Vitamin D deficiency is associated with pulmonary exacerbations in children with cystic fibrosis

Abstract

Rationale: Recent literature suggests vitamin D has an effect on lung function and on the lung's ability to fight infection, both important in the cystic fibrosis (CF) population as predictors of morbidity and mortality.

Objectives: Our study assessed associations between vitamin D and % predicted lung function, pulmonary exacerbations, and first Pseudomonas aeruginosa infection in children with CF. We hypothesized that children with CF who have 25-hydroxy vitamin D (25-OHD) levels less than 30 μg/L would have lower % predicted lung function and more pulmonary exacerbations than those with 25-OHD greater than or equal to 30 μg/L.

Methods: This retrospective longitudinal study of 130 children aged 6 to 18 years between 2000 and 2012 examined 25-OHD levels classed in three vitamin D groups: sufficient (≥30 μg/L), insufficient (20-29 μg/L), and deficient (<20 μg/L). Longitudinal models followed individuals' changing vitamin D groups over time to compare numbers of pulmonary exacerbations (defined by hospitalization), incidence of first P. aeruginosa infection, and % predicted lung function. Cross-sectional comparisons between vitamin D groups were performed at ages 8, 12, and 16 years.

Measurements and main results: The prevalence of vitamin D deficiency and insufficiency increased slowly through adolescence. The rate of exacerbations for the deficient vitamin D group, aged 15 to 18 years, was 13.1 per 10 patient-years, significantly higher than 4.3 per 10 patient-years for the insufficient and sufficient vitamin D groups (P < 0.05), which were not significantly different There were no differences between vitamin D groups in pulmonary function or incidence of first P. aeruginosa infection, which was about 2 per 10 patient-years.

Conclusions: Higher 25-OHD levels in children with CF were associated with lower rates of pulmonary exacerbations and, in adolescents, higher FEV1.

Figure 1.

Percent predicted FVC, FEV₁, and the ratio FEV₁/FVC, age 6 to 18 years. Light gray line segments show measurements for each child in the study. Green curve (age 6−18 yr) is fitted mean for sufficient vitamin D group; blue curve (age 7−18 yr) is fitted mean for insufficient vitamin D group; red curve (age 11−18 yr) is fitted mean for deficient vitamin D group. Fitted means are shown only for years in which a group contained at least four children.

Figure 2.

Numbers of hospitalizations for exacerbation per 10 patient-years, by vitamin D group and age category. Green line connects rates for sufficient vitamin D group; blue line connects rates for insufficient vitamin D group; red line connects rates for deficient vitamin D group. The rate of exacerbations for the deficient vitamin D group, ages 15 to 18 years (marked b), was significantly higher than for the insufficient and sufficient vitamin D groups (marked a, P < 0.05).