Bone mineral density, lung function, vitamin D and body composition in children and adolescents with cystic fibrosis:...

cystic fibrosis (CF) is the most common inherited disease in Caucasian population. Nowadays, long survival has led to the emergence of new complications, such as CF bone disease (CFBD), which is characterized by increased fracture risk.

evaluate the association of bone mineral density (BMD) with lung function and BMD with 25-hydroxivitamin D (25OHD) plasmatic levels in children/adolescents with CF.

we conducted a multicenter, cross-sectional study with clinically stable CF patients between five and 18 years. Weight, height, pubertal development, BMD and body composition (DXA), pulmonary function (FEV1 and FEF25-75) and 25OHD plasmatic levels were measured. Patients answered food intake and physical activity surveys. p values under 0.05 were considered as statistically significant.

thirty-seven patients were enrolled, 51% with normal respiratory function. Mean BMD Z-score in lumbar spine and in total body less head were -0.4 and -0.5 respectively. Twenty seven percent had a fat free mass index below the third percentile, 89% had 25OHD levels lower than 30 ng/ml and 78.4% had a low calcium intake. We did not find any correlations between BMD Z-scores, lung function or 25OHD levels. Patients with fat free mass (FFM) below the third percentile had BMD Z-score lower than -1 more frequently, in both locations (p < 0.006 and p < 0.001, respectively).

although most assessed patients had normal BMD and normal lung function, a high proportion had low: FFM, calcium intake and 25OHD levels. The association between low FFM and low BMD highlights the importance of improving body composition in CF patients, in order to prevent future CFBD.