Objective: To evaluate the endogenous vitamin D level and its correlation with bone mineral density (BMD) in children under 7 years old.
Methods: Totally 6 838 children who visited the Growth and Development Clinic due to "growth retardation, night terrors, hyperhidrosis, and dysphoria" were enrolled in the study. Serum 25-hydroxyvitamin D [25(OH)D] level was measured by chemiluminescence, whereas individual BMD was measured by quantitative ultrasound.
Results: Among all subjects, serum 25(OH)D level was 34 ± 14 ng/mL, and the Z value of BMD was -0.49 ± 0.54. With increasing age, serum 25(OH)D level and BMD decreased gradually (P<0.01), and the detection rates for vitamin D deficiency and low BMD increased gradually (P<0.01). Compared with those with sufficient vitamin D, children with vitamin D deficiency had a significantly lower BMD (P<0.01) and a significantly higher detection rate for low BMD (P<0.01). 25-(OH)D level showed a positive linear correlation with BMD in children with vitamin D deficiency (P<0.01).
Conclusions: Preschool and school-age children have severer vitamin D deficiency than infants. Vitamin D level may be correlated with BMD within a certain range.