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Objective To analyse the status and related factors of physical development of ninth grade students in China,so as to provide reference and scientific basis for the development of adolescent’ physical health promotion programs.Methods Multiple linear regression and binomial Logistic regression models were used to analyse the data from 7 840 ninth grade students in the 2016 China Education Panel Survey.Results There were differences in the distribution of height and weight between urban and rural and between boys and girls.From the age of 14 to 16,boys were taller and heavier than girls(height cm：171.69±6.95 vs 161.54±5.58, weight kg：60.43±13.19 vs 53.21±11.69), and urban students were taller and heavier than rural students(height cm：167.93±8.16 vs 165.80±7.94；weight kg：58.18±13.16 vs 55.94±12.78). The rate of physical fitness of boys was lower than that of girls(51.8% vs 87.8%), and that of urban boys was lower than that of rural boys(45.7% vs 58.9%), and that of urban girls was higher than that of rural girls(92.0% vs 84.6%). The average age of first spermatorrhea was 13.62±1.23 years for boys and 12.87±1.07 years for girls. Sexual development of urban students appeared earlier than rural students. Multivariate linear regression analysis showed that height and weight were related to bring single-child and sleep time. Height was also related to parents’height, nationality, family economic level and exercise time, weight was also related to parents’ weight (all P<0.05). Binomial Logistic regression analysis showed that physical fitness level was related to gender, nationality, nutritional status, weight, high calorie intake, exercise time, etc (all P<0.05). Correlative factors of male first spermatorrhea were nationality, urban residence, singleton , sleep time, physical fitness level, while female menarche was related to exercise time, lunch spot and nutritional status (all P<0.05). Conclusions Comprehensive efforts and cooperation are needed to promote the normal development and physical health of the students.
ABSTRACT
<p><b>OBJECTIVE</b>To explore the effects of particulate matters less than 2.5 μm in aerodynamic diameter (PM2.5) on heart repolarization/depolarization and heart rate variability (HRV).</p><p><b>METHODS</b>We conducted a panel study for elderly subjects with heart disease in Beijing from 2007 to 2008. PM2.5 was measured at a fixed station for 20 h continuously each day while electrocardiogram (ECG) indexes of 42 subjects were also recorded repeatedly. Meteorological data was obtained from the China Meteorological Data Sharing Service System. A mixed linear regression model was used to estimate the associations between PM2.5 and the ECG indexes. The model was adjusted for age, body mass index, sex, day of the week and meteorology.</p><p><b>RESULTS</b>Significant adverse effects of PM2.5 on ECG indexes reflecting HRV were observed statistically and the strongest effect of PM2.5 on HRV was on lag 1 day in our study. However, there were no associations between PM2.5 and ECG indexes reflecting heart repolarization/depolarization. Additionally, the effects of PM2.5 on subjects with hypertension were larger than on the subjects without hypertension.</p><p><b>CONCLUSION</b>This study showed ambient PM2.5 could affect cardiac autonomic function of the elderly people with heart disease, and subjects with hypertension appeared to be more susceptive to the autonomic dysfunction induced by PM2.5.</p>