INFLUENCE OF AGING AND MENOPAUSE IN DETERMINING VERTEBRAL AND DISTAL FOREARM BONE LOSS IN ADULT HEALTHY WOMEN

In order to assess the relative influence of aging and menopause in de termining the decrease of bone mass in adult women, two groups of norm al subjects were examined in this retrospective, cross-sectional study . In group A, bone mineral density (BMD) was evaluated at spine (L2-L4 ) by dual X-ray absorptiometry (DXA) (Hologic QDR-1000); in group B, B MD was measured at the distal forearm by single photon absorptiometry (SPA) (Osteometer DT 100). Both groups were further divided into two s ubgroups: A1 and BI included women with the same postmenopausal, but d ifferent chronological age; A2 and B2 included women with the same chr onological, but different postmenopausal age. BMD and BMI-corrected BM D (cBMD) were plotted versus age and years since menopause, respective ly. Mathematical analysis of the correlation curves between BMD and ch ronological age showed that the decrease of BMD is very similar at spi ne and forearm, and is better fitted by a quadratic function. Age-rela ted fractional bone diminution shows a progressive increase with aging (at spine: -0.38%/year at 45 years, -0.81%/year at 50, -1.3%/year at 55 and -1.9%/year at 60. At forearm: -0.5%/year at 50 years, - 1.1%/ye ar at 55 and - 1.68%/year at 60). On the other hand, menopause-related BMD decrement is very evident during the first year since menopause ( at spine: -8.1%/year; at forearm: -3.4%/year), and progressively decre ases, according to a logarithmic function. Ten years later, yearly dim inution of BMD is below 1%/year and 0.4%/year at spine and forearm, re spectively. At this time, age contributes to determine bone loss for 2 /3 and menopause for 1/3.