Effects of growth during infancy and childhood on bone mineralization and turnover in preterm children aged 8-12 years.

To investigate the effect of growth on later bone mass and turnover, bone mineral content (BMC) and density (BMD: dual X-ray absorptiometry (QDR 1000W) and single photon absorptiometry (Lunar SP2)) and bone turnover (plasma osteocalcin, urine deoxypyridinoline) were measured at 8-12 y in 244 preterm children who had weight and height measured at 18 mo and 7.5-8 y corrected age. Weight and length at birth, 18 mo, 7.5-8 y and current follow-up showed increasingly strong, positive correlations with bone area, BMC and BMD. After adjusting for current size, there were significant negative associations between earlier size measurements and later whole body and lumbar spine bone mass which were stronger for length than for weight, and a negative relationship between birthweight for gestation and later radial bone mass; but no relationship with bone turnover. Current calcium intake and activity level had no independent effect on bone mass. Bone mass at 8-12 y is related to current bone and body size, which tracks throughout childhood. However, amongst children of the same current size, those who have shown the greatest increase in size, particularly in height, have the highest bone mass. These findings raise the hypothesis that improving linear growth in vulnerable children may be important in maximizing bone mass.