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AGEING: BIOLOGY AND NUTRITION: Edited by Jürgen M. Bauer and John E. Morley


Body composition measurements in older adults

Bauer, Jüergen M.a; Morley, John E.b

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Current Opinion in Clinical Nutrition and Metabolic Care: January 2020 - Volume 23 - Issue 1 - p 1-3
doi: 10.1097/MCO.0000000000000620
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Since the sentinel article by Baumgartner et al.[1] in 1998, there has been an increased interest in the importance of muscle mass loss (sarcopenia) as a cause of multiple health-related problems in older persons. Loss of skeletal muscle is associated with weakness, falls, fractures, fear of falling, fatigue, depression, cognitive impairment, frailty, disability, and death [2]. Despite this observation there has been increasing recognition that muscle mass is weakly related to muscle strength and function [3,4]. This has led to a shift in recent sarcopenia definitions with a greater emphasis on muscle strength and muscle function rather than on muscle mass [5–11]. Recently the GLIM (Global Leadership Initiative on Malnutrition) criteria included reduced muscle mass as a phenotypic criterion for the diagnosis of malnutrition, a condition with the highest prevalence rates in older patients [12]. These two examples may illustrate the growing interest in body composition measurements in the older population.

Numerous methods for the assessment of muscle mass have been developed. Calf circumference was the original surrogate marker for calf muscle and it was reasonably correlated with calf muscle mass as measured by magnetic resonance imaging [13]. Calf circumference corrected for sex, age, and ethnicity was also highly correlated with Dual-energy X-ray absorptiometry (DEXA) measurements of appendicular skeletal mass [14]. The SARC-F is a highly specific rapid screen for sarcopenia [15] whose sensitivity is greatly improved by adding calf circumference [16].

Bioelectrical impedance analysis (BIA) is used to estimate muscle mass on the basis of the measurement of tissue conductivity and algorithms that are developed with the help of a reference method. BIA is therefore considered as a doubly indirect method. A recent overview concluded that there is still a lack of standardization of BIA for the assessment of muscle mass which may have contributed to the wide range of prevalence rates in different studies [17]. BIA may overestimate muscle mass by approximately 2 kg [18]. Both fluid overload and dehydration alter the accuracy of the measurements. Recently measuring phase angle has become popular but it is dependent on age, sex, BMI, and fat mass. The agreement between computed tomography and BIA does not show precise agreement [19] and it showed poor correlations with sarcopenia in active older women [20].

Dual-energy X-ray absorptiometry (DXA) has been considered the gold standard for measuring muscle mass [21]. It has been validated against post mortem measurement of muscle, skin, and viscera, but it can be inaccurate on the basis of hydration status and thickness of lean tissue [22]. In addition, different DEXA machines can lead to different results. It measures lean mass rather than muscle mass.

Both computed tomography and magnetic resonance imaging represent trusted methods to measure muscle mass, but their cost makes their use prohibitive for regular clinical use [21].

Ultrasound is a portable relatively simple method to measure quadriceps mass [23–25]. It is somewhat dependent on operator skill and among other details related to the applied probe pressure. It can also provide the angle of pennation which provides information on the ability of the muscle to generate force. At present, it has been underused to measure muscle mass. But with the increasing availability of affordable but reliable ultrasound devices, it may become a valuable tool in the clinic and in physician offices as well, especially if international standardization of its application will be achieved in the near future.

Most recently, it has been suggested that D3-creatine dilution may be the most accurate measure of muscle mass [26]. More than 95% of body creatine is present in muscle. Creatine is converted to creatinine and is not synthesized in muscle. For this reason, orally ingested creatine which is labeled by deuterium will lead to excretion of D3-creatinine in the urine providing an estimate of muscle mass. In a preliminary study, Clark et al.[27] found that orally administered D3-creatine produced a steady state of D3-creatinine in the urine after 30 h allowing an estimate of muscle mass [24]. This estimate correlated with magnet resonance imaging (MRI) measurements of muscle mass and was more accurate than DXA measurements. In a second study, muscle mass measured by the D3-creatine dilution technique correlated with bioelectrical impedance [28]. The D3-creatine dilution method for muscle mass was related to fall injuries, slow gait speed, SPPB, and mobility limitation [29]. In a recent study, the D3-creatine dilution method was superior to DEXA with regard to the detection of age-associated changes of muscle mass over a follow-up interval of 1.6 years [30]. In addition, the D3-creatine results correlated with the observed change of handgrip strength and walking speed.

This editorial has briefly reviewed the methods available to measure muscle and lean body mass. The advantages and disadvantages of each technique are outlined in Table 1. It would appear that in the future the D3-creatine dilution technique may become the best method to measure metabolically active muscle. However, at the moment additional studies are warranted that would allow to draw this conclusion on a sound basis.

Table 1
Table 1:
Comparison of methods to measure muscle (lean body) mass



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