Relationships between serum 25-hydroxyvitamin D and quantitative ultrasound bone mineral density in 0-6 year old children

The relationship between serum 25-hydroxyvitamin D and quantitative ultrasound bone mineral density in young children remains unclear. In addition, consensus has not been reached with regard to the concentration of 25(OH)D to define vitamin D deficiency for infants and children. In the present study, 203 children 0-6 years old were recruited in Shanghai, China. The concentrations of serum 25(OH)D, weight, length, and quantitative ultrasound bone mineral density (BMD) of left mid-tibia were determined. Low BMD was defined as <20th percentile of given age and sex. Low 25(OH)D was defined as 25(OH)D<20 ng/ml. The results showed that median serum 25(OH)D level was 19.0 ng/ml, and 58.6% had a serum 25(OH)D below 20 ng/ml. After adjusting for potential confounders, a linear relationship between serum 25(OH)D and BMD was observed. Serum 25(OH)D was positively associated with BMD (ß=323.3, 95% CI=201.0-445.7, p<0.001), and low 25(OH)D (<20 ng/ml) had a high risk for low BMD (OR=5.5, 95% CI=2.5-12). In addition, there is a nonlinear relationship between 25(OH)D and low BMD, and a threshold for 25(OH)D of 20 ng/ml existed for low BMD. The prevalence of low BMD was 47.1% in the group of 25(OH)D<20 ng/ml, much higher than 16.7% in the group of 25(OH)D ≥ 20 ng/ml (p<0.05). The results suggested that quantitative ultrasound BMD could be an indicator for vitamin D status in young children, and also provided further evidence to define vitamin D deficiency for infants and children.