ECE2014 Poster Presentations Calcium and Vitamin D metabolism (68 abstracts)
1Department of Health Sciences, University of Piemonte Orientale, Novara, Italy; 2Department of Translational Medicine, University of Piemonte Orientale, Novara, Italy.
Introduction: The association between vitamin D (25(OH)D) levels and metabolic parameters is not confirmed in some population studies. 25(OH)D concentration in blood is influenced by seasons and this covariate may explain some discordant results. The first aim of our study was to evaluate the prevalence of 25(OH)D deficiency in a population of obesity children (218 years) living in the North of Italy (latitude, 45°27′n) with respect to the season. The second aim was to decipher whether the association between 25(OH)D levels and metabolic parameters is influenced by different indexes of sunlight power as covariates.
Methods: Clinical and metabolic evaluations including an OGTT were performed in 640 obese children and adolescents (BMI IOTF classification). 25(OH)D levels were stratified according to classical cut-off ranges (deficiency: <20 ng/ml; hypovitaminosis: 2030 ng/ml, and normal values: ≥30 ng/ml) and also divided in quartiles. Sunlight power was evaluated as season, month radiation, or u.v. index.
Results: 291 subjects (45.5%) had 25(OH)D deficiency. 25(OH)D deficiency showed a seasonal trend (χ2=113.4, P<0.0001) with a higher prevalence in autumn and winter. The correction for month radiation or u.v. index showed more significant results than that for seasonality. Levels of total cholesterol (P<0.001), triglycerides (P<0.001), insulin during OGTT (P<0.01) were negatively predicted by 25(OH)D quartiles independently by BMISDS, puberty, and month radiation. The correction for the u.v. index strengthened the significance of previous results, and showed other correlations with blood pressure (P<0.02), HOMA index (P<0.01), and insulin levels at fasting (P<0.01), at 60′ (P<0.04) and 90′ min (P<0.002).
Conclusions: The prevalence of 25(OH)D deficiency is high in the obese pediatric population and has a seasonal trend. Since sunlight exposure has a role, studies on vitamin D should use correction for indexes of sunlight exposure. Some indexes seem more accurate than others and these aspects could explain some discordant results in literature.