Objective: To evaluate the relationship between chronic glucocorticoid (GC) exposure and bone mineral density (BMD) in children with rheumatic diseases and inflammatory bowel disease.
Study design: Lumbar spine BMD was measured by DXA in 86 GC-treated children (66% female, age 8-20 years, mixed ethnicity) screened for a multi-center intervention trial. Predictors of spine BMD z-score and vitamin D [25(OH)D] were examined by multivariable linear regression.
Results: Mean prior year and lifetime cumulative GC exposure was 77.8 mg/kg and 224.6 mg/kg, respectively. BMD z-scores ranged from -3.7 to 2.2 SD (-1.1 +/- 1.2, mean +/- SD). Lower BMD z-scores were associated with increased prior year average daily GC dose (p = 0.03), decreased height z-score (p = 0.003), and decreased 25(OH)D concentrations (p = 0.03), but explained only a small proportion of BMD variability (adjusted R2 = 0.29). The 25(OH)D levels were <20 ng/ml in 45% of patients, and low 25(OH)D was associated with non-Caucasian ethnicity (p <0.001), increased age (p = 0.004), increased parathyroid hormone (p = 0.03), and residing in the Boston area (p <0.001).
Conclusions: Although GC exposure is significantly associated with BMD z-score, the association is too variable to serve as a consistent predictor of reduced BMD in children. Vitamin D insufficiency is common and may contribute to skeletal deficits in this population.