Osteopenia in Adults with Cystic Fibrosis

Purpose: To examine the frequency and severity of osteopenia in adults with cystic fibrosis and the clinical variables associated with reduced bone mineral.

Patients And Methods: The bone mineral status of 22 white adults (14 women) with cystic fibrosis was compared with normative data from healthy white control subjects in a university medical center. Lumbar spine, femoral neck, and whole-body bone mineral was determined by dual energy x-ray absorptiometry and expressed as bone mineral content (g), bone mineral density (g/cm2), and bone mineral apparent density (g/cm3). Bone mass was related to age, body mass, gonadal function, pulmonary status, and glucocorticoid exposure to identify variables associated with reduced bone mineral in cystic fibrosis.

Results: Bone mineral in adults with cystic fibrosis was significantly below expected values for age and sex at all sites using all expressions of bone mass. The mean Z-score was -2.8 for the lumbar spine bone density, -2.5 for the femoral neck, and -2.0 for the whole body. Bone mineral apparent density (a term that minimizes the influence of bone dimensions) was also significantly reduced in patients at the lumbar spine (p < 0.0001) and femoral neck (p < 0.001 to p < 0.0001), indicating that the bone mineral deficit seen in adults with cystic fibrosis could not be attributed to differences in bone size. Age, weight, height, and body mass index were significantly correlated with bone mineral. Pulmonary status, glucocorticoid use, and gonadal function failed to predict bone mineral status.

Conclusions: Osteopenia and osteoporosis occur commonly in young adults with cystic fibrosis. Age and body mass are predictive of bone mineral, although the pathogenesis of this bone mineral deficit is likely multifactorial.