BONE-MINERAL DENSITY IN CHILDREN AND ADOLESCENTS - RELATION TO PUBERTY, CALCIUM INTAKE, AND PHYSICAL-ACTIVITY

The association of height, weight, pubertal stage, calcium intake, and physical activity with bone mineral density (BMD) was evaluated in 50 0 children and adolescents (205 boys and 295 girls), aged 4-20 yr. The BMD (grams per cm(2)) of lumbar spine and total body was measured wit h dual energy x-ray absorptiometry. Lumbar spine volumetric BMD was ca lculated to correct for bone size. BMD and volumetric BMD increased wi th age. During puberty, the age-dependent increment was higher. After adjustment for age, the Tanner stage was significantly associated with all three BMD variables in girls and with spinal BMD in boys. In boys , positive correlations were found between BMD and both calcium intake and physical activity after adjustment for age. Stepwise regression a nalysis with weight, height, Tanner stage, calcium intake, and physica l activity as determinants with adjustment for age resulted in a model with Tanner stage in girls and weight in boys for all three BMD varia bles. The major independent determinant of BMD was the Tanner stage in girls and weight in boys.