Increased Rate of Fractures and Severe Kyphosis: Sequelae of Living into Adulthood with Cystic Fibrosis

doi:10.1059/0003-4819-128-3-199802010-00004

Increased Rate of Fractures and Severe Kyphosis: Sequelae of Living into Adulthood with Cystic Fibrosis

From the University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; and Duke University Medical Center, Durham, North Carolina. Acknowledgments: The authors thank Susan Hayden for support and patience; Drs. Thomas Egan, Frank Detterbeck, and Linda Paradowski (lung transplantation physicians) and Kristi Gott, Jean Rea, and Judy McSweeney (lung transplantation coordinators) for managing the cystic fibrosis lung transplant center, which encouraged the referrals that allowed this study to be done; and Mary Bates for manuscript assistance. Grant Support: By Cystic Fibrosis Foundation grant A936 and the Verne S. Caviness General Center for Clinical Research (NIH RR00046). Requests for Reprints: Robert Aris, MD, Division of Pulmonary Medicine, CB# 7020, 724 Burnett-Womack Building, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7524. Current Author Addresses: Drs. Aris and Winders: Division of Pulmonary Medicine, CB# 7020, 724 Burnett-Womack Building, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7524.

Abstract

Background: Osteoporosis occurs in patients with cystic fibrosis as they age, but its clinical implications are not well defined.

Objective: To determine the clinical effect of decreased bone mineral density in adults with cystic fibrosis and to assess possible clinical predictors of osteoporosis.

Design: Retrospective cohort study.

Setting: Academic cystic fibrosis center.

Patients: 70 adults with late-stage cystic fibrosis who were referred for lung transplantation.

Measurements: Bone mineral density was measured with dual-energy x-ray absorptiometry, patient-reported fracture events were confirmed by radiography, and kyphosis angles were measured by using the Cobb method.

Results: Mean bone mineral densities for the spine, femur, and total body were severely depressed in patients with cystic fibrosis, averaging 2 SDs below those of age-matched normal controls (P < 0.001). Patient interviews showed that 54 fractures had occurred over 1410 patient-years, and chest radiographs showed evidence of 14 additional rib and 62 additional vertebral compression fractures. The database (which covered 1410 patient-years) showed that fracture rates were approximately twofold greater in women with cystic fibrosis aged 16 to 34 years (P = 0.015) and men with cystic fibrosis aged 25 to 45 years (P = 0.04) than in the general population. Vertebral compression and rib fractures were 100- and 10-fold more common than expected, respectively (P < 0.001 for both comparisons). The mean kyphosis angle (±SD) for this group was markedly abnormal (44 ± 14 degrees; 62% ≥ 40 degrees) and probably contributed to diminished stature (mean height loss, 5.8 cm in men with cystic fibrosis and 5.9 cm in women with cystic fibrosis). Cumulative prednisone dose, body mass index, and age at puberty were the strongest predictors of bone mineral density.

Conclusions: Osteoporosis is universal in adults with late-stage cystic fibrosis, and its complications include increased fracture rates and severe kyphosis.