Objective:To analyze the secular growth trends of the Chinese urban youth from 1979 to 2005,in order to make national intervention strategies and measures to improve their physical fitness and health.Methods:Subjects were sampled from 16 provincial-capital cities in China.They were all Han primary and secondary school students aged 7 to 18 years.The increments of stature,weight and BMI,and the increments per decade of these indicators at different stages were analyzed.Results:In recent 26 years,the overall increments were 6.5 and 4.7 cm for stature,and 8.9 and 5.2 kg for weight,for boys and girls,respectively.Swiftest rates were found in the period of 1985-1995,with the increments which were as high as 3.8 and 3.0 cm/decade for height,and 4.7 and 3.1 kg/decade for weight,for boys and girls respectively.These trends are still strong at present,without any tendency of going to the plateau.Advanced puberty plays the most contributing role in these trends,with the peak height rates being 2.4 cm/decade for girls at the age of 12 and 3.3 cm/decade for boys at the age of 14,respectively.The increments of adult height were 3.2 and 2.1 cm,while the rates were 1.2 and 0.8 cm/decade,for males and females,respectively.The distributing curves of BMI show an accelerating tendency of going to the right side,which suggests that the prevalence of childhood obesity is increasing rapidly.Conclusion:China is now experiencing an overall and positive secular trend,which is reflected not only by the accelerating physical growth in childhood,advanced puberty,and steady increments of adult height,but also by the dramatic changes of body shape.We should not only feel proud of the achievements of these secular growth changes and the active socioeconomic influences,but also pay much attention to their negative effects,especially those that may induce the dangers of hypertension,hyperglycemia,type 2 diabetes mellitus and other adulthood diseases,as well as the disease risks of metabolic syndrome that may even occur early in childhood and adolescence.

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.

Objective:To analyze the current situation of age at menarche ( AAM) in Chinese ethnic minority girls aged 9 -18 years, and compare the AAM with that of Chinese Han girls from the same province or autonomous region .Methods:Probit analyses were used to calculate the AAM in various eth-nic minority groups of Chinese girls who participated in 2010 National Physical Fitness and Health Sur-veillance .The sample size of ethnic minority girls was 31 711, and the ethnic minorities were Mongolian , Hui, Tibetan, Uighur, Miao, Yi, Zhuang, Buyi, Korean, Dong, Yao, Bai, Tujia, Hani, Kazak, Dai, Li, Lisu, Wa, Shui, Dongxiang, Naxi, Kirgiz, Tu, Qiang and Sala.The local Han girls to compare with the AAM were also surveyed in 2010 National Physical Fitness and Health Surveillance .Results:In the 13-year-old group, the percentage of menarche in Sala was the lowest (32.17%), while that in Korean was the highest (93.23%).At the age of 18, 99.60%ethnic minority girls appeared menstruating .The AAM of the top 3 ethnic minority groups were Korean ( 11 .79 years ) , Mongolian ( 12 .44 years ) and Zhuang (12.52 years); and the last 3 ethnic minority groups were Dongxiang (14.36 years), Sala (14.32 years) and Shui (14.02 years).The AAM in Korean was 0.93 years earlier than that of the Han girls from Jilin province;the AAM in Mongolian was 0 .14 years earlier than that of the Han girls from Neimenggu autonomous region;the AAM in Naxi and Qiang was close to that of the Han girls in the same province (region) (P>0.05);and the AAM in Hui, Uighur, Miao, Yi, Zhuang, Buyi, Dong, Yao, Bai, Tujia, Hani, Kazak, Dai, Li, Lisu, Wa, Shui, Dongxiang, Kirgiz, Tu, and Sala was later than that of the Han girls in the same province ( region) .The cluster analysis indicated that the 26 ethnic mi-nority groups could be classified as three groups: Korean were classified into the earlier age group of AAM;Dongxiang, Sala, Uighur, Yi and Shui belonged to the later age group of AAM;and the other 20 ethnic minority groups were into the middle age group of AAM .Conclusion:There was a large variation among different ethnic minority groups in China .The AAM was earlier in Korean , and Mongolian , com-pared with the local Han girls , and the AAM in other ethnic minority groups was the same or later com-pared with the local Han girls .

Objective:To analyze the prevalence of anemia and its proportions of severity,and to exa-mine 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 Mongoli-an,Hui,Zhuang and Korean students aged 7,9,1 2,1 4 and 1 7 years,sampled from the 201 0 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 ana-lyzed.The nutritional status was defined according to the growth references of body mass index (BMI)-for-age z-score for 5 -1 9 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 minori-ties.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%,1 2.9%,1 .6% and 1 .9% in Mongolian,Hui,Zhuang and Korean students,respectively.Stepwise Logistic regression showed that the girls,rural students,students aged 1 2 years and 1 7 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 con-trolled (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 eth-nic minorities in rural areas,especially for rural girls.The nutritional status of students could not be a ba-sis or judgement for anemia as there was no significant association between anemia and nutritional status.

Objective:To analyze the secular trends of height among Chinese students aged 17 in dif-ferent ethnic minorities from 1985 to 2010. Methods:A total of 18 Chinese ethnic minorities’ students, including Mongolian, Hui, Uygur, Zhuang, Korean, Tibetan, Miao, Buyi, Dong, Bai, Tujia, Hani, Dai, Lisu, Wa, Nakhi, Tu and Qiang as subjects were sampled from the 1985, 1995, 2000, 2005 and 2010 Chinese National Surveys on Students’ Constitution and Health. The heights of 17 years old people by gender in various ethnic minorities were analyzed and compared. Results:From 1985 to 2010, the in-crements of adult heights increased significantly in many ethnic minorities’ boys. In 2010, the average height of boys aged 17 years in each minority group was higher than 162 cm and was higher than 170 cm among boys from Hui, Mongolian and Korean groups. The ethnics with height growth rates of more than 2 cm per decade in boys were Hui (2. 64 cm/decade) and Dong (2. 05 cm/decade) and the ethnics with height growth rates of more than 1 cm per decade were Korean (1. 99 cm/decade), Tibetan (1. 90 cm/decade), Hani (1. 80 cm/decade) and the other 9 minority groups. The average height of girls aged 17 years in each minority group was higher than 150 cm in 2010 . The heights showed an upward trend in 15 minority groups, but with different degrees. The ethnics with height growth rates of more than 1 cm per decade were Hui (1. 56 cm/decade) and Korean (1. 29 cm/decade). The increments that were signifi-cant between 1985 and 2010 were Hui (3. 89 cm), Korean (3. 23 cm), Dong (2. 35cm) and the other 6 minority groups ( P<0 . 05 ) . Conclusion: Our data suggest that the increments of adult heights may reflect the secular growth change in the major minority groups during the past 25 years, but there was an obvious disequilibrium among various ethnic minorities. We should pay more attention to the minority groups with poor growth and give them more help. Meanwhile, we should also pay attention to the nega-tive effects of the secular growth trend on those minority groups with fast increasing adult height.

Objective: To compare the prevalence of growth retardation in students aged 7-18 years from 26 minority ethnic groups in China and provides reference evidence to promote the growth and improve the health status of students in minority ethnic groups. Methods: The body height data of students aged 7-18 years in 26 minority ethnic groups in 2014 Chinese National Surveys on Students’ Constitution and Health were used for the analysis and comparison. Growth retardation was defined according to the school-aged child and adolescent malnutrition screening standard (WS/T 456-2014). Results: In 2014, the average body heights of school boys and school girls aged 18 years in 26 ethnic minority groups were (168.3±6.8) cm and (156.2±5.9) cm respectively. The overall growth retardation prevalence rate of school boys and school girls in 26 ethnic groups were 5.4% and 5.1%, respectively. The growth retardation prevalence rate was highest in students of Shui ethnic group (24.5% for boys and 23.0% for girls), and lowest in students of Hui ethnic group (0.1% for boys and 0.3% for girls). The growth retardation prevalence rates in 9 ethnic minority groups were higher than the average level, in these 9 ethnic groups, the differences in prevalence rates of boys of Buyi ethnic group, girls of Lisu ethnic group and girls of Hani ethnic group had no significance among four age groups. Growth retardation in students of Sala ethnic group was mainly observed in age group 7-9 years, but in others ethnic group, for example, Wa ethnic, it was mainly observed in older age group. The students in minority ethnic groups in southwestern China had the highest growth retardation prevalence rate (8.1%), significantly higher than that in northern China (0.8%) (OR=10.6, 95%CI: 7.8-14.4). The overall growth retardation prevalence rate between 7 and 17 years old was negatively correlated with the body height of 18 years old (boys: r=-0.811, P<0.001; girls: r=-0.715, P<0.001). Conclusions In 2014, the differences in body height among students aged 18 years in 26 minority ethnic groups in China were significant. In general, the first five minority ethnic groups with high detection rate of growth retardation in boys were Shui, Wa, Buyi, Yao and Yi, and the five minority ethnic groups with high detection rate of growth retardation in girls were Shui, Yao, Buyi, Wa and Miao. The detection rate of growth retardation was highest in students of minority ethnic groups in southwestern China. Nutritional interventions and healthy education should be carried out in minority ethnic groups and areas with high growth retardation prevalence rate to promote the growth of the students.

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.

Objective: To understand the current situation of infrastructure construction and sanitation practice of school canteens in China and to provide a reference for improving food safety in school canteen and sanitation management level. Methods: Stratified sampling method was adopted to select the surveyed schools. Information regarding school canteen infrastructure and sanitation practice was collected through questionnaires. Chi-square test was used to compare the difference in passing rate on the survey indices among different school types. Results: In environmental sanitation, 91.0% of the school canteen was rated as good and in personal hygiene, 92.8% of the employees were rated as good. The overall health level of urban schools was better than that of township schools, and non-boarding schools was better than that of boarding schools, with statistically significant differences(P<0.01). 67.1% of school canteens provided with independent food outlets while 98.7% of school canteens without independent food stores. The qualified rate of washing facilities in the dining area was 94.7%, and the qualified rate of distance between the canteen and the pollution source was 92.5%. Nearly all the employees held canteen catering service license (99.0%) and the health qualification certificate (99.5%). Most of the school canteens (98.7%) established the safety rules and regulations, including the food retention sample system. Nearly 61.5% schools initiated the principal meal program. Conclusion Sanitation management in the canteens of primary and secondary schools in China is generally satisfactory, with some canteens still fail to meet the standard requirements. More supervision from schools and relevant government departments (market supervision, health and education departments) is needed to provide students with a clean and heathy campus canteen.

Objective: To investigate indoor air quality monitoring and management in primary and secondary schools, so as to provide scientific basis for health protection of students and healthy school environment. Methods: Stratified sampling method was adopted to select schools for investigation. Data of daily ventilation and ventilation was collected from relevant principals of schools through questionnaire survey. Chi-square test was used to analyze the difference of ventilation and ventilation among different types of schools. Results: Daily indoor air quality testing indicators: 317 schools (13.2%) have tested the concentration of CO2 in the air environment. Daily detection of CO2 in urban schools was significantly better than that in township schools, and the difference is statistically significant(χ2=72.06, P<0.01); Non-boarding schools were superior than boarding schools(χ2=21.89, P<0.01). The proportion of schools that routinely tested for carbon monoxide, particulate matter and volatile pollutants was 6.5%, 7.5% and 9.3%, respectively. Of the schools that participated in the survey, 80.8% had a daily ventilation system. Among them, 925 schools (38.5%) had a cumulative daily ventilation time of more than 90 minutes in cold season, and 331 schools (13.8%) had a daily ventilation time of less than 30 minutes. Conclusion Regulations and standards for school air quality monitoring needs to be improved. The Center for Disease Control and Prevention or other qualified institutions are suggested to lead air quality monitoring in schools testing, creating a healthy learning and living environment for primary and secondary school students.

Objective: To describe the subnational disparity of anemia among Chinese Han students aged 7-14 years, and to provide a reference for making intervention measures to improve anemia among Chinese children. Methods: A total of 71 115 Chinese Han students aged 7-14 years were selected from the project ‘2014 Chinese National Survey on Students’ Constitution and Health'. Anemia and its severity were defined according to the diagnosis criteria of World Health Organization (WHO). The rank sum test was used to compare anemia distribution of different subgroups. Logistic regression models were established to analyze the influencing factors of anemia and moderate-to-severe anemia. Results: In the 71 115 students with measured hemoglobin concentrations in the 2014 CNSSCH, the overall prevalence rate of anemia was 8.9%, with 5.8% to be mild anemia and 3.1% to be moderate-to-severe anemia. For boys aged 7-14 years, the hemoglobin concentration increased with age; Boys aged 7 years had the highest anemia prevalence (9.8%) and moderate-to-severe anemia prevalence(4.4%). For girls aged 7-12 years, the hemoglobin concentration increased with age, but the concentration decreased a little when girls reached 14 years of age; 14-year-old girls had the highest prevalence of anemia(13.3%), and 7-year-old girls had the highest prevalence of moderate-to-severe anemia(4.8%). The highest prevalence rates of anemia were found in Hainan (24.1%) and Gansu(19.6%), while the lowest was in Beijing(2.0%). Logistic regression models revealed that, for children aged 7 and 9 years, when comparing to those lived in urban areas, living in rural areas appeared to be a risk factor for anemia (OR=1.34) and moderate-to-severe anemia(OR=1.48); when comparing to living in cities of upper socio-economic status, living in cities of intermediate socio-economic status appeared to be a risk factor for anemia (OR=1.43) and moderate-to-severe anemia(OR=1.41), and living in cities of lower socio-economic status also appeared to be a risk factor for anemia (OR=1.26) and moderate-to-severe anemia(OR=1.35). For students aged 12 and 14 years, girls were at higher risks for anemia and moderate-to-severe anemic(OR=2.41，2.20). Conclusion The overall prevalence of anemia was low in Chinese school-aged children, but substantial subnational disparity and subgroup disparity exists. Our data called for setting up context-specific measures, such as deworming and iron supplementation, to deal with child anemia. Intervention programs need to be implemented among adolescent girls and those with relatively low socioeconomic status.