Low bone mineral density in adults with cystic fibrosis
- C S Hawortha,
- P L Selbyb,
- A K Webba,
- M E Dodda,
- H Mussona,
- R McL Nivena,
- G Economoua,
- A W Horrocksa,
- A J Freemontc,
- E B Mawerb,
- J E Adamsd
- aAdult Cystic Fibrosis Unit, Wythenshawe Hospital, Manchester M23 9LT, UK, bDepartment of Medicine, University of Manchester, Manchester Royal Infirmary, Manchester M13 9WL, UK, cOsteoarticular Pathology, Department of Rheumatology, dDepartment of Diagnostic Radiology, eUniversity of Manchester, Manchester M13 9PT, UK
- Dr A K Webb.
- Received 4 January 1999
- Revision requested 10 March 1999
- Revised 21 June 1999
- Accepted 24 June 1999
Abstract
BACKGROUND Patients with cystic fibrosis have several risk factors for the development of low bone mineral density (BMD). To identify the prevalence and clinical correlates 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 energyx ray absorptiometry (DXA) and quantitative 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 anthropometric variables were also assessed.
RESULTS The mean (SD) BMD Z score was –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 using DXA, –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 positively related to the mean BMD Z score. Levels of C reactive protein (–0.328, p = 0.01), parathyroid hormone (–0.311, p = 0.01) and biochemical markers of bone turnover (osteocalcin –0.261 and bone specific alkaline phosphatase –0.249, p = 0.05) were negatively related to the mean BMD Z score. Vitamin D insufficiency (25-hydroxyvitamin D <15 ng/ml) was prevalent (53/139 patients, 38%) despite supplementation with 900 IU vitamin D per day.
CONCLUSIONS Low bone density is prevalent in adult patients with cystic fibrosis. Current levels of vitamin D supplementation appear to be inadequate.
