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Vitamin D insufficiency (VDI) contributes to low bone mineral density (BMD) in adults with cystic fibrosis (CF). Vitamin D may improve skeletal/respiratory muscle function and upregulate antimicrobial peptides, improving immunity. This 2-year retrospective study reviewed medical records of 185 adults of mean (SD) age 29 (9) years with CF. Parameters of bone health and the relationship between vitamin D status and forced expiratory volume in 1 s (FEV1) were investigated.
The subjects (93% white, 17% black) had a mean body mass index (BMI) of 21.2 kg/m2; 70% used multivitamins and 47.6% took vitamin D. VDI was found in 76% of patients (25-hydroxyvitaminD (25(OH)D) <75 nmol/l) and vitamin D deficiency in 23% (25(OH)D <37.5 nmol/l). VDI was associated with race (black>white), lack of vitamin D use and season. The vitamin D status was positively associated with lowest FEV1, independent of age, gender, BMI and race. BMD was low (lumbar spine T-scores of <−1.0 and <−2.5 in 52% and 10% subjects, respectively), non-significantly associated with vitamin D status. Over 2 years, 27% of subjects had ⩾1 vertebral fracture associated with lower FEV1 (p<0.001) but not age, BMI, vitamin D or multivitamin supplementation. Multivitamins did not prevent VDI.
Patients with CF with more severe disease (greater fat malabsorption) and lower FEV1 may have decreased physical activity and sun exposure, all contributing to VDI. Low BMD is associated with vertebral fractures and kyphosis, reducing FEV1 further. This cross-sectional study could not demonstrate causality between vitamin D status and fractures or FEV1, but highlights the extent of VDI and skeletal morbidity in adults with CF, calling for improved screening for vitamin D status.
▸ Wolfenden LL, Judd SE, Shah R, et al. Vitamin D and bone health in adults with cystic fibrosis. Clin Endocrinol 2008;69:374–81.