Vitamin D Status Among Infants And Toddlers In Lanzhou And Zhuanglang: A Cross-sectional Study

Objective We designed the experiment with the purpose of assessing the status of vitamin D among infants and toddlers aged 0-36 months living in Lanzhou and Zhuanglang in northwest of China. The two centers represented industrially polluted urban area and economically underdeveloped rural area respectively.Methods A cross-sectional study was conducted in a random sample of 759 subjects aged from 0 to 36 months in Lanzhou and Zhuanglang. Serum 25-(OH)D levels were measured by isotope-dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS). Vitamin D External Quality Assessment Scheme (DEQAS) was used to ensure the accuracy of test method. The group differences were compared by R X C chi square test. We used Logistic regression to analyze potential risk factors of vitamin D deficiency surveyed by a questionnaire.Results The media serum 25-(OH)D level of 759 infants and toddlers enrolled in this study was 23.2 ng/mL, with IQR ranging from 11.1 to 33.0. Of all the subjects,315(42%) had deficient levels (<20ng/mL),199(26%) had insufficient level (20-29ng/mL) and 245(32%) had sufficient levels (≥30ng/mL) of serum 25-(OH)D. Serum 25-(OH)D levels significantly differ among the children living in urban and rural areas(x22=146.77, P=0.000). The subjects with deficient levels of 25-(OH)D are 64% and 20% in Zhuanglang and Lanzhou, respectively. Logistic regression analysis showed that vitamin D deficiency was significantly more prevalent in infants aged 0 to 3 months [OR 6.752(95%CI:3.853,11.832)], subjects living in rural area [OR 7.098(95%CI:5.104, 9.872)] and during spring and winter season [OR 2.824(95%CI:1.664,4.792),2.411(95%CI: 1.418,4.102)].Conclusions Vitamin D deficiency is found to be very prevalent in Lanzhou and Zhuanglang in infants and toddlers. Infants aged 0 to 3 months, residency of rural area as well as the winter and spring seasons are independent risk factors for vitamin D deficiency.