Normal bone mineral density in cystic fibrosis

Background-Osteoporosis has been reported as a complication of cystic fibrosis (CF). Aims-To measure bone mineral density (BMD) in non-acutely ill adults and bone mineral content (BMC) in children with CF. Methods -We analysed data from 28 adults and 13 children with CF. Corticosteroid use was minimal for the year prior to study in both groups. Dual x ray absorptiometry was used to measure total body and regional bone mineral density in adults. In children, whole body BMC was measured. Lean tissue mass (LTM) was also measured in all subjects. There were two control groups: A (matched for LTM and height, in addition to age and gender); and B (matched for age and gender only). Results-There was no difference in whole body or regional BMD density between adult CF patients and control A subjects. Both whole body and regional BMD were significantly lower in adult CF patients than in control B subjects. Total body BMD was correlated with body mass index, LTM, and percent fat in both CF and control subjects. There was no significant correlation between total body BMD or regional BMD and either NIH clinical status scores, or pulmonary function tests in adults. There was no difference in total body BMC between CF children and control A subjects. Total body BMC was significantly lower in CF children than in control B subjects. There was no correlation between pulmonary function results and BMC in children. Conclusion-Osteopenia and osteoporosis in CF may be caused more by malnutrition and chronic use of intravenous or oral corticosteroids than by a CF related inherent defect in BMD. Appropriate "normal" data should be selected when determining whether or not osteoporosis is present in a CF patient.