Association of vitamin D status with lung function measurements in children and adolescents with cystic fibrosis

Background Vitamin D status is considered a potential determinant of lung function in cystic fibrosis (CF). The aim of this retrospective longitudinal study was to investigate the decline of spirometric values in association with vitamin D status. Methods The data regarding 25-hydroxy vitamin D (25OHD) serum levels, spirometric measurements (FEV1, FVC, FEF25-75%), and factors known to be associated with the decline of lung function in CF were retrospectively collected over a 5-year period. The spirometric indices were recorded as the best and the average value of each year, as well as the value, recorded concurrently or closely with 25OHD level measurement. Results A significantly positive relationship was observed between 25OHD serum levels and the best annual value of FEV1 (P = .034), and the values of FEV1 (P = .010) and FVC (P = .018) measured concurrently or closely with serum 25OHD levels. The evolution of the best annual value of FEV1 was worse in patients with a mean 5-year value of 25OHD levels less than 20 ng/mL compared with patients with a mean 5-year value of >= 30 ng/mL (P < .001), or >= 20 to <30 (P < .001). There was no significant difference between patients with mean 5-year 25OHD levels >= 30 ng/mL and >= 20 to <30 ng/mL (P = .76). Conclusions Vitamin D status is associated with lung function in patients with CF. Levels of 25OHD above 20 ng/mL were associated with higher best annual FEV1.