DETERMINANTS OF BONE MINERAL DENSITY IN CHILDREN WITH CHRONIC INFLAMMATORY BOWEL DISEASE

Abstract

Osteoporosis has been reported in adult patients with inflammatory bowel disease. The aims of this study were to evaluate bone mineral density (BMD), nutritional status and determinants of BMD of children with inflammatory bowel disease. Patients: Fifty-five patients (34 boys and 21 girls), aged 4 to 18 years, participated in the study. 22 children suffered from Crohn's disease and 33 children from ulcerative colitis. Methods: Lumbar spine and total body BMD and body composition were assessed by Dual Energy X-ray Absorptiometry (DXA). The results were expressed as standard deviation scores (SDS). Lean body mass was also assessed by Bio-electrical impedance analysis (BIA). An X-ray of the left hand was taken for the assessment of bone age. Patients with BMD SDS below -1.5 received calcium and vitamin D supplementation. Yearly measurements during two years were performed in 21 patients. Results: The mean lumbar spine BMD and total body BMD SDS were lower than normal (-0.75 and -0.95, both p<0.001). Also height SDS and body mass index SDS were decreased. The decrease in BMD SDS could not be explained by delay in bone maturation. The cumulative dose of prednisone correlated negatively with lumbar spine BMD SDS (r=-0.32, p<0.02). Body mass index SDS correlated positively with total body BMD SDS (r=0.36, p<0.02). Patients with Crohn's disease had lower lumbar spine and total body BMD SDS than patients with ulcerative colitis, even after adjustment for cumulative dose of prednisone. In the longitudinal data cumulative dose of prednisone between the measurements correlated negatively with the change in lumbar spine and total body BMD SDS. BMD SDS change of patients who received calcium and vit. D did not differ from patients who did not get this supplementation. Lean tissue mass measured by DXA had a strong correlation with lean body mass measured by BIA (r=0.98). Conclusions: Children with inflammatory bowel disease have a decreased BMD. Children with Crohn's disease have a higher risk to develop osteopenia than children with ulcerative colitis. Corticosteroid therapy and nutritional status are important determinants of BMD in these patients.