[Assessment of prevalence of malnutrition among Chinese primary and secondary school students and analysis of policy effect during the period of the Program for the Development of Chinese Children 2011-2020].

OBJECTIVE: To evaluate the change of prevalence of malnutrition among Chinese primary and secondary school students and to analyze the policy effect during the period of the Program for the Development of Chinese Children 2011-2020 (PDCC 2011-2020). METHODS: The data of Chinese students aged 7 to 18 years were extracted from 8 successive cross-sectional surveys of the Chinese National Survey on Students ' Constitution and Health (CNSSCH) from 1985 to 2019. Malnutrition of students was evaluated according to the screening standard for malnutrition of school-age children and adolescents. The changes of prevalence of malnutrition among primary and secondary school students were described by gender, urban and rural areas, age group and province, from 2010 to 2019. The Joinpoint regression model was used to analyze the trajectory of the prevalence of malnutrition among students aged 7 to 18 years from 1985 to 2019, so as to evaluate the policy effect of the PDCC 2011-2020. RESULTS: The prevalence of malnutrition among primary and secondary school students in China decreased from 12.7% in 2010 to 8.5% in 2019. The prevalence of malnutrition among boys and girls, urban and rural students, and students of all age groups showed a continuous downward trend (Ptrend < 0.001) from 2010 to 2019. From 2010 to 2019, 27 of the 31 provinces (autonomous regions and municipalities) saw a significant decrease in the prevalence of malnutrition among primary and secondary school students. Joinpoint regression model showed that the prevalence of malnutrition among Chinese primary and secondary school students continued to decline from 1985 to 2019, but 2010 was the turning point in the downward trend. From 1985 to 2010, the prevalence of malnutrition among primary and secondary school students decreased by an average of 2.4% per year (95%CI: 1.9%-2.8%, P < 0.001), and the downward trend accelerated after 2010, with an average annual decline of 4.3% (95%CI: 2.4%-6.2%, P < 0.001). CONCLUSION: The prevalence of malnutrition among primary and secondary school students in China continued to decline from 2010 to 2019, achieving the goal of controlling the prevalence of malnutrition among primary and secondary school students in the PDCC 2011-2020. The PDCC 2011-2020 may have played an important role in improving the malnutrition among primary and secondary school students. However, the problem of malnutrition among primary and secondary school students still exists, and it is still necessary to adhere to the coverage and financial support of the nutrition improvement plan in areas with high incidence of malnutrition.

[Association of outdoor artificial light at night exposure with overweight and obesity among children and adolescents aged 9 to 18 years in China].

OBJECTIVE: To analyze the association between outdoor artificial light-at-night (ALAN) exposure and overweight and obesity among children and adolescents aged 9 to 18 years in China. METHODS: Using follow-up data of 5 540 children and adolescents aged 9 to 18 years conducted from November 2019 to November 2020 in eight provinces of China, latitude and longitude were determined based on school addresses, and the mean monthly average nighttime irradiance at the location of 116 schools was extracted by the nearest neighbor method to obtain the mean outdoor ALAN exposure [unit: nW/(cm2·sr)] for each school. Four indicators of overweight and obesity outcomes were included: Baseline overweight and obesity, persistent overweight and obesity, overweight and obesity progression and overweight and obesity incidence. Mixed effects Logistic regression was used to explore the association between ALAN exposure levels (divided into quintiles Q1-Q5) and baseline overweight and obesity, persistent overweight and obesity, overweight and obesity progression and overweight and obesity incidence. In addition, a natural cubic spline function was used to explore the exposure response association between ALAN exposure (a continuous variable) and the outcomes. RESULTS: The prevalence of baseline overweight and obesity, persistent overweight and obesity, overweight and obesity progression and overweight and obesity incidence among the children and adolescents in this study were 21.6%, 16.3%, 2.9% and 12.8%, respectively. The OR value for the association between ALAN exposure and baseline overweight and obesity was statistically significant when ALAN exposure levels reached Q4 or Q5, 1.90 (95%CI: 1.26-2.86) and 1.77 (95%CI: 1.11-2.83), respectively, compared with the children and adolescents in the Q1 group of ALAN exposure. Similar to the results for baseline overweight and obesity, the OR values for the association with persistent overweight and obesity were 1.89 (95%CI: 1.20-2.99) and 1.82 (95%CI: 1.08-3.06) when ALAN exposure levels reached Q4 or Q5, respectively, but none of the OR values for the association between ALAN and overweight and obesity progression and overweight and obesity incidence were statistically significant. Fitting a natural cubic spline function showed a non-linear trend between ALAN exposure and persistent overweight and obesity. CONCLUSION: There is a positive association between ALAN exposure and overweight and obesity in children and adolescents, and the promotion of overweight obesity in children and adolescents by ALAN tends to have a cumulative effect rather than an immediate effect. In the future, while focusing on the common risk factors for overweight and obesity in children and adolescents, there is a need to improve the overweight and obesity-causing nighttime light exposure environment.

[Trends of age of menarche among Chinese Han girls aged 9 to 18 years from 2010 to 2019].

Objective: To analyze the trends of the age of menarche among Chinese Han girls aged 9 to 18 years from 2010 to 2019. Methods: Data were extracted from the Chinese National Surveys on Students' Constitution and Health in 2010, 2014 and 2019. A total of 253 037 Han girls aged 9 to 18 years with complete data on menarche were selected in this study. They were asked one-on-one about their menstrual status, age and residence information. The median age of menarche was estimated by probability regression. U tests were used to compare the difference in median age at menarche in different years. Results: The median age at menarche (95%CI) among Chinese Han girls was 12.47 (12.09-12.83) years in 2010, 12.17 (11.95-12.38) years in 2014 and 12.05 (10.82-13.08) years in 2019, respectively. Compared with that in 2010, the median age at menarche in 2019 decreased by 0.42 years (U=-77.27, P<0.001). The annual average changes were-0.076 years from 2010 to 2014 (U=-57.19, P<0.001) and-0.023 years from 2014 to 2019 (U=-21.41, P<0.001), respectively. The average annual changes in urban areas in the periods of 2010 to 2014 and 2014 to 2019 were-0.071 years and 0.006 years, respectively, while those in rural areas were-0.082 years and-0.053 years, respectively. The average annual changes in the regions of north, northeast, east, south central, southwest and northwest were-0.064, -0.099, -0.091, -0.080, -0.096 and-0.041 years in the period of 2010 to 2014 and 0.001, -0.040, -0.002, -0.005, -0.043 and-0.081 years in the period of 2014 to 2019. Conclusion: The age of menarche among Chinese Han girls aged 9 to 18 years shows an advanced trend from 2010 to 2019, and the trends in urban and rural areas and different regions have different characteristics.

[Long-term trend of the age of spermarche and its association with nutritional status among Chinese Han boys aged 11-18 from 2010 to 2019].

Objective: To analyze the long-term trend of the age of spermarche among Chinese Han boys aged 11 to 18 from 2010 to 2019 and its association with nutritional status. Methods: The data from Chinese National Surveys on Students' Constitution and Health in 2010, 2014 and 2019 were used. The age, residence and spermarche of the participants were collected by questionnaire, and their height and weight were measured. A total of 184 633 Han boys aged 11‒18 years with complete data on spermarche, height, and weight were included in this study. The probability regression method was used to calculate the median age (95%CI) at spermarche in different areas, and the trend of age at spermarche in different groups was compared. The multivariate logistic regression model was used to analyze the association between nutritional status and spermarche of Chinese Han boys aged 11‒18 years. Results: The median age of spermarche (95%CI) was 13.85 (13.45-14.22) years old among Chinese Han boys aged 11‒18 years in 2019, with 0.18 years earlier than that in 2010. The median age at spermarche in urban and rural boys was 13.89 and 13.81 years, respectively. Compared with that in 2010, the age at spermarche in urban and rural boys was 0.08 and 0.27 years earlier, respectively. After adjusting for age, province and urban/rural areas, compared with normal weight, spermarche was negatively associated with wasting and positively associated with overweight and obesity, with OR (95%CI) about 0.73 (0.67-0.80), 1.09 (1.02-1.17) and 1.09 (1.01-1.18), respectively. Conclusion: The age of spermarche generally shows an advanced trend among Chinese Han boys and is associated with nutritional status.

[Epidemiology and prediction of overweight and obesity among children and adolescents aged 7-18 years in China from 1985 to 2019].

Objective: To analyze and predict the epidemic trend of overweight and obesity among children and adolescents aged 7-18 years in China from 1985 to 2019. Methods: Data were collected from the Chinese National Survey on Students Constitution and Health in 1985, 1995, 2000, 2005, 2010, 2014, and 2019 with the sample size of 409 945, 204 931, 209 209, 234 420, 215 317, 214 353, and 212 711, respectively. Overweight and obesity were evaluated according to the "classification standard of the weight index value of overweight and obesity screening for Chinese school-age children and adolescents" of the Working Group on Obesity in China (WGOC). The detection rate and average annual growth rate of overweight and obesity, and single obesity among children and adolescents aged 7-18 years were calculated, and ArcGis10.6 software was used to analyze the difference in the prevalence of overweight and obesity among children and adolescents in different regions in 2019. Polynomial regression function was used to fit the prevalence and average annual growth rate of overweight and obesity, and single obesity among children and adolescents from 1985 to 2019, and to predict the prevalence of overweight and obesity and single obesity among children and adolescents in China. Results: In 2019, the total prevalence of overweight and obesity among children and adolescents aged 7-18 years in China was 23.4%, and the prevalence of single obesity was 9.6%. The prevalence of overweight and obesity among urban children and adolescents was higher than that in rural areas (25.4% vs. 21.5%), and the prevalence in boys was higher than that in girls (28.4% vs. 18.4%) (both P values<0.001). In 2019, there was a large regional disparity in the prevalence of overweight and obesity in different provinces, with the lowest in Guangdong (12.2%) and the highest in Shandong (38.9%), and the high epidemic areas were mainly concentrated in North China and Northeast China. From 1985 to 2019, the prevalence of overweight and obesity among children and adolescents aged 7-18 years in China increased from 1.2% to 23.4%, with an increase of 18.1 times, while the prevalence of obesity alone increased from 0.1% to 9.6%, with an increase of 75.6 times. The prevalence of overweight and obesity in urban boys, urban girls, rural boys and rural girls increased from 1.3%, 1.5%, 0.5%, and 1.6% in 1985 to 31.2%, 19.4%, 25.6%, and 17.4% in 2019, with an increase of 22.3, 11.7, 54.2, and 10.1 times, respectively. According to the prediction model, the prevalence of overweight and obesity among children and adolescents aged 7-18 years in China will increase from 23.4% in 2019 to 32.7% in 2030, and the prevalence of obesity alone will increase from 9.6% in 2019 to 15.1% in 2030. The growth of rural children and adolescents is obvious. By 2025, the prevalence of overweight and obesity among rural children and adolescents in China will comprehensively exceed that of urban, and there will be an "urban-rural reversal" phenomenon. At the same time, the prevalence of children's obesity in China's low, medium and high epidemic areas will also continue to increase. By 2035, the prevalence of overweight and obesity among children and adolescents in medium epidemic areas will exceed that in high epidemic areas, and there will be a "provincial reversal" phenomenon. Conclusion: From 1985 to 2019, the overweight and obesity of children and adolescents in China will continue to grow rapidly with large regional differences.

[Prevalence trend of malnutrition among Chinese Han children and adolescents aged 7-18 years from 2010 to 2019].

Objective: To analyze the prevalence trend of malnutrition among Chinese Han children and adolescents aged 7-18 years from 2010 to 2019. Methods: Based on the data from the Chinese National Surveys on Students' Constitution and Health in 2010, 2014 and 2019, about 215 102, 214 268 and 212 713 Han students aged 7-18 years were included in this study. According to the National Screening Standard for Malnutrition of School-age Children and Adolescents, the detection rate of malnutrition among Chinese Han children and adolescents aged 7-18 was calculated, and the prevalence trend of malnutrition from 2010 to 2019 was analyzed. Results: In 2019, the detection rate of malnutrition among Chinese Han students aged 7-18 years was 8.64% (18 381/212 713), of which the rate of growth retardation, moderate-to-severe wasting and mild wasting was 0.50% (1 062/212 713), 3.25% (6 914/212 713) and 4.89% (10 405/212 713), respectively. In 2019, the detection rate of malnutrition in these boys was higher than that of girls (9.97% vs. 7.31%), and the detection rate in rural areas was higher than that in cities (9.30% vs. 7.98%). The detection rates were 9.74% (5 252/53 916), 8.17% (4 408/53 937), 7.29% (3 885/53 310), and 9.38% (4 836/51 550) in 7-9, 10-12, 13-15, and 16-18 years groups, and 8.14% (6 563/80 618), 7.61% (4 237/55 694) and 9.92% (7 581/76 401) in the eastern, central, and western regions. Malnutrition among students in China was mainly caused by mild wasting, and the detection rate of growth retardation accounted for only 5.78% (1 062/18 381). Malnutrition was mostly concentrated in the southwest region, and the rate was relatively low in eastern provinces. In three surveys from 2010 to 2019, the detection rate of malnutrition among Han students aged 7-18 in China decreased gradually, and the differences were statistically significant (P<0.05). Among them, the detection rates in western rural areas decreased significantly, as well as the gap between urban and rural areas. Compared with that in 2014, the detection rate of malnutrition in Shandong, Hunan, Qinghai and Hainan provinces in 2019 decreased significantly (P<0.05). Conclusion: In 2019, the malnutrition of Chinese children and adolescents aged 7-18 years is dominated by wasting malnutrition. The detection rate shows a downward trend from 2010 to 2019, with regional differences.

[Trend of the detection rate of myopia among Chinese Han children and adolescents aged 7-18 years from 2010 to 2019].

Objective: To analyze the trend of the detection rate of myopia among Chinese Han children and adolescents aged 7-18 years from 2010 to 2019. Methods: Data from the Chinese National Survey on Students' Constitution and Health in 2010, 2014 and 2019 were used, and about 213 833, 212 742 and 209 942 Han students aged 7-18 years were included in this study. The χ² test was used to compare the differences in the prevalence of myopia among the subgroups in the survey year, and logistic regression was used to compare the differences in the prevalence of myopia between different years. A curve-fitting method was used to obtain the growth rate of myopia among Han Chinese students from 2010 to 2019, and the differences in the change of myopia between different age groups were analyzed. Results: In 2019, the overall detection rate of myopia among Chinese Han children and adolescents aged 7-18 was 60.1%. The detection rate of urban students (62.7%) was higher than that of rural students (57.4%) and the detection rate of girls (63.5%) was higher than that of boys (56.7%). In 2019, the regional disparities were large in the detection rate of myopia in various provinces, with the lowest in Guizhou (49.6%) and the highest in Zhejiang (71.3%). The detection rate of myopia showed an upward trend from 2010 to 2019, from 55.5% in 2010 to 57.1% in 2014, and finally to 60.1% in 2019. The gap in the detection rate of myopia between urban and rural children and adolescents gradually shrank. The average annual growth rate of myopia detection rate from 2014 to 2019 was 0.6 percentage points per year, higher than that from 2010 to 2014 about 0.4 percentage points per year. The peak age of the growth rate of myopia detection rate decreased from 12 years in 2010 to 10 years in 2014, and finally to 7 years in 2019. Conclusions: The detection rate of myopia among Chinese Han children and adolescents is still at a high level, and the peak age of the growth rate of myopia detection rate continues to advance.

[Trend of age of menarche among Chinese Han girls aged 9 to 18 years from 2010 to 2019].

Objective: To analyze the trends of the age of menarche among Chinese Han girls aged 9 to 18 years from 2010 to 2019. Methods: Data were extracted from the Chinese National Surveys on Students' Constitution and Health in 2010, 2014 and 2019. A total of 253 037 Han girls aged 9 to 18 years with complete data on menarche were selected in this study. They were asked one-on-one about their menstrual status, age and residence information. The median age of menarche was estimated by probability regression. U tests were used to compare the difference in median age at menarche in different years. Results: The median age at menarche (95%CI) among Chinese Han girls was 12.47 (12.09-12.83) years in 2010, 12.17 (11.95-12.38) years in 2014 and 12.05 (10.82-13.08) years in 2019, respectively. Compared with that in 2010, the median age at menarche in 2019 decreased by 0.42 years (U=-77.27, P<0.001). The annual average changes were -0.076 years from 2010 to 2014 (U=-57.19, P<0.001) and -0.023 years from 2014 to 2019 (U=-21.41, P<0.001), respectively. The average annual changes in urban areas in the periods of 2010 to 2014 and 2014 to 2019 were -0.071 years and 0.006 years, respectively, while those in rural areas were -0.082 years and -0.053 years, respectively. The average annual changes in the regions of north, northeast, east, south central, southwest and northwest were -0.064, -0.099, -0.091, -0.080, -0.096 and -0.041 years in the period of 2010 to 2014 and 0.001, -0.040, -0.002, -0.005, -0.043 and -0.081 years in the period of 2014 to 2019. Conclusion: The age of menarche among Chinese Han girls aged 9 to 18 years shows an advanced trend from 2010 to 2019, and the trends in urban and rural areas and different regions have different characteristics.

[Regional inequality of height among Chinese Han students aged 7 to 18 years from 1985 to 2014].

Objective: To analyze the regional inequality of height among Chinese Han students aged 7 to 18 years from 1985 to 2014. Methods: The Chinese Han students aged 7 to 18 years with complete basic information and height data from 30 mainland provinces (excluding Hong Kong, Macao, Taiwan and Tibet in China) were extracted as participants from 6 successive cross-sectional surveys of the Chinese National Survey on Student's Constitution and Health (CNSSCH). After excluding extreme and illogical cases, a total of 1 495 182 students were included in the analysis. The data of gross domestic product (GDP) per capita of each province at each survey year were collected from the website of National Bureau of statistics of China. Mann-Kendall trend test was used to analyze the trend of mean height across years. Weighted linear regression model was used to analyze the association between mean height of students aged 7 to18 years and GDP per capita at provincial level. Height difference, height ratio, slope index of inequality (SII) and relative index of inequality (RII) were used to measure the height inequality by gender and age groups. Results: The mean height of Chinese Han students aged 7 to 18 years increased from 144.9 cm in 1985 to 151.8 cm in 2014 (P<0.05). The height difference between urban and rural students in all age groups was reducing (P<0.05). The height difference between urban and rural boys aged 13 to 15 years decreased from 5.3 cm in 1985 to 2.5 cm in 2014, and the difference between urban and rural girls aged 7 to 12 years decreased from 4.6 cm in 1985 to 2.4 cm in 2014. The mean height of students aged 7 to 18 years was positively associated with GDP per capita in all survey years for both genders (P<0.001). Taking Shanghai and Guizhou as the representatives of economically developed and underdeveloped provinces, from 1985 to 2014, the height differences between two provinces were 6.8-9.2 cm, 8.0-12.4 cm and 6.3-8.8 cm for boys aged 7 to 12 years, 13 to 15 years and 16 to 18 years, respectively, and the height ratios were stable at 1.05-1.07, 1.05-1.08 and 1.04-1.05 respectively. From 1985 to 2014, the SII of mean height for boys in three age groups were 4.4-6.2, 4.9-6.7 and 2.5-4.7, respectively. The RII of mean height of boys in three age groups were 1.03-1.05, 1.03-1.04 and 1.01-1.03, respectively. In the same period, the SII of mean height for girls in three age groups were 4.2-6.2, 2.8-4.5 and 2.5-3.9, and the RII were 1.03-1.05, 1.02-1.03 and 1.02, respectively. Conclusion: From 1985 to 2014, the urban-rural inequality of height development among Chinese Han students aged 7 to 18 years was narrowing, but the socio-economic inequality of height persisted and remained at a relatively stable level.

[Subnational inequalities of early marriage and fertility among Chinese females from 1990 to 2010].

OBJECTIVE: To analyze the inequality of early marriage and adolescent fertility with respect to local economic development among Chinese females aged 15-19 years from 1990 to 2010. METHODS: Aggregated data were extracted from the Chinese National Census from 1990 to 2010. We calculated the ever-married rate and fertility rate of female adolescents aged 15-19 years. Using gross domestic product (GDP) per capita as an indicator for socio-economic status of a province, we calculated the slope index of inequality (SII) and the concentration index (CI) to analyze the subnational inequalities of early marriage and adolescent fertility. Weighted linear regression models were also established to assess the associations between GDP per capita and the ever-married rate/fertility rate. RESULTS: The ever-married rate for Chinese female adolescents aged 15-19 years decreased from 4.7% in 1990 to 1.2% in 2000, and rebounded to 2.1% in 2010. From 1990 to 2000, the fertility rate decreased from 22.0 per 1 000 to 6.0 per 1 000, and further decreased to 5.9 per 1 000 in 2010. In 1990, the socio-economic inequalities of the ever-married rate and fertility rate for female adolescents aged 15-19 years were not statistically significant (P for SII or CI>0.05). The values of SII revealed that, in 2000 and 2010, female adolescents with the lowest GDP per capita had an ever-married rate 2.4% (95%CI: 0.4-4.4) and 2.3% (95%CI: 0.3-4.2) higher than those with the highest GDP per capita, respectively. In the meantime, in 2000 and 2010, female adolescents with the lowest GDP per capita had a fertility rate 12.9 per 1 000 (95%CI: 5.4-20.5) and 9.3 per 1 000 (95%CI: 4.6-14.0) higher than those with the highest, respectively. In 2000 and 2010, the CIs for marriage were -0.32 (P=0.02) and -0.17 (P=0.03), respectively, and the CIs for childbirth were -0.37 (P<0.01) and -0.26 (P<0.01), respectively. In 2000, the ever-married rate and the fertility rate were estimated to increase by 1.4% (95%CI: 0.1-2.7) and 7.9 per 1 000 (95%CI: 2.9-12.8) with 100% increase in GDP per capita, respectively; in 2010, the numbers were 1.5% (95%CI: 0.1-2.9) and 6.7 per 1 000 (95%CI: 3.2-10.1), respectively. CONCLUSION: Subnational socio-economic inequality of early marriage and adolescent fertility existed in 2000 and 2010. Female adolescents residing in less-developed areas were more likely to engage in early marriage and childbirth. Reducing income inequality and increasing education investment for poverty-stricken areas seem to be effective measures to reduce this inequality.

[Trends of prevalence of excellent health status and physical fitness among Chinese Han students aged 13 to 18 years from 1985 to 2014].

OBJECTIVE: To analyze the trends of prevalence of excellent health status and physical fitness among Chinese Han students aged 13 to 18 years from 1985 to 2014. METHODS: In the study, 738 523 students aged 13 to 18 years were extracted from the 1985 to 2014 Chinese National Survey on Students' Constitution and Health. Height, weight, vital capacity and indicators of physical fitness were measured for each student. According to National Standards for Students' Physical Health (2014 Revision), students meeting an overall score ≥ 90.0 were considered to be of excellent health status and physical fitness. We used the Chi-square test to compare the differences in prevalence of excellent health status and physical fitness among different subgroups and draw maps of regional distribution of prevalence by using ArcGIS. RESULTS: From 1985 to 2014, the average height, weight, and BMI for Chinese Han students aged 13 to 18 years increased consistently, while the average vital capacity and indicators of physical fitness fluctuated largely. The overall prevalence of excellent health status and physical fitness increased from 2.7% in 1985 to 4.4% in 1995, dropped consistently to 1.1% in 2005, rebounded 0.6 percentage points in 2010, and increased to 2.2% in 2014. In each survey year, the prevalence for the boys was always higher than for the girls (P<0.001), the prevalence for middle school students aged 13 to 15 years was always higher than for high school students aged 16-18 years (P<0.001), and the prevalence for students in eastern region was higher than in western and central regions (P<0.001). In 1985 and 1995, the prevalence in certain provinces in eastern and central regions was <1%. In 2005, almost half provinces (14/30) had a prevalence <1%. In 2014, provinces in eastern coastal areas had relatively high prevalence of excellent health status and physical fitness in students aged 13 to 18 years, while provinces in central and western regions had relatively low prevalence. CONCLUSION: A fluctuating trend of the prevalence of excellent health status and physical fitness has been observed among Chinese Han students aged 13 to 18 years during the past three decades. There is great difference between the current prevalence of excellent health status and physical fitness and the goal of Outline of the Healthy China 2030 Plan, thus, the effective interventions and strategies for promoting students' physical activity and physical fitness are urgently needed in China.

[Analysis on the trend of prevalence of excellent and good physical fitness and health status among Chinese Han students aged 13 to 18 years and related influencing factors from 1985 to 2014].

Objective: Using the Chinese National Survey on Students' Constitution and Health data from 1985 to 2014 to analyze the trend of excellent and good physical fitness and health status among Chinese Han students aged 13 to 18 years and the related influencing factors. Methods: 738 523 students aged 13 to 18 years with completed data of gender, age, urban and rural, physical form, vital capacity and physical fitness were selected from the six Chinese National Surveys on Students' Constitution and Health. According to National Standards for Students' Physical Health (2014 revision), the comprehensive scores and the prevalence of excellent and good physical fitness and health status were calculated (90.0-120.0 was classified as excellent, and 80.0-89.9 was classified as good). The trend of prevalence of excellent and good physical fitness and health status in different years and the corresponding differences among students with different characteristics were analyzed and compared. The log-binomial regression model was used to analyze related factors of physical fitness and health status. Results: From 1985 to 2014, the overall prevalence of excellent and good physical fitness and health status increased from 27.6% in 1985 to 35.6% in 1995, and then declined to 13.9% in 2005. In the 2010 and 2014 cycles, the prevalence increased steadily, at 16.5% and 19.1% respectively. Except for 1995 and 2014, the prevalence of boys was higher than that of girls (P<0.001). The prevalence of students aged 13 to 15 was higher than that of students aged 16 to 18 (P<0.001). Log-binomial regression model analysis showed that girls ï¼»PR（95%CI）=1.03（1.00-1.05）, P=0.021ï¼½, rural area ï¼»PR（95%CI）=1.09（1.07-1.12）, P<0.001ï¼½, 13-15 years oldï¼»PR（95%CI）=1.89（1.84-1.94）, P<0.001ï¼½, eastern regionï¼»PR（95%CI）=1.94（1.88-2.00）, P<0.001ï¼½, middle regionï¼»PR（95%CI）=1.15（1.11-1.20）, P<0.001ï¼½, Exercise time ≥1 h/dï¼»PR（95%CI）=1.41（1.37-1.45）, P<0.001ï¼½, parents support participation in sports activities after schoolï¼»PR（95%CI）=1.10（1.06-1.15）, P<0.001ï¼½, TV time ≤1 h/dï¼»PR（95%CI）=1.26（1.21-1.30）, P<0.001ï¼½, playing video games, watching videos or e-books ≤1 h/dï¼»PR（95%CI）=1.05（1.02-1.09）, P<0.001ï¼½ were all related to the high prevalence of excellent and good physical fitness and health status. Conclusion: The prevalence of excellent and good physical fitness and health status among students aged 13 to 18 was changing between 1985 and 2014. Gender, age, area, physical exercise time, screen time for non-learning purposes, and parents' attitudes toward students' participation in physical activities were all related to the excellent and good physical fitness and health status of students.

Intra-articular injection of magnesium chloride attenuates osteoarthritis progression in rats.

OBJECTIVE: To explore the effects of Mg2+ on the expression of osteoarthritic markers in human cartilage and synovium tissue explants. To investigate the therapeutic effect of intra-articular injection of Mg2+ in an established rat OA (Osteoarthritis) model of anterior cruciate ligament transection with partial medial meniscectomy (ACLT + PMM). DESIGN: Human cartilage and synovium explants were collected from total knee replacement surgeries and incubated with MgCl2 (20 mmol/L) in vitro. A rat OA model was established by ACLT + PMM surgery in 450-500 g male Sprague Dawley (SD) rats. To select the optimal dose, intra-articular injections of MgCl2 (0.05, 0.5, 5 mol/L) were performed at 4 weeks after the surgery every 3 days for 2 weeks. The effect of optimized MgCl2 was further determined by histology, immunohistochemistry, and quantitative real-time polymerase chain reaction. RESULTS: The expressions of osteoarthritic markers in human cartilage and synovium explants were inhibited by Mg2+in vitro. Immunohistochemical analysis further suggested the inhibitory effects of Mg2+ on the expression of MMP-13 and IL-6 in the human tissue explants. Cartilage degeneration and synovitis in ACLT + PMM rats were significantly improved by intra-articular injections of Mg2+ (0.5 mol/L). Immunohistochemical analysis also showed the regulatory effects of Mg2+ on osteoarthritic markers in both cartilage and synovium in rats, consistent with in vitro results. CONCLUSION: Intra-articular injections of Mg2+ at 0.5 mol/L attenuate the progression of OA in the ACLT + PMM rat model. Such effect was at least in part explained by the promotion of cartilage matrix synthesis and the suppression of synovial inflammation.

[The status of spermarche, menarche and corresponding relationships with nutritional status among students of 13 ethnic minorities in Southwest China in 2014].

Objective: To describe the current situation of spermarche/menarche of 13 ethnic minority groups in China in 2014, and analyze the association between spermarche/menarche and nutritional status among ethnic minority groups. Methods: The sample of 13 ethnic minorities (Bai, Hani, Dai, Lisu, Wa, Naxi, Miao, Shui, Buyi, Dong, Zhuang, Yao and Qiang) from Yunnan, Guizhou, Sichuan province and Guangxi Zhuang autonomous region were selected from Chinese National Survey on Students' Constitution and Healthy of 2014. A total of 25 964 students with completed records of height, weight, spermarche and menarche were selected, including 11 276 boys aged 11-18 years old and 14 688 girls aged 9-18 years old. Probit analysis was used to calculate the median age at spermarche or menarche. All subjects were classification into four nutritional status groups (normal, malnutrition, overweight and obesity) according to the Screening standard for malnutrition of school-age children and adolescents (WS/T 456-2014) and the Screening for overweight and obesity among school-age children and adolescent (WS/T 586-2018) of China. Binary logistic regression was used to analyze the association between spermarche, menarche and nutritional status. Results: The median age at spermarche (95%CI) of 13 ethnic minorities were ranged from 13.4 (13.1, 13.7) years old to 15.3 (15.1, 15.5) years old. In the 11 -year age group, all ethnic girls experienced menarche. The median age at menarche (95%CI) of 13 ethnic minorities were ranged from 12.1 (11.4, 12.7) years old to13.6 (13.4, 13.7) years old. Logistics regression analysis showed that students with malnutrition experienced spermarche or menarche later than normal weight students, the OR (95%CI) for boys about 0.49 (0.42, 0.56) and girls about 0.15 (0.12, 0.19), while overweight and obese students entered puberty at earlier age, the OR (95%CI) for boys about 1.37(1.10, 1.72) and girls about 3.21(2.51, 4.12). Conclusion: Boys from 13 ethnic minorities began to have spermatorrhea at the age of 13, and girls from 13 ethnic minorities began menstruating at the age of 9 in 2014. Nutrition status was closely related to spermarche and menarche.

[Analysis on the urban-rural disparity of childhood stunting and its association with economic growth among Chinese Han students aged 7-18 years old].

Objective: To analyze the urban-rural disparity of childhood stunting and its association with subnational economic growth among Chinese Han students aged 7-18 years. Methods: We used the data from 2014 Chinese National Survey on Students' Constitution and Health. 213 940 Chinese Han students aged 7-18 years with complete height records were included in this study. Stunting was defined according to the Screening Criteria of Malnutrition for School-age Children and Adolescents(2014 version, in Chinese). We divided students into two groups (economically developed and underdeveloped areas) according to the provincial GDP per capita. Spearman correlation coefficient was used to explore the association between the difference of urban-rural stunting prevalence and the provincial GDP per capita. Logistic regression models were established to assess the risk of stunting in rural children compared with urban children. Results: Among 213 940 students, 107 033 (50.0%) were from urban areas. The average height of 7-18 years old and 18 years old [(152.9±15.7) and (166.1±8.7) cm] of urban students were both higher than those of rural students [(150.7±16.0) and (165.1±8.6) cm] (P<0.001). The stunting prevalence of Chinese urban students (0.4%) was statistically significant lower than that of rural students (1.1%) (P<0.001), which was consistent in all age groups (P<0.05). The urban-rural disparity was found in 60% (18/30) of Chinese provinces. The difference of urban-rural stunting prevalence was negatively associated with provincial GDP per capita (r=-0.62, P<0.001). In economically underdeveloped areas, the risk of stunting for rural students aged 7-9 years was 4.69 (95%CI: 2.93-7.52) times that for urban children, while for students aged 10-18 years, the odds ratio was 2.44 (95%CI: 2.02-2.96). In economically developed areas, the risk of stunting for rural students aged 7-9 years was 5.43 (95%CI: 3.67-8.03) times that for urban children, while for students aged 10-18 years, the odds ratio was 2.15 (95%CI: 1.85-2.49). Conclusions: The urban-rural disparity of childhood stunting existed in most places in China. The difference of growth retardation between urban and rural areas was related to regional economic development.

[Situation analysis of physical fitness among Chinese Han students in 2014].

OBJECTIVE: To analyze the situation of physical fitness among Chinese Han students in 2014, so as to develop the guideline of physical activity regarding to the targeted students and to provide bases for the improvements of students' physical fitness. METHODS: Subjects were from 2014 Chinese National Surveys on Students' Constitution and Health (CNSSCH). In this survey, 212 401 Han students aged 7-18 years participated and the measurement of physical fitness completed. The qualified rates of indicators regarding to physical fitness were evaluated based on "National Students Constitutional Health Standards" (2014 revised edition). Logistic regression was used to assess the association between the indicators of pull ups (boys) and endurance run (boys and girls) and influencing factors. RESULTS: In 2014, among the boys, the qualified rates of pull ups and endurance run were 18.7% and 76.6% respectively, while the qualified rate of endurance run was 80.6% among the girls. These two indicators were the weak items of physical fitness among the Chinese Han students. There was regional difference in the qualified rates of physical fitness, and the students in Zhejiang and Jiangsu provinces had higher qualified rates. Logistic regression showed that the urban students (OR=0.67), the students with malnutrition (OR=0.76), overweight (OR=0.32) or obesity (OR=0.12) were less likely to be qualified to pull ups; the students who had physical activity more than 1 h per day (OR=1.31) was more likely to be qualified to pull ups. The influencing factors of endurance run showed the similar pattern, in addition, the students with enough physical education (PE) were more likely to be qualified to endurance run, while the students with "Squeeze" or "no" PE class were less likely to be qualified to endurance run. CONCLUSION: The pull ups and endurance run have become the weak items of the physical fitness among primary and secondary school students in our national and provincial levels. Based on ensuring physical exercise time and PE curriculum and class hours, as well as improving students' nutrition, we should also strengthen the rational design of physical exercise and ensure the balanced development of various items so as to improve the overall development of students' physical fitness.

[The prevalence of snoring and its association with academic performance among school-aged children in Beijing].

Objective: To investigate the snoring status of school-aged children in Beijing and explore the association of snoring and academic performance. Methods: A total of 7 925 children aged from 6 to 14 were selected from 15 primary and middle schools at 7 districts (Xicheng, Chaoyang, Changping, Shunyi, Fangshan, Huairou and Mentougou) in Beijing in 2015, using multi-stage stratified cluster random sampling method. The recruited children were asked to complete the Pediatric Sleep Questionnaire (PSQ) and a questionnaire related to sleep behavior. The multiplelogistic regression was used to analyze the association of snoring and academic performance. Results: A total of 794 (12.44%) children showed a decline in academic performance among 6 383 eligible respondentsfor data analysis. 580 (9.08%) children with snoring was identified, of which 333 and 247 were in frequency of 1-2 times per week and frequency of ≥3 times per week, respectively; 357, 170 and 53 were in snoring grade Ⅰ, grade Ⅱ and grade Ⅲ, respectively. Compared with the children without snoring, the OR (95%CI) for children with 1-2 times per week and ≥3 times per week was 1.363 (1.000-1.857) and 1.605 (1.135-2.269), respectively; and the OR (95%CI) for children with grade Ⅰ, grade Ⅱ and grade Ⅲ of snoring was 1.226 (0.893-1.683), 1.595 (1.062-2.397) and 2.31 (1.17-4.565), respectively. Conclusion: There is a statistical relationship between snoring and the decline of academic performance. The decline of academic performance positively associated with increased frequency and grade of snoring.

[Prevalence of reduced visual acuity among Chinese Han students in 2014].

OBJECTIVE: To analyze the prevalence of reduced visual acuity (VA) and to examine the association between reduced visual acuity and influencing factors among Chinese Han students, so as to provide bases for the prevention and treatment of reduced visual acuity. METHODS: Subjects were from 2014 Chinese National Surveys on Students' Constitution and Health (CNSSCH). In this survey, 261 832 Han students aged 7-22 years participated. Unaided distance VA was measured using a retro-illuminated lgMAR chart with tumbling-E optotypes. Ametropia was determined by using serial bronchoscopy. Logistic regression was used to assess the association between reduced visual acuity and influencing factors. ArcMap 10 was used to map the regional distribution of reduced visual acuity. RESULTS: Nationwide, the overall prevalence of reduced visual acuity was 66.6%, and was highest among the urban girls (73.5%). The prevalence of myopia was 60.8% and accounted for more than 90% among the students with reduced visual acuity. Compared with 2010 CNSSCH, the increments of reduced visual acuity were highest in the students aged 13-15 years (6.8 percentage points). The prevalence of reduced visual acuity ranged from 50.6% to 76.2% in each province (autonomous region, municipality) in 2014 CNSSCH. The top three of the prevalence of reduced visual acuity were Jiangsu (76.2%), Zhejiang (76.0%) and Shandong (75.9%), and the lowest three were Hainan (50.6%), Guizhou (53.9%) and Xinjiang (57.6%). Logistic regression showed that the girls, urban students, and students who spent ≥2 h per day in their after school homework were more likely to develop reduced visual acuity, but the students with physical activity time ≥2 h per day were less likely to develop reduced visual acuity. CONCLUSION: Although the situation was different in each province (autonomous region, municipality), reduced visual acuity has become a public concern affecting the health of students in China. Based on the intervention on the key populations, such as urban girls and pre adolescent students, we should also continue to strengthen the prevention and control for reduced visual acuity among all students.

[The combined effect of spermarche, menarche and obesity on elevated blood pressure among Chinese students].

Objective: To investigate the association between the combined effect of spermarche/menarche and obesity with elevated blood pressure among Chinese students. Methods: A total of 106 009 primary and secondary school students (55 614 boys and 50 395 girls) were selected from " 2014 National Physical Fitness and Health Surveillance" (including 31 provinces, with the exception of Hong Kong, Macao, and Taiwan) with full record of height, weight, blood pressure, puberty development data of spermarche/menarche. The level of blood pressure, as well as the prevalence of high blood pressure(HBP), were compared between different subgroups (pre-spermarche/menarche and non-obesity group, pre-spermarche/menarche and obesity group, pro-spermarche/menarche and non-obesity group, pro-spermarche/menarche and obesity group), and mulilevel logistic model was used to investigate the relationship between puberty development, obesity and blood pressure. Results: Among 55 614 boys aged 11 to 17 years old, the prevalence of spermarche was 62.1% (34 512/55 614), the prevalence of obesity was 7.5% (4 166/55 614), and the mean values of systolic pressure and diastolic pressure were 110.7/68.2 mmHg (1 mmHg=0.133 kPa). While among 50 395 girls aged 9-14 years, the prevalence of menarche was 48.2% (24 301/50 395), the prevalence of obesity was 5.8% (2 942/50 395), and the mean values of systolic pressure and diastolic pressure was 102.9/64.8 mmHg. The prevalence of high blood pressure was 5.2% (1 003/19 274), 17.9% (328/1 828), 6.6% (2 132/32 174), and 23.9% (558/2 338) in pre-spermarche and non-obesity boys, pre-spermarche and obesity boys, pro-spermarche and non-obesity boys and pro-spermarche and obesity boys, respectively. The prevalence of high blood pressure was 5.9% (1 439/24 570), 17.2% (262/1 524), 5.0% (1 147/22 883), and 17.0% (241/1 418) in pre-menarche and non-obesity girls, pre-menarche and obesity girls, pro-menarche and non-obesity girls and pro-menarche and obesity girls, respectively. After adjustment of region, age, height and urban/rural area by multilevel model, the students in pro-spermarche/menarche and obesity group were more likely to have high blood pressure (boys: OR(95% CI)=4.93 (4.30-5.66); girls: OR(95% CI) =3.77(3.16-4.50)) Conclusion: Puberty development and obesity were closed associated with blood pressure. Both boys and girls who enter puberty earlier and were in obesity status were more likely to have high blood pressure. Therefore, interventions focused on obesity prevetion and intervention among prepuberty students may be beneficial to reduce their prevalence of high blood pressure in the future.

[Prevalence of anemia and its association with nutritional status among Chinese students of ethnic minorities in 2010].

OBJECTIVE: To analyze the prevalence of anemia and its proportions of severity, and to examine the association between anemia and nutritional status among Chinese students of ethnic minorities, so as to provide bases for the prevention and treatment of anemia. METHODS: The subjects were Mongolian, Hui, Zhuang and Korean students aged 7, 9, 12, 14 and 17 years, sampled from the 2010 Chinese National Surveys on Students' Constitution and Health. World Health Organization (WHO) criteria for screening anemia (2001) was used, and the proportion rates of mild, moderate and severe were analyzed. The nutritional status was defined according to the growth references of body mass index (BMI)-for-age z-score for 5-19 years developed by the WHO. Stepwise Logistic regression was used to assess the association between anemia and nutritional status, gender, urban/rural areas, age and ethnic minorities. RESULTS: The prevalences of anemia were 4.4%, 26.4%, 6.6% and 5.8% in Mongolian, Hui, Zhuang and Korean students, respectively, of whom, the prevalence of anemia was highest in rural girls and reached 4.8%, 42.0%, 9.0% and 6.7%, respectively. Most of the ethnic minorities' students belonged to mild anemia, and the prevalence of severe anemia was 1.4%, 12.9%, 1.6% and 1.9% in Mongolian, Hui, Zhuang and Korean students, respectively. Stepwise Logistic regression showed that the girls, rural students, students aged 12 years and 17 years, Hui, Zhuang and Korean students were more likely to develop anemia than the boys, urban students, students aged 7 years and Mongolian students. The overweight students were less likely to develop anemia compared with the normal students and there was no significant association between anemia and thinness or obesity when the other factors were controlled (P>0.05). CONCLUSION: The epidemic of anemia was different in the different ethnic minorities and the prevalence of anemia in Hui students was of moderate public health concern according to the WHO's criteria. We should pay more attention to the prevention and treatment of anemia for Hui and ethnic minorities in rural areas, especially for rural girls. The nutritional status of students could not be a basis or judgement for anemia as there was no significant association between anemia and nutritional status.