The bioelectrical impedance analysis (BIA) international database: aims, scope, and call for data.

BACKGROUND: Bioelectrical impedance analysis (BIA) is a technique widely used for estimating body composition and health-related parameters. The technology is relatively simple, quick, and non-invasive, and is currently used globally in diverse settings, including private clinicians' offices, sports and health clubs, and hospitals, and across a spectrum of age, body weight, and disease states. BIA parameters can be used to estimate body composition (fat, fat-free mass, total-body water and its compartments). Moreover, raw measurements including resistance, reactance, phase angle, and impedance vector length can also be used to track health-related markers, including hydration and malnutrition, and disease-prognostic, athletic and general health status. Body composition shows profound variability in association with age, sex, race and ethnicity, geographic ancestry, lifestyle, and health status. To advance understanding of this variability, we propose to develop a large and diverse multi-country dataset of BIA raw measures and derived body components. The aim of this paper is to describe the 'BIA International Database' project and encourage researchers to join the consortium. METHODS: The Exercise and Health Laboratory of the Faculty of Human Kinetics, University of Lisbon has agreed to host the database using an online portal. At present, the database contains 277,922 measures from individuals ranging from 11 months to 102 years, along with additional data on these participants. CONCLUSION: The BIA International Database represents a key resource for research on body composition.

Can change in phase angle predict the risk of morbidity and mortality during an 18-year follow-up period? A cohort study among adults.

Introduction: Phase angle (PhA, degrees), measured via bioimpedance (BIA, 50 kHz), is an index that has been used as an indicator of nutritional status and mortality in several clinical situations. This study aimed to determine the relationship between 6-year changes in PhA and total mortality as well as the risk of incident morbidity and mortality from cardiovascular disease (CVD) and coronary heart disease (CHD) during 18 years of follow-up among otherwise healthy adults. Methods: A random subset (n = 1,987) of 35-65 years old men and women was examined at the baseline in 1987/1988 and 6 years later in 1993/1994. Measures included weight, height, and whole-body BIA, from which PhA was calculated. Information on lifestyle was obtained through a questionnaire. The associations between 6-year PhA changes (ΔPhA) and incident CVD and CHD were assessed by Cox proportional hazard models. The median value of ΔPhA was used as the reference value. The hazard ratio (HR) model and confidence intervals (CIs) of incident CVD and CHD were used according to the 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentiles of ΔPhA. Results: During 18 years of follow-up, 205 women and 289 men died. A higher risk of both total mortality and incident CVD was present below the 50th percentile (Δ = -0.85°). The highest risk was observed below the 5th percentile (ΔPhA = -2.60°) in relation to total mortality (HR: 1.55; 95% CI: 1.10-2.19) and incident CVD (HR: 1.52; 95% CI: 1.16-2.00). Discussion: The larger the decrease in PhA, the higher the risk of early mortality and incident CVD over the subsequent 18 years. PhA is a reliable and easy measure that may help identify those apparently healthy individuals who may be at increased risk of future CVD or dying prematurely. More studies are needed to confirm our results before it can be definitively concluded that PhA changes can improve clinical risk prediction.

Can Phase Angle Be Associated With Muscle Strength in Healthy Male Army Cadets?

INTRODUCTION: Phase angle (PhA) determined by bioelectrical impedance (BIA) is related to body fluid balance and cell membrane integrity. Handgrip strength (HGS) is used to assess muscle strength and as an indicator of health. We aimed to determine the relationship between PhA and HGS in healthy young males and to verify whether this relationship is dependent on body components. MATERIALS AND METHODS: Hundred and sixty-three healthy male army cadets (18.8 ± 0.6 years old) participated in the study. PhA was determined by BIA, HGS was assessed by a hydraulic dynamometer, and dual-energy X-ray absorptiometry determined: fat mass (FM), bone mineral content (BMC), and lean soft tissue (LST). Participants were divided according to the PhA tertile (first tertile: PhA < 7.14°, second tertile: 7.14° ≤ PhA < 7.83°, and third tertile: PhA ≥ 7.83°). RESULTS: Youth from the first tertile of PhA had lower BMC (2.8 kg vs. 3.0 kg and vs. 3.1 kg) and LST (51.7 vs. 53.8 kg and vs. 57.6 kg) compared to youth from the second and third tertile of PhA (P < .001), respectively. Additionally, lower HGS (83.0 kg vs. 93.1 kg) was found in the first tertile compared to the third tertile of PhA (P < .001). PhA explained 3% of the HGS variation (R2 = 0.029), while LST and BMC explained 39% (R2 = 0.385) and 22% (R2 = 0.221), respectively. Furthermore, the correlation between PhA and HGS was dependent on LST (P = .567) and BMC (P = .182). CONCLUSION: In this sample, PhA showed a small relationship with HGS, remaining dependent on BMC and LST values. These results reinforce the importance of maintaining a physically active lifestyle with great lean mass and muscle strength values.

Phase angle measured by bioelectrical impedance analysis and the risk of cardiovascular disease among adult Danes.

OBJECTIVE: This study aimed to examine associations between phase angle (PhA) and incident cardiovascular disease (CVD) morbidity and mortality in a healthy Danish subpopulation free of major chronic diseases. METHODS: A random subset (n = 2601) of adult men and women born in 1922, 1932, 1942, and 1952 and examined in 1987 and 1988 were included, and followed over 24 y during which 643 men and 570 women developed CVD. Measures at baseline included age, weight, height, whole-body bioimpedance, from which PhA was calculated, and information on lifestyle, obtained by a self-administered questionnaire. The association between PhA and incident CVD was assessed by Cox proportional hazard model with age as the underlying time scale and with additional adjustment for covariates. To explore nonlinear associations, all results were presented using restricted cubic splines, with the median value of PhA as the reference. RESULTS: PhA was lower among women who later developed CVD than among women who did not (6.3 vs. 6.0; P < 0.001). The highest risk of CVD was observed at the 5th percentile (hazard ratio: 1.33; 95% confidence interval, 1.11-1.60). Among men, PhA was not significantly associated with risk of CVD (7.1 vs. 7.0; P = 0.246). CONCLUSIONS: Among apparently healthy Danish men and women, a lower PhA value was associated with a higher incidence of CVD over 24 y, also after adjusting for potential confounders, and particularly among women. These findings may encourage the future use of PhA as an additional index in predicting CVD. However, more studies are needed to confirm our results.

Physical training over 6 months is associated with improved changes in phase angle, body composition, and blood glucose in healthy young males.

OBJECTIVES: The aim of this study was to evaluate the association between phase angle, body composition, and blood glucose changes in healthy young males after 6 months of physical training. METHODS: Volunteers, 98 healthy males (18.8 ± 0.5 years), had 6 months of progressive physical training (5 days a week, 90 minutes a day). Resistance, reactance, and phase angle were obtained by bioelectrical impedance analysis, body composition (fat mass, bone mineral content [BMC], and lean soft tissue [LST]) by dual-energy X-ray absorptiometry, and blood glucose by reflectance photometry. Measurements were made at rest and in a fasted state, both before and after the training period. RESULTS: Phase angle, reactance, BMC, and LST significantly increased (0.6°, 3.8 Ω, 0.1 kg, and 1.9 kg, respectively; P < .01), whereas resistance and blood glucose decreased (-11.2 Ω and -4.1 mg/dL; P < .01). Changes in resistance and reactance explained those changes observed in LST (R2 = .26 and .16, respectively), but phase angle changes were not related to body composition and blood glucose alterations (P < .05). CONCLUSIONS: A 6-month period of physical training was associated with positive changes in phase angle, body composition, and blood glucose in healthy young males, reinforcing the importance of maintaining a physically active lifestyle.

Adaptive thermogenesis and changes in body composition and physical fitness in army cadets.

BACKGROUND: To analyze the association between a 34-week military training on body composition, physical fitness and compensatory changes in resting energy expenditure (REE) recognized as adaptive thermogenesis (AT). We also explored if regional body composition changes were related to AT. METHODS: Twenty-nine male army cadets, aged 17 to 22 years were tested at baseline (T0) and after 34-weeks military training (T1). Physical training was performed 5 days/week during 90 minutes/day. Measurements included body composition by dual-energy x-ray absorptiometry; physical fitness by 3000-m running, pull-up, 50-m freestyle swimming, push-up and sit-up tests; REE measured by indirect calorimetry (REEm) and predicted from fat-free mass (FFM), fat mass (FM) and ethnicity at T0 (REEp). %AT was calculated using values at T1: 100(REEm/REEp-1); and AT (kcal/day) as %AT/100 multiplied by baseline REEm. RESULTS: Physical training was associated with increases of lean soft tissue (LST) (∆1.2±1.3 kg), FM (∆1.4±1.3 kg), FFM (∆1.2±1.3 kg) and physical fitness (P<0.01), but no REE changes (∆59.6±168.9 kcal/day) and AT were observed (P>0.05). Though a large variability was found, AT was partially explained by trunk LST (r2=0.17, P=0.027). Individuals showing a higher AT response demonstrated a higher trunk LST increase (∆0.8±0.7 kg, P<0.05). CONCLUSIONS: The military training increased LST, FM, FFM and physical fitness. Though no mean changes in AT occurred, a large individual variability was observed with some participants increasing REE beyond the expected body composition changes, suggesting a spendthrift phenotype. Changes of trunk LST may play an important role in the AT response observed in these individuals.

Accuracy of Bioelectrical Impedance Analysis in Estimated Longitudinal Fat-Free Mass Changes in Male Army Cadets.

Introduction: Bioelectrical impedance analysis (BIA) is a practical and rapid method for making a longitudinal analysis of changes in body composition. However, most BIA validation studies have been performed in a clinical population and only at one moment, or point in time (cross-sectional study). The aim of this study is to investigate the accuracy of predictive equations based on BIA with regard to the changes in fat-free mass (FFM) in Brazilian male army cadets after 7 mo of military training. The values used were determined using dual-energy X-ray absorptiometry (DXA) as a reference method. Materials and Methods: The study included 310 male Brazilian Army cadets (aged 17-24 yr). FFM was measured using eight general predictive BIA equations, with one equation specifically applied to this population sample, and the values were compared with results obtained using DXA. The student's t-test, adjusted coefficient of determination (R2), standard error of estimation (SEE), Lin's approach, and the Bland-Altman test were used to determine the accuracy of the predictive BIA equations used to estimate FFM in this population and between the two moments (pre- and post-moment). Results: The FFM measured using the nine predictive BIA equations, and determined using DXA at the post-moment, showed a significant increase when compared with the pre-moment (p < 0.05). All nine predictive BIA equations were able to detect FFM changes in the army cadets between the two moments in a very similar way to the reference method (DXA). However, only the one BIA equation specific to this population showed no significant differences in the FFM estimation between DXA at pre- and post-moment of military routine. All predictive BIA equations showed large limits of agreement using the Bland-Altman approach. Conclusion: The eight general predictive BIA equations used in this study were not found to be valid for analyzing the FFM changes in the Brazilian male army cadets, after a period of approximately 7 mo of military training. Although the BIA equation specific to this population is dependent on the amount of FFM, it appears to be a good alternative to DXA for assessing FFM in Brazilian male army cadets.

Validity of Bioelectrical Impedance Analysis to Estimation Fat-Free Mass in the Army Cadets.

BACKGROUND: Bioelectrical Impedance Analysis (BIA) is a fast, practical, non-invasive, and frequently used method for fat-free mass (FFM) estimation. The aims of this study were to validate predictive equations of BIA to FFM estimation in Army cadets and to develop and validate a specific BIA equation for this population. METHODS: A total of 396 males, Brazilian Army cadets, aged 17-24 years were included. The study used eight published predictive BIA equations, a specific equation in FFM estimation, and dual-energy X-ray absorptiometry (DXA) as a reference method. Student's t-test (for paired sample), linear regression analysis, and Bland-Altman method were used to test the validity of the BIA equations. RESULTS: Predictive BIA equations showed significant differences in FFM compared to DXA (p < 0.05) and large limits of agreement by Bland-Altman. Predictive BIA equations explained 68% to 88% of FFM variance. Specific BIA equations showed no significant differences in FFM, compared to DXA values. CONCLUSION: Published BIA predictive equations showed poor accuracy in this sample. The specific BIA equations, developed in this study, demonstrated validity for this sample, although should be used with caution in samples with a large range of FFM.

Minimum Time to Achieve the Steady State and Optimum Abbreviated Period to Estimate the Resting Energy Expenditure by Indirect Calorimetry in Healthy Young Adults.

BACKGROUND: The optimum abbreviated period for measurement by indirect calorimetry (IC) to estimate the resting energy expenditure (REE), including the acclimation period, in healthy individuals has not been established. This study aimed to determine the acclimation time required to achieve the REE steady state during a 30-minute IC measurement and to define the optimum abbreviated measurement period in the steady state to estimate the REE in healthy young adults. METHODS: Thirty-nine volunteers (27 men and 12 women; age, 18-31 years) were recruited. The REE was obtained by IC over 30 minutes. Friedman's test was used to compare the coefficient of variation (CV%) among all 5-minute intervals (REE5). To compare the REE values obtained during the first REE5 interval in the steady state with the REE average values of the subsequent measurements, Student paired t test, linear regression, and Bland-Altman test were used. RESULTS: The CV% of the first REE5 (mean ± standard deviation: 19.9% ± 13.2%) was significantly higher (P < .0001) than that of all other REE5 (second REE5: 7.4% ± 3.8%; third: 7.8% ± 5.2%; fourth: 7.1% ± 3.9%; fifth: 8.0% ± 5.7%; sixth: 8.0% ± 4.5%). No significant difference was found between the second REE5 and the REE average values of the last 20 minutes. The second REE5 explained 90% of the REE average of the last 20 minutes, with the 95% limits of agreement by the Bland-Altman test ranging from -142.92 to 150.44 kcal/d. CONCLUSION: Ten minutes can be used as an abbreviated alternative for IC measurements in healthy young adults, and values of the first 5-minute interval should be discarded.