Purpose To investigate the age-related changes in muscle density and the relationship between muscle density and bone mineral density (BMD). Materials and Methods The QCT BMD was obtained in a cohort of 685 patients (aged 20-80 years,271 males,median age 58 years; 414 females,median age 60.5 years). Bilateral paraspinal muscle density in L3 level and bilateral psoas muscle density in L5 level were determined on the axial QCT images. Patients were grouped according to age on a 10-year scale. Changes in muscle density among each group were calculated and correlated with BMD. The mean annual decrease rates of muscle density were analyzed. Regression analyses were made with BMD as the dependent variable,age as the single independent variable as well as using age and muscle density as independent variables. Results The paraspinal muscle density began to decrease from 60-70 years of age in males and 40-50 years in females,with the mean annual decrease rates of 0.5% and 0.9% respectively. The psoas muscle density decreased slower than the paraspinal muscle density,with the mean annual decrease rates of 0.3% in males and 0.4% in females. The adjust R2s of the formulas of linear regressions of BMD vs. Age are 0.27 and 0.33 in males and females respectively,which increased to 0.33 and 0.57 when adding muscle density as an independent variable. Conclusion The muscle density decreases with age. Besides the co-effect with age,muscle density itself is positively correlated with BMD.%目的 探讨肌肉密度随年龄的变化趋势及其与骨密度的关系.资料与方法 以2009-11～2010-10因各种原因来北京积水潭医院行QCT骨密度测量的685例20～80岁之间的患者为测量对象,女414例,中位年龄60.5岁,男271例,中位年龄58.0岁,使用定量CT (QCT)软件在L3水平轴位图像上测量双侧竖脊肌密度,在L5水平轴位图像上测量双侧腰大肌密度.以10岁为一个年龄段分析肌肉密度变化趋势,并计算肌肉密度的年平均下降率.以骨密度为因变量,以年龄为单一自变量和加入肌肉密度作为自变量分别进行回归分析.结果 男、女竖脊肌密度分别从60～70岁组、40～50岁组开始有显著下降,年平均下降率分别为0.5％、0.9％.男、女腰大肌密度下降速度较竖脊肌慢,年平均下降率分别为0.3％、0.4％.加入肌肉密度作为自变量之后,与单独使用年龄作为自变量相比,男、女性回归方程校正决定系数分别由0.27、0.53升高至0.33、0.57,均具有统计学意义.结论 肌肉密度随年龄增长而下降,且肌肉密度对于骨密度有除年龄以外的正性促进作用.
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