Risk Factors of Hypovitaminosis D in Adolescents, Shanghai, China: A Cross-Sectional Study

Abstract Background and Objectives: Hypovitaminosis D is prevalent worldwide. Accumulating researches suggested vitamin D deficiency is associated with obesity and dyslipidemia. But the relationship is still controversial. This study was aimed to evaluate the vitamin D status in Chinese adolescents, to find out the risk factors of hypovitaminosis D and its association with obesity. Methods: A cross-sectional survey of serum 25(OH)D, glycolipids, anthropometric measurements and life style investigation was done in 441 youths. The prevalence of hypovitaminosis D was determined. The influence factors of 25(OH)D concentration were analysed. Multi-variation logistic regression was utilized to find the risk factors of hypovitaminosis D. The association of vitamin D3 and the metabolic indice was analysed by gender. Results: The mean serum 25(OH)D concentration was 21.9 ± 8.1 ng/ml. Boys had higher 25(OH)D than girls (22.4 ± 8.1 ng/ml vs. 19.0 ng/ml (P25: 15.5 ng/ml, P75: 25.2 ng/ml), p<0.05). The prevalence of hypovitaminosis D was 42.4%. The prevalence of vitamin D deficiency in girls was significantly higher than in boys (55.4% vs. 39.8%, p<0.01). The mean concentration of 25(OH)D in winter was 19.6ng/ml, significantly lower than that in summer(25.6 ± 7.8 ng/ml, p<0.001). Significant differences were found in gender (p=0.005), age (p<0.001), BMI-SDS (p=0.003), WCSDS (p=0.005), seasons (p<0.001) and NAFLD ratios (p=0.018) among groups of vitamin D sufficiency, insufficiency and deficiency. The logistic regression suggested that female (OR=2.45, p=0.001), older ages (OR=1.29, p=0.011) and winter (OR=1.96, p=0.038) were risk factors of vitamin D deficiency. In male adolescents, HDL was protective factor of 25(OH)D concentrations (OR=0.22, p=0.009). BMI and WC were of no association with vitamin D. No relationship between 25(OH)D and metabolic indice or anthropometric measurements in girls was found. Conclusions: The vitamin D3 status in adolescents was very worrying. The risk factors of hypovitaminosis D were female, older ages and winter. 25(OH)D concentration had no relationship with BMI, WC, NAFLD in both genders.