Bone acquisition and loss in children and adults with cystic fibrosis: A longitudinal study,☆☆,,★★

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Abstract

Objectives: To determine patterns of bone mineral acquisition in children and young adults with cystic fibrosis (CF) and to identify clinical and laboratory correlates of change in bone mineral density (BMD).

Study design: Bone mineral and clinical status were assessed in 41 patients with CF (26 female, aged 9 to 50 years) at baseline and 1.5 years later. Bone mineral content of the lumbar spine, femoral neck, and whole body was determined by dual-energy x-ray absorptiometry and expressed as BMD and bone mineral apparent density (BMAD). Changes in weight, height, pubertal status, glucocorticoid use, physical activity, disease severity, and biochemical markers of bone turnover were examined for associations with changes in BMD and BMAD.

Results: Mean BMD Z-scores (adjusted for age and sex) were reduced at the spine, hip, and whole body at baseline in both adults and youths, and decreased further at all sites among youths at follow-up (-0.4 at spine, p < 0.05; —0.3 at hip, p < 0.10; —0.5 for whole body, p < 0.0005). These data indicate failure to gain bone mineral at the expected rate. BMAD was also reduced at follow-up, suggesting that the observed osteopenia could not be explained by small bone size. Bone loss at multiple sites was observed in four youths and two adults. In general, glucocorticoid use, change in body mass, physical activity, and disease severity were the most significant correlates of change in BMD and in BMD Z-score.

Conclusions: Osteopenia in CF generally reflects inadequate gains in bone mineral, although bone loss may occur, particularly in patients requiring glucocorticoid therapy. Late gains in bone mineral may accompany weight gain and pubertal development, but the catch-up appears to be incomplete. (J Pediatr 1998;133:18-27)

Abbreviations

BMAD
Bone mineral apparent density
BMD
Bone mineral density
BMI
Body mass index
CF
Cystic fibrosis
FVC
Forced vital capacity
S-K
Shwachman-Kulczycki score

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From the Departments of Pediatrics and Medicine, Stanford University School of Medicine, Stanford, California, and the Musculoskeletal Research Laboratory, Veterans Affairs Medical Center, Palo Alto, California.

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Supported by National Institutes of Health Grant DK45226 and Cystic Fibrosis Research, Inc. (Dr. Bachrach), the Palo Alto Institute for Research and Education, and the Research Service of the Department of Veterans Affairs (Dr. Marcus).

Reprint requests: Laura K. Bachrach, MD, Room S302, Department of Pediatrics, Stanford Medical Center, Stanford, CA 94305-5208.

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0022-3476/98/$5.00 + 0  9/21/89715