Sarcopenia is a medical condition that is frequent and important. According to The European Working Group on Sarcopenia in Older People (EWGSOP), "sarcopenia is a syndrome characterised by progressive and generalised loss of skeletal muscle mass and strength with a risk of adverse outcomes such as physical disability, poor quality of life and death" . Iannuzzi-Sucich, et al found that the prevalence of sarcopenia over the age of 64 was 22.6% in women and 26.8% in men. A subgroup analysis of women and men 80 years or older revealed prevalence rates of 31.0% and 52.9%, respectively .
Sarcopenia can cause morbidity and mortality. According to Sarcopenia: Revised European Consensus on Definition and Diagnosis published in 2018:
...sarcopenia increases risk of falls and fractures; impairs ability to perform activities of daily living; is associated with cardiac disease, respiratory disease and cognitive impairment; leads to mobility disorders; and contributes to lowered quality of life, loss of independence or need for long-term care placement, and death. In ﬁnancial terms, sarcopenia is costly to healthcare systems. The presence of sarcopenia increases risk for hospitalisation and increases cost of care during hospitalisation. Among older adults who are hospitalised, those with sarcopenia on admission were more than 5-fold more likely to have higher hospital costs than those without sarcopenia. Results of a large, community-based study in the Czech Republic showed that direct healthcare costs were more than 2-fold higher for older people with sarcopenia than for those without .
Fortunately, sarcopenia may be treated with diet and exercise. The European Society for Clinical Nutrition and Metabolism (ESPEN) Expert Group stated:
Regular aerobic and resistance exercise programs have been shown to counteract most aspects of sarcopenia. In addition, good nutrition, especially adequate protein and energy intake, can help limit and treat age-related declines in muscle mass, strength, and functional abilities. Protein nutrition in combination with exercise is considered optimal for maintaining muscle function .
Unfortunately, sarcopenia is too often undiagnosed. The European Working Group on Sarcopenia in Older People 2 (EWGSOP2) recommends the following methods for identifying sarcopenia in clinical practice: 1. the SARC-F questionnaire for case finding; 2. grip strength and the chair stand test for skeletal muscle strength; 3. dual-energy x-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA) for measuring skeletal muscle mass. SARC-F is questionnaire that asks about strength, walking, rising from a chair, climbing stairs, and falls. Grip strength requires a calibrated handheld dynamometer. The chair stand test measures the time required to rise five times from a seated position.
For measuring muscle mass, DXA is generally preferred by clinicians because of greater accuracy, but x-ray equipment and a physician order are required. BIA is the easiest and least expensive method for estimating muscle mass and can be performed serially at home to monitor the course of sarcopenia. BIA estimates the volume of fat and lean body mass by measuring the electrical resistance of the body using an imperceptibly low electrical current. The test equipment itself is widely available, inexpensive and easy to use. However, it is contraindicated in pregnancy, and in people with cardiac pacemakers and other internal and external medical devices.
According to the EWGSOP2:
Bioelectrical impedance analysis (BIA) has been explored for estimation of total or ASM [appendicular skeletal muscle]. BIA equipment does not measure muscle mass directly, but instead derives an estimate of muscle mass based on whole-body electrical conductivity. BIA uses a conversion equation that is calibrated with a reference of DXA-measured lean mass in a speciﬁc population. BIA equipment is affordable, widely available and portable, especially single-frequency instruments... BIA prediction models are most relevant to the populations in which they have been derived...Age, ethnicity and other related discrepancies between those populations and patients should be considered in the clinic. In addition, BIA measurements can also be inﬂuenced by hydration status of the patient. For affordability and portability, BIA-based determinations of muscle mass may be preferable to DXA; however, more study is necessary to validate prediction equations for speciﬁc populations.
Janssen et al developed prediction equations for skeletal muscle mass.
In summary, BIA prediction equations for whole body SM mass were developed and cross-validated in Caucasian subjects in two laboratories. The cross-validation of the BIA equations for predicting SM mass was successful, and the magnitude of the error in predicting SM mass from BIA was small. These observations are encouraging and suggest that BIA can provide rapid and accurate estimates of SM in adult populations. Our results indicate that the derived equation is applicable for Caucasian, African-American, and Hispanic populations but not for Asian populations. The validity of the BIA method in individuals whose hydration status may be altered, such as athletes, extreme elderly, and diseased individuals, requires investigation. Studies are also needed to determine the sensitivity of BIA to detect changes in SM mass in response to nutritional and exercise interventions and to develop a race-specific equation for predicting SM from BIA measurements in Asians .
BIA permits the prediction of ASMM in healthy volunteers and patients between 22 and 94 year of age. A slightly larger, though clinically not significant, error was noted in patients .
In 2013 Mijnarends DM, et al reviewed 62 studies of the validity of methods for muscle mass and strength measurement that included MRI, CT, DXA, BIA, dynamometry, and gait speed, though they found that " ...reliability data of the BIA are lacking". They stated:
It can be concluded that several tools are available for valid and reliable measurements of muscle mass, strength, and performance in clinical settings. For a home-setting BIA, handheld dynamometry and gait speed or a short physical performance battery are the most valid, reliable, and feasible. The combination of selected instruments and its use for the screening and identification of sarcopenia in community-dwelling older people need further evaluation .
In 2015 Buckinx et al studied the concordance between BIA and DXA in measuring muscle mass and stated:
In conclusion, our results show that the measure of muscle mass by BIA, using the InBody S10, is reproducible, when performed by the same operator and when performed by two different ones. Nevertheless, the concordance between muscle mass measured by BIA and by DXA is low. Indeed, BIA seems to overestimate muscle mass compared to DXA. Consequently, it is important to use a formula to obtain an adapted muscle mass value by BIA close to that measured by DXA to make of the BIA a portable and easy to use alternative to DXA .
In 2016 Yu studied the performance of five BIA equations in Australians and concluded:
BIA-derived PEs [prediction equations] can be used to estimate ASM. The PE developed by Sergi appears to provide a reasonable estimate of ASM [appendicular muscle mass] in Australians of Caucasian decent. Where greater accuracy is required, the Kyle equation can be used in men. Given the multicultural composition of the Australian population, it will be important to validate equations for use in other ethnic groups, in underweight groups (i.e., BMI < 18 kg/m2) and for both single- as well as multi-frequency BIA machines. It is also important to validate equations for common chronic diseases/comorbidities in this group .
In 2018 Gonzalez et al reviewed BIA in the assessment of sarcopenia. They stated:
...the accuracy of muscle mass assessment from a BIA device depends on how the relation equation/device/population/cut-off is respected. Good accuracy for muscle mass prediction will be obtained when the equation developed for a specific device in a define population is used along with the cut-off levels for low muscle mass developed for that population.
Although BIA can be an option for the muscle mass assessment in the diagnosis of sarcopenia, there are fundamental conditions to be met for the results to be considered valid. An adequate hydration,
absence of severe obesity, and an adequate relation between the device, equation, population, and adopted cut-off’ are essential for reliable results. There is an urgent need for a standardization of
the terminology employed to describe muscularity and cross-validation studies among the most used BIA devices. Furthermore, results from new studies suggest that specific cut-off values for each population and device should be developed .
There are several manufacturers of BIA equipment. One manufacturer for which there is published validity data is Omron. The Omron Full Body Sensor HBF-514C is a body composition monitor and scale that estimates body fat percentage, skeletal muscle percentage, resting metabolism, BMI (body mass index) and visceral fat levels using bioelectrical impedance and weight. The device takes measurements from both hands and feet, which according to Omron reduces the influence of water movement on body composition results. It can store data in memory but does not transmit information to a healthcare provider. It is intended to be used by healthy individuals between the age of 18 to 80 years, and not by people with a cardiac pacemaker or other implanted or external medical device, and by pregnant women. Omron advises that:
body fat percentage measured by this monitor may significantly differ from the actual body fat percentage for the following people:
- Elderly people
- People with a fever
- Body builders or highly trained athletes
- Persons undergoing dialysis
- Persons with osteoporosis who have very low bone density
- Persons with edema
- Children in growth stage
The accuracy of skeletal muscle measurement by Omron equipment has been evaluated in clinical studies. Pietiläinen KH, Kaye S, Karmi A, Suojanen L, et al. compared bioelectrical impedance analysis (BIA) using the Omron BF-500 with dual-energy X-ray absorptiometry (DXA) and MRI in estimating body fat, skeletal muscle and visceral fat during a 12-month weight loss intervention. BIA, as compared to DXA, accurately assessed loss of fat (7·0 (SE 1·5) v. 7·0 (SE 1·4)kg, P¼0·94) and muscle (1·0 (SE 0·2) v. 1·4 (SE 0·3)kg, P¼0·18), though skeletal muscle was underestimated by 1–2 kg using BIA at each time point.
The authors warn that the:
Reproducibility of BIA measures depends on several factors, including length of fasting, changes in hydration, previous food choice, drinking and exercise patterns. Therefore, the use of BIA in unsupervised settings needs careful attention.
The authors concluded:
the results of the present study confirm the high level of preciseness of the Omron BF-500 (Omron Medizintechnik) BIA for predicting fat mass change during long-term weight loss. Skeletal muscle mass may be slightly underestimated by BIA, as compared with calculated estimations from DXA, but there was no systematic bias in the estimation in subjects with larger or smaller amounts of muscle tissue. Changes in skeletal muscle are better assessed in long- than in short-term periods. The visceral fat index captures the direction of change, but with systemic errors before and after weight loss, prediction of true visceral fat may be limited, especially in males.
The authors summarized that "BIA is at its best when assessing the amount or changes in fat mass. It is a useful method for measuring skeletal muscle, but limited in its ability to measure visceral fat" .
BIA is widely used for assessing body composition including muscle mass. However, it is contraindicated in people with cardiac pacemakers and other external and internal medical devices, with several medical conditions, with abnormal hydration, with weight extremes, and in pregnancy. Furthermore, the validity of BIA depends upon using the correct measurement technique and an accurate analysis equation considering sex, age and ethnicity. Thus, it would be prudent for an individual to discuss BIA with a medical care provider prior to its use to ensure that BIA is safe and appropriate for that person. Also, results should be reviewed by their medical care provider, and if necessary confirmed with DXA, which is considered more accurate though less convenient and more expensive.
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9. The Performance of Five Bioelectrical Impedance Analysis Prediction Equations against Dual X-ray Absorptiometry in Estimating Appendicular Skeletal Muscle Mass in an Adult Australian Population. Solomon C. Y. Yu, Alice Powell, Kareeann S. F. Khow, and Renuka Visvanathan. Nutrients. 2016 Mar 29;8(4):189.
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11. Agreement of bioelectrical impedance with dual-energy X-ray absorptiometry and MRI to estimate changes in body fat, skeletal muscle and visceral fat during a 12-month weight loss intervention. Pietiläinen KH, Kaye S, Karmi A, Suojanen L, Rissanen A, Virtanen KA. Br J Nutr. 2013 May 28;109(10).
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