Spine and femur density using dual-photon absorptiometry in US white women.

Bone mineral density (BMD) of the spine (n = 892) and femur (n = 634) was measured using dual-photon absorptiometry in normal white women from seven diverse locations. The same model commercial scanner with a 153Gd source was used in all locations (SD = 1.3% among locations). There was not an age-associated decrease of spinal BMD during young adulthood (20-40 years); the correlation of age and femoral BMD in this period was low but significant (r = -0.21). There was a narrow range of intra-population variation at all ages (10-12%). The cross-sectional data showed an average diminution of about 20% in the spine and 25% in the femur between 40 and 70 years of age, followed by a continued but slower, decrease of density in older women. Adjustment of values for height and weight was called for mainly at extremes of body size.