Risk factors for low bone mineral density in pediatric inflammatory bowel disease: the positive role of physical activity.

Objective: In pediatric inflammatory bowel disease (IBD), the prevalence of low bone mineral density (BMD) and bone fractures and the relationship between these are still debated. Our aim was to report data from a cohort of pediatric patients with IBD.

Patients And Methods: Cross-sectional assessment of growth and BMD [(dual-energy x-ray absorptiometry (DXA)] and retrospective chart review were performed to report the lifetime prevalence of bone fractures and clinical associations with patients' data.

Results: We examined 216 patients with IBD, 8-25 years old (median: 14 years). Low BMD was found in 12.5% (spine) and 27% (total body). Multiple regression analysis showed that BMD was predicted by Z-scores for height and weight at DXA. History of menstrual irregularities and nasogastric tube feedings was associated with lower BMD, whereas physical activity and higher Z-score for height at DXA were associated with higher BMD.The prevalence of lifetime fractures was 11.8%. Patients with a history of fractures had lower Z-scores for spine BMD (-1.20 vs. -0.69, P=0.020) and total-body BMD (-1.30 vs. -0.75, P=0.014) compared with those without a history of fractures. Patients with spine BMD Z-score of up to -2 SD score had significantly increased prevalence of fractures compared with those with Z-score more than -2 SD score (28 vs. 10%, P=0.015).

Conclusion: This study provides further insight into risk factors for low BMD in pediatric IBD. Novel findings were the association between low BMD and fractures, and the positive relationship between BMD and physical activity.