Determinants of One-year Response of Lumbar Bone Mineral Density to Alendronate Treatment in Elderly Japanese Women with Osteoporosis

The purpose of this study was to determine factors that could predict the one-year response of the lumbar bone mineral density (BMD) to alendronate treatment in elderly Japanese women with osteoporosis. Eighty-five postmenopausal women with osteoporosis, all of whom were between 55-88 years of age, were treated with alendronate (5 mg daily) for 12 months. Serum calcium, phosphorus, and alkaline phosphatase (ALP) and urinary NTX levels were measured at the baseline and 6 months, and lumbar (L1-L4) BMD was measured by dual energy X-ray absorptiometry at the baseline and 12 months. Multiple regression analysis was used to determine factors that were correlated with the percent change in lumbar BMD at 12 months. Lumbar BMD increased by 8.1 % at 12 months with a reduction in the urinary NTX level by 51.0 % at 6 months. Baseline lumbar BMD (R²=0.226, p < 0.0001) and percent changes in serum ALP and urinary NTX levels (R²=0.044, p < 0.05 and R²=0.103, p < 0.001, respectively) had a negative correlation with the percent change in lumbar BMD at month 12, while the baseline number of prevalent vertebral fractures (R²=0.163, p < 0.001), serum ALP level, and urinary NTX level (R²=0.074, p < 0.05 and R²=0.160, p < 0.001, respectively) had a positive correlation with it. However, baseline age, height, body weight, body mass index, years since menopause, serum calcium and phosphorus levels, and percent changes in serum calcium and phosphorus levels at 6 months did not have any significant correlation with the percent change in lumbar BMD at 12 months. These results suggest that lumbar BMD was more responsive to one-year of alendronate treatment in elderly osteoporotic Japanese women with lower lumbar BMD, more prevalent vertebral fractures, and higher bone turnover, who showed a greater decrease in bone turnover at 6 months, regardless of age, years since menopause, and physique. Alendronate may be efficacious in elderly Japanese women with evident osteoporosis that is associated with high bone turnover, and the percent changes in serum ALP and urinary NTX levels at 6 months could predict the one-year response of lumbar BMD to alendronate treatment.