Bioelectrical impedance analysis models for prediction of total body water and fat-free mass in healthy and HIV-infected children and adolescents

Sex differences in responses to antiretroviral treatment in South African HIV-infected children on ritonavir-boosted lopinavir- and nevirapine-based treatment

BACKGROUND

While studies of HIV-infected adults on antiretroviral treatment (ART) report no sex differences in immune recovery and virologic response but more ART-associated complications in women, sex differences in disease progression and response to ART among children have not been well assessed. The objective of this study was to evaluate for sex differences in response to ART in South African HIV-infected children who were randomized to continue ritonavir-boosted lopinavir (LPV/r)-based ART or switch to nevirapine-based ART.

METHODS

ART outcomes in HIV-infected boys and girls in Johannesburg, South Africa from 2005-2010 were compared. Children initiated ritonavir-boosted lopinavir (LPV/r)-based ART before 24 months of age and were randomized to remain on LPV/r or switch to nevirapine-based ART after achieving viral suppression. Children were followed for 76 weeks post-randomization and then long-term follow up continued for a minimum of 99 weeks and maximum of 245 weeks after randomization. Viral load, CD4 count, lipids, anthropometrics, drug concentrations, and adherence were measured at regular intervals. Outcomes were compared between sexes within treatment strata.

RESULTS

A total of 323 children (median age 8.8 months, IQR 5.1-13.5), including 168 boys and 155 girls, initiated LPV/r-based ART and 195 children were randomized. No sex differences in risk of virological failure (confirmed viral load >1000 copies/mL) by 156 weeks post-randomization were observed within either treatment group. Girls switched to nevirapine had more robust CD4 count improvement relative to boys in this group through 112 weeks post-randomization. In addition, girls remaining on LPV/r had higher plasma concentrations of ritonavir than boys during post-randomization visits. After a mean of 3.4 years post-randomization, girls remaining on LPV/r also had a higher total cholesterol:HDL ratio and lower mean HDL than boys on LPV/r.

CONCLUSIONS

Sex differences are noted in treated HIV-infected children even at a young age, and appear to depend on treatment regimen. Future studies are warranted to determine biological mechanisms and clinical significance of these differences.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00117728.

The effect of puberty on fat oxidation rates during exercise in overweight and normal-weight girls

Excess weight is often associated with insulin resistance (IR) and may disrupt fat oxidation during exercise. This effect is further modified by puberty. While studies have shown that maximal fat oxidation rates (FOR) during exercise decrease with puberty in normal-weight (NW) and overweight (OW) boys, the effect of puberty in NW and OW girls is unclear. Thirty-three NW and OW girls ages 8–18 yr old completed a peak aerobic capacity test on a cycle ergometer. FOR were calculated during progressive submaximal exercise. Body composition and Tanner stage were determined. For each participant, a best-fit polynomial curve was constructed using fat oxidation vs. exercise intensity to estimate max FOR. In a subset of the girls, IR derived from an oral glucose tolerance test ( n = 20), and leptin and adiponectin levels ( n = 11) were assessed in relation to FOR. NW pre-early pubertal girls had higher max FOR [6.9 ± 1.4 mg·kg fat free mass (FFM)−1·min−1] than NW mid-late pubertal girls (2.2 ± 0.9 mg·kg FFM−1·min−1) ( P = 0.002), OW pre-early pubertal girls (3.8 ± 2.1 mg·kg FFM−1·min−1), and OW mid-late pubertal girls (3.3 ± 0.9 mg·kg FFM−1·min−1) ( P < 0.05). Bivariable analyses showed positive associations between FOR with homeostatic model assessment of IR ( P = 0.001), leptin ( P < 0.001), and leptin-to-adiponectin ratio ( P = 0.001), independent of percent body fat. Max FOR decreased in NW girls during mid-late puberty; however, this decrease associated with puberty was blunted in OW girls due to lower FOR in pre-early puberty. The presence of IR due to obesity potentially masks the effect of puberty on FOR during exercise in girls.

Bioelectrical impedance analysis to estimate body composition in children and adolescents: a systematic review and evidence appraisal of validity, responsiveness, reliability and measurement error

Bioelectrical impedance analysis (BIA) is a practical method to estimate percentage body fat (%BF). In this systematic review, we aimed to assess validity, responsiveness, reliability and measurement error of BIA methods in estimating %BF in children and adolescents.We searched for relevant studies in Pubmed, Embase and Cochrane through November 2012. Two reviewers independently screened titles and abstracts for inclusion, extracted data and rated methodological quality of the included studies. We performed a best evidence synthesis to synthesize the results, thereby excluding studies of poor quality. We included 50 published studies. Mean differences between BIA and reference methods (gold standard [criterion validity] and convergent measures of body composition [convergent validity]) were considerable and ranged from negative to positive values, resulting in conflicting evidence for criterion validity. We found strong evidence for a good reliability, i.e. (intra-class) correlations ≥0.82. However, test-retest mean differences ranged from 7.5% to 13.4% of total %BF in the included study samples, indicating considerable measurement error. Our systematic review suggests that BIA is a practical method to estimate %BF in children and adolescents. However, validity and measurement error are not satisfactory.

Contact investigation for active tuberculosis among child contacts in Uganda

BACKGROUND

Tuberculosis is a large source of morbidity and mortality among children. However, limited studies characterize childhood tuberculosis disease, and contact investigation is rarely implemented in high-burden settings. In one of the largest pediatric tuberculosis contact investigation studies in a resource-limited setting, we assessed the yield of contact tracing on childhood tuberculosis and indicators for disease progression in Uganda.

METHODS

Child contacts aged <15 years in Kampala, Uganda, were enrolled from July 2002 to June 2009 and evaluated for tuberculosis disease via clinical, radiographic, and laboratory methods for up to 24 months.

RESULTS

Seven hundred sixty-one child contacts were included in the analysis. Prevalence of tuberculosis in our child population was 10%, of which 71% were culture-confirmed positive. There were no cases of disseminated tuberculosis, and 483 of 490 children (99%) started on isoniazid preventative therapy did not develop disease. Multivariable testing suggested risk factors including human immunodeficiency virus (HIV) status (odds ratio [OR], 7.90; P < .001), and baseline positive tuberculin skin test (OR, 2.21; P = .03); BCG vaccination was particularly protective, especially among children aged ≤5 years (OR, 0.23; P < .001). Adult index characteristics such as sex, HIV status, and extent or severity of disease were not associated with childhood disease.

CONCLUSIONS

Contact tracing for children in high-burden settings is able to identify a large percentage of culture-confirmed positive tuberculosis cases before dissemination of disease, while suggesting factors for disease progression to identify who may benefit from targeted screening.

A PRISMA-driven systematic review of predictive equations for assessing fat and fat-free mass in healthy children and adolescents using multicomponent molecular models as the reference method

Simple methods to assess both fat (FM) and fat-free mass (FFM) are required in paediatric populations. Several bioelectrical impedance instruments (BIAs) and anthropometric equations have been developed using different criterion methods (multicomponent models) for assessing FM and FFM. Through childhood, FFM density increases while FFM hydration decreases until reaching adult values. Therefore, multicomponent models should be used as the gold standard method for developing simple techniques because two-compartment models (2C model) rely on the assumed adult values of FFM density and hydration (1.1 g/cm(3) and 73.2%, respectively). This study will review BIA and/or anthropometric-based equations for assessing body composition in paediatric populations. We reviewed English language articles from MEDLINE (1985-2012) with the selection of predictive equations developed for assessing FM and FFM using three-compartment (3C) and 4C models as criterion. Search terms included children, adolescent, childhood, adolescence, 4C model, 3C model, multicomponent model, equation, prediction, DXA, BIA, resistance, anthropometry, skinfold, FM, and FFM. A total of 14 studies (33 equations) were selected with the majority developed using DXA as the criterion method with a limited number of studies providing cross-validation results. Overall, the selected equations are useful for epidemiological studies, but some concerns still arise on an individual basis.

An evaluation of early cardiometabolic risk factors in children and adolescents with Turner syndrome

BACKGROUND AND OBJECTIVES

Turner syndrome (TS) confers increased lifetime risk of type 2 diabetes mellitus and cardiovascular disease. We compared cardiometabolic risk factors and measures of subcutaneous, visceral adipose tissue and intra-myocellular lipid between young TS girls and an age- and BMI-standard deviation scores (SDS)-matched healthy female cohort.

PATIENTS AND METHODS

A cross-sectional cohort study was conducted at the Hospital for Sick Children, Toronto. Nineteen TS and 17 control girls (13.7 ± 2.5 vs 12.7 ± 3.4 years of age, respectively, P = 0.30). Multiple-sample oral glucose tolerance test with measurement of fasting insulin, LDL, HDL, triglycerides, adiponectin and highly sensitive C-reactive protein (hsCRP) was performed. Subcutaneous adipose tissue, visceral adipose tissue intramyocellular lipid levels evaluated by magnetic resonance techniques. Insulin secretion (IS), sensitivity (Si) and the insulin secretion-sensitivity index (ISSI-2) were calculated from oral glucose tolerance test data.

RESULTS

Five TS and no controls had impaired fasting glucose or impaired glucose tolerance; none had type 2 diabetes mellitus. Insulin sensitivity and insulin secretion were similar between groups; ISSI-2 was lower in TS (923.5 ± 307.3 vs 659.1 ± 387.3; P = 0.03). TS girls had higher blood pressure (82.5 ± 13.6 vs 73.5 ± 5.5 mmHg; P = 0.0146), waist circumference (76.0 ± 11.8 vs 65.9 ± 9.7; P = 0.0087) and subcutaneous adipose tissue (135.6 ± 88.6 vs 69.3 ± 59.9; P = 0.01) than controls. Visceral adipose tissue, intramyocellular lipid levels and adiponectin were not different between groups. TS girls also had higher triglycerides (1.1 ± 0.6 vs 0.7 ± 0.3; P = 0.003), total cholesterol (4.4 ± 0.7 vs 3.9 ± 0.4; P = 0.02) and hsCRP (2.0 ± 1.9 vs 0.8 ± 0.3; P = 0.01).

CONCLUSIONS

TS girls exhibit more cardiometabolic risk factors and reduced beta cell function compared with age- and BMI-SDS-matched girls. Increased awareness of early risk of type 2 diabetes mellitus and hypertension in TS girls is needed.

Metabolic abnormalities and body composition of HIV-infected children on Lopinavir or Nevirapine-based antiretroviral therapy

BACKGROUND

Few studies have assessed metabolic and body composition alterations in perinatally HIV-infected African children on antiretroviral therapy (ART). We compared metabolic profiles and regional fat of children on ritonavir-boosted lopinavir (lopinavir/ritonavir), lamivudine and stavudine to those switched to nevirapine, lamivudine and stavudine.

METHODS

This study evaluated metabolic and body composition outcomes in 156 HIV-infected children completing a randomised trial that assessed the continued use of lopinavir/ritonavir-based ART or switch to nevirapine-based ART in Johannesburg, South Africa (2005-2010). Fasting total cholesterol (TC), high-density lipoprotein (HDL), low-density lipoprotein (LDL), triglycerides total and regional body fat (BF) were measured. A clinical assessment for lipodystrophy (LD) was conducted.

RESULTS

156 children (mean age 5.1±0.8 years, mean duration of treatment 4.2±0.7 years, mean time since randomisation 3.4±0.7 years) were enrolled. 85 were randomised to the lopinavir/ritonavir group and 71 to the nevirapine group. The lopinavir/ritonavir group had lower mean HDL (1.3±0.4 vs 1.5±0.4 mmol/l, p<0.001) and higher mean TC (4.4±1.0 vs 4.1±0.8 mmol/l, p=0.097), LDL (2.6±0.9 vs 2.3±0.7 mmol/l, p=0.018) and triglycerides (1.1±0.4 vs 0.8±0.3 mmol/l, p<0.001). The lopinavir/ritonavir group had more total BF by mean skinfold sum (43±11.1 vs 39±10.1 mm, p=0.031) and BF% by bioelectrical impedance analysis (17.0±7.0 vs 14.1±8.0%, p=0.022). Thirteen (8.4%) met criteria for LD.

CONCLUSIONS

Unfavourable alterations in lipid profile and triglycerides, and differences in fat are detectable in young HIV-infected South African children receiving lopinavir/ritonavir-based regimens versus those switched to nevirapine-based regimens. Interventions to mitigate these alterations are warranted to reduce long-term cardiovascular disease risk.

Effects of heavy prenatal alcohol exposure and iron deficiency anemia on child growth and body composition through age 9 years

BACKGROUND

Prenatal alcohol exposure has been associated with pre- and postnatal growth restriction, but little is known about the natural history of this restriction throughout childhood or the effects of prenatal alcohol on body composition. The objective of this study was to examine the effects of heavy prenatal alcohol exposure on longitudinal growth and body composition.

METHODS

Eighty-five heavy drinking pregnant women (≥2 drinks/d or ≥4 drinks/occasion) and 63 abstaining and light-drinking controls (<1 drink/d, no binging) were recruited at initiation of prenatal care in an urban obstetrical clinic in Cape Town, South Africa and prospectively interviewed during pregnancy about alcohol, smoking, drug use, and demographics. Among their children, length/height, weight, and head circumference were measured at 6.5 and 12 months and at 5 and 9 years. Percent body fat (BF) was estimated at age 9 years using bioelectric impedance analysis.

RESULTS

In multiple regression models with repeated measures (adjusted for confounders), heavy alcohol exposure was associated with reductions in weight (0.6 SD), length/height (0.5 SD), and head circumference (0.9 cm) from 6.5 months to 9 years that were largely determined at birth. These effects were exacerbated by iron deficiency in infancy but were not modified by iron deficiency or measures of food security at 5 years. An alcohol-related postnatal delay in weight gain was seen at 12 months. Effects on head circumference were greater at age 9 than at other age points. Although heavy alcohol exposure was not associated with changes in body composition, children with fetal alcohol syndrome (FAS) and partial fetal alcohol syndrome (PFAS) had lower percent BF than heavy exposed nonsyndromal and control children.

CONCLUSIONS

Heavy prenatal alcohol exposure is related to prenatal growth restriction that persists through age 9 years and an additional delay in weight gain during infancy. FAS and PFAS diagnoses are associated with leaner body composition in later childhood.

Impaired aerobic exercise adaptation in children and adolescents with craniopharyngioma is associated with hypothalamic involvement

OBJECTIVE

Many patients treated for craniopharyngioma (CP) complain of a relative incapacity for physical activity. Whether this is due to an objective decrease in adaptation to exercise is unclear. We assessed exercise tolerance in children with surgically treated CP and appropriate pituitary hormone replacement therapy compared with healthy controls and we examined the potential relationships with hypothalamic involvement, GH replacement, and the catecholamine deficiency frequently observed in these subjects.

DESIGN AND METHODS

Seventeen subjects (12 males and five females) with CP and 22 healthy controls (14 males and eight females) aged 15.3±2.5 years (7.3-18 years) underwent a standardized cycle ergometer test. Maximum aerobic capacity was expressed as the ratio of VO(2max) to fat-free mass (VO(2max)/FFM), a measure independent of age and fat mass in children.

RESULTS

VO(2max)/FFM was 20% lower in children with CP compared with controls (P<0.05), even after adjustment for gender. Children with hypothalamic involvement (n=10) had a higher percentage of fat mass (P<0.05) than those without hypothalamic involvement (n=7) and lower VO(2max)/FFM (P<0.05), whereas children without hypothalamic involvement had VO(2max)/FFM close to that of controls (P>0.05). GH treatment was associated with a significant positive effect on aerobic capacity (P<0.05) only in the absence of hypothalamic involvement. No relationship was found between exercise capacity parameters and daily urine epinephrine excretion or epinephrine peak response to insulin-induced hypoglycemia.

CONCLUSIONS

Children with CP have a decrease in aerobic capacity mainly related to hypothalamic involvement. The hypothalamic factors altering aerobic capacity remain to be determined.

Relationship of insulin resistance to psychobehavioral characteristics of overweight and obese African American children

OBJECTIVES

The objective of this study was to evaluate the relationships of insulin resistance to positive as well as negative dimensions of the child's emotions, behavior and personality (hereafter referred to as "psychobehavioral characteristics") in a convenience sample of inner-city, overweight and obese, African American children.

METHODS

A secondary analysis was performed on a sample of 127 children ages 9-12 yr old who were participating in a community-based, Type 2 diabetes prevention program. Psychobehavioral characteristics of children were assessed using both child and parent ratings derived from the Behavioral Assessment for Children, 2nd edition (BASC-2). Body fatness was evaluated using anthropometric techniques, and insulin resistance (HOMA-IR) was calculated from fasting glucose and insulin concentrations. Hierarchical multiple linear regression models were employed with BASC scales as dependent variables and HOMA-IR as the independent variable of interest.

RESULTS

After adjusting for child age, pubertal stage, gender, family socioeconomic index, and intervention group assignment, child HOMA-IR was related at p<0.05 to less favorable scores for parent-report of behavioral symptoms and externalizing problems composites, and to content scales for bullying and negative emotionality. Additionally, child HOMA-IR was related at p<0.01 to less favorable scores for child-report inattention/hyperactivity composite. Body fatness suppressed the unfavorable relationship between HOMA-IR and these and other psychobehavioral characteristics as the degree of significance was higher following adjustment for body fatness in this cohort.

CONCLUSION

More than one psychobehavioral characteristic were associated with body fatness and insulin resistance in the overweight children of this study. Whether the associations are due to several, or only one, of these psychobehavioral characteristics could not be determined. A much larger and future study will be needed to determine which, if any, of these psychobehavioral characteristics are independently associated with insulin resistance in overweight children.

Measuring body composition and energy expenditure in children with severe neurologic impairment and intellectual disability

BACKGROUND

Accurate prediction equations for estimating body composition and total energy expenditure (TEE) in children with severe neurologic impairment and intellectual disability are currently lacking.

OBJECTIVE

The objective was to develop group-specific equations to predict body composition by using skinfold-thickness measurements and bioelectrical impedance analysis (BIA) and to predict TEE by using data on mobility, epilepsy, and muscle tone.

DESIGN

Measures of body composition with the use of skinfold-thickness measurements (percentage of body fat) and BIA (total body water) were compared with those from isotope dilution (reference method) by using intraclass correlation coefficients (ICCs) and Bland and Altman limits of agreement analyses. With the use of the same methods, the outcomes of cerebral palsy-specific TEE equations were compared with those of the doubly labeled water method (reference method). Group-specific regression equations were developed by using forward-stepwise-multiple-correlation-regression analyses.

RESULTS

Sixty-one children with a mean (±SD) age of 10.1 ± 4.3 y (32 boys) were studied. A new equation based on the sum of 4 skinfold-thickness measurements did not improve agreement (n = 49; ICC = 0.61), whereas the newly developed BIA equation-which includes tibia length as an alternative for standing height-did improve agreement (n = 61; ICC = 0.96, SEE = 1.7 kg, R(2) = 0.92). The newly developed TEE equation, which uses body composition, performed better (n = 52; ICC = 0.87, SEE = 180 kcal, R(2) = 0.77) than did the equation of Schofield (n = 52; ICC = 0.82, SEE = 207 kcal, R(2) = 0.69).

CONCLUSIONS

Current cerebral palsy-specific equations for measuring body composition and energy expenditure are inaccurate. BIA is more accurate at assessing nutritional status in this population than is the measurement of skinfold thickness. The newly developed TEE equation, which uses body composition, provides a reasonable estimate of energy expenditure in these children despite its variability.

Longitudinal analysis of sleep in relation to BMI and body fat in children: the FLAME study

OBJECTIVES

To determine whether reduced sleep is associated with differences in body composition and the risk of becoming overweight in young children.

DESIGN

Longitudinal study with repeated annual measurements.

SETTING

Dunedin, New Zealand.

PARTICIPANTS

244 children recruited from a birth cohort and followed from age 3 to 7.

MAIN OUTCOME MEASURES

Body mass index (BMI), fat mass (kg), and fat free mass (kg) measured with bioelectrical impedance; dual energy x ray absorptiometry; physical activity and sleep duration measured with accelerometry; dietary intake (fruit and vegetables, non-core foods), television viewing, and family factors (maternal BMI and education, birth weight, smoking during pregnancy) measured with questionnaire.

RESULTS

After adjustment for multiple confounders, each additional hour of sleep at ages 3-5 was associated with a reduction in BMI of 0.48 (95% confidence interval 0.01 to 0.96) and a reduced risk of being overweight (BMI ≥ 85th centile) of 0.39 (0.24 to 0.63) at age 7. Further adjustment for BMI at age 3 strengthened these relations. These differences in BMI were explained by differences in fat mass index (-0.43, -0.82 to -0.03) more than by differences in fat free mass index (-0.21, -0.41 to -0.00).

CONCLUSIONS

Young children who do not get enough sleep are at increased risk of becoming overweight, even after adjustment for initial weight status and multiple confounding factors. This weight gain is a result of increased fat deposition in both sexes rather than additional accumulation of fat free mass.

Desempenho de diferentes equações antropométricas na predição de gordura corporal excessiva em crianças e adolescentes

OBJETIVO: O objetivo do presente estudo foi analisar a eficiência de diferentes equações antropométricas para a identificação de excesso de gordura corporal entre crianças e adolescentes. MÉTODOS: A amostra foi composta por 1.498 indivíduos (678 meninos e 820 meninas), com idade entre 7 e 17 anos (M=13,7, DP=2,0), da cidade de Presidente Prudente (SP). A massa corporal e a estatura foram mensuradas para o cálculo do Índice de Massa Corporal. Também foi realizada a mensuração da circunferência de cintura e das dobras cutâneas subescapular, tricipital, abdominal e da panturrilha. O percentual de gordura corporal foi calculado por meio de quatro equações: Slaughter et al., Slaughter II et al., Dezenberg et al., e Deurenberg et al.. Para indicar a eficiência das diferentes equações antropométricas na indicação da obesidade, foi utilizada a análise da curva Receiver Operating Characteristic Curve. RESULTADOS: No grupo masculino, foram observados valores de sensibilidade elevados (82,4% a 100,0%) e valores oscilando de baixo a alto, para a especificidade (20,9% a 94,9%). Para o sexo feminino, os valores de sensibilidade variaram entre moderado e alto (72,2% a 99,4%); e os de especificidade apresentaram, também, grande oscilação entre baixo e alto (21,6% a 98,2%). CONCLSÃO: A equação proposta por Deurenberg et al., apresentou o melhor desempenho no diagnóstico tanto da presença como da ausência de obesidade na amostra investigada.

Insulin resistance and self-perceived scholastic competence in inner-city, overweight and obese, African American children

PURPOSE

scholastic competence is a predictor of future achievement, yet there is little research about health factors that influence the development of self-perceived scholastic competence (SPSC). This study examined the relationship of insulin resistance and body fatness with SPSC in low-income, overweight and obese, African American children.

METHODS

data were analyzed from a convenience sample of 9-10years old African American children (89 boys and 113 girls) enrolled in a type 2 diabetes prevention study. Health variables analyzed for their influence on SPSC (Harter scale) included insulin resistance (Homeostatic model-derived insulin sensitivity, HOMA-IR) and body fatness (% body fat). Adjustments were made for self-esteem (Global Self Worth).

RESULTS

there was a significant gender by insulin resistance interaction effect on the child's SPSC, so separate regression models were developed for each gender. In boys, neither insulin resistance nor body fatness was related to SPSC. In girls, however, insulin resistance was negatively related to SPSC scores, and the significance of the relationship increased further after adjusting for body fatness. Body fatness alone was not significantly related to SPSC in girls, but after adjusting for insulin resistance, body fatness was positively related to SPSC. Thus, insulin resistance and body fatness mutually suppressed SPSC in girls.

CONCLUSION

high SPSC was associated with lower insulin resistance and, with insulin resistance held constant, with higher body fatness in girls but not in boys. These relationships were not influenced by self-esteem in these children.

Measures of obesity associated with asthma diagnosis in ethnic minority children

Objective. The study objective was to examine relationships between different body size measurements and asthma in ethnic minority children. Methods. We used data from a community-based study of 505 children aged 6-to-8 years old to study the association of percent body fat, fat distribution, and BMI percentile with asthma diagnosis. Poisson regression models were used to compute prevalence ratios (PRs) for sex-specific quintiles of the body fat measures on the main outcome of asthma. Results. When comparing the highest quintile of each body fat measure to the combined lowest two quintiles, higher body mass index percentile, percent body fat, and waist circumference all were associated with a higher likelihood of physician-diagnosed asthma (PR = 1.63 (95% CI 1.12-2.39), 1.50 (95% CI 1.02-2.21), and 1.56 (95% CI 1.04-2.34), resp.). Conclusions. This study found a significant association between increased body size and asthma diagnosis, regardless of the measurement examined.

Associations of proinflammatory cytokine levels with lipid profiles, growth, and body composition in HIV-infected children initiating or changing antiretroviral therapy

OBJECTIVES

To measure proinflammatory cytokines (PIC) in HIV-infected children beginning or changing antiretroviral therapy (ART), evaluating associations with virologic, immunologic, serum lipid, growth, and body composition measures, markers of growth hormone action and glucose metabolism.

METHODS

Forty-nine prepubertal HIV-infected children had measurements of viral load (VL), CD4 lymphocyte count and percentage, serum lipids, apolipoprotein AI/B, IGF-1, IGFBP-1, and IGFBP-3, anthropometry, bioelectrical impedance analysis, TNF-α, IL-1 β, and IL-6 at baseline and 48 weeks of ART.

RESULTS

Baseline levels were detectable (>0.1 pg/mL) for IL-1 β in 28 of 48, and for TNF-α and Il-6 in all 49 children. TNF-α decreased with ART (P < 0.001) and IL-6 demonstrated a similar trend (P = 0.065). Children with 48-week VL <400 copies/mL had greater declines in TNF-α (mean 45%) than subjects with higher VL (5%; P = 0.009). Each 10% improvement in CD4% was associated with 26% lower TNF-α (P = 0.002) and 31% lower IL-6 (P = 0.016). Greater reductions in TNF-α were associated with lower total/HDL cholesterol ratio (P = 0.003) at week 48.

CONCLUSIONS

In HIV-infected children initiating or changing ART, PIC were detectable at baseline and decreased over 48 weeks. Better immunologic responses were associated with greater reductions in TNF-α and IL-6. Reductions in TNF-α were associated with improved total/HDL cholesterol ratio.

Anthropometric correlates of lipoprotein profile and blood pressure in high BMI African American children

OBJECTIVE

To explore the association of anthropometric indices with lipoprotein profile and blood pressure as risk factors of cardiovascular disease, in African American (AA) children.

METHODS

A cross-sectional analysis was carried out on children aged 9-13 years with BMI >85th percentile. Height, weight, waist and hip circumferences, % body fat and blood pressure [systolic (sBP) and diastolic (dBP)] were measured. Fasting plasma levels of triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), intermediate density lipoprotein cholesterol (IDL-C) and very low-density lipoprotein cholesterol (VLDL-C) were analysed.

RESULTS

After accounting for age, gender and pubertal status of the child, multiple linear regression models showed that waist circumference and BMIz were strong predictors for lipoprotein variables. In independent analysis, waist circumference and BMI z-scores were found to be interdependently associated with TG, LDL-C:HDL-C ratio, VLDL-C and sBPz. However, for HDL-C, TG:HDL-C ratio and dBPz, waist circumference was independently and more strongly associated with these risk factors than BMI.

CONCLUSION

Waist circumference was a stronger predictor for lipoprotein variables and blood pressure in high BMI AA children than other anthropometric indices, and may be adequate as a screening test to identify children who are at increased risk for cardiovascular disease.

Taking Action Together: a YMCA-based protocol to prevent type-2 diabetes in high-BMI inner-city African American children

Background

Associated with a tripling in obesity since 1970, type 2 diabetes mellitus (T2DM) in children has risen 9-10 fold. There is a critical need of protocols for trials to prevent T2DM in children.

Methods/Design

This protocol includes the theory, development, evaluation components and lessons learned from a novel YMCA-based T2DM prevention intervention designed specifically for high-BMI African American children from disadvantaged, inner-city neighborhoods of Oakland, California. The intervention was developed on the basis of: review of epidemiological and intervention studies of pediatric T2DM; a conceptual theory (social cognitive); a comprehensive examination of health promotion curricula designed for children; consultation with research, clinical experts and practitioners and; input from community partners. The intervention, Taking Action Together, included culturally sensitive and age-appropriate programming on: healthy eating; increasing physical activity and, improving self esteem.

Discussion

Evaluations completed to date suggest that Taking Action Together may be an effective intervention, and results warrant an expanded evaluation effort. This protocol could be used in other community settings to reduce the risk of children developing T2DM and related health consequences.

Trial registration

ClinicalTrials.gov NCT01039116.

Predictors of growth and body composition in HIV-infected children beginning or changing antiretroviral therapy

OBJECTIVES

The aim of the study was to describe growth and body composition changes in HIV-positive children after they had initiated or changed antiretroviral therapy (ART) and to correlate these with viral, immune and treatment parameters.

METHODS

Ninety-seven prepubertal HIV-positive children were observed over 48 weeks upon beginning or changing ART. Anthropometry and bioelectrical impedance analysis results were compared with results from the National Health and Nutrition Examination Survey 1999-2002 (NHANES) to generate z-scores and with results for HIV-exposed, uninfected children from the Women and Infants Transmission Study (WITS). Multivariate analysis was used to evaluate associations between growth and body composition and disease parameters.

RESULTS

All baseline lean and fat mass measures were below those of controls from NHANES. Weight, height and fat free mass (FFM) index (FFM/height(2)) z-scores increased over time (P = 0.004, 0.037 and 0.027, respectively) and the waist:height ratio z-score decreased (P = 0.045), but body mass index and per cent body fat z-scores did not change. Measures did not increase more than in uninfected WITS controls. In multivariate analysis, baseline height, mid-thigh circumference and FFM z-scores related to CD4 percentage (P = 0.029, P = 0.008 and 0.020, respectively) and change in FFM and FFM index z-scores to CD4 percentage increase (P = 0.010 and 0.011, respectively). Compared with WITS controls, baseline differences in height and mid-thigh muscle circumference were also associated with CD4 percentage. Case-control differences in change in both subscapular skinfold (SSF) thickness and the SSF:triceps skinfold ratio were inversely associated with viral suppression. No measures related to ART class(es) at baseline or over time.

CONCLUSIONS

In these HIV-positive children, beginning or changing ART was associated with improved growth and lean body mass (LBM), as indicated by FFM index. Height and LBM related to CD4 percentage at baseline and over time. Altered fat distribution and greater central adiposity were associated with detectable virus but not ART class(es) received.

Insulin sensitivity and secretion in children and adolescents with hypothalamic obesity following treatment for craniopharyngioma

BACKGROUND

Craniopharyngioma (CP), a tumour occurring in the hypothalamic-pituitary area, results in morbid obesity in 25-60% of affected children. It has been suggested that abnormalities of insulin secretion and/or insulin action due to hypothalamic injury may be associated with weight gain and the metabolic syndrome in this population.

AIM

To evaluate: (i) insulin secretion (IS) and insulin sensitivity (Si); (ii) features of the metabolic syndrome (MS) and (iii) factors involved in risk for diabetes and heart disease in obese youth treated for CP.

METHODS

Obese subjects treated for CP were compared to BMI-matched control subjects. All subjects underwent anthropometric, blood pressure, resting energy expenditure and body fat assessment. Cholesterol and inflammatory markers, oral glucose tolerance test (OGTT) and frequent sampling intravenous glucose tolerance test (FSIGT), with calculation of IS and Si, were performed.

RESULTS

Fifteen CP subjects and 15 controls (C) were studied. There were no differences between CP and C for age, gender, BMI or pubertal status. MS was present in 10/15 CP and 3/15 C (P = 0.03), including impaired glucose tolerance (IGT) in 6/15 CP and 0/15 C (P = 0.02). Measures of IS, including first and second phase IS, and insulin area-under-the-curve (AUC(ins)) during OGTT, were significantly higher in CP. Si, measured by frequent sampled intravenous glucose tolerance test (Si-FSIGT), was significantly lower in CP subjects (0.96 +/- 0.34 vs. 1.67 +/- 0.7; P = 0.01). AUC(ins) was negatively correlated with Si-FSIGT (r = -0.62; P = 0.003).

CONCLUSION

Children with CP and hypothalamic obesity have more features of MS, increased IS and IGT prevalence and lower Si compared with BMI-matched controls.

Prediction of fatness by standing 8-electrode bioimpedance: a multiethnic adolescent population

The objective of this study was to validate an 8-electrode bioimpedance analysis (BIA(8)) device (BC-418; Tanita, Tokyo, Japan) for use in populations of European, Maori, Pacific Island, and Asian adolescents. Healthy adolescents (215 M, 216 F; 129 Pacific Island, 120 Asian, 91 Maori, and 91 European; age range 12-19 years) were recruited by purposive sampling of high schools in Auckland, New Zealand. Weight, height, sitting height, leg length, waist circumference, and whole-body impedance were measured. Fat mass (FM) and fat-free mass (FFM) derived from the BIA(8) manufacturer's equations were compared with measurements by dual-energy X-ray absorptiometry (DXA). DXA-measured FFM was used as the reference to develop prediction equations based on impedance. A double cross-validation technique was applied. BIA(8) underestimated FM by 2.06 kg (P < 0.0001) and percent body fat (%BF) by 2.84% (P < 0.0001), on average. However, BIA(8) tended to overestimate FM and %BF in lean and underestimate FM and %BF in fat individuals. Sex-specific equations developed showed acceptable accuracy on cross-validation. In the total sample, the best prediction equations were, for boys: FFM (kg) = 0.607 height (cm)(2)/impedance ( ohm) + 1.542 age (y) + 0.220 height (cm) + 0.096 weight (kg) + 1.836 ethnicity (0 = European or Asian, 1 = Maori or Pacific) - 47.547, R(2) = 0.93, standard error of estimate (SEE) = 3.09 kg; and, for girls: FFM (kg) = 0.531 height (cm)(2)/impedance ( ohm) + 0.182 height (cm) + 0.096 weight (kg) + 1.562 ethnicity (0 = non-Pacific, 1 = Pacific) - 15.782, R(2) = 0.91, SEE = 2.19 kg. In conclusion, equations for fatness estimation using BIA(8) developed for our sample perform better than reliance on the manufacturer's estimates. The relationship between BIA and body composition in adolescents is ethnicity dependent.

Macronutrient intakes and cardio metabolic risk factors in high BMI African American children

BACKGROUND

The aim of this study was to evaluate the relationship between intakes of energy-providing macronutrients, and markers of cardio metabolic risk factors in high BMI African American (AA) children.

METHODS

A cross sectional analysis of a sample of 9-11 year old children (n = 80) with BMI greater then the 85th percentile. Fasting hematological and biochemical measurements, and blood pressure were measured as selected markers of cardio metabolic risk factors and their relationships to dietary intakes determined.

RESULTS

After adjusting for gender, pubertal stage and waist circumference (WC), multivariate regression analysis showed that higher total energy intakes (when unadjusted for source of energy) were associated with higher plasma concentrations of intermediate density lipoprotein cholesterol (IDL-C) and very low density lipoprotein cholesterol (VLDL-C). Higher intakes of carbohydrate energy (fat and protein held constant) were associated with higher IDL-C, VLDL-C, triglycerides (TG) and homeostasis model assessment of insulin resistance (HOMA-IR). Higher intakes of fat (carbohydrate and protein held constant), however, were associated with lower IDL-C; and higher protein intakes (fat and carbohydrate held constant) were associated with lower HOMA-IR.

CONCLUSION

The specific macronutrients that contribute energy are significantly associated with a wide range of cardio metabolic risk factors in high BMI AA children. Increases in carbohydrate energy were associated with undesirable effects including increases in several classes of plasma lipids and HOMA-IR. Increases in protein energy were associated with the desirable effect of reduced HOMA-IR, and fat energy intakes were associated with the desirable effect of reduced IDL-C. This analysis suggests that the effect of increased energy on risk of developing cardio metabolic risk factors is influenced by the source of that energy.

Accuracy of self-assessed Tanner staging against hormonal assessment of sexual maturation in overweight African-American children

AIM

To evaluate the accuracy of self-reported Tanner (SRT) staging against a proxy method of physician's assessment of sexual maturation, using pubertal hormones in overweight African-American (AA) children.

METHODS

Cross-sectional data from 196 children (113 girls, 83 boys) aged 9-11 years, who were 'overweight' (>85th and <95th percentile for age- and gender-matched BMI; n = 43) or 'obese' (>95th percentile; n = 153) were used. Children assessed their breast or genital and pubic hair development using standardized Tanner drawings representing different stages of sexual maturity. SRT data were compared to pubertal stage assessed by measuring fasting serum concentrations of luteinizing hormone (LH) in boys, and LH and estradiol (E2) in girls, which were used to stage children into pubertal stages 1-5.

RESULTS

SRT stages of genital and pubic hair assessments in boys, and breast and pubic hair assessments in girls, yielded 15-20% concordance (kappa statistic = 0.02-0.12) compared to their hormone-derived pubertal stages.

CONCLUSIONS

Among overweight AA 9-11 year-old children, self-assessment of Tanner staging did not accurately assess their pubertal development when compared to a hormone-derived pubertal assessment method.

Influence of a lifestyle intervention in preschool children on physiological and psychological parameters (Ballabeina): study design of a cluster randomized controlled trial

BACKGROUND

Childhood obesity and physical inactivity are increasing dramatically worldwide. Children of low socioeconomic status and/or children of migrant background are especially at risk. In general, the overall effectiveness of school-based programs on health-related outcomes has been disappointing. A special gap exists for younger children and in high risk groups.

METHODS/DESIGN

This paper describes the rationale, design, curriculum, and evaluation of a multicenter preschool randomized intervention study conducted in areas with a high migrant population in two out of 26 Swiss cantons. Twenty preschool classes in the German (canton St. Gallen) and another 20 in the French (canton Vaud) part of Switzerland were separately selected and randomized to an intervention and a control arm by the use of opaque envelopes. The multidisciplinary lifestyle intervention aimed to increase physical activity and sleep duration, to reinforce healthy nutrition and eating behaviour, and to reduce media use. According to the ecological model, it included children, their parents and the teachers. The regular teachers performed the majority of the intervention and were supported by a local health promoter. The intervention included physical activity lessons, adaptation of the built infrastructure; promotion of regional extracurricular physical activity; playful lessons about nutrition, media use and sleep, funny homework cards and information materials for teachers and parents. It lasted one school year. Baseline and post-intervention evaluations were performed in both arms. Primary outcome measures included BMI and aerobic fitness (20 m shuttle run test). Secondary outcomes included total (skinfolds, bioelectrical impedance) and central (waist circumference) body fat, motor abilities (obstacle course, static and dynamic balance), physical activity and sleep duration (accelerometry and questionnaires), nutritional behaviour and food intake, media use, quality of life and signs of hyperactivity (questionnaires), attention and spatial working memory ability (two validated tests). Researchers were blinded to group allocation.

DISCUSSION

The purpose of this paper is to outline the design of a school-based multicenter cluster randomized, controlled trial aiming to reduce body mass index and to increase aerobic fitness in preschool children in culturally different parts of Switzerland with a high migrant population.

TRIAL REGISTRATION

Trial Registration: (clinicaltrials.gov) NCT00674544.

Aggregate predictions improve accuracy when calculating metabolic variables used to guide treatment

BACKGROUND

Many components of clinical management are tailored to metabolic variables, such as fat-free mass, fat mass, resting metabolic rate (RMR), and body surface area. However, these traits are difficult to measure in routine care and are typically predicted from simple anthropometric or bedside body-composition measurements. Many prediction equations have been published, but validation studies have shown that these equations tend to have limited accuracy in individuals and many have significant average bias.

OBJECTIVE

We tested a mathematical approach that assumes that the aggregate of many independent predictions is more accurate than the best single prediction.

DESIGN

Body composition was measured in 196 children aged 4-16 y by using the 4-component model. RMR was measured in 142 adult women. Data on weight, height, age, skinfold thickness, and body impedance were used in published equations to predict body composition (12 equations) or RMR (13 equations). The accuracy of individual compared with aggregate predictions, relative to the reference measurements, was compared by using the Bland and Altman method.

RESULTS

For children's body composition and adult RMR, the aggregate predictions had lower mean biases and lower limits of agreement than did the individual predictions, and the aggregate predictions performed better than did any individual prediction.

CONCLUSIONS

Aggregate predictions perform better than single predictions at predicting fat-free mass, fat mass, total body water, and RMR. Our findings indicate that the accuracy of calculating variables such as energy requirements and drug and dialysis dosages can be improved significantly with the use of our mathematical approach.

Baseline correlates of insulin resistance in inner city high-BMI African-American children

To characterize the influence of diet-, physical activity-, and self-esteem-related factors on insulin resistance in 8- 10-year-old African-American (AA) children with BMI greater than the 85th percentile who were screened to participate in a community-based type 2 diabetes mellitus (T2DM) prevention trial. In 165 subjects, fasting glucose- and insulin-derived values for homeostasis model assessment of insulin resistance (HOMA-IR) assessed insulin resistance. Body fatness was calculated following bioelectrical impedance analysis, and fitness was measured using laps from a 20-m shuttle run. Child questionnaires assessed physical activity, dietary habits, and self-esteem. Pubertal staging was assessed using serum levels of sex hormones. Parent questionnaires assessed family demographics, family health, and family food and physical activity habits. Girls had significantly higher percent body fat but similar anthropometric measures compared with boys, whereas boys spent more time in high-intensity activities than girls. Scores for self-perceived behavior were higher for girls than for boys; and girls desired a more slender body. Girls had significantly higher insulin resistance (HOMA-IR), compared with boys (P < 0.01). Adjusting for age, sex, pubertal stage, socioeconomic index (SE index), and family history of diabetes, multivariate regression analysis showed that children with higher waist circumference (WC) (P < 0.001) and lower Harter's scholastic competence (SC) scale (P = 0.044) had higher insulin resistance. WC and selected self-esteem parameters predicted insulin resistance in high-BMI AA children. The risk of T2DM may be reduced in these children by targeting these factors.

Evaluation of between-methods agreement of extracellular water measurements in adults and children

BACKGROUND

Extracellular water (ECW), a relevant molecular level component for clinical assessment, is commonly obtained by 2 methods that rely on assumptions that may not be possible to test at the time the measurements are made.

OBJECTIVE

The aim of the current study was to evaluate the degree of agreement between ECW assessment by the sodium bromide dilution (ECW(NaBr)) and total body potassium (TBK; whole-body (40)K counting) to total body water (TBW; isotope dilution) methods (ECW(TBK-TBW)) in an ethnically mixed group of children and adults.

DESIGN

ECW was measured with the ECW(NaBr) and ECW(TBK-TBW) methods in 526 white and African American males and females (86 nonobese children, 193 nonobese adults, and 247 obese adults). Fat mass was assessed with dual-energy X-ray absorptiometry. Multiple regression analysis was used to examine the variables related to between-ECW method differences.

RESULTS

Significant but generally small group mean (+/-SD) differences in ECW were found in the obese adults (1.28 +/- 2.54 kg) and children (-0.71 +/- 1.78 kg). The magnitude of the differences was related to mean ECW in obese adults, children, and nonobese adults, and the relations between these variables were modified by sex for nonobese adults. ECW differences were also dependent on age, weight, sex, and race or on interactions between these variables.

CONCLUSIONS

Overall, although good between-method agreement was found across the 3 groups, the degree of agreement varied according to subject characteristics, particularly at the extremes of ECW and body weight. We advance a possible mechanism that may link subject characteristics with the degree of agreement between ECW measurement methods and their underlying assumptions.

Reproducibility of short-term food intake and subjective appetite scores after a glucose preload, ventilation threshold, and body composition in boys

The objective of these studies was to assess the reproducibility of (i) short-term food intake (FI) and subjective appetite following a glucose preload, (ii) ventilation threshold (VT) and subjective appetite after short-duration exercise, and (iii) body composition assessed by bioelectrical impedance (BIA). On two separate weekend mornings, boys (n = 11; aged 9–14 years) received drinks containing 50 g glucose made up to 250 mL with water 2 h after a standardized breakfast. FI from a pizza meal was measured 30 min later. Subjective appetite was measured before and after the glucose loads and the VT measures. VTs were measured on 2 weekday evenings, 1 week apart. BIA was measured during the FI assessment sessions. Short-term FI after the glucose preload was highly reproducible. Mean energy intake was 925 ± 139 kcal on the first day and 988 ± 147 kcal on the second day (coefficient of repeatability (CR) = 259 kcal; intra-class correlation coefficient (ICC) = 0.96). Moderate reproducibility of the average appetite score was found at 30 min (CR = 24 mm; ICC = 0.82). Subjective appetite was increased similarly by short-duration exercise on both days (CR = 19 mm). Absolute VT was more highly reproducible (CR = 359 mL O2·min–1, ICC = 0.85) than VT expressed on the basis of body weight (CR = 8.0 mL O2·kg–1·min–1, ICC = 0.59). Fat mass (FM) estimated from BIA was highly reproducible (CR = 2.7 kg, ICC = 0.95), but underestimated FM compared with skinfolds. In conclusion, FI and subjective appetite scores in response to glucose preloads, VT, subjective appetite after short-duration exercise, and estimates of FM from BIA are reproducible in boys.

Prediction of fat-free body mass from bioelectrical impedance among 9- to 11-year-old Swedish children

AIM

Predictive equations for estimating body composition from bioelectrical impedance analysis (BIA) among Scandinavian children are lacking. In the present study, equations for estimation of fat-free body mass (FFM) and lean tissue mass (LTM) were developed and cross-validated from BIA using dual-energy X-ray absorptiometry (DXA) as the reference measurement of body composition.

METHODS

The study population consisted of 49 girls and 52 boys aged 9-11 years from Malmö, Sweden. Bioelectrical impedance was measured between hand and foot at 50 kHz. Predictive equations were developed by multiple linear regression and cross-validated against DXA measurements of body composition.

RESULTS

FFM was predicted from BIA and anthropometric variables with an adjusted R(2)= 0.95 and root mean square error (RMSE) = 0.84 kg, and LTM was predicted with an adjusted R(2)= 0.95 and RMSE = 0.87 kg. Cross-validation revealed a mean RMSE = 0.95 kg FFM and a mean RMSE = 0.96 kg LTM. Prediction of body composition from equations developed in previous literature was mixed when applied to the present cohort of children.

CONCLUSIONS

FFM and LTM are predicted with sufficient accuracy at the population level. We recommend that the predictive equations developed in the present study are used in prepubescent European children aged 9-11 years only in order to minimize confounding of results because of possible differences in population samples.

Body composition of preterm infants measured during the first months of life: bioelectrical impedance provides insignificant additional information compared to anthropometry alone

Detailed knowledge of body composition in preterm neonates during their later postnatal period may be important for the treatment process. However, little consideration has been given to test whether bioelectrical impedance analysis (BIA) is a useful bedside method to predict fat-free mass (FFM). The aim of the study is to assess whether BIA is a bedside method to measure FFM in preterm neonates. FFM of 118 white subjects (51 males, 67 females), mean gestational age of 30.1+/-3.1 weeks and birth weight of 1.26+/-0.47 kg, was measured at a gestational age of 38.6+/-3.8 weeks and actual body weight of 2.6+/-0.54 kg using dual energy X-ray absorptiometry (FFM(DXA)). Weight (W), height (Ht), and bioelectric impedance (I) measurements were collected. Multiple regression analysis was performed to develop prediction equations to estimate FFM with impedance index (Ht(2)/I, cm(2)/Omega) and W (kg) as predictor variables. Bootstrap analysis was performed for validating the derived prediction equations. Correlations between FFM(DXA) and weight were 0.96, 0.98, and 0.97 in boys, girls, and both sexes, respectively. Those between FFM(DXA) and Ht(2)/I were: 0.73, 0.81, and 0.79. Equations used to predict FFM (kg) were for boys: FEM = 0.05Ht(2)/I + 0.68W + 0.40(R2 = 0.919) and for girls: FFM = 0.04Ht(2)/I + 0.71W + 0.29(R2 = 0.957).

CONCLUSIONS

In preterm neonates, weight is a more effective predictor of FFM than impedance index. The study provides a bedside procedure for estimating FFM, mainly based on anthropometric parameters rather than BIA.

Use of bioelectrical impedance analysis and anthropometry to measure fat-free mass in children and adolescents with Crohn disease

OBJECTIVES

To investigate the precision of published prediction equations for fat-free mass (FFM) from bioimpedance measurements in children with Crohn disease using dual-energy X-ray absorptiometry (DXA) as an in vivo gold standard.

METHODS

Fat-free mass of 49 white boys and girls ages 7.3 to 16.9 y suffering from Crohn disease was measured by DXA. Body weight, height and bioimpedance measurements were also collected. FFM measured by DXA (FFM(DXA)) was compared with FFM predicted by the only 5 published prediction equations available for children and adolescents. An equation was developed for predicting FFM and was validated using a bootstrap method.

RESULTS

When correlating predicted FFM with FFM(DXA), Schaefer's equation showed the highest R2 (0.950), the smallest standard error of estimate (SEE) (2.05 kg) and the smallest percentage error (0.28%). Our prediction equation for estimating FFM was FFM = 0.652 Ht2/Z + 0.0385 Wt + 0.586 Age - 0.327, R2 = 0.951, SEE = 2.08, P < 0.0005, where Ht2/Z is the impedance index in cm2/ohm, Wt is body weight in kilograms, age is in years. R2 value from bootstrap method was 0.950 +/- 0.01 (95% confidence interval 0.927-0.968), indicating an acceptable validation of the derived formula.

CONCLUSIONS

The formula of Schaefer is the best for predicting FFM. The present study provides a new prediction equation for estimating FFM in children with Crohn disease that may be used in clinical settings in which more sophisticated body composition measuring equipments are not available.

Metabolic consequences of body size and body composition in hemodialysis patients

Small body mass index is associated with increased mortality in chronic hemodialysis patients. The reasons for this observation are unclear but may be related to body composition. This study aimed to investigate the body composition in chronic hemodialysis patients. The difference between body mass and the sum of muscle, bone, subcutaneous, and visceral adipose tissue masses, measured by whole body magnetic resonance imaging, was defined as the high metabolic rate compartment representing the visceral mass. Protein catabolic rate was calculated from urea kinetics. Forty chronic hemodialysis patients (mean age 54.7 years; 87.5% African Americans; 45% females) were studied. High metabolic rate compartment expressed in percent of body weight was inversely related to body weight (r=-0.475; P=0.002) and body mass index (r=-0.530; P<0.001). In a multiple linear regression model, protein catabolic rate was significantly correlated only with high metabolic rate compartment (r=0.616; P<0.001). Assuming that protein catabolic rate in addition to protein intake reflects urea and uremic toxin generation, it follows that high metabolic rate compartment is the major compartment involved in their generation. Consequently, uremic toxin production rate may be relatively higher in patients with low body weight and low body mass index as compared to their heavier counterparts. The poorer survival observed in smaller dialysis patients may be related to these relative differences.

Assessment of body composition in long-term hemodialysis patients: rationale and methodology

Protein-energy malnutrition is seen in patients with advanced stages of chronic kidney disease (CKD) and is even more pronounced in patients receiving long-term hemodialysis treatment. Both entities have great impact on patient morbidity and mortality. Analysis of body composition is an integral part of nutritional assessment and includes the estimation of muscle, fat, and fat-free mass, as well as the extracellular water compartment. Clinical assessment of these compartments is difficult, and gold-standard methods such as tracer dilution, magnetic resonance imaging, and dual-energy x-ray absorptiometry are expensive, cumbersome, and rarely available. We report an ongoing study of body composition in hemodialysis patients involving deuterium and sodium bromide dilution, total body potassium counting, magnetic resonance imaging, whole-body and segmental bioimpedance spectroscopy, and anthropometry. The goals of the study are (1) to validate bioimpedance technology against gold-standard methods for assessment of the various body compartments, (2) to directly quantify visceral adipose tissue mass, a potential source of cytokine production (adipokines) promoting chronic inflammation, and to study its relation to inflammatory markers, and (3) to directly quantify visceral organ mass and to study its relation to uremia toxin generation as assessed by protein catabolic rate and resting energy expenditure. Preliminary results based on up to 40 hemodialysis patients are reported.

Body fluid volume determination via body composition spectroscopy in health and disease

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.

Feasibility of bioelectrical impedance analysis in children with a severe generalized cerebral palsy

OBJECTIVE

The need is strong for an accurate and easy-to-perform test to evaluate the nutritional state of children who have a severe generalized cerebral palsy, defined as a severe motor handicap and an intellectual disability. For that purpose, we determined the feasibility of bioelectrical impedance analysis (BIA) in these children and evaluated their nutritional state.

METHODS

BIA recordings were done in 35 children who had a severe generalized cerebral palsy using a single-frequency BIA device. In addition, arm span and body weight were determined. Components of feasibility were whether the children tolerated the recording and felt comfortable and whether the recording could be performed in a reproducible way (prescribed body position and stable resistance and reactance values). All recordings were performed at specialized children's daycare centers or schools.

RESULTS

One child (3%) did not tolerate the recording, whereas the remaining 34 children (71%) felt comfortable. Most children (74%) could be placed in the prescribed position, but stability of resistance values was low. Stability of resistance values was positively influenced by older age, a quiet location for the recording, feeling comfortable, and a small number of people in the room. For 29 children, we were able to calculate values for total body water and fat-free mass. Compared with age-matched reference values, these values were significantly decreased in all age groups.

CONCLUSIONS

The present pilot study has demonstrated that BIA recording is a feasible nutritional assessment method in children who have severe generalized cerebral palsy. Because the test procedure was well tolerated by most children, its value for use in this specific population deserves further investigation.

Segment-specific resistivity improves body fluid volume estimates from bioimpedance spectroscopy in hemodialysis patients

Discrepancies in body fluid estimates between segmental bioimpedance spectroscopy (SBIS) and gold-standard methods may be due to the use of a uniform value of tissue resistivity to compute extracellular fluid volume (ECV) and intracellular fluid volume (ICV). Discrepancies may also arise from the exclusion of fluid volumes of hands, feet, neck, and head from measurements due to electrode positions. The aim of this study was to define the specific resistivity of various body segments and to use those values for computation of ECV and ICV along with a correction for unmeasured fluid volumes. Twenty-nine maintenance hemodialysis patients (16 men) underwent body composition analysis including whole body MRI, whole body potassium (40K) content, deuterium, and sodium bromide dilution, and segmental and wrist-to-ankle bioimpedance spectroscopy, all performed on the same day before a hemodialysis. Segment-specific resistivity was determined from segmental fat-free mass (FFM; by MRI), hydration status of FFM (by deuterium and sodium bromide), tissue resistance (by SBIS), and segment length. Segmental FFM was higher and extracellular hydration of FFM was lower in men compared with women. Segment-specific resistivity values for arm, trunk, and leg all differed from the uniform resistivity used in traditional SBIS algorithms. Estimates for whole body ECV, ICV, and total body water from SBIS using segmental instead of uniform resistivity values and after adjustment for unmeasured fluid volumes of the body did not differ significantly from gold-standard measures. The uniform tissue resistivity values used in traditional SBIS algorithms result in underestimation of ECV, ICV, and total body water. Use of segmental resistivity values combined with adjustment for body volumes that are neglected by traditional SBIS technique significantly improves estimations of body fluid volume in hemodialysis patients.

Bioimpedance analysis and HIV-related fatigue

Although various physiological and psychological causes of fatigue in HIV-positive persons have been proposed, it is still not well understood. Bioimpedance analysis has proved to be an easily used, non-invasive measurement of body composition and cellular integrity. This study, looking at whether body composition as measured by bioimpedance analysis is associated with fatigue, is part of a pilot study looking for physiological and psychological biomarkers that could be factors in the fatigue experienced by HIV-positive people. Twenty-nine men and eleven women were measured for height, weight, and bioimpedance analysis. Correlations were examined between fatigue intensity and weight, body mass index, body cell mass, fat-free mass, extracellular mass, and phase angle. Because of the fat redistribution that has occurred with some people taking protease inhibitors, we also examined differences in weight, body mass index, body cell mass, fat-free mass, and fatigue intensity between those taking and those not taking protease inhibitors. There was no association between fatigue intensity and weight, body mass index, body cell mass, fat-free mass, or phase angle, nor were there differences between those taking and those not taking protease inhibitors. However, it was noted that both the phase angle and the ratio of extracellular mass to body cell mass (extracellular mass:body cell mass) were below their respective normal ranges, indicating that the participants were somewhat compromised nutritionally and with regard to cell membrane integrity. Although fatigue was not shown to be related to body composition measurement in this study, further work is needed on the causes of fatigue, because its effects on the lives of HIV-positive people can be devastating.

Dual-energy X-ray absorptiometry lean soft tissue hydration: independent contributions of intra- and extracellular water

Dual-energy X-ray absorptiometry (DEXA) provides a measure of lean soft tissue (LST). LST hydration, often assumed to be constant, is relevant to several aspects of DEXA body composition estimates. The aims of this study were to develop a theoretical model of LST total body water (TBW) content and to examine hydration effects with empirically derived model coefficients and then to experimentally test the model's prediction that, in healthy adults, LST hydration is not constant but varies as a function of extra- and intracellular water distribution (E/I). The initial phase involved TBW/LST model development and application with empirically derived model coefficients. Model predictions were then tested in a cross-sectional study of 215 healthy adults. LST was measured by DEXA, extracellular water (ECW) by NaBr dilution, intracellular water (ICW) by whole body (40)K counting, and TBW by (2)H(2)O dilution. TBW estimates, calculated as ECW + ICW, were highly correlated with (r = 0.97, SEE = 2.1 kg, P < 0.001) and showed no significant bias compared with TBW measured by (2)H(2)O. Model-predicted TBW/LST was almost identical to experimentally derived values (means +/- SD) in the total group (0.767 vs. 0.764 +/- 0.028). LST hydration was significantly correlated with E/I (total group, r = 0.30, SEE = 0.027, P < 0.001). Although E/I increased with age (men, r = 0.48; women, r = 0.37; both P < 0.001), the association between TBW/LST and age was nonsignificant. Hydration of the DEXA-derived LST compartment is thus not constant but varies predictably with ECW and ICW distribution. This observation has implications for the accuracy of body fat measurements by DEXA and the use of TBW as a means of checking DEXA system calibration.

Effects of GH and insulin-like growth factor-I on body composition

In this review, different methods to estimate body composition are discussed shortly. The effects by GH on total and visceral fat mass, lean mass, muscle strength and body water are described. Gender differences in the sensitivity to GH administration are reviewed. Finally, a short description of the effects of insulin-like growth factor-I (IGF-I) administration on body composition has been included.

Synergistic effects of testosterone and growth hormone on protein metabolism and body composition in prepubertal boys

During human puberty there is a substantial increase in growth hormone (GH) and sex steroidal hormone concentrations, as well as in GH production rates and insulin-like growth factor-I (IGF-I) These studies were designed to investigate some of the interactions of testosterone (T) and GH in the metabolic changes of puberty. Ten boys with severe GH deficiency (GHD) were studied (mean age, 12.5 +/- 0.5 years) using stable isotope infusions, indirect calorimetry, and body composition analysis. After the baseline study, they received 2 doses of T enanthate (50 to 75 mg, intramuscular [IM]), and they were studied again 4 weeks later. The boys were then begun on daily subcutaneous (SC) GH (0.3 mg/kg/wk), while T therapy was continued for another 4 weeks and the studies repeated a third time. The treatment order was randomized. Protein oxidation rates decreased after T alone (-28%, P <.01), decreasing further after combined T/GH treatment (-36% v baseline, P <.01). The nonoxidative leucine disposal (NOLD), a measure of whole body protein synthesis, increased significantly after combined T/GH regardless of treatment order. The combination of T/GH also resulted in greater changes in body composition than T alone, with comparable decreases in %FM and corresponding increases in fat free mass (FFM). Measures of carbohydrate (CHO) metabolism, including glucose production and oxidation rates, were unaffected by either T or T/GH combination. Plasma IGF-I concentrations increased after T treatment and even more after T/GH combination, regardless of the treatment order. In conclusion GH and T are synergistic on whole body protein anabolism and body composition in males, even at a young age, but the positive effects of T on protein anabolism and body composition appear to need a basal amount of GH for those effects to be observed. GH and T both potentiate the development of the full body composition and metabolic changes of puberty.

Plasma Adiponectin and Hyperglycaemia in Diabetic Patients

The insulin-sensitising adipose hormone adiponectin is reduced in type 2 diabetic patients. We assessed the relationships between plasma adiponectin and chronic hyperglycaemia. Adiponectin levels and glycated haemoglobin (HbA1c) were measured at enrolment and after 90 days in 16 patients with type 2 diabetes aged (mean +/- SEM) 63.0 +/- 0.6 years, with body mass index (BMI) 30.2 +/- 0.5 kg/m2 and HbA1c concentration 7.4 +/- 0.1%, who did not modify their hypoglycaemic treatment during the observation period. Furthermore, plasma adiponectin was measured in 29 adult patients with type 1 diabetes and compared with 29 control subjects matched for sex, age, BMI, waist circumference and bioimpedance-estimated fat mass. In type 2 diabetic patients at enrolment, adiponectin concentration correlated with BMI (r = -0.46; p < 0.05), but not with HbA1c. During the prospective observation, variations of adiponectin showed a significant correlation with variations of BMI (r = -0.47; p < 0.01), but not with variations of HbA1c concentration. These results were confirmed by multivariate analysis after adjustment for sex and age. Adiponectin levels in type 1 diabetic patients (380.8 +/- 13.7 ng/ml in women, 192.5 +/- 13.9 ng/ml in men) were significantly (p < 0.05) higher than in control subjects (277.6 +/- 11.0 ng/ml in women, 102.7 +/- 5.1 ng/ml in men); plasma adiponectin correlated significantly with BMI and waist circumference, but not with HbA1c. In conclusion, the reduction of plasma adiponectin levels in type 2 diabetic patients does not appear to be determined by chronic hyperglycaemia. Adiponectin levels are increased in type 1 diabetes, but this phenomenon is not attributable to differences in nutritional status or body composition.