Serum 25-hydroxyvitamin D levels in relation to lung function and exhaled nitric oxide in children.

OBJECTIVE: To investigate the relationship of vitamin D status with lung function and fraction of exhaled nitric oxide (FeNO) in a population sample of children. STUDY DESIGN: A total of 1315 children aged 5-18 years were evaluated using serum 25-hydroxyvitamin D [25(OH)D] levels, spirometry, a single-breath online FeNO measurement, and questionnaires. RESULTS: After adjusting for confounders, the mean forced vital capacity was 53.4 mL (SE, 26.5 mL; P = .045), and the mean forced expiratory volume in 1 second was 48.2 mL (SE, 23.6 mL; P = .042) lower for children with insufficient serum 25(OH)D levels (20-29.9 ng/mL) compared with those with sufficient 25(OH)D levels (≥30 ng/mL). The mean difference between children with deficient (<20 ng/mL) and sufficient levels of serum 25(OH)D was 81.9 mL (SE, 26.7 mL; P = .002) for forced vital capacity and 55.2 mL (SE, 23.7 mL; P = .020) for forced expiratory volume in 1 second. There was no significant association between serum 25(OH)D levels and FeNO after adjusting for confounders. CONCLUSIONS: Our results demonstrate a significant relationship between insufficient serum vitamin D levels and worse lung function in children in the community with a suggested dose-response effect. Our findings also suggest that vitamin D status is not a significant determinant of FeNO in children in the general population.