Evidence for both generalized and regional low bone mass among elderly women

The consistency of bone mass measurements across bone sites was examined in a cohort of elderly Japanese-American women. The study included 744 women of mean age 66.6 years (age range 47-82 years) who had bone densitometry measurements at the spine, calcaneus, and distal and proximal radius. The women were classified at the four bone sites as in the lower, middle, or upper bone mass tertile for their age. Slightly more than half (56%) of the women were in the lower tertile at one or more of the bone sites, and such women were usually in the lower category at more than one site. Of the women, 24% were classified in the lower tertile at all four sites. Furthermore, as a group, women classified as in the low bone mass category at any one site had a low average bone mass at all four sites. Prospectively, the number of low bone mass sites predicted the risk of new spine fractures after adjusting for age and the number of spine and nonspine prevalent fractures. The risk increased approximately 1.3-fold for each additional low bone mass site. A subgroup (15%) of the population had marked heterogeneity in bone mass between sites. These women had one or more lower tertile bone mass site(s) and one or more upper tertile bone mass site(s). The results suggest that osteoporosis may occur as either a generalized or as a regional disorder.