Segmental bioelectrical impedance analysis in children aged 8-12 y: 2. The assessment of regional body composition and muscle mass

Mother-child correlation of kidney function: data from the Yamanashi Adjunct Study of Japan Environment and Children's Study (JECS)

BACKGROUND

Individual variation in kidney function can be affected by both congenital and acquired factors, and kidney function in children is possibly correlated with that in their mothers. However, the mother-child correlation in kidney function remains directly unconfirmed.

METHODS

We conducted a cross-sectional study of 655 healthy pairs of 7- or 8-year-old children and their mothers as an adjunct study of a nationwide epidemiological study (Japan Environment and Children's Study).

RESULTS

Both serum creatinine level (all children, r = 0.324, p < 0.001; girls, r = 0.365, p < 0.001; boys, r = 0.278, p < 0.001) and estimated glomerular filtration rate (eGFR) (r = 0.274, p < 0.001; r = 0.352, p < 0.001; r = 0.195, p < 0.001, respectively) in children were weakly associated with their maternal values. In the single linear regression analyses, maternal values of serum creatinine and eGFR were significantly associated with the children's values. Moreover, several body composition values in children, such as weight-SDS, fat (%), and predicted muscle weight, were also significantly associated with kidney function values in children. In the multiple linear regression analysis for serum creatinine levels in children, in which weight-SDS and predicted muscle weight in children were selected as adjustment factors, maternal serum creatinine level showed a significant positive association (B = 0.214, p < 0.001 in the adjusted model). Moreover, in the multiple linear regression analysis for eGFR value in children, in which fat (%) and predicted muscle weight in children were selected as adjustment factors, maternal eGFR values showed a significant positive association (B = 0.319, p < 0.001).

CONCLUSIONS

We directly confirmed mother-child correlations in both serum creatinine levels and eGFR values, particularly in girls. Graphical abstract A higher resolution version of the Graphical abstract is available as Supplementary information.

The relevance of left ventricular functions to clinical and metabolic characteristics of prepubertal children with obesity

BACKGROUND

Paediatric obesity is a worldwide health burden, with growing evidence linking obesity to myocardial function impairments. The study aims to evaluate left ventricular functions among prepubertal obese children to obesity-related clinical and metabolic parameters.

METHODS

Between June 2019 and March 2020, 40 prepubertal children with obesity were recruited and compared to 40 healthy controls. Patients were assessed for body mass index z scores, waist circumference, body adiposity by bioimpedance analysis, and obesity-related laboratory tests, for example, serum chemerin. Left ventricular functions were assessed using variable echocardiographic modalities, such as M-mode, tissue Doppler, and two-dimensional speckle tracking.

RESULTS

Mean patients' age was 9.25 ± 1.05 years. Left ventricular mass index, E/E', and myocardial performance index were significantly increased in obese children than controls. Although M-mode-derived ejection fraction was comparable in both groups, two-dimensional speckle tracking-derived ejection fraction, global longitudinal strain, and global circumferential strain were significantly lower in cases than controls. Left ventricular mass index displayed a positive correlation with body mass index z score (p = 0.003), fat mass index (p = 0.037), and trunk fat mass (p = 0.021). Global longitudinal strain was negatively correlated with body mass index z score (p = 0.015) and fat mass index (p = 0.016). Serum chemerin was positively correlated with myocardial performance index (p = 0.01).

CONCLUSION

Alterations of left ventricular myocardial functions in prepubertal obese children could be detected using different echocardiographic modalities. Chemerin, body mass index z score, fat mass index, and trunk fat mass were correlated with subclinical left ventricular myocardial dysfunction parameters before puberty. Our results reinforce early and strict management of childhood obesity upon detection of changes in anthropometric and body adiposity indices.

Using bioelectrical impedance analysis in children and adolescents: Pressing issues

Single- and multifrequency bioelectrical impedance analysis (BIA) has gained popularity as a tool to assess body composition and health status of children and adolescents, but many questions and misconceptions remain. This review addresses pressing issues researchers and health care providers may encounter when using BIA in the young population. The importance of choosing population-specific and device-specific equations to estimate body composition as well as the use of BIA in longitudinal analyses are discussed. When specific equations are not available, raw bioimpedance values (i.e., resistance, reactance, and impedance) can be used to compute bioimpedance parameters, such as phase angle, impedance ratio, and bioelectrical impedance vector analysis. As interpreting these parameters is challenging, suggestions are provided on the use of reference data, cut-off points, and adjustment factors. Furthermore, unsolved technical and analytical issues are listed. Based on existing issues and potential for future development, a greater interaction between industry and academic researchers to improve the validity of BIA measurements among children and adolescents across their developmental stages is encouraged.

Health Risks of Sarcopenic Obesity in Overweight Children and Adolescents: Data from the CHILT III Programme (Cologne)

Sarcopenic obesity is increasingly found in youth, but its health consequences remain unclear. Therefore, we studied the prevalence of sarcopenia and its association with cardiometabolic risk factors as well as muscular and cardiorespiratory fitness using data from the German Children’s Health InterventionaL Trial (CHILT III) programme. In addition to anthropometric data and blood pressure, muscle and fat mass were determined with bioelectrical impedance analysis. Sarcopenia was classified via muscle-to-fat ratio. A fasting blood sample was taken, muscular fitness was determined using the standing long jump, and cardiorespiratory fitness was determined using bicycle ergometry. Of the 119 obese participants included in the analysis (47.1% female, mean age 12.2 years), 83 (69.7%) had sarcopenia. Affected individuals had higher gamma-glutamyl transferase, higher glutamate pyruvate transaminase, higher high-sensitivity C-reactive protein, higher diastolic blood pressure, and lower muscular and cardiorespiratory fitness (each p < 0.05) compared to participants who were ‘only’ obese. No differences were found in other parameters. In our study, sarcopenic obesity was associated with various disorders in children and adolescents. However, the clinical value must be tested with larger samples and reference populations to develop a unique definition and appropriate methods in terms of identification but also related preventive or therapeutic approaches.

Sarcopenia in children and adolescents with chronic liver disease

OBJECTIVE

To investigate the occurrence of sarcopenia in children and adolescents with chronic liver disease.

METHODS

A series of cases, with patients aged 6-19 years of both genders, who were treated in Liver Outpatient Clinics. Weight, height, muscle strength (assessed by manual grip strength), and muscle mass (estimated through dual-energy X-ray absorptiometry) were measured. Sarcopenia was diagnosed based on the simultaneous presence of muscle mass and muscle strength déficits, defined as the values below the mean for muscle mass and strength of the studied population, according to gender. A descriptive analysis (mean and standard deviation) was performed, and the difference of means was calculated by Student's t-test.

RESULTS

A total of 85 patients were studied, mostly females (64.7%), with a mean age of 11.7 (SD=3.4) years. Sarcopenia was identified in 40% of the patients. Muscle strength déficit was found in 54.1% of the subjects, and 50.6% showed muscle mass déficit. The mean muscle mass for males was higher than that for females (6.07; SD=1.22kg/m²vs. 5.42; SD=1.10kg/m²; p=0.016). However, there was no significant difference in sex-related muscle strength (male=0.85; SD=0.52kgf/kgm² and female=0.68; SD=0.30kgf/kgm²; p=0.113).

CONCLUSION

The research findings identified that sarcopenia is a condition found in pediatric patients treated at a public referral institution for chronic liver disease.

Muscle development in healthy children evaluated by bioelectrical impedance analysis

OBJECTIVES

This study aimed to use bioelectrical impedance analysis (BIA) to generate a new muscle density index (MDI), the MDI_BIA, to evaluate muscle development, and to demonstrate the changes that occur in the BIA-based muscle cross-sectional area index (MCAI_BIA) that accompany growth. We also sought to determine the traceability of chronological changes in the MDI_BIA and MCAI_BIA.

METHODS

Healthy children (n=112) aged 8.68±3.16years (0.33-14.00years) underwent bioelectrical impedance (BI) measurements of their upper arms, thighs, and lower legs. The MDI_BIA and MCAI_BIA were calculated, and cross-sectional investigations were conducted into the changes in these indices that accompanied growth. Data collected after 1.10±0.08years from 45 participants determined the traceability of the chronological changes in the MDI_BIA and MCAI_BIA.

RESULTS

The MDI_BIA and MCAI_BIA were significantly positively correlated with age and height at all locations (P<0.01). The relationships between the locations and the MDI_BIA and MCAI_BIA differed, indicating that these indices evaluated the muscles from different perspectives. Except for the upper arm MDI_BIA, both indices at all locations regardless of age, showed significant chronological increases after an average period of 1.10years.

CONCLUSIONS

The MDI_BIA and MCAI_BIA were significantly correlated with age and height in healthy children, and they showed significant chronological increases. Hence, these indices could be used to represent muscle development and muscle mass increases. BIA is non-invasive, convenient, and economical and it may be useful in evaluating muscle development and muscle cross-sectional areas in children.

Validity of segmental bioelectrical impedance analysis for estimating fat-free mass in children including overweight individuals

This study examined the validity of segmental bioelectrical impedance (BI) analysis for predicting the fat-free masses (FFMs) of whole-body and body segments in children including overweight individuals. The FFM and impedance (Z) values of arms, trunk, legs, and whole body were determined using a dual-energy X-ray absorptiometry and segmental BI analyses, respectively, in 149 boys and girls aged 6 to 12 years, who were divided into model-development (n = 74), cross-validation (n = 35), and overweight (n = 40) groups. Simple regression analysis was applied to (length)²/Z (BI index) for each of the whole-body and 3 segments to develop the prediction equations of the measured FFM of the related body part. In the model-development group, the BI index of each of the 3 segments and whole body was significantly correlated to the measured FFM (R² = 0.867-0.932, standard error of estimation = 0.18-1.44 kg (5.9%-8.7%)). There was no significant difference between the measured and predicted FFM values without systematic error. The application of each equation derived in the model-development group to the cross-validation and overweight groups did not produce significant differences between the measured and predicted FFM values and systematic errors, with an exception that the arm FFM in the overweight group was overestimated. Segmental bioelectrical impedance analysis is useful for predicting the FFM of each of whole-body and body segments in children including overweight individuals, although the application for estimating arm FFM in overweight individuals requires a certain modification.

The use of measures of obesity in childhood for predicting obesity and the development of obesity-related diseases in adulthood: a systematic review and meta-analysis

BACKGROUND

It is uncertain which simple measures of childhood obesity are best for predicting future obesity-related health problems and the persistence of obesity into adolescence and adulthood.

OBJECTIVES

To investigate the ability of simple measures, such as body mass index (BMI), to predict the persistence of obesity from childhood into adulthood and to predict obesity-related adult morbidities. To investigate how accurately simple measures diagnose obesity in children, and how acceptable these measures are to children, carers and health professionals.

DATA SOURCES

Multiple sources including MEDLINE, EMBASE and The Cochrane Library were searched from 2008 to 2013.

METHODS

Systematic reviews and a meta-analysis were carried out of large cohort studies on the association between childhood obesity and adult obesity; the association between childhood obesity and obesity-related morbidities in adulthood; and the diagnostic accuracy of simple childhood obesity measures. Study quality was assessed using Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) and a modified version of the Quality in Prognosis Studies (QUIPS) tool. A systematic review and an elicitation exercise were conducted on the acceptability of the simple measures.

RESULTS

Thirty-seven studies (22 cohorts) were included in the review of prediction of adult morbidities. Twenty-three studies (16 cohorts) were included in the tracking review. All studies included BMI. There were very few studies of other measures. There was a strong positive association between high childhood BMI and adult obesity [odds ratio 5.21, 95% confidence interval (CI) 4.50 to 6.02]. A positive association was found between high childhood BMI and adult coronary heart disease, diabetes and a range of cancers, but not stroke or breast cancer. The predictive accuracy of childhood BMI to predict any adult morbidity was very low, with most morbidities occurring in adults who were of healthy weight in childhood. Predictive accuracy of childhood obesity was moderate for predicting adult obesity, with a sensitivity of 30% and a specificity of 98%. Persistence of obesity from adolescence to adulthood was high. Thirty-four studies were included in the diagnostic accuracy review. Most of the studies used the least reliable reference standard (dual-energy X-ray absorptiometry); only 24% of studies were of high quality. The sensitivity of BMI for diagnosing obesity and overweight varied considerably; specificity was less variable. Pooled sensitivity of BMI was 74% (95% CI 64.2% to 81.8%) and pooled specificity was 95% (95% CI 92.2% to 96.4%). The acceptability to children and their carers of BMI or other common simple measures was generally good.

LIMITATIONS

Little evidence was available regarding childhood measures other than BMI. No individual-level analysis could be performed.

CONCLUSIONS

Childhood BMI is not a good predictor of adult obesity or adult disease; the majority of obese adults were not obese as children and most obesity-related adult morbidity occurs in adults who had a healthy childhood weight. However, obesity (as measured using BMI) was found to persist from childhood to adulthood, with most obese adolescents also being obese in adulthood. BMI was found to be reasonably good for diagnosing obesity during childhood. There is no convincing evidence suggesting that any simple measure is better than BMI for diagnosing obesity in childhood or predicting adult obesity and morbidity. Further research on obesity measures other than BMI is needed to determine which is the best tool for diagnosing childhood obesity, and new cohort studies are needed to investigate the impact of contemporary childhood obesity on adult obesity and obesity-related morbidities.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42013005711.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Mean Expected Error in Prediction of Total Body Water: A True Accuracy Comparison between Bioimpedance Spectroscopy and Single Frequency Regression Equations

For several decades electrical bioimpedance (EBI) has been used to assess body fluid distribution and body composition. Despite the development of several different approaches for assessing total body water (TBW), it remains uncertain whether bioimpedance spectroscopic (BIS) approaches are more accurate than single frequency regression equations. The main objective of this study was to answer this question by calculating the expected accuracy of a single measurement for different EBI methods. The results of this study showed that all methods produced similarly high correlation and concordance coefficients, indicating good accuracy as a method. Even the limits of agreement produced from the Bland-Altman analysis indicated that the performance of single frequency, Sun's prediction equations, at population level was close to the performance of both BIS methods; however, when comparing the Mean Absolute Percentage Error value between the single frequency prediction equations and the BIS methods, a significant difference was obtained, indicating slightly better accuracy for the BIS methods. Despite the higher accuracy of BIS methods over 50 kHz prediction equations at both population and individual level, the magnitude of the improvement was small. Such slight improvement in accuracy of BIS methods is suggested insufficient to warrant their clinical use where the most accurate predictions of TBW are required, for example, when assessing over-fluidic status on dialysis. To reach expected errors below 4-5%, novel and individualized approaches must be developed to improve the accuracy of bioimpedance-based methods for the advent of innovative personalized health monitoring applications.

Prediction equation for lower limbs lean soft tissue in circumpubertal boys using anthropometry and biological maturation

Lean soft tissue (LST), a surrogate of skeletal muscle mass, is largely limited to appendicular body regions. Simple and accurate methods to estimate lower limbs LST are often used in attempts to partition out the influence of body size on performance outputs. The aim of the current study was to develop and cross-validate a new model to predict lower limbs LST in boys aged 10–13 years, using dual-energy X-ray absorptiometry (DXA) as the reference method. Total body and segmental (lower limbs) composition were assessed with a Hologic Explorer-W QDR DXA scanner in a cross-sectional sample of 75 Portuguese boys (144.8±6.4 cm; 40.2±9.0 kg). Skinfolds were measured at the anterior and posterior mid-thigh, and medial calf. Circumferences were measured at the proximal, mid and distal thigh. Leg length was estimated as stature minus sitting height. Current stature expressed as a percentage of attained predicted mature stature (PMS) was used as an estimate of biological maturity status. Backward proportional allometric models were used to identify the model with the best statistical fit: ln (lower limbs LST)  = 0.838× ln (body mass) +0.476× ln (leg length) – 0.135× ln (mid-thigh circumference) – 0.053× ln (anterior mid-thigh skinfold) – 0.098× ln (medial calf skinfold) – 2.680+0.010× (percentage of attained PMS) (R = 0.95). The obtained equation was cross-validated using the predicted residuals sum of squares statistics (PRESS) method (R²_PRESS = 0.90). Deming repression analysis between predicted and current lower limbs LST showed a standard error of estimation of 0.52 kg (95% limits of agreement: 0.77 to −1.27 kg). The new model accurately predicts lower limbs LST in circumpubertal boys.

Skeletal muscle mass reference curves for children and adolescents

BACKGROUND

Skeletal muscle is key to motor development and represents a major metabolic end organ that aids glycaemic regulation.

OBJECTIVES

To create gender-specific reference curves for fat-free mass (FFM) and appendicular (limb) skeletal muscle mass (SMMa) in children and adolescents. To examine the muscle-to-fat ratio in relation to body mass index (BMI) for age and gender.

METHODS

Body composition was measured by segmental bioelectrical impedance (BIA, Tanita BC418) in 1985 Caucasian children aged 5-18.8 years. Skeletal muscle mass data from the four limbs were used to derive smoothed centile curves and the muscle-to-fat ratio.

RESULTS

The centile curves illustrate the developmental patterns of %FFM and SMMa. While the %FFM curves differ markedly between boys and girls, the SMMa (kg), %SMMa and %SMMa/FFM show some similarities in shape and variance, together with some gender-specific characteristics. Existing BMI curves do not reveal these gender differences. Muscle-to-fat ratio showed a very wide range with means differing between boys and girls and across fifths of BMI z-score.

CONCLUSIONS

BIA assessment of %FFM and SMMa represents a significant advance in nutritional assessment since these body composition components are associated with metabolic health. Muscle-to-fat ratio has the potential to provide a better index of future metabolic health.

Muscle strength and its relationship with skeletal muscle mass indices as determined by segmental bio-impedance analysis

PURPOSE

Despite increasing interest in bio-impedance analysis (BIA) for estimation of segmental skeletal muscle mass (SMM), published results have not been entirely convincing. Furthermore, a better understanding of the relationship between muscle strength and SMM will be useful in interpreting outcomes of physical/training interventions particularly in groups with diverse body sizes (e.g. men vs women). This study aimed to measure SMM in the upper body (upper extremity and torso), to determine its correlation with muscle strength and to examine the effects of gender on muscle strength-muscle mass relationship.

METHODS

Segmental (upper extremity and torso) SMM and muscle strength in five distinct shoulder planes (forward flexion, abduction in scapular plane, abduction in coronal plane, internal and external rotation) were measured in 45 healthy participants (22 males, 23 females) with mean age 30.3 years. Statistical analysis included independent t tests, Pearson correlation, and multiple regression analysis.

RESULTS

Men and women differed significantly in body mass (BMI: 25.9 ± 4.3 vs 23 ± 3.6) and SMM (p < 0.01). A strong relationship correlation was found between the five shoulder strength measurements and upper extremity SMM (r = 0.66-0.80, p < 0.01), which was not affected by gender. There was a significant gender difference (p < 0.01) in absolute shoulder strength, but not after normalisation to the SMM.

CONCLUSION

BIA-estimated SMM of upper extremity and torso was highly correlated with upper extremity (shoulder) strength independent of gender. SMM may, therefore, be useful for the normalisation of muscle strength allowing size-independent comparisons of muscle strength in individuals with diverse physical characteristics.

Comparison of DEXA-derived body fat measurement to two race-specific bioelectrical impedance equations in healthy Indians

AIM

Prevalence of obesity is increasing in Asian Indians. Reliable, precise and convenient methods to estimate body composition are required. This study aimed to test the accuracy of bioelectrical impedance analysis (BIA) estimates of body composition among Asian Indians according to two BIA equations--one developed for Asians, the other for Caucasians.

METHODS

Two hundred apparently healthy Asian Indians (100 males, 100 females; mean age 36.6 ± 7.6 years; mean BMI 16.6-46.7 kg/m(2)) underwent BIA assessment of fat mass (FM), fat free mass (FFM) and percentage body fat (%BF) using Tanita Multi-Frequency Body Composition Analyzer MC-180MA (Tanita Corporation, Tokyo, Japan). One set of BIA values was automatically calculated by the analyzer (Caucasian figures), the other set by Tanita (Japanese Asian figures). Results were compared to dual X-ray absorptiometry (DEXA) as the standard measure.

RESULTS

A moderate level of relative agreement was found between the DEXA-derived measurement of %BF and the estimate from both the Caucasian (r(2)=0.75; p<0.001) and Asian equation (r(2)=0.7; p<0.001). Despite this, the level of absolute agreement was poor, with large bias and wide limits of agreement. According to the Caucasian equation the mean difference between methods was -8.3 ± 3.9 (95% limits of agreement -20.10 to 9.40), for the Asian equations mean difference was -5.4 ± 4.3 (95% limits of agreement -20.63 to 11.41).

INTERPRETATION AND CONCLUSIONS

When compared to DEXA, the current Asian and Caucasian Tanita formulae significantly under-estimate the %BF of Asian Indians.

The recognition and treatment of growth disorders - a 50-year retrospective

The past 50 years have seen great progress in the understanding and treatment of classic growth disorders. Advances such as the recognition of hormone receptor defects, the development of recombinant growth hormone, and the expanding awareness of epigenetic phenomena affecting growth are among these great achievements. Yet growth failure remains a pervasive problem among children with complex health conditions, such as survivors of childhood cancers, premature infants, organ transplant recipients, and children with cystic fibrosis. The significant increases in life expectancy among these groups underscores the potential consequences of poor growth, whether due to the underlying conditions or medical treatments, as they may have long-lasting effects into adulthood. The ongoing contributions of human biologists to the study of human growth remain essential in the recognition and treatment of growth disorders, by defining normal patterns of growth and body composition, the interplay of growth and maturation, the role of environmental, behavioral and genetic factors, and the long-term consequences of growth patterns. Examples will be given based on two common genetic disorders, cystic fibrosis and sickle-cell anemia, to highlight the relationships between growth failure, survival, and malnutrition. Also, a study of bone mineral accretion in children with cystic fibrosis will illustrate the importance of understanding patterns of growth in healthy children, and their application in the diagnosis and management of children with chronic disease. These examples accentuate the need for continued participation of human biologists in the study of growth and development and the care of children.

Body composition in childhood: effects of normal growth and disease

Body composition in children is of increasing interest within the contexts of childhood obesity, clinical management of patients and nutritional programming as a pathway to adult disease. Energy imbalance appears to be common in many disease states; however, body composition is not routinely measured in patients. Traditionally, clinical interest has focused on growth or nutritional status, whereas more recent studies have quantified fat mass and lean mass. The human body changes in proportions and chemical composition during childhood and adolescence. Most of the weight gain comprises lean mass rather than fat. In general, interest has focused on percentage fat, and less attention has been paid to the way in which lean mass varies within and between individuals. In the general population secular trends in BMI have been widely reported, indicating increasing levels of childhood obesity, which have been linked to reduced physical activity. However, lower activity levels may potentially lead not only to increased fatness, but also to reduced lean mass. This issue merits further investigation. Diseases have multiple effects on body composition and may influence fat-free mass and/or fat mass. In some diseases both components change in the same direction, whereas in other diseases, the changes are contradictory and may be concealed by relatively normal weight. Improved techniques are required for clinical evaluations. Both higher fatness and reduced lean mass may represent pathways to an increased risk of adult disease.

Cross-validation of bioelectrical impedance analysis for the assessment of body composition in a representative sample of 6- to 13-year-old children

BACKGROUND/OBJECTIVES

(1) To cross-validate tetra- (4-BIA) and octopolar (8-BIA) bioelectrical impedance analysis vs dual-energy X-ray absorptiometry (DXA) for the assessment of total and appendicular body composition and (2) to evaluate the accuracy of external 4-BIA algorithms for the prediction of total body composition, in a representative sample of Swiss children.

SUBJECTS/METHODS

A representative sample of 333 Swiss children aged 6-13 years from the Kinder-Sportstudie (KISS) (ISRCTN15360785). Whole-body fat-free mass (FFM) and appendicular lean tissue mass were measured with DXA. Body resistance (R) was measured at 50 kHz with 4-BIA and segmental body resistance at 5, 50, 250 and 500 kHz with 8-BIA. The resistance index (RI) was calculated as height(2)/R. Selection of predictors (gender, age, weight, RI4 and RI8) for BIA algorithms was performed using bootstrapped stepwise linear regression on 1000 samples. We calculated 95% confidence intervals (CI) of regression coefficients and measures of model fit using bootstrap analysis. Limits of agreement were used as measures of interchangeability of BIA with DXA.

RESULTS

8-BIA was more accurate than 4-BIA for the assessment of FFM (root mean square error (RMSE)=0.90 (95% CI 0.82-0.98) vs 1.12 kg (1.01-1.24); limits of agreement 1.80 to -1.80 kg vs 2.24 to -2.24 kg). 8-BIA also gave accurate estimates of appendicular body composition, with RMSE < or = 0.10 kg for arms and < or = 0.24 kg for legs. All external 4-BIA algorithms performed poorly with substantial negative proportional bias (r> or = 0.48, P<0.001).

CONCLUSIONS

In a representative sample of young Swiss children (1) 8-BIA was superior to 4-BIA for the prediction of FFM, (2) external 4-BIA algorithms gave biased predictions of FFM and (3) 8-BIA was an accurate predictor of segmental body composition.

Modeling upper and lower limb muscle volume by bioelectrical impedance analysis

Most studies employing bioelectrical impedance analysis (BIA) for estimating appendicular skeletal muscle mass using descriptive BIA models rely on statistical rather than biophysical principles. The aim of the present study was to evaluate the feasibility of estimating arm and leg muscle volume (MV) based on multiple bioimpedance measurements and using a recently proposed mathematical model and to compare this technique to conventional segmental BIA at high and low frequencies. MV of the arm and leg, respectively, was determined in 15 young, healthy, active men [age 22 ± 2 (SD) yr, total body fat 15.6 ± 5.1%] by magnetic resonance imaging (MRI) and BIA using a conventional and new bioimpedance model. MRI-determined MV for leg and arm was 6,268 ± 1,099 and 1,173 ± 172 cm3, respectively. Estimated MV by the new BIA model [leg: 6,294 ± 1,155 cm3 (50 kHz), 6,278 ± 1,103 cm3 (500 kHz); arm: 1,216 ± 172 cm3 (50 kHz), 1,155 ± 157 cm3 (500 kHz)] was not statistically different from MRI-determined MV (leg: P= 0.958; arm: P= 0.188). The new BIA model was superior to conventional BIA and performed best at 500 kHz for estimating leg MV as indicated by the lower relative total error [new: 3.6% (500 kHz), 5.2% (50 kHz); conventional: 7.6% (500 kHz) and 8.3% (50 kHz)]. In contrast, the new BIA model, both at 50 and 500 kHz, did not improve the accuracy for estimating arm MV [new: 10.8% (500 kHz), 10.6% (50 kHz); conventional: 11.8% (500 kHz), 11.4% (50 kHz)]. It was concluded that modeling of multiple BIA measurements has advantages for the determination of lower limb muscle volume in healthy, active adult men.

A new total body potassium method to estimate total body skeletal muscle mass in children

A whole body skeletal muscle [(SM); kg] mass estimation model, based on total body potassium [(TBK); mmol] measured by whole body (40)K counting (WBC) was developed (SM = 0.0082.TBK) and validated in adults in a previous study. It is unknown whether the adult TBK SM prediction model is applicable for pediatric use. The aim of this study was to derive and validate a pediatric TBK SM prediction equation. SM measured by MRI was used as the criterion and TBK was measured by WBC. The protocol was completed in 116 healthy children, 66 males and 50 females, 11.7 +/- 3.5 y (mean +/- SD, range = 5-17 y). A strong linear correlation was observed between TBK and SM (r = 0.984; P < 0.001). The SM:TBK ratio was 0.0071 +/- 0.0008 kg/mmol in the children studied, much lower than the corresponding value of 0.0082 kg/mmol in adults. An empirical SM prediction equation was developed using TBK alone: SM = 0.0085.TBK - 2.83, r(2) = 0.97, SEE = 1.39 kg. Bland-Altman analysis did not disclose a significant bias in the prediction of SM. When biological factors entered along with TBK in the general linear model, another prediction equation was developed: SM = 5.52 + 0.001.TBK (mmol) + 0.081.weight (kg) - 0.049.height (cm) + 0.00004.TBK . height + race (-0.60 for Caucasian, 0.49 for African-American, and 0 for Hispanic). Because the adult TBK SM prediction model is not applicable for pediatric use, this study provides new empirical TBK SM prediction equations that should prove useful for studies on nutrition, growth, and development in children.

Total-body skeletal muscle mass: estimation by dual-energy X-ray absorptiometry in children and adolescents

BACKGROUND

Skeletal muscle (SM) is an important compartment but is difficult to quantify in children and adolescents.

OBJECTIVE

We investigated the potential of dual-energy X-ray absorptiometry (DXA) for measuring total-body SM in pediatric subjects.

DESIGN

A previously published adult DXA SM prediction formula was evaluated in children and adolescents aged 5-17 y (n = 99) who varied in pubertal maturation stage. SM estimated by whole-body magnetic resonance imaging (MRI) was used as the reference. The adult SM model was not accurate for subjects below Tanner stage 5 (n = 65; aged 5-14 y). New pediatric SM prediction models were therefore developed and validated in a separate group (n = 18).

RESULTS

The adult DXA SM prediction model was valid in subjects at Tanner stage 5 but significantly (P < 0.001) overestimated SM in subjects below Tanner stage 5. New SM prediction formulas were developed with appendicular lean soft tissue (ALST) estimates by DXA as the main predictor variable (eg, model 1, ALST alone: R(2) = 0.982, SEE = 0.565 kg, P < 0.001). The new models were validated by the leave-one-out method and were cross-validated in a separate validation group.

CONCLUSIONS

A previously reported adult DXA SM prediction model is applicable in children and adolescents late in pubertal development (Tanner stage 5). A new DXA SM prediction model was developed for prepubertal and pubertal subjects (Tanner stage </=4) aged >/=5 y. DXA thus provides an important opportunity for quantifying total-body SM mass across most of the human life span.

The validity of bioelectrical impedance models in clinical populations

Bioelectrical impedance analysis (BIA) is the most commonly used body composition technique in published studies. Herein we review the theory and assumptions underlying the various BIA and bioelectrical impedance spectroscopy (BIS) models, because these assumptions may be invalidated in clinical populations. Single-frequency serial BIA and discrete multifrequency BIA may be of limited validity in populations other than healthy, young, euvolemic adults. Both models inaccurately predict total body water (TBW) and extracellular water (ECW) in populations with changes in trunk geometry or fluid compartmentalization, especially at the level of the individual. Single-frequency parallel BIA may predict body composition with greater accuracy than the serial model. Hand-to-hand and leg-to-leg BIA models do not accurately predict percent fat mass. BIS may predict ECW, but not TBW, more accurately than single-frequency BIA. Segmental BIS appears to be sensitive to fluid accumulation in the trunk. In general, bioelectrical impedance technology may be acceptable for determining body composition of groups and for monitoring changes in body composition within individuals over time. Use of the technology to make single measurements in individual patients, however, is not recommended. This has implications in clinical settings, in which measurement of individual patients is important.

New bioimpedance analysis system: improved phenotyping with whole-body analysis

OBJECTIVE

Bioimpedance analysis (BIA) is a potential field and clinical method for evaluating skeletal muscle mass (SM) and %fat. A new BIA system has 8-(two on each hand and foot) rather than 4-contact electrodes allowing for rapid 'whole-body' and regional body composition evaluation.

DESIGN

This study evaluated the 50 kHz BC-418 8-contact electrode and TBF-310 4-contact electrode foot-foot BIA systems (Tanita Corp., Tokyo, Japan).

SUBJECTS

There were 40 subject evaluations in males (n=20) and females (n=20) ranging in age from 6 to 64 y. BIA was evaluated in each subject and compared to reference lean soft-tissue (LST) and %fat estimates in the appendages and remainder (trunk+head) provided by dual-energy X-ray absorptiometry (DXA). Appendicular LST (ALST) estimates from both BIA and DXA were used to derive total body SM mass.

RESULTS

The highest correlation between total body LST by DXA and impedance index (Ht(2)/Z) by BC-418 was for the foot-hand segments (r=0.986; left side only) compared to the arm (r=0.970-0.979) and leg segments (r=0.942-0.957)(all P<0.001). The within- and between-day coefficient of variation for %fat and ALST evaluated in five subjects was <1% and approximately 1-3.7%, respectively. The correlations between 8-electrode predicted and DXA appendicular (arms, legs, total) and trunk+head LST were strong and highly significant (all r> or =0.95, P<0.001) and group means did not differ across methods. Skeletal muscle mass calculated (Kim equation) from total ALST by DXA (X+/-s.d.)(23.7+/-9.7 kg) was not significantly different and highly correlated with BC-418 estimates (25.2+/-9.6 kg; r=0.96, P<0.001). There was a good correlation between total body %fat by 8-electrode BIA vs DXA (r=0.87, P<0.001) that exceeded the corresponding association with 4-electrode BIA (r=0.82, P<0.001). Group mean segmental %fat estimates from BC-418 did not differ significantly from corresponding DXA estimates. No between-method bias was detected in the whole body, ALST, and skeletal muscle analyses.

CONCLUSIONS

The new 8-electrode BIA system offers an important new opportunity of evaluating SM in research and clinical settings. The additional electrodes of the new BIA system also improve the association with DXA %fat estimates over those provided by the conventional foot-foot BIA.

Estimation of Total-Body Skeletal Muscle Mass in Children and Adolescents

PURPOSE

The estimation of total-body skeletal muscle mass (SMM) has been predicted in healthy adults using anthropometric measurements and urine creatinine excretion. SMM measurement is compulsory to evaluate exercise performance and the influence of physical training on muscle mass. However, there is a lack of information on children and adolescents when quantifying appendicular skeletal muscle mass.

METHODS

Thirty-nine Caucasian children and adolescents (male and female, 7-16 yr old) and 20 adults (men and women, 20-24 yr old) were tested for total-body SMM using dual-energy x-ray absorptiometry measurement (DEXA), anthropometric measurements (ANTHR), and urine creatinine (UCrn) determination. Skinfold thickness and circumference were measured at mid-arm (CAG), mid-thigh (CTG), and mid-calf (CCG) and the skin-corrected circumferences (cm), together with height (Ht; m), age (yr), and sex (0 for female, 1 for male). The UCrn excretion (g.24 h(-1)) was also determined in all subjects. The ANTHR and UCrn measurements were then compared with DEXA as reference value.

RESULTS

The multiple linear regression from anthropometric measurements gave the following equation to evaluate the total-body skeletal muscle mass (SMM) in children and adolescents: SMM (kg) = Ht x [(0.0064 x CAG) + (0.0032 x CTG) + (0.0015 x CCG)(2)] + (2.56 x sex) + (0.136 x age). The prediction of SMM from a 24-h urine collection was obtained with the following equation: SMM (kg) = (10.62 x Crn) + 6.63. The correlation coefficient (r(2)) was 0.966 and 0.710 for the anthropometric and creatinine methods, respectively (P < 0.001).

CONCLUSION

Besides DEXA technique, the determination of total-body skeletal muscle mass in children and adolescents can be highly validated with satisfactory confidence by simple anthropometric measurements or 24-h urine creatinine excretion.

Segmental bioelectrical impedance analysis

PURPOSE OF REVIEW

The bioelectrical impedance analysis method is a non-invasive, rapid accurate and practical method for assessing body composition. During last decade evidence has been gathered that supports the use of this method to monitor hydration status. This review critically examines different approaches and applications of segmental bioelectrical impedance analysis in the healthy and clinical situations.

RECENT FINDINGS

Segmental bioelectrical impedance analysis may be useful to assess appendicular lean body mass, to estimate muscle volume and to investigate possible relationships between muscle size and strength in a limited segment of the limb. The method may become a tool for the bedside detection of fluid accumulation in critical care.

SUMMARY

This is a review of segmental bioelectrical impedance. The preponderance of the published applications of bioelectrical impedance analysis focused on applications in a healthy population and in the field indicate the validity of the methods. A short description of the set-up of the segmental method is also given. This review discusses the application of segmental bioelectrical impedance analysis in children in different ethnic populations, in clinical situations. We also examine the application of the method to assessing body composition, and monitoring rapid changes in internal fluid balance in the field of haemodialysis and during surgery.

Detection of segmental internal fat by bioelectrical impedance analysis in a biological phantom

OBJECTIVE

Quantification of internal adipose tissue such as visceral adipose tissue currently relies on expensive, cross-sectional imaging modalities. The purpose of this study was to test the hypothesis that surface impedance, determined by bioimpedance analysis, might be used to predict regional internal fat content change in a phantom model.

METHODS

Fresh hollowed-out cucumbers were used as cylindrical biological phantoms to test this hypothesis. After removal of the seeds, the cucumbers were filled with normal saline, mixture of saline and corn oil, or porcine adipose tissue bathed in saline. Surface resistance and reactance were measured with a bioimpedance analyzer accurate to 0.1 Omega (Quantum 10X, RJL Systems), and impedance was calculated. A linear regression model was used to interpret the association between composition and impedance.

RESULTS

Surface impedance varied linearly with changes in the relative internal corn oil portions (r- = 0.98). A similar relation was noted with porcine adipose tissue bathed in saline (r(2) = 0.95) regardless of the specific position of adipose tissue within the cucumber.

CONCLUSION

Surface impedance measured by bioimpedance analysis can detect variations in fat content in the interior of a cylindrical phantom.

Transition of care between paediatric and adult gastroenterology. Assessment of growth and nutrition

Growth is a dynamic process that is characterized by physiological changes in an individual from infancy into adulthood. Growth should be monitored sequentially and is an important tool in the early detection of chronic disease in children. Growth occurs in three phases: infancy, childhood and puberty (adolescence). The adequacy of nutritional status can be assessed by anthropometric measurements that include height, weight and body composition as well as laboratory evaluations. Individual patients can then be compared to normative or expected values. Impaired growth and nutritional status can be seen in a variety of gastrointestinal disorders and are described in this chapter.

Segmental bioelectrical impedance analysis in children aged 8-12 y: 1. The assessment of whole-body composition

OBJECTIVES

To investigate the potential of segmental bioelectrical impedance analysis (BIA) for estimating whole-body composition in children.

DESIGN

Strengths of relationships were determined between indices of impedance or specific resistivities of body segments and reference four-component model (4-CM) assessments of body composition.

SUBJECTS

Eighteen boys and 19 girls aged 8-12 y.

MEASUREMENTS

Whole-body and segment BIA and anthropometry were used to calculate impedance indices of the whole body and segments and specific resistivities of segments; total body water (TBW), fat-free mass (FFM) and body fat were assessed using the 4-CM.

RESULTS

Segmental BIA indices were significantly related to body composition, provided that appropriate comparisons were undertaken for each index: impedance adjusted for unit segment length was better related to TBW and FFM, whereas segment specific resistivity was better related to body fat. Differences between body composition estimates obtained with the 4-CM and predicted using BIA were partly dependent on limb-to-trunk ratios of BIA indices.

CONCLUSION

Segmental BIA has potential for providing additional alternative approaches to the assessment of whole-body composition in children: (a) FFM and TBW were best related to impedance adjusted for segment length; (b) body fat was best related to segment specific resistivity; and (c) the relative influences of different segment BIA indices may be utilisable for generating more valid whole-body composition estimates.