolian students aged 7-18 years into four groups of urban girls,urban boys,rural girls,and rural boys,and dynamic analyses on the height level and difference between urban and rural students,change of rapid growth period and the age of growth peak,and gender difference at age of 18 years were conducted. Results From 1985 to 2010,the height of Mongolian children and adolescents aged 7-18 years had an obvious secular increasing trend and the height for the urban girls,urban boys,rural girls and rural boys increased by 5.79 cm,5.26 cm,3.66 cm,and 4.27 cm,respectively,from 2001-2010.The increasing speed of height form 1985-2000 was higher than that from 2001-2010.For the urban girls,urban boys,rural girls,and rural boys,the height increase was 3.32 cm,2.84 cm,2.04 cm,and 2.47 cm during the former 15 years and 0.81 cm,1.00 cm,0.60 cm,and 0.57cm duing the later 10 years,respectively,indicating a slowdown increase trend.Among the students,the average height of urban students was higher than that of the rural ones;the growth speed of boys was higher than that of the girls,and ealier age of growth peak was observed among urban boys,urban girls,and rural girls groups(urban:t=4.15,P<0.01;rural:t=1.42,P>0.05).The gender difference was kept increasing in the students during the period with the gaps between the boys and girls of 9.28 cm(95% confidence interval95% CI:8.26-10.30 cm),12.96 cm(95%CI:12.16-13.76 cm),and 13.50 cm(95%CI:12.70-14.30)for the urban students and 10.37(95%CI:9.79-10.95 cm),10.97 cm(95%CI:10.24-11.70 cm),and 11.66 cm(95%CI:10.89-12.43 cm)for the rural students,respectively,at the year of 1985,2000,and 2010(P<0.05 for all) Conclusion There is a significant secular increase trend in the height of Mongolian children and adolescents,but there is still a gap between urban and rural students in the height level.