To evaluate the relationship between chronic glucocorticoid (GC) exposure and bone mineral density (BMD) in children with rheumatic diseases and inflammatory bowel disease.
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.
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).
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.