[Research on the association between the occurrence of spermarche and menarche and psychological distress among Chinese children and adolescents aged 9-18 years].

Objective: To analyze the association between the occurrence of spermarche and menarche and psychological distress among Chinese Han children and adolescents aged 9 to 18 years. Methods: Data were drawn from the 2019 Chinese National Survey on Students' Constitution and Health, and a total of 54 438 boys aged 11 to 18 years and 76 376 girls aged 9 to 18 years with psychological distress, spermarche/menarche records were included in the final analysis. The occurrence of spermarche/menarche was recorded by physicians, and psychological distress was classified according to the Kessler Psychological Distress Scale scores. The chi-square test was used to compare the difference between groups in the occurrence of spermarche/menarche, and the multinomial logistic regression model and stratification analysis was established to analyze the association between psychological distress and spermarche/menarche. Results: The incidence of spermarche/menarche in 2019 ranged from 6.3% to 96.5% for eight age groups of Chinese boys and 2.8% to 99.0% for ten age groups of girls. The rates of high psychological distress among boys and girls were 32.5% and 32.7%. Among boys aged 11 to 18 years, the rate of high psychological distress increased with age, with a trend test P<0.001, and the difference in the rate of high psychological distress between those who had and had not had their spermarche was not statistically significant in all age groups. Among girls aged 9 to 18 years, the rate of high psychological distress increased with age, with a trend P<0.001; the rate of high psychological distress was higher in the group with menarche at age 10 and 12 than in the group without menarche (all P<0.05). High psychological distress was positively correlated with spermarche among boys aged 13-15 years living in urban areas and hight level economic development areas (OR=1.11, 95%CI: 1.02-1.21;OR=1.18, 95%CI: 1.06-1.32). Overall, high psychological distress was positively correlated with menarche in girls aged 9-12 and 13-15 years (OR=1.33, 95%CI: 1.25-1.42; OR=1.22, 95%CI: 1.07-1.39). High psychological distress was positively correlated with menarche among girls aged 9-12 years living in different regions except for the Northeast region, in areas with different levels of economic development, and in urban and rural areas, in girls aged 13-15 years living in urban, central, and western regions, and in girls aged 16-18 years residing in the central region. Conclusions: This study found an association between the occurrence of spermarche/menarche and psychological distress among Chinese Han children and adolescents aged 9 to 18 years in 2019, which was particularly significant among girls aged 9 to 12 years and boys aged 13 to 15 years living in areas with higher levels of socioeconomic development.

[Research on the association between the status of physical fitness and psychological distress among Chinese children and adolescents aged 13-18 years].

Objective: To describe the status of physical fitness of children and adolescents aged 13-18 years in China in 2019 and analyze its association with psychological distress. Methods: Data were drawn from the 2019 Chinese National Survey on Students' Constitution and Health, and 90 633 Han children and adolescents aged 13-18 years were included. Physical fitness was evaluated by "National Students Constitutional Health Standards" (2014 revised edition). Psychological distress was classified according to the scores of the Kessler Psychological Distress Scale: ≤19, 20-24, 25-29, and ≥30 scores indicated no, mild, moderate, and severe psychological distress, respectively, with moderate and severe psychological distress collectively referred to as high psychological distress. The χ2 test was used to compare the distribution differences between boys and girls, the Cochran-Armitage test was used to analyze the trend, and the multinomial logistic regression in the mixed effect model was established to analyze the association between physical fitness and psychological distress. Results: In 2019, the unqualified rate of physical fitness among children and adolescents aged 13-18 years in China was 17.2%, and the prevalence of excellent and good physical fitness was 18.2%, which was lower among boys (15.9%) than girls (20.5%) with a statistically significant difference (P<0.05). The excellent and good physical fitness rate showed a significantly decreasing trend with age (trend test P<0.05). The rate of high psychological distress among children and adolescents aged 13-18 years in China in 2019 was 39.3%, with boys (37.0%) having a lower prevalence than girls (41.6%), supported by a statistically significant difference (P<0.05), and a decreasing trend with the degree of physical fitness was observed both in boys and girls (trend test P<0.05). The multinomial logistic regression model showed that the prevalence of moderate (OR=0.83, 95%CI: 0.79-0.88, P<0.001) and severe (OR=0.81, 95%CI: 0.77-0.86, P<0.001) psychological distress were both lower in children and adolescents with excellent and good physical fitness. Conclusion: The status of physical fitness and psychological distress of Chinese children and adolescents aged 13-18 in 2019 was not optimistic, with physical fitness showing a significantly negative association with psychological distress.

[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.

[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.

[Perceived exercise benefits and barriers and their association with physical activity time in Chinese Han children and adolescents aged 9 to 18 years].

Objective: To analyze the perceived exercise benefits and barriers and their association with physical activity time in Chinese Han children and adolescents aged 9-18 years. Methods: Data were extracted from the 2019 Chinese National Survey on Students' Constitution and Health and a total of 163 656 children and adolescents aged 9-18 years in Han ethnic group were included in the analysis. Mann-Whitney U test and Kruskal-Wallis test were used to compare the perceived exercise benefits score, perceived exercise barriers score and perceived exercise benefits to barriers ratio in the children and adolescents with different demographic characteristics and physical activity time. The differences in physical activity time in subgroups were compared with χ2 tests. log-binomial regression model was used to evaluate the association between physical activity time and perceived exercise benefits and barriers. Results: The M (Q1,Q3) of the perceived exercise benefits score, perceived exercise barriers score, and perceived exercise benefits to barriers ratio in the children and adolescents were 4.11 (3.78, 4.78), 2.70 (2.10, 3.20) and 1.55 (1.22, 2.07), respectively. Children and adolescents living in urban area, boys, those at younger age and those with physical activity time ≥1 hour had higher perceived exercise benefits score and perceived exercise benefits to barriers ratio, but lower perceived exercise barriers score (all P<0.001). The prevalence of physical activity time ≥1 hour was 41.4% in the children and adolescents. In the log-binomial model with two variables of perceived exercise benefits score and perceived exercise barriers score, for each 1-point increase in the perceived exercise benefits, the possibility of physical activity time ≥1 hour increased by 11% (OR=1.11, 95%CI: 1.10-1.12), and for each 1-point increase in the perceived exercise barriers, the possibility of physical activity time ≥1 hour decreased by 15% (OR=0.85, 95%CI: 0.84-0.85). In the log-binomial model with variable of perceived exercise benefits to barriers ratio, for each 1-point increase in the perceived exercise benefits to barriers ratio, the possibility of physical activity time ≥1 hour increased by 12% (OR=1.12, 95%CI: 1.11-1.12). Conclusion: The perceived exercise benefits and barriers are significantly associated with physical activity time in children and adolescents in China.

[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.

[Gender difference in secular trends of body height in Chinese Han adolescents aged 18 years, 1985-2014].

Objective: To analyze the gender difference in secular trends of body height in Chinese Han adolescents aged 18 years from 1985 to 2014. Methods: Data were extracted from 1985, 1995, 2000, 2005, 2010 and 2014 Chinese National Surveys in Students' Constitution and Health. A total of 124 099 Chinese Han adolescents aged 18 years were included in the analysis. ANOVA test was used to compare the body height between different subgroups stratified by gender and the mean difference and ratio in body height were calculated. Quantile regression model was used to assess the association between body height and gender over time in the adolescents stratified by region or area. Results: The mean body height of adolescents aged 18 years increased significantly from 1985 to 2014 with the rate of 1.3 cm/decade in male adolescents and 0.8 cm/decade in female adolescents, and the highest increment occurred from 1995 to 2005 in both groups. Male adolescents were taller than female adolescents at each subgroup (P<0.05). Gender difference in body height increased from 11.1 cm in 1985 to 12.6 cm in 2014 and ratio remained to be 1.07-1.08. The body height was taller in adolescents in urban area than in rural area (P<0.05) and in northeastern China than in other regions (P<0.05) in both male and female adolescents. The body height of obese male adolescents had been taller since 2000 and the body height of obese female adolescents had been taller since 2010 than other groups. When adjusted for urban-rural areas, region, socioeconomic status and nutritional status, the body height increased over time at P5, P25, P50, P75 and P95 in both male and female adolescents, and the increments of gender difference in body height at different percentile ranged from 0.45 cm/decade to 0.57 cm/decade. When stratified by region, the gender difference in body height showed similar trend with total sample except P5 and P95 in northeastern China, the difference of increments were not significant. Conclusions: From 1985 to 2014, the gender difference in body height of Chinese Han adolescents aged 18 years increased, and male adolescents showed greater increase than female adolescents. Moreover, the adolescents in northeastern and eastern China had larger increment in body height. It is necessary to paid more attention to the adolescents in central and western China to promote their physical development.

[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.

[Association between endurance quality and blood pressure levels in Han students aged 13-18 years in China, 2014].

Objective: To analyze the association between the endurance quality and blood pressure levels in Han students aged 13-18 years in China. Methods: We used the data of Han students aged 13-18 years from 2014 Chinese National Survey on Students' Constitution and Health. Elevated blood pressure and its components, including isolated elevated SBP, isolated elevated DBP, and mix elevated blood pressure, were evaluated according to the reference of screening for elevated blood pressure among children and adolescents aged 7-18 years. The students' endurance quality was scored according to the National Standards for Students' Physical Health (2014 revision) and categorized based on their percentiles into four groups as follows: P(0)-, P(25)-, P(50)-, and P(75)-P(100). Trend χ(2) test was used to analyze the trend of the detection rates of elevated blood pressure and its components in different groups of endurance quality. Logistic regression model was used to estimate the odds ratio (OR) for elevated blood pressure and its components in different endurance quality groups and P(0)-group was set as reference group. Quantile regression model was used to analyze the association between different blood pressure levels and endurance quality. Results: The detection rate of elevated blood pressure in the students aged 13-18 years in China in 2014 was 9.2%. The detection rate of elevated blood pressure and its components decreased with the improvement of endurance quality (P<0.001). With the P(0)-endurance quality group as reference, the OR(95%CI) were 0.89(0.84-0.95), 0.81(0.76-0.86) and 0.79(0.74-0.84) respectively in P(25)-, P(50)- and P(75)-P(100) endurance quality groups respectively. The negative association existed between endurance quality and elevated blood pressure in overweight, obese and normal students, but not in malnourished students. The quantile regression analysis results showed that in overweight and obese students, the SBP levels at the P(10), P(25), P(50), P(75), P(9)0 and P(95) groups were negatively associated with the endurance quality, and the DBP levels at the P(25) and above group were negatively associated with the endurance quality. In malnourished and normal students, only some levels of DBP were negatively associated with the endurance quality. Conclusions: The negative association existed between endurance quality and elevated blood pressure in Han students aged 13-18 years in China. In overweight and obese students, the association between endurance quality and blood pressure level was stronger. Improving students' endurance quality may facilitate the prevention of elevated blood pressure.

[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.

[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.

[Comparison of status of physical activity time at school and influencing factors in students in China, 2010 and 2014].

Objective: To compare the probability of physical activity (PA) time ≥1 hour at school and influencing factors in students in China between 2010 and 2014. Methods: We used the data of 2010 and 2014 Chinese National Survey on Students' Constitution and Health (CNSSCH). The surveys covered the Han students aged 9-22 years and Tibetan students aged 9-18 years (Tibet). The participants were primary school students (9-12 years old), junior high school students (13-15 years old), senior high school students (16-18 years old) and college students (19-22 years old). The probability of PA time ≥1 hour at school was compared using χ(2) tests between 2010 and 2014 survey years. Log-binomial Regression was used to estimate the relative risk (RR) for the probability of PA time ≥1 hour at school in different age groups. Results: The overall probability of PA time ≥1 hour at school in students aged 9-22 years was 20.5% in 2010, and 23.8% in 2014. The difference between 2010 and 2014 was significant (P<0.001). On the whole, the probability of PA time ≥1 hour at school increased in the eastern, central and western areas in 2014 compared with 2010 (P<0.05), and the increase range was highest in eastern area, followed by western area and central area (P<0.05). The probability of PA time of 1 hour at school in all age groups increased in 2014 compared with 2010 (P<0.05). The increase in the probability of PA time ≥1 hour at school was larger in primary school students than that in high school students and college students (P<0.05). The probability of PA time ≥1 hour at school increased in all age groups in three areas, except in junior and senior high school students in the central area where the probability of PA time ≥1 hour at school decreased. The probability of PA time ≥1 hour at school in primary and junior/senior high school students in the eastern area had the greatest increase, but in college students it had the smallest increase in the three areas. From 2010 to 2014, the changes in the probability of PA time ≥1 hour at school in students in different provinces were quite different, especially in primary school students. The probability of PA time ≥1 hour at school in four age groups increased in only three provinces. With the probability of PA time ≥1 hour at school in primary school students as the reference, the RR in junior high students had no significant change between 2010 and 2014. The RR in senior high school increased from 0.34 (0.33-0.35) in 2010 to 0.36 (0.36-0.37) in 2014, and the RR in college students increased from 0.33 (0.32-0.34) in 2010 to 0.43 (0.42-0.44) in 2014. Conclusions: The probability of PA time ≥1 hour at school in all age groups increased in 2014 compared with 2010, but there were great differences among provinces. The findings of our study suggests that although the national policy played a certain role, the provinces should take specific measures to improve the probability of PA time ≥1 hour at school in students according to their own conditions. In addition, more attention should be paid to PA of older students.

[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.

[Secular trends and geographic disparities of all-cause mortality among Chinese adolescents aged 10-24 years, between 1953 and 2010].

Objective: To analyze the secular trends and geographic disparities of all-cause mortality among Chinese adolescents aged 10-24 years over the period of 1953-2010. Methods: Data were extracted from the Chinese National Census in 1953-2010. We calculated the all-cause mortality and annualized rates of the changes. Using the provincial gross domestic product (GDP) per capita as an indicator of regional socio-economic development level, we calculated the Wagstaff normal concentration indices for adolescent mortality. Results: Over the period of 1953-2010, the general patterns of Chinese adolescent mortality appeared higher in males than those in females, higher in the 20-24-year-old than those in the 15-19 year-old and in the 10-14 year-old groups, higher in adolescents from the western than those in the eastern regions. The mortality of adolescents decreased from 554.6/100 000 in 1953-1964 to 55.7/100 000 in 2010 in males and decreased from 488.4/100 000 to 26.7/100 000 in females, respectively. The percentage of decrease for females (94.5%) was higher than that for males (90.0%). In 1981-2010, the highest annualized rate of decline for males was seen in Beijing (4.4%), with the lowest seen in Qinghai (0.1%). For girls, Hubei showed the highest annualized rate of decline (6.4%) while Qinghai the lowest (0.8%). Provinces that with higher mortality tended to have lower annualized rate of decline. The concentration indices for boys were -0.07 (95%CI: -0.11- -0.03), -0.13 (95%CI: -0.18- -0.08), and -0.16 (95%CI: -0.22- -0.10) in 1990, 2000, and 2010, respectively, and were -0.07 (95%CI: -0.13- -0.02), -0.18 (95%CI: -0.24- -0.12), and -0.18 (95%CI: -0.26- -0.09) respectively in girls. The indices among 1990, 2000, and 2010 did not show statistically significantly differences, both for boys and girls (P>0.05). Conclusions: Over the half century, the mortality of Chinese adolescents showed dramatic decreasing trend. However, in terms of death rates, gender and geographic disparities were consistently seen in the adolescents.

[The prevalence of snoring and its related family factors of children from 3 to 14 years old in Beijing].

Objective: To investigate the snoring status and related family factors of children from 3 to 14 years old in Beijing. Methods: From May to July, 2015, data of children from 3 to 14 years old were obtained from a status survey from 7 districts(Xicheng, Chaoyang, Changping, Shunyi, Fangshan, Huairou and Mentougou) in Beijing. A total of 11 420 children from 25 primary and middle schools were randomly selected. Pediatric Sleep Questionnaire (PSQ) and a self-administered questionnaire were carried out for the adopted children. Self-administered questionnaire included the snoring related family factors. Logistic regression was used to estimate the odd ratio(OR) with 95% confidence intervals for variables. Results: A total of 9 198 children meet the inclusion criteria and are analyzed in the study, of whom 901 (9.80%) were found with snoring behavior. The incidence of boys is higher than girls. Obese children take higher risk of snoring. Compared with younger children (≤6 years old), older children (≥12 years old) have a significantly lower risk of snoring (OR=0.464, 95%CI 0.368-0.585). There is no statistical association between full-term infants, infant feeding pattern, parental cigarette smoking and child snoring.The children with family history of snoring have a significantly higher risk of snoring occurrence. The educational background of mother is statistically related to children snoring (OR=1.241, 95%CI 1.058-1.457). Conclusions: The incidence of children snoring in Beijing is 9.80%, male gender, obesity, and young age are all risk factors for children snoring. There is a significantly statistical relationship between snoring and related family factors, such as family snoring history and education experience.