Specific bioelectrical impedance vector reference values for assessing body composition in the Italian elderly.

OBJECTIVE: To obtain specific bioelectrical impedance vector reference values for the healthy elderly Italian population, and to study age- and sex-related differences in body composition. DESIGN: The study group consisted of 560 healthy individuals (265 men and 295 women) aged 65 to 100 y, whose anthropometric (height, weight, and calf, arm and waist circumferences) and bioelectrical measurements (resistance [R] and reactance [Xc], at 50 kHz and 800 µA) were recorded. R (Ω) and Xc (Ω) values were standardized for stature (H, m) to obtain the classic bioelectrical values. Specific values (resistivity [Rsp] and reactivity [Xcsp], Ω·cm) were obtained by multiplying R and Xc by a correction factor (A/L) that includes an estimate of the cross-sectional area of the body (A=0.45 arm area+0.10 waist area+0.45 calf area), where L=1.1H. RESULTS: Descriptive statistics were: Rsp (391.8±57.9), Xcsp (42.6±9.9), Zsp (394.2±58.2), phase angle (6.2°±1.2) in men; Rsp (462.0±80.1), Xcsp (47.9±11.2), Zsp (464.6±80.5), phase angle (5.9°±1.0) in women. The Xcsp and phase angle values showed a significant age-related decrease in both sexes, but especially in men, possibly relating to a gradual loss of muscle mass. Women's Rsp and Zsp values tended to drop, attributable to their declining proportion of fat mass. A declining sexual dimorphism was also apparent. CONCLUSIONS: Specific tolerance ellipses can be used for reference purposes for the Italian population when assessing body composition in gerontological practice and for epidemiological purposes.

Accuracy of specific BIVA for the assessment of body composition in the United States population.

BACKGROUND: Bioelectrical impedance vector analysis (BIVA) is a technique for the assessment of hydration and nutritional status, used in the clinical practice. Specific BIVA is an analytical variant, recently proposed for the Italian elderly population, that adjusts bioelectrical values for body geometry. OBJECTIVE: Evaluating the accuracy of specific BIVA in the adult U.S. population, compared to the 'classic' BIVA procedure, using DXA as the reference technique, in order to obtain an interpretative model of body composition. DESIGN: A cross-sectional sample of 1590 adult individuals (836 men and 754 women, 21-49 years old) derived from the NHANES 2003-2004 was considered. Classic and specific BIVA were applied. The sensitivity and specificity in recognizing individuals below the 5(th) and above the 95(th) percentiles of percent fat (FMDXA%) and extracellular/intracellular water (ECW/ICW) ratio were evaluated by receiver operating characteristic (ROC) curves. Classic and specific BIVA results were compared by a probit multiple-regression. RESULTS: Specific BIVA was significantly more accurate than classic BIVA in evaluating FMDXA% (ROC areas: 0.84-0.92 and 0.49-0.61 respectively; p = 0.002). The evaluation of ECW/ICW was accurate (ROC areas between 0.83 and 0.96) and similarly performed by the two procedures (p = 0.829). The accuracy of specific BIVA was similar in the two sexes (p = 0.144) and in FMDXA% and ECW/ICW (p = 0.869). CONCLUSIONS: Specific BIVA showed to be an accurate technique. The tolerance ellipses of specific BIVA can be used for evaluating FM% and ECW/ICW in the U.S. adult population.

Elderly subjects with type 2 diabetes show altered tissue electrical properties.

OBJECTIVE: The aim of the present research was to show the characteristics of body composition in a sample of elderly subjects with type 2 diabetes compared with healthy controls matched by age and body mass index (BMI) by bioelectrical impedance vector analysis. METHODS: The sample consisted of 144 free-living patients (84 women and 60 men) with type 2 diabetes 60 to 84 y old and 209 age-matched controls (116 women and 93 men). Anthropometric measurements (weight; height; upper arm, hip, waist, and calf circumferences; biceps; triceps; and subscapular and suprailiac skinfolds) were taken. Blood samples for the assessment of plasma glucose and glycated hemoglobin were collected. The BMI, upper arm muscular area, and waist-to-hip ratio were calculated. Bioelectrical impedance vector analysis was applied. The analysis was performed in the entire diabetic sample and the healthy BMI-matched groups. RESULTS: Compared with healthy subjects, patients had greater weight (P < 0.01 in women), higher BMI (P < 0.01 in women), smaller muscular area (P < 0.01 in men), and thicker skinfolds (P < 0.01 in women and men). Female and male patients showed larger phase angles (P < 0.01). Moreover, female patients showed a shorter vector length and lower resistance (P < 0.01) and male patients showed a higher reactance (P < 0.01). The BMI-matched analysis confirmed that patients were characterized by larger phase angles. CONCLUSIONS: Older patients with type 2 diabetes were characterized by peculiar anthropometric and bioelectrical patterns, which can be related to their smaller appendicular muscular area and lower extracellular/intracellular water ratio.

The potential of classic and specific bioelectrical impedance vector analysis for the assessment of sarcopenia and sarcopenic obesity.

PURPOSE: The aim of this paper is to investigate whether bioelectrical impedance vector analysis (BIVA) can be a suitable technique for the assessment of sarcopenia. We also investigate the potential use of specific BIVA as an indicator of sarcopenic obesity. SUBJECTS AND METHODS: The sample comprised 207 free-living elderly individuals of both sexes, aged 65 to 93 years. Anthropometric and bioelectrical measurements were taken according to standard criteria. The "classic" and "specific" BIVA procedures, which respectively correct bioelectrical values for body height and body geometry, were used. Dual energy X-ray absorptiometry (DXA) was used as the reference method for identifying sarcopenic and obese sarcopenic individuals. Bioelectrical and DXA values were compared using Student's t-test and Hotelling's T(2) test, as well as Pearson's correlation coefficient. RESULTS: According to classic BIVA, sarcopenic individuals of both sexes showed higher values of resistance/height (R/H; p < 0.01) and impedance/height (Z/H; p < 0.01), and a lower phase angle (p < 0.01). Similarly, specific BIVA showed significant differences between sarcopenic and nonsarcopenic individuals (men: T(2) = 15.7, p < 0.01; women: T(2) = 10.7, p < 0.01), with the sarcopenic groups showing a lower specific reactance and phase angle. Phase angle was positively correlated with the skeletal muscle mass index (men: r = 0.52, p < 0.01; women: r = 0.31, p < 0.01). Specific BIVA also recognized bioelectrical differences between sarcopenic and sarcopenic obese men (T(2) = 13.4, p < 0.01), mainly due to the higher values of specific R in sarcopenic obese individuals. CONCLUSION: BIVA detected muscle-mass variations in sarcopenic individuals, and specific BIVA was able to discriminate sarcopenic individuals from sarcopenic obese individuals. These procedures are promising tools for screening for presarcopenia, sarcopenia, and sarcopenic obesity in routine practice.