Smith D M, Khairi M R, Norton J, Johnston C C
J Clin Invest. 1976 Sep;58(3):716-21. doi: 10.1172/JCI108518.
It has been postulated that the rate of mineral loss in postmenopausal women remains constant with aging and that the decreased activities of daily living associated with aging contribute to mineral loss. These hypothese were examined by measuring the bone mineral content at the midshaft of the radius with the photon absorption technique. The estimated rate of loss was calculated in a cross-sectional study as the regression coefficient of bone mineral content vs. age and in a longitudinal study as the regression coefficient of bone mineral content vs. time. In the cross-sectional study, Group A, which consisted of 264 women aged 50-72 yr, had an estimated rate of loss of -0.0114 +/- 0.0014 (SE) g/cm per yr. Group B, which consisted of 266 women aged 73-96 yr, had an estimated rate of loss of -0.0055 +/- 0.0017 g/cm per yr. In the longitudinal study, Group C consisted of 33 women aged 51-65 yr who were followed for an average of 4.5 yr with a mean number of 16 visits per subject; they were found to have a mean rate of loss of -0.00990 +/- 0.00107 g/cm per yr. Group D consisted of 38 women aged 70-91 yr who were followed for an average of 3.8 yr with a mean number of 31 visits per subjects; they were found to have a mean rate of loss of -0.00020 +/- 0.00236 g/cm per yr. The estimated and directly measured rates of loss were more rapid in the younger groups than in the older groups (A vs. B, P less than 0.001; C vs. D, P less than 0.001). These data demonstrate that the mean rate of mineral loss is not constant with aging and that in elderly subjects it is significantly slower than that of the earlier postmenopausal years. Since the elderly women were the less active, these findings suggest that factors other than decreased physical activity are more important in determining the rates of mineral loss.
据推测，绝经后女性矿物质流失速率随年龄增长保持恒定，且与衰老相关的日常生活活动减少会导致矿物质流失。通过光子吸收技术测量桡骨中段的骨矿物质含量，对这些假设进行了检验。在横断面研究中，将骨矿物质含量对年龄的回归系数计算为估计的流失速率；在纵向研究中，则将骨矿物质含量对时间的回归系数计算为估计的流失速率。在横断面研究中，A组由264名年龄在50 - 72岁的女性组成，估计流失速率为每年-0.0114±0.0014（标准误）g/cm。B组由266名年龄在73 - 96岁的女性组成，估计流失速率为每年-0.0055±0.0017 g/cm。在纵向研究中，C组由33名年龄在51 - 65岁的女性组成，平均随访4.5年，每位受试者平均就诊16次；她们的平均流失速率为每年-0.00990±0.00107 g/cm。D组由38名年龄在70 - 91岁的女性组成，平均随访3.8年，每位受试者平均就诊31次；她们的平均流失速率为每年-0.00020±0.00236 g/cm。较年轻组的估计流失速率和直接测量的流失速率比年长组更快（A组与B组比较，P＜0.001；C组与D组比较，P＜0.001）。这些数据表明，矿物质流失的平均速率并非随年龄增长而恒定，且在老年受试者中明显慢于绝经后早期。由于老年女性活动较少，这些发现表明，除了身体活动减少之外，其他因素在决定矿物质流失速率方面更为重要。
