Mehlig K, Freyer E, Tognon G, Malmros V, Lissner L, Bosaeus I
Dept. of Public Health and Community Medicine, Sahlgrenska Academy, University of Gothenburg, Sweden.
Dept. of Public Health and Community Medicine, Sahlgrenska Academy, University of Gothenburg, Sweden.
Clin Nutr ESPEN. 2015 Feb;10(1):e26-e32. doi: 10.1016/j.clnme.2014.11.001. Epub 2014 Nov 8.
Bioelectrical impedance spectroscopy (BIS) is a versatile field tool to obtain information about body composition (BC), if prediction equations are available that are valid for the group under consideration. We aimed to validate prediction equations for total body skeletal muscle mass (TBSMM) developed in healthy 75-year olds from the Gothenburg area (Sweden) in a similar sample examined at age 80. We give new prediction equations for fat mass (FM), fat-free mass (FFM), and TBSMM that are based on the entire group of elderly subjects, using values from Dual-energy X-ray spectrometry (DXA) as reference standard. Finally, we describe the longitudinal change in BC in the subset of subjects, who participated at both age 75 and 80.
Body composition was measured by DXA and multiple-frequency BIS at age 75 (n = 111) and 80 (n = 91) years. Ordinary and mixed linear regression was used to examine previous and new prediction equations. Longitudinal change was assessed by paired sample t-test.
The prediction equations for TBSMM developed in 75-year old subjects showed good validity when applied to the sample of 80 year olds. The results were independent of the presence of a metal prosthesis in hip or knee. New, sex-specific prediction equations for FM, FFM, and TBSMM were derived for 75 - 80 year-old subjects that further improved the accuracy of prediction. Using DXA-derived BC at ages 75 and 80, we observed a decline in TBSMM in both sexes, which was mainly due to muscle loss in the legs. In men, the decrease in trunk FFM was accompanied by an increase in FM, leaving no overall weight change in the trunk. When the 5-year change in TBSMM was based on longitudinal BIS measurements, the results from DXA were reproduced only when the prediction was based on BIS-values at 50 kHz.
Good cross-sectional validity of BIS equations for TBSMM was found in a population sample of 80-year olds. The presence of a metal prosthesis did not influence the quality of prediction. New prediction equations for FM, FFM, and TBSMM need to be evaluated in an independent sample.
如果有适用于所研究群体的预测方程，生物电阻抗光谱法（BIS）是一种获取身体成分（BC）信息的通用现场工具。我们旨在验证在瑞典哥德堡地区75岁健康人群中开发的全身骨骼肌质量（TBSMM）预测方程在80岁的类似样本中的有效性。我们给出了基于全体老年受试者的脂肪量（FM）、去脂体重（FFM）和TBSMM的新预测方程，以双能X线吸收法（DXA）测量值作为参考标准。最后，我们描述了在75岁和80岁均参与研究的受试者亚组中身体成分的纵向变化。
在75岁（n = 111）和80岁（n = 91）时，通过DXA和多频BIS测量身体成分。使用普通线性回归和混合线性回归来检验先前的和新的预测方程。通过配对样本t检验评估纵向变化。
在75岁受试者中开发的TBSMM预测方程应用于80岁样本时显示出良好的有效性。结果不受髋部或膝部金属假体的影响。为75 - 80岁受试者推导了新的、性别特异性的FM、FFM和TBSMM预测方程，进一步提高了预测准确性。使用75岁和80岁时DXA得出的身体成分数据，我们观察到两性的TBSMM均下降，这主要是由于腿部肌肉流失。在男性中，躯干FFM的减少伴随着FM的增加，躯干总体重没有变化。当基于纵向BIS测量得出TBSMM的5年变化时，仅当预测基于50kHz的BIS值时，DXA的结果才能重现。
在80岁人群样本中发现BIS方程对TBSMM具有良好的横断面有效性。金属假体的存在不影响预测质量。FM、FFM和TBSMM的新预测方程需要在独立样本中进行评估。
