ABSTRACT
BACKGROUND AND AIMS: The assessment of body composition is an important measure to monitor the process of healthy aging and detect early signs of disease. Dual X-ray absorptiometry (DXA) is considered a valid technique for the assessment of body composition but is confined to the clinical environment. Multi-frequency bio-electrical impedance analysis (MF-BIA) might be a versatile alternative to DXA. We aimed to assess whether a segmental MF-BIA scale can be an accurate and reliable tool for the monitoring of body composition in the elderly and whether the presence of metallic prostheses can influence the agreement between the two techniques. SUBJECTS AND METHODS: Weight and height were measured in 92 healthy subjects (53 women) aged 80-81 years from the H70 Gerontological and Geriatric study in Gothenburg. Total and segmental fat mass (FM) and lean soft tissue (LST) were estimated by DXA (Lunar Prodigy, Scanex, Sweden) and segmental MF-BIA (MC-180MA, Tanita, Japan). Bland-Altman analyses were performed to assess the agreement between the two techniques. The prediction of DXA-FM by MF-BIA was compared to that of the body mass index (BMI). RESULTS AND DISCUSSION: MF-BIA showed a significant underestimation of FM and an overestimation of LST that was larger in men than in women. Smaller but significant deviations were found for appendicular LST and SMM. MF-BIA was not superior to BMI at predicting DXA-FM. The lack of agreement between MF-BIA and DXA was not due to the presence of metal prostheses or diagnoses such as hypertension and edema. The prediction equations applied by the device used in this study should be adapted to the elderly population and details about the reference population(s) should be disclosed.
Subject(s)
Absorptiometry, Photon , Adiposity , Body Mass Index , Body Weight , Geriatric Assessment/methods , Aged, 80 and over , Electric Impedance , Female , Healthy Volunteers , Humans , Linear Models , Male , Reproducibility of Results , SwedenABSTRACT
BACKGROUND & AIMS: To validate the bioelectrical impedance spectroscopy (BIS) model against dual-energy X-ray absorptiometry (DXA), to develop and compare BIS estimates of skeletal muscle mass (SMM) to other prediction equations, and to report BIS reference values of body composition in a population-based sample of 75-year-old Swedes. METHODS: Body composition was measured by BIS in 574 subjects, and by DXA and BIS in a subset of 98 subjects. Data from the latter group was used to develop BIS prediction equations for total body skeletal muscle mass (TBSMM). RESULTS: Average fat free mass (FFM) measured by DXA and BIS was comparable. FFM(BIS) for women and men was 40.6 kg and 55.8 kg, respectively. Average fat free mass index (FFMI) and body fat index (BFI) for women were 15.6 and 11.0. Average FFMI and BFI for men were 18.3 and 8.6. Existing bioelectrical impedance analysis equations to predict SMM were not valid in this cohort. A TBSMM prediction equation developed from this sample had an R(2)(pred) of 0.91, indicating that the equation would explain 91% of the variability in future observations. CONCLUSIONS: BIS correctly estimated average FFM in healthy elderly Swedes. For prediction of TBSMM, a population specific equation was required.
Subject(s)
Absorptiometry, Photon , Adipose Tissue/metabolism , Body Composition/physiology , Electric Impedance , Muscle, Skeletal/metabolism , Absorptiometry, Photon/methods , Absorptiometry, Photon/standards , Aged , Aging , Algorithms , Body Water/metabolism , Cohort Studies , Female , Humans , Male , Predictive Value of Tests , Reference Values , Reproducibility of Results , Sensitivity and Specificity , SwedenABSTRACT
The assessment of extra-, intracellular and total body water (ECW, ICW, TBW) is important in many clinical situations. Bioimpedance spectroscopy (BIS) has advantages over dilution methods in terms of usability and reproducibility, but a careful analysis reveals systematic deviations in extremes of body composition and morbid states. Recent publications stress the need to set up and validate BIS equations in a wide variety of healthy subjects and patients with fluid imbalance. This paper presents two new equations for determination of ECW and ICW (referred to as body composition spectroscopy, BCS) based on Hanai mixture theory but corrected for body mass index (BMI). The equations were set up by means of cross validation using data of 152 subjects (120 healthy subjects, 32 dialysis patients) from three different centers. Validation was performed against bromide/deuterium dilution (NaBr, D2O) for ECW/TBW and total body potassium (TBK) for ICW. Agreement between BCS and the references (all subjects) was -0.4 +/- 1.4 L (mean +/- SD) for ECW, 0.2 +/- 2.0 L for ICW and -0.2 +/- 2.3 L for TBW. The ECW agreement between three independent reference methods (NaBr versus D2O-TBK) was -0.1 +/- 1.8 L for 74 subjects from two centers. Comparing the new BCS equations with the standard Hanai approach revealed an improvement in SEE for ICW and TBW by 0.6 L (24%) for all subjects, and by 1.2 L (48%) for 24 subjects with extreme BMIs (<20 and >30). BCS may be an appropriate method for body fluid volume determination over a wide range of body compositions in different states of health and disease.
