Bone Mineral Accretion in Young Children

Compromised bone strength and increased fracture susceptibility pose significant morbidity and health care costs in children. Inadequate childhood bone accretion also may have lifelong consequences. Bone fragility among children with chronic medical conditions is a special concern. Identifying children at-risk for bone fragility and factors affecting bone strength requires understanding normal bone development. Dual energy x-ray absorptiometry (DXA) is the most common method for measuring bone mineral content and bone density in children. There are bone density reference data for children ages 5-20 years. An important gap is the lack of reference data for children ages \< 5 years, who also experience numerous medical conditions that threaten their bone health. Growth and body composition influence bone mineral accrual, and are important for interpreting bone density measurements in children with conditions that threaten bone health. Gross motor skills and subsequent physical activity may also affect bone accrual. Children with chronic illness are at risk of altered body composition, delayed growth and gross motor skills, and restricted physical activity. Understanding independent effects of growth, body composition, gross motor skills and physical activity on bone accrual will improve interpretation of bone density measurements and has important research and clinical applications for identifying risk factors and therapies for young children. This study will involve a longitudinal cohort of 280 children studied every 6 months for 3 years, and a cross-sectional cohort of 240 children measured once. The study will be conducted at 2 clinical centers \[Cincinnati Children's Hospital Medical Center (CCHMC) and the Children's Hospital of Philadelphia (CHOP)\] with equal enrollment at both centers. Measurements will include bone density, growth and body composition, dietary intake, sleep, physical activity and gross motor skills. Results from this study will enable clinical bone health assessment of young children with disorders that threaten bone health, and identify factors that affect bone accrual.