CORRELATES OF OSTEOPENIA IN PATIENTS WITH CYSTIC-FIBROSIS

Objective. As the expected survival improves for individuals with cyst ic fibrosis, these individuals face myriad medical complications. The goals of this study were to examine the prevalence of osteopenia in ch ildren and adults with cystic fibrosis and to elucidate the risk facto rs associated with deficits in bone mineral. Methodology. We compared bone mineral levels in 49 patients (30 female and 19 male) ages 8 thro ugh 48 years with those of age- and sex-matched control subjects. Lumb ar spine, femoral neck, and whole-body bone mineral were measured by d ual-energy radiographic absorptiometry and expressed in terms of bone mineral content, areal bone density (BMD), and bone mineral apparent d ensity (BMAD), which corrects for differences in bone size. Clinical v ariables were evaluated as potential correlates of bone mineral. Resul ts. Patients with cystic fibrosis had significantly less bone mineral than did control subjects at all sites using all expressions of bone m ass. Mean BMD z scores were -1.7 (lumbar spine), -1.9 (femoral neck), and -1.2 (whole body). BMAD z scores also were significantly low for a ge and gender. Twenty-six of the 49 patients (8 adolescents) had signi ficant osteopenia according to their BMD z scores; 14 of the 45 patien ts (5 adolescents) with available BMAD z scores had significantly low values at one or more sites. Age, pubertal stage, body mass, caloric e xpenditure, illness severity, glucocorticoid therapy, and gonadal func tion predicted bone mineral status. Serum parathyroid hormone and calc ium, carbohydrate intake, and weight-bearing activity had limited pred ictive value. Daily calcium intake and cystic fibrosis transmembrane r egulator genotype did not predict bone mineral status. Conclusions. Os teopenia is common at all ages in cystic fibrosis, suggesting that ina dequate bone mineral accretion as well as increased bone loss contribu te to the deficits in bone mineral observed. Several clinical factors seem to contribute to these deficits.