[Vitamin D status and distribution in Beijing school aged children in 2016-2018].

Objective: To evaluate the nutritional status of vitamin D in school-age children in Beijing.

Methods: The data was part of the monitoring data of Beijing in "Chinese Nutrition and Health Monitoring of Children and Nursing Mothers 2016-2017". A total of 1385 students were recruited from 10 primary schools, 10 junior middle schools and 5 senior high schools. The concentrations of serum vitamin D were determined using electrochemiluminescence immunoassay. The distribution of serum vitamin D in school-age children was further described for different regions, age, body mass index(BMI), waistline, outdoor activity time and myopia. The prevalence of the insufficiency and deficiency of vitamin D was compared in different subgroups.

Results: The median concentration of serum 25(OH)D_3 [M(P25, P75)] of students aged 6-11 and 12-17 were 20.86(16.48, 25.31) ng/mL and 14.12(11.04, 19.17) ng/mL. The serum 25(OH)D_3 of male school-age children was higher than that of female. The serum 25(OH)D_3 of students aged 12-17 was lower than that of students aged 6-11. The serum 25(OH)D_3 of urban students was lower than that of rural students, and the serum 25(OH)D_3 of myopia students was lower than that of non-myopia students(P<0.01). There was no significant difference in serum 25(OH)D_3 between students with outdoor activity time greater than or equal to 2 hours and students with less than 2 hours, normal weight and overweight and obese students, normal waist and abdominal obesity students. The vitamin D deficiency rate, insufficiency rate, insufficiency and deficiency rate of school-age children were 18.8%(261), 40.1%(556) and 59.0%(817). The vitamin D deficiency in girls was more serious than that in boys, and the vitamin D insufficiency and deficiency of students aged 12-17 were more serious than that of students aged 6-11. The vitamin D deficiency of students in urban areas was more serious than that in rural areas, and the vitamin D deficiency of myopia students was more serious than that of non-myopia(P<0.01). There was no significant difference in vitamin D deficiency between students with outdoor activity time greater than or equal to 2 hours and students with less than 2 hours, normal weight and overweight and obese students, normal waist and abdominal obesity students. The statistically significant variables(gender, age, region, outdoor activity time, overweight, obesity, abdominal obesity and myopia) were included in the multivariate Logistic regression model for analysis. The result showed that girls(OR = 2.005, P<0.001), 12-17 years old(OR=4.310, P<0.001), rural(OR=0.586, P<0.001) with vitamin D deficiency and insufficiency were more likely.

Conclusion: The vitamin D status of students in Beijing is not ideal, and the deficiency and insufficiency of vitamin D in girls is more serious than that in boys; The deficiency and insufficiency of vitamin D in 12-17 years old is more serious than that in 6-11 years old; The vitamin D deficiency of urban students is more serious than that of rural students.