研究目的：

依据全国一至八次全国体质健康调研数据分析从1985年到2019年我国青少年青春发育时相长期变化，结合青春发育时相相关指标与BMI指标进行分析探究青春发育时相异动对BMI有无影响。

研究方法：

根据文献资料法与数据对比分析法对依据全国一至八次全国体质健康调研数据分析，研究我国汉族青少年青春发育时相变化趋势以及汉族学生城乡之间差异和男女之间差异，并对青春发育时相与BMI进行分析，探究青春发育时相的异动对BMI有无影响以及造成青春发育时相异动的原因。

研究结果：

我国汉族女生青春发育时相整体呈提前趋势，但是城市女生与乡村女生有所差别，城市女生月经初潮平均年龄从1985年的13.09岁到2019年已经提前到12.1岁，30年间提前了0.99岁平均每年提前0.033岁，城市女生提前速度逐渐下降到2019年出现滞后现象。乡村女生月经初潮平均年龄从1985年的13.8岁到2019年已经提前到12.0岁，30年间提前了1.8岁平均每年提前0.06岁。乡村女生提前速度也在下降但是下降速度低于城市女生，到2019年乡村女生仍然保持提前。我国汉族男生青春发育时相整体趋势同样呈现提前趋势，城市男生首次遗精从1991年的13.09岁到2019年的12.1岁，25年间提前了0.99岁，平均每年提前0.0396岁。乡村男生首次遗精从1991年13.8岁到2019年的12岁,25年间提前了1.8岁，平均每年提前0.072岁。城市男生提前速度始终低于乡村男生，到2019年汉族男生都出现滞后现象。我国汉族学生青春发育时相男女差别一直保持在1-2岁之间，城市男女差别一直高于乡村，但是到2019年城市男女差别与乡村男女差别重合。

城市女生青春发育时相与BMI P值是0.022呈负相关；乡村女生青春发育时相与BMI p值为0.01呈负相关；城市男生青春发育时相与BMI P值为0.007呈负相关；乡村男生青春发育时相与BMI P值0.075没有相关性。

研究结论：

我国学生青春发育时相整体呈提前趋势，1985-2019年间，女生青春发育时相提前速度逐步下降，男生青春发育时相提前速度先上升在下降，到2019年出现滞后现象。青春发育时相男女相差城市高于乡村到2019年重合，城乡差异到2019年基本消失。

城市男生、城市女生、乡村女生、青春发育时相与BMI呈负相关，乡村男生青春发育时相与BMI没有相关性。具体原因和机制需进一步研究。

影响中国汉族学生青春发育时相提前因素包括：社会经济发展水平，身体活动时间，体育锻炼和运动参与时间。

Purpose of the study:

Based on the analysis of data from 1985 to 2019, the relationship between youth development and BMI was analyzed to explore the influence of youth development on BMI.

Research Methodology:

According to the analysis of literature and data, this paper analyzes the trend of youth development and the differences between urban and rural areas and between men and women of han nationality students in china, and analyzes the relationship between youth development and bmi.

Findings:

The overall trend in the youth development of Han Chinese girls is early, but there is a difference between urban girls and rural girls. The average age of menstruation of urban girls has increased from 13.09 years in 1985 to 12.1 years in 2019, with an average advance of 0.99 years per year over 30 years. The average age of rural girls menstruating has risen from 13.8 years in 1985 to 12.0 years in 2019, 1.8 years in advance and an average of 0.06 years each year over 30 years. Rural girls are also getting ahead but at a slower rate than urban girls, and rural girls are still getting ahead in 2019. The overall trend in the youth development of Han Chinese boys in China is also precocious. The first male inseminate in urban areas was 0.99 years precocious from 13.09 years in 1991 to 12.1 years in 2019, an average of 0.0396 years precocious in 25 years. Country boys first faeced between the ages of 13.8 in 1991 and 12 in 2019, 1.8 years earlier in 25 years and an average of 0.072 years earlier each year. Urban boys were consistently slower to advance than rural boys, and Han boys lagged behind in 2019. The gender gap in the youth development of Han Chinese students in our country has remained between 1-2 years of age. The gender gap in urban areas has always been higher than in rural areas, but in 2019 the gender gap in urban areas overlapped with the gender gap in rural areas.

There was a negative correlation between BMI P of 0.022 and adolescent development of urban girls. There was a negative correlation between youth development and BMI of 0.01 in rural girls. There was a negative correlation between BMI P of 0.007 and youth development of urban male students. Rural boys had no correlation with BMI P of 0.075 during puberty.

Findings:

During the period 1985-2019, the rate of advance in the youth development of Han Chinese girls gradually decreased, while the rate of advance in the youth development of Han Chinese boys rose and fell, and lagged in 2019. The gap between men and women in youth development overlapped more in urban areas than in rural areas by 2019, and urban / rural disparities largely disappeared by 2019.

Han urban boys, urban girls, rural girls, youth development were negatively correlated with BMI, while rural boys were not correlated with BMI. The specific causes and mechanisms need further study.

Factors affecting the early development of Han Chinese students include the level of socio-economic development, time of physical activity, time of physical exercise and participation in spo