LA VITAMINA D IN PATOLOGIE RESPIRATORIE DI INTERESSE PEDIATRICO

Introduction: Vitamin D and its effects on human health are topics that are attracting great interest, and in recent years there is a rapid increase in the number of publications about vitamin D and its relationship to asthma, allergies and respiratory infections. This discovery, together with the realization that essentially every tissue and cell in the body has vitamin D receptors, has prompted new interests in the vitamin D system and its previously unrecognized actions. Recent data suggest that hypovitaminosis D is associated with many nonskeletal conditions such as asthma. Objectives: We investigated the relationship between vitamin D serum levels, lung function and asthma control in children and smoking habits of their parents. Materials and Methods: We estimated the correlation between the concentration of 25-hydroxycholecalciferol [25(OH)D], lung function parameters obtained from baseline spirometry and levels of asthma control, according to the guidelines Global Initiative for Asthma (GINA) and the Childhood Asthma Control Test (C- ACT), in 152 children with asthma (aged 5-15 years, 84 males) in a cross-sectional study conducted during the winter and spring. We have also studied the existence of a possible association between the smoking habits of parents and the vitamin D levels of these children with asthma. Results: Only 9.9 % of our children had sufficient vitamin D serum levels (between 30 and 40 ng / ml). We found a moderate positive correlation between the forced vital capacity percent predicted and the vitamin levels ( Spearman ρ = 0.36 , 95% CI = 0.22 to 0.50, P <0.001). This finding was also found for the forced expiratory volume in 1 second ( ρ = 0.36 , 95% CI = 0.23 to 0.50, P <0.001). Patients with well-controlled asthma showed serum levels of vitamin D higher than children with not or partly controlled asthma, with median values equal to 22.4 ng/ml (IQR = 18.2 - 26.0 ng / ml), 17.8 ng/ml (IQR = 12.6 - 22.0 ng/ml) and 13.5 ng/ml (IQR = 10.1 - 18.1 ng / ml), respectively (P <0.001) . We have also identified a moderately positive correlation between 25(OH)D levels of and the C -ACT score (r = 0:49, 95% CI = 0.36-0.62 , P <0.001). By analyzing the smoking habits of parents in relation to vitamin D serum levels, a statistically significant association between the two parameters was present. In particular, serum levels appear to be significantly reduced if both parents report smoking regularly (P <0.001). Conclusions: Our results suggest that hypovitaminosis D is frequent in children with asthma living in a Mediterranean country. In these children, lower vitamin D serum levels are associated with reduced asthma control and lung function. The study also suggests that passive smoking could be a causal factor for hypovitaminosis D in children with asthma. However, further studies to verify this relationship, in particular by analyzing biomarkers of exposure to cigarette smoke are necessary.