DETERMINANTS OF RADIAL BONE-DENSITY AS MEASURED BY PQCT IN PREMENOPAUSAL AND POSTMENOPAUSAL WOMEN - THE ROLE OF BONE SIZE

The aim of the present study was to examine the influence of anthropom etric, hormonal, and geometric factors on the variability of radial bo ne mineral density (BMD) in women. In 583 healthy pre- and postmenopau sal females (aged 40-60 years) radial total (ED) and trabecular BMD (T BD) was measured by peripheral quantitative computerized tomography at the nondominant distal forearm. In addition, 29 women who had suffere d a Colles' fracture after minor trauma were also evaluated. There was no age-dependent change in radial ED and TBD before menopause. We fou nd a negative correlation between BMD and age and years since menopaus e (YSM) in postmenopausal women (BD = 422.73 - 2.342 age - 6.308YSM; r = 0.36,p = 0.0001, n = 128). The variation of YSM, body mass index (B MI), and age accounted for 20% of the variability of ED in postmenopau sal women. In contrast, in premenopausal women, only 3% of the variabi lity could be explained by anthropometric variables. Bone mineral cont ent (BMC) and bone area, but not BMD at the distal radius, were signif icantly correlated to grip strength (r = 0.25, p = 0.006 for BMC, r = 0.26, p = 0.003 for area). The cross-sectional bone area of the CT sli ce showed a significant increase with aging (y = 263.02 + 1.25x; r = 0 .14, p = 0.0009). There was a strong negative correlation between bone area and ED and TBD (y = 516.04 - 0.668x; r = -0.57, p < 0.0001 for E D). If BMD is normalized for BA, variation is reduced by 32% (for ED) and 10% (for TBD), respectively. Women with Colles' fracture had a sig nificantly lower TBD normalized for BA (fracture group [-0.71 +/- 0.88 ] vs. normals [0.03 +/- 0.99]; p = 0.00009). Our results show that YSM and BMI are predictors of postmenopausal BMD. However, radial BMD is influenced strongly by geometric variables such as cross-sectional bon e area.