Abstract
BACKGROUND: Assessment of bone health in young children has been hampered by limited reference values for bone mineral content (BMC) and areal bone mineral density (aBMD) by dual energy X-ray absorptiometry (DXA). OBJECTIVES: To identify age, sex, and population ancestry effects on BMC and aBMD and develop smoothed reference ranges for BMC and aBMD in young children. To quantify precision of bone measurements and influence of height-for-age Z-scores on bone Z-scores. METHODS: We recruited 484 healthy children ages 1 to 2 years or 4.5 to 5 years at 2 clinical centers, who were seen once or up to 7 times over a 3-year period. Lumbar spine, distal forearm, and whole-body subtotal (ages ≥ 3 years) BMC and aBMD were measured by DXA. These data were combined with data from the Bone Mineral Density in Childhood Study from children ages 5 to 8.9 years to create the smoothed reference curves. RESULTS: For 1- to 5-year-olds, BMC and aBMD at all skeletal sites increased with age. Age trends differed by sex for BMC and aBMD of the spine, distal one-third radius, ultradistal radius, and by ancestry (Black vs non-Black) for all measures. BMC and aBMD precision (% coefficient of variation) ranged from 1.0% to 4.4%. Height Z-scores were positively associated with bone Z-scores and accounted for 4% to 45% of the variance. CONCLUSIONS: We demonstrate the feasibility of bone density measurements in young children and provide robust reference ranges and stature adjustments for calculation of bone Z-scores at multiple skeletal sites to enable bone health assessments.