Relation of height and weight to the regional variations in bone mass among Japanese-American men and women.

We examined the magnitude of regional variations in bone mass among elderly, Japanese-American men and women. All subjects had bone measurements at the calcaneus, and at the distal and proximal radius sites. A subset of the women had, in addition, spine bone mass measurements. To provide a common measurement scale, the bone measurements were converted to age- and sex-specific Z-scores. The Z-scores between pairs of bone sites were then subtracted to yield the differences in bone mass between bone sites (expressed in Z-score units). For most individuals the differences were less than 1.0 Z-score; however, 12%-20% of the differences were at least 1 Z-score apart. The most similar sites were the distal and proximal radius: different regions within the same bone. Among the other bone pairs, the calcaneus and spine were the most similar to one another. The magnitudes of the differences in bone mass were associated with height and weight. Heavier subjects, for instance, had greater calcaneus than radius bone mass measurements, and greater spine than radius measurements. The spine and calcaneus are more weight-bearing than the radius sites. Associations were observed up to 0.25 Z-score per 10 kg difference in weight. Height was associated with bone mass differences in an opposite direction to weight. Taller subjects had greater bone mass at the radius sites than expected from their calcaneus or spine bone measurements (0.1 to 0.2 Z-score difference per 5 cm difference in height). Bone width partly explained the associations with height; that is, adjusting the radius widths reduced the associations with height. Overall, our results indicate that small to moderate differences between bone sites were common among our study population, and that the magnitudes of the differences were associated with height and weight.