Original articles Low bone mineral density in adults with cystic fibrosis

Background—Patients with cystic fibrosis have several risk factors for the develop-ment of low bone mineral density (BMD). To identify the prevalence and clinical cor-relates of low BMD in adult patients with cystic fibrosis, densitometry was performed in 151 patients (83 men) aged 15–52 years. Methods—BMD was measured in the lumbar spine (L1–4) using dual energy x ray absorptiometry (DXA) and quantita-tive computed tomography (QCT). It was also measured in the proximal femur (total hip and femoral neck) using DXA, and in the distal and ultra distal forearm using single energy x ray absorptiometry (SXA). Biochemical markers of bone turnover, vitamin D levels, parathyroid hormone levels, and a variety of anthropo-metric variables were also assessed. Results—Themean (SD) BMDZ scorewas –0.73 (0.85) in the distal forearm, –0.31 (0.92) in the ultra distal forearm, –1.21 (1.18) in the lumbar spine usingDXA, –0.56 (1.36) in the lumbar spine using QCT, –1.25 (1.30) in the femoral neck, and –1.01 (1.14) in the total hip. 34 % of patients had a BMD Z score of –2 or less at one or more skeletal sites. Body mass index (0.527, p = 0.01), percentage predicted forced expiratory volume in one second (0.388, p = 0.01), and physical activity (0.249, p = 0.05) were posi-tively related to the mean BMD Z score. Levels of C reactive protein (–0.328, p = 0.01), parathyroid hormone (–0.311, p = 0.01)andbiochemicalmarkersofbone turn-over (osteocalcin –0.261 and bone specific alkaline phosphatase –0.249, p = 0.05) were negatively related to the mean BMD Z score. Vitamin D insuYciency (25-hydroxyvitamin D <15 ng/ml) was preva-lent (53/139 patients, 38%) despite supplementation with 900 IU vitamin D per day. Conclusions—Low bone density is preva-lent in adult patients with cystic fibrosis. Current levels of vitamin D supplementa-tion appear to be inadequate