The academic value of the "Hu Line" has been extended to other related disciplines. Considering China's large population and obvious differences in distribution, this study draws on the research results of population geography to explore the population density and distribution criteria of the "Hu Line".

To investigate and analyze the current situation of health literacy and sedentary time among urban and rural high school students in the southeast and northwest halves of the "Hu Line", and to provide a basis for improving the physical and mental health of high school students in China.

A stratified cluster random sampling method was used to study the health literacy and sedentary time of freshmen and sophomores in 62 schools in 31 provinces (municipalities directly under the central government and autonomous regions) of China from January to March 2019 (12 400 questionnaires on health literacy and 12 400 questionnaires on sedentary time each were uniformly mailed and distributed in advance). Multiple linear regression models were used to analyze the coefficient of variance expansion, and after correcting for confounding factors, we analyzed the factors affecting the length of meditation time of high school students in the southeastern and northwestern halves of both sides of the "Hu Line".

Finally, 9 057 health literacy questionnaires were included, of which 7 489 (82.7%) were from the southeast half of China and 1 568 (17.3%) from the northwest half of China, and 8 031 questionnaires on sedentary time were included, of which 6 614 (82.4%) were from the southeast half of China and 1 417 (17.6%) from the northwest half of China. Health literacy scores and sedentary time of high school students in the southeast half of China were higher than those in the northwest half of China (Z=-4.009, -9.198; P<0.001). The health literacy scores of high school students in the southeastern half of China aged 17 and 18, female, urban and rural, with father's education of less than college and college, mother's education of college and bachelor's degree, annual family income of 10 000-, 50 000-, 80 000-, and >100 000 yuan, and family size of 1, 3, 7, 9, and ≥10 were higher than those of the northwestern half of China (P<0.05) ; Those high school students in the southeastern half of China aged 15, 16, 18, and male and female, urban and rural, father's education less than college, college, mother's education less than college, annual family income <10 000, 25 000-, 50 000-, 80 000-, and >100 000 yuan, and the number of people in the family of 3, 4, 5, and 6 people were higher than those in the northwestern half of China in terms of the number of hours spent in meditation (P<0.05). The results of the multiple linear regression model analysis showed that after correcting for confounders, the length of time high school students in the southeastern half of China spent sedentary still was positively correlated with annual family income (β=0.324) and mother's educational attainment (β=0.644) but negatively correlated (P<0.05) with both the health literacy scores (β=-0.015) and the father's educational attainment (β=-0.212) were negatively correlated (P<0.05) ; standardized regression coefficients β were compared with annual family income (0.164) > mother's educational attainment (0.131) > father's educational attainment (-0.056) > health literacy score (-0.050). The length of sedentary time of high school students in the northwestern half of China was positively correlated with health literacy score (β=0.017), father's education (β=0.789), and mother's education (β=0.540) (P<0.05) ; standardized regression coefficients β were compared with father's education (0.163) > mother's education (0.111) > health literacy score (0.056) .

Health literacy scores and meditation hours of high school students in the southeastern half of China were higher than those in the northwestern half of China. Meditation duration of high school students in the southeastern half of China was positively correlated with annual family income and mother's education, but negatively correlated with health literacy scores and father's education, while meditation duration of high school students in the northwestern half of China was positively correlated with health literacy scores parent's education. Annual family income had the highest weight on the effect of meditation duration for high school students in the southeast half of China, and father's education had the highest weight on the effect of meditation duration for high school students in the northwest half of China.

目前"胡焕庸线"的学术价值已经延伸至其他相关学科，考虑到我国人口众多且分布差异较为明显的特点，本研究借鉴人口地理学的研究成果，旨在探索按照"胡焕庸线"的人口密度分布界定标准，深入研究了"胡焕庸线"两侧城乡高中生的健康素养和静坐时长的态势特征。

调查分析"胡焕庸线"两侧东南半壁与西北半壁的城乡高中生健康素养与静坐时长的现状态势特征，为改善我国高中生的身心健康水平提供依据。

采用分层整群随机抽样方法，于2019年1—3月对我国31个省（直辖市、自治区）在内的62所学校高一、高二学生进行健康素养与静坐时长的调研（统一提前邮寄配发健康素养调查问卷与静坐时间调查问卷各12 400份）。采用多元线性回归模型分析方差膨胀系数，校正混杂因素后分析"胡焕庸线"两侧东南半壁与西北半壁高中生静坐时长的影响因素。

最后纳入健康素养调查问卷9 057份，其中东南半壁7 489份（82.7%），西北半壁1 568份（17.3%）；纳入静坐时间调查问卷8 031份，其中东南半壁6 614份（82.4%），西北半壁1 417份（17.6%）。东南半壁高中生健康素养评分、静坐时长均高于西北半壁（Z=-4.009、-9.198，P<0.001）。东南半壁年龄为17、18岁，女性，城乡，父亲学历为大专以下、大专，母亲学历为大专、本科，家庭年收入为1~万、5~万、8~万、>10万元，家庭人口数为1、3、7、9、≥10人的高中生健康素养评分均高于西北半壁（P<0.05）；东南半壁年龄为15、16、18岁，男女，城乡，父亲学历为大专以下、大专，母亲学历为大专以下，家庭年收入为<1万、2.5~万、5~万、8~万、>10万元，家庭人口数为3、4、5、6人的高中生静坐时长均长于西北半壁（P<0.05）。多元线性回归模型分析结果显示，校正混杂因素后，东南半壁高中生静坐时长与家庭年收入（β=0.324）和母亲学历（β=0.644）均呈正相关，但与健康素养评分（β=-0.015）和父亲学历（β=-0.212）均呈负相关（P<0.05）；标准化回归系数β比较，家庭年收入（0.164）>母亲学历（0.131）>父亲学历（-0.056）>健康素养评分（-0.050）。西北半壁高中生静坐时长与健康素养评分（β=0.017）、父亲学历（β=0.789）、母亲学历（β=0.540）均呈正相关（P<0.05）；标准化回归系数β比较，父亲学历（0.163）>母亲学历（0.111）>健康素养评分（0.056）。

东南半壁高中生健康素养评分、静坐时长均高于西北半壁。东南半壁高中生静坐时长与家庭年收入和母亲学历呈正相关，但与健康素养评分和父亲学历呈负相关；西北半壁高中生静坐时长与健康素养评分父母亲学历均呈正相关。家庭年收入对东南半壁高中生静坐时长影响的权重最高，父亲学历对西北半壁高中生静坐时长影响的权重最高。