The prevalence of vitamin D deficiency among schoolchildren: a cohort study from Xinxiang, China.

Aim: Vitamin D deficiency (VDD) in children is widespread. Therefore, the present study was conducted to assess the prevalence of VDD in schoolchildren from Henan Province, China. Methods: The study was conducted on school students from areas of Xinxiang, one of the largest cities of Henan Province in China, in the winter of 2013. A questionnaire on demographic data, socioeconomic status, sun exposure, and times of acute respiratory infections (RTI) in the past 12 months were completed for each student. Blood samples were taken to assess serum levels of 25-hydroxyvitamin D [25(OH)D]. Results: In our study, 606 schoolchildren completed the questionnaire. The median serum level of 25(OH)D was 20.5 ng/mL (interquartile range: 15.9-25.1). The prevalence of VDD and insufficiency was 46.9% (284/606) and 85.8% (520/606), respectively. VDD was more associated with female gender, high body mass index, lower socio-professional status, residence in urban areas, and less time spent outdoors. There was an inverse correlation between levels of 25(OH) and times of RTI (p<0.001). Conclusion: VDD and insufficiency are common among schoolchildren in Xinxiang. Supplementation with food fortification or vitamin D for Chinese children is warranted.