Objective: To understand the vitamin D nutritional status and associated factors of children and adolescents aged 6-18 in Yinchuan, so as to provide theoretical basis for improving the vitamin D malnutrition status of children and adolescents. Methods: Using stratified cluster sampling method, 1 615 children and adolescents from 36 classes in 2 primary schools, junior high schools and high schools were randomly selected from Yinchuan, Ningxia. Venous blood sampling,physical examinations and questionnaires were conducted. Results: The vitamin D deficiency rate and appropriate rate for students were 66.9% and 33.1%, respectively. There was a statistically significant difference in vitamin D deficiency among different age groups(χ2=25.65, P<0.05). The 6-year-old group had the highest(79.2%), followed by the 13-year-old group (76.6%), and the 12-year-old group (75.3%). The results of binary Logistic regression showed that the factors influencing the vitamin D nutritional status of children and adolescents included age(OR=0.95), daily outdoor exercise time(OR=0.49), exclusive breastfeeding (OR=0.63) and mother’s education(OR=0.73, 0.43). The decision tree QUEST and Logistic regression combination model results show that the key factors affecting vitamin D nutrition status include daily outdoor exercise time, age, mother’s education, BMI, and interaction between outdoor exercise time and age, interaction between outdoor exercise time and mother’s education, interaction between age and mother’s education, interaction between exclusive breastfeeding and BMI. Conclusion The detection rate of vitamin D deficiency in children and adolescents aged 6-18 in Yinchuan is high, factors associated with vitamin D nutritional status includes daily outdoor exercise time, age, mother’s education, BMI, and interaction between outdoor exercise time and age, interaction between outdoor exercise time and mother’s education, interaction between age and mother’s education, interaction between exclusive breastfeeding and BMI.

Objective: To analyze the trend of overweight and obesity among Han students aged 7-18 years in Ningxia from 2000 to 2014, and to provide scientific basis for child and adolescent obesity prevention and control in Ningxia. Methods: Based on data of the height and weight of Han students aged 7-18 in the four waves of national student physical surveys in Ningxia from 2000 to 2014, SPSS 21.0 was used for trend analysis. Results: From 2000 to 2014, the overweight and obesity rate of Han students in Ningxia from 7 to 18 years old showed an upward trend. Compared with the year of 2000, the total overweight rate increased by 2.06 times in 2014 and the obesity rate increased by 4.40 times. The overweight and obesity rate of boys was higher than that of girls in 2005 and 2014, and the difference was statistically significant(χ2=4.91, 6.20, P<0.05). The overweight and obesity rates of urban students were higher than those of rural students in 2005 and 2010(χ2=9.63, 5.97, P<0.05). The correlation analysis between the overweight and obesity rate of Ningxia students and socioeconomic indicators showed that the overweight and obesity of Ningxia students from 2000 to 2014 was closely related to the level of Ningxia socioeconomic development, especially the obesity detection rate of rural students was related to Ningxia’s GDP and The correlation between GDP, per capita disposable income, per capita consumption expenditure, and urbanization rate is stronger(r=0.98, 0.98, 0.99, 1.00, 0.93, P<0.05). Conclusion Socioeconomic of Ningxia is rapidly increasing, and the overweight and obesity rate of Han students aged 7 to 18 is also increasing. It is suggested that society, schools and parents should pay great attention to this phenomenon, build community-wide efforts to prevent childhood obesity, and prevent chronic diseases caused by overweight and obesity occurrence risk.