Bone mineral measurements and their relation to body density in children, youth and adults

This study was designed to examine the relation of bone mineral measurements and body density and to develop estimates of changes in the mineral content of the fat-free body during growth and development. Bone mineral measurements and body densities were determined on 292 children and adults in samples of subjects drawn from two geographic locations in the United States. A 4 x 2 x 2 factorial plan was used with 4 maturation groups, males and females, and blacks and whites. The study was conducted in central Illinois (N = 164) and replicated in Arizona (N = 128). Bone mineral measurements included both bone mineral content (gm/cm) and bone width (cm) of the radius and ulna using photon absorptiometry. Body density was determined by underwater weighing and measurement of residual lung volume. Large changes occurring in bone mineral from prepubescence to adult are in accord with previous published bone mineral data. Significant positive associations were found between bone mineral measurements and body density for both correlation, partial correlation and multiple regression analysis. Based on the association (partial regression coefficient) of radius bone mineral with body density (holding skinfolds constant), the estimation of fat-free body mineral content in the prepubescent child was derived. An estimated mineral content of 5.2% was found for the prepubescent child as compared to 6.6% for adult men and 6.0% for adult females. These results support the concept that children have a lower mineral content of the fat-free body than the adults and that body density and fat-free density are significantly affected by the lower bone mineral content.