Vitamin D deficiency is associated with pulmonary dysfunction in cystic fibrosis

BackgroundVitamin D deficiency is common in CF. Whether vitamin D affects pulmonary function in CF is unknown.MethodsData were abstracted from clinically stable CF patients who had pulmonary function studies and serum 25-hydroxyvitamin D [25(OH)D, ng/ml] levels drawn within 2 months of each other. Findings were adjusted for multiple variables known to affect pulmonary function in CF.ResultsEnrollees totaled 597. Overall mean 25(OH)D level was 29.6 ± 12.8 ng/ml (SD). Serum 25(OH)D levels showed a significant correlation with forced expiratory volume in 1 s (FEV1) % predicted (r = 0.20, p < 0.0001) and forced vital capacity % predicted (r = 0.13, p = 0.0019). Multivariate analysis revealed that serum 25(OH)D remained an independent predictor of FEV1 % predicted even after controlling for multiple other factors known to affect CF lung function.ConclusionsSerum 25(OH)D levels are significantly associated with pulmonary function in CF. Further study is required to determine whether this association is causal.