Associations of early childhood body mass index trajectories with body composition and cardiometabolic markers at age 10 years: the Ethiopian infant anthropometry and body composition (iABC) birth cohort study

BACKGROUND

Variability in body mass index (BMI) (kg/m2) trajectories is associated with body composition and cardiometabolic markers in early childhood, but it is unknown how these associations track to later childhood.

OBJECTIVES

We aimed to assess associations of BMI trajectories from 0 to 5 y with body composition and cardiometabolic markers at 10 y.

METHODS

In the Ethiopian infant anthropometry and body composition (iABC) birth cohort, we previously identified 4 distinct BMI trajectories from 0 to 5 y: stable low BMI (19.2%), normal BMI (48.8%), rapid growth to high BMI (17.9%), and slow growth to high BMI (14.1%). At 10 y, we obtained data from 320 children on anthropometry, body composition, abdominal subcutaneous and visceral fat, and cardiometabolic markers. Associations of BMI trajectories and 10-y outcomes were analyzed using multiple linear regression.

RESULTS

Compared with children with the normal BMI trajectory, those with rapid growth to high BMI had 1.7 cm (95% CI: 0.1, 3.3) larger waist circumference and those with slow growth to high had 0.63 kg/m2 (95% CI: 0.09, 1.17) greater fat mass index and 0.19 cm (95% CI: 0.02, 0.37) greater abdominal subcutaneous fat, whereas those with stable low BMI had -0.28 kg/m2 (95% CI: -0.59, 0.03) lower fat-free mass at 10 y. Although the confidence bands were wide and included the null value, children with rapid growth to high BMI trajectory had 48.6% (95% CI: -1.4, 123.8) higher C-peptide concentration and those with slow growth to high BMI had 29.8% (95% CI: -0.8, 69.8) higher insulin and 30.3% (95% CI: -1.1, 71.6) higher homeostasis model assessment of insulin resistance, whereas those with rapid growth to high BMI had -0.23 mmol/L (95% CI: -0.47, 0.02) lower total cholesterol concentration. The trajectories were not associated with abdominal visceral fat, blood pressure, glucose, and other lipids at 10 y.

CONCLUSIONS

Children with rapid and slow growth to high BMI trajectories before 5 y tend to show higher measures of adiposity and higher concentrations of markers related to glucose metabolism at 10 y.

CLINICAL TRIAL REGISTRY

ISRCTN46718296 (https://www.isrctn.com/ISRCTN46718296).

Associations of weight and body composition at birth with body composition and cardiometabolic markers in children aged 10 y: the Ethiopian infant anthropometry and body composition birth cohort study

BACKGROUND

Although birth weight (BW) has been associated with later cardiovascular disease and type 2 diabetes, the role of birth fat mass (BFM) and birth fat-free mass (BFFM) on cardiometabolic health is unclear.

OBJECTIVES

To examine associations of BW, BFM, and BFFM with later anthropometry, body composition, abdominal fat, and cardiometabolic markers.

METHODS

Birth cohort data on standardized exposure variables (BW, BFM, and BFFM) and follow-up information at age 10 y on anthropometry, body composition, abdominal fat, and cardiometabolic markers were included. A linear regression analysis was used to assess associations of exposures with outcome variables, adjusting for maternal and child characteristics at birth and current body size in separate models.

RESULTS

Among 353 children, mean (SD) age was 9.8 (1.0) y, and 51.5% were boys. In the fully adjusted model, 1-SD higher BW and BFFM were associated with 0.81 cm (95% CI: 0.21, 1.41 cm) and 1.25 cm (95% CI: 0.64, 1.85 cm) greater height at 10 y, respectively. The 1-SD higher BW and BFM were associated with 0.32 kg/m2 (95% CI: 0.14, 0.51 kg/m2) and 0.42 kg/m2 (95% CI: 0.25, 0.59 kg/m2) greater fat mass index at 10 y, respectively. In addition, 1-SD higher BW and BFFM were associated with 0.22 kg/m2 (95% CI: 0.09, 0.34 kg/m2) greater FFM index, whereas a 1-SD greater BFM was associated with a 0.05 cm greater subcutaneous adipose tissue (95% CI: 0.01, 0.11 cm). Furthermore, 1-SD higher BW and BFFM were associated with 10.3% (95% CI: 1.4%, 20.0%) and 8.3% (95% CI: -0.5%, 17.9%) greater insulin, respectively. Similarly, 1-SD higher BW and BFFM were associated with 10.0% (95% CI: 0.9%, 20.0%) and 8.5% (95% CI: -0.6%, 18.5%) greater homeostasis model assessment of insulin resistance, respectively.

CONCLUSIONS

BW and BFFM rather than BFM are predictors of height and FFM index at 10 y. Children with higher BW and BFFM showed higher insulin concentrations and homeostasis model assessment of insulin resistance at 10 y of age. This trial was registered at ISRCTN as ISRCTN46718296.

Metabolizable Energy Content of Breastmilk Supports Normal Growth in Exclusively Breastfed Icelandic Infants to Age 6 Months

BACKGROUND

Neither the global population nor individual countries have reached the World Health Organization (WHO) target of ≥50% of infants exclusively breastfed (EBF) until 6 mo. This may partly be because of the perceptions of insufficient milk and energy supply to meet rapid growth and development needs.

OBJECTIVES

In a longitudinal observational study, we aimed to determine whether breastmilk energy content is sufficient to support growth during EBF until 6 mo.

METHODS

A sample of 27 EBF infants was dosed with doubly labeled water (DLW) at 5.6 mo to measure body composition, breastmilk intake, energy intake, and the metabolizable energy (ME) content of their mother's breastmilk over the following week. Z-scores were calculated for anthropometry using WHO reference data and for fat-free mass (FFM) and fat mass (FM) using United Kingdom reference data.

RESULTS

Anthropometric z-scores from birth indicated normal weight and length growth patterns. At ∼6 mo, the mean ± standard deviation (SD) FFM z-score was 0.22 ± 1.07, and the FM z-score was 0.78 ± 0.70, significantly >0. In the 22 infants with acceptable data, the mean ± SD measured intake of breastmilk was 983 ± 170 g/d and of energy, 318 ± 60 kJ/kg/d, equivalent to 75.9 ± 14.3 kcal/kg/d. The mean ME content of breastmilk was 2.61 kJ/g [standard error (SE) 0.1], equivalent to 0.62 kcal/g (SE 0.02). Mothers were positive toward breastfeeding, on paid maternity leave (planned mean 10 mo), and many (56%) had received specialized breastfeeding support.

CONCLUSIONS

The evidence from this study confirms that when mothers are motivated and supported without economic restraints, breastmilk intake and the energy supplied by breastmilk to EBF infants at 6 mo of age is sufficient to support normal growth patterns. There was no evidence of constraint on FFM, and other studies show that high FM in EBF infants is likely to be transient. These data further support the recommendation for EBF ≤6 mo of age for body composition. This trial was registered at clinicaltrials.gov as NCT02586571.

Effects of relaxation therapy on maternal psychological status and infant growth following late preterm and early-term delivery: a randomized controlled trial

BACKGROUND

Maternal stress is one modifiable variable that could influence mother-infant signaling and negatively affect breastfeeding and infant growth.

OBJECTIVES

This study aimed to test the hypothesis that relaxation therapy would reduce maternal stress and improve infant growth, behavior, and breastfeeding outcomes after late preterm (LP) and early-term (ET) delivery.

METHODS

A single-blind randomized controlled trial was conducted in healthy Chinese primiparous mother-infant pairs after LP or ET delivery (34⁺⁰-37⁺⁶ gestation weeks). Mothers were randomly assigned to the intervention group (IG, listening to relaxation meditation at least once a day) or control group (CG, normal care). Primary outcomes-changes in maternal stress (perceived stress scale), anxiety (Beck Anxiety Inventory), and infant weight and length standard deviation score-were assessed at 1 wk and 8 wks postpartum. Secondary outcomes-breast milk energy and macronutrient composition, maternal breastfeeding attitudes, infant behaviors (3-d diary), and 24-hour milk intake-were assessed at 8 wks.

RESULTS

In total, 96 mother-infant pairs were recruited. There was a significantly greater reduction in maternal perceived stress (Perceived Stress Scale score) (mean difference [MD] = 2.65; 95% CI: 0.8, 4.5) and significantly greater infant weight standard deviation score gain (MD = 0.51; 95% CI: 0.2, 0.9) from 1 wk to 8 wks in the IG than those in the CG. Exploratory analyses showed a significant interaction between intervention and sex, with greater effects on weight gain in female infants. Mothers of female infants used the intervention more frequently with significantly higher milk energy observed at 8 wks.

CONCLUSIONS

The relaxation meditation tape is a simple, effective practical tool that could easily be used in clinical settings to support breastfeeding mothers after LP and ET delivery. The findings need confirmation in larger groups and in other populations.

Childhood BMI and other measures of body composition as a predictor of cardiometabolic non-communicable diseases in adulthood: a systematic review

OBJECTIVE

There is growing evidence that childhood malnutrition is associated with non-communicable diseases (NCD) in adulthood and that body composition mediates some of this association. This review aims to determine if childhood body composition can be used to predict later-life cardiometabolic NCD and which measures of body composition predicts future NCD.

DESIGN

Electronic databases were searched for articles where: children aged under 5 years had body composition measured; cardiometabolic health outcomes were measured a minimum of 10 years later.

SETTING

The databases Embase, Medline and Global Health were searched through July 2020.

PARTICIPANTS

Children aged under 5 years with a follow-up of minimum 10 years.

RESULTS

Twenty-nine studies met the inclusion criteria. Though a poor proxy measure of body composition, body mass index (BMI) was commonly reported (n 28, 97 %). 25 % of these studies included an additional measure (ponderal index or skinfold thickness). Few studies adjusted for current body size (n 11, 39 %).

CONCLUSIONS

Many studies reported that low infant BMI and high childhood BMI were associated with an increased risk of NCD-related outcomes in later life but no conclusions can be made about the exact timing of child malnutrition and consequent impact on NCD. Because studies focussed on BMI rather than direct measures of body composition, nothing can be said about which measures of body composition in childhood are most useful. Future research on child nutrition and long-term outcomes is urgently needed and should include validated body composition assessments as well as standard anthropometric and BMI measurements.

Industry Funding of Oncology Randomised Controlled Trials: Implications for Design, Results and Interpretation

AIMS

Most randomised controlled trials (RCTs) in oncology are now funded by the pharmaceutical industry. We explore the extent to which RCT design, results and interpretation differ between industry-funded and non-industry-funded RCTs.

MATERIALS AND METHODS

In this cross-sectional analysis, a structured literature search was used to identify all oncology RCTs published globally during 2014-2017. Industry funding was identified based on explicit statements in the publication. Descriptive statistics were used to compare elements of trial methodology and output between industry- and non-industry-funded RCTs.

RESULTS

The study sample included 694 RCTs; 71% were funded by industry. Industry-funded trials were more likely to test systemic therapy (97% versus 62%; P < 0.001), palliative-intent therapy (71% versus 41%; P < 0.001) and study breast cancer (20% versus 12%; P < 0.001). Industry-funded trials were larger (median sample size 474 versus 375; P < 0.001) and more likely to meet their primary end point (49% versus 41%; P < 0.001). Among positive trials, there were no differences in the magnitude of benefit between industry- and non-industry-funded RCTs. Trials funded by industry were published in journals that had a significantly higher median impact factor (21, interquartile range 7, 28) than non-industry-funded trials (impact factor 12, interquartile range 5, 24; P = 0.005); this persisted when adjusted for whether a trial was positive or negative.

CONCLUSIONS

The vast majority of oncology RCTs are now funded by industry. Industry-funded trials are larger, more likely to be positive, predominantly test systemic therapies in the palliative setting and are published in higher impact journals than trials without industry support.

The impact of the Covid-19 lockdown on the experiences and feeding practices of new mothers in the UK: Preliminary data from the COVID-19 New Mum Study

BACKGROUND

The COVID-19 New Mum Study is recording maternal experiences and infant feeding during the UK lockdown. This report from week 1 of the survey describes and compares the delivery and post-natal experiences of women who delivered before (BL) versus during (DL) the lockdown.

METHODS

Women living in the UK aged ≥18 years with an infant ≤12 months of age completed an anonymous online survey (https://is.gd/covid19newmumstudy). Information/links are shared via websites, social media and existing contacts.

RESULTS

From 27.5.20-3.6.20, 1365 women provided data (94% white, 95% married/with partner, 66% degree/higher qualification, 86% living in house; 1049 (77%) delivered BL and 316 (23%) DL. Delivery mode, skin-to-skin contact and breastfeeding initiation did not differ between groups. DL women had shorter hospital stays (p < 0.001). 39% reported changes to their birth plan. Reflecting younger infant age, 59% of DL infants were exclusively breast-fed/mixed fed versus 39% of BL (p < 0.05). 13% reported a change in feeding; often related to lack of breastfeeding support, especially with practical problems. Important sources of feeding support were the partner (60%), health professional (50%) and online groups (47%). 45% of DL women reported insufficient feeding support. Among BL women, 57% and 69% reported decreased feeding support and childcare, respectively. 40% BL/45% DL women reported insufficient support with their own health, 8%/9% contacted a mental health professional; 11% reported their mental health was affected. 9% highlighted lack of contact/support from family and distress that they had missed seeing the baby.

CONCLUSION

Lockdown has impacted maternal experiences, resulting in distress for many women. Our findings suggest the need for better infant feeding support, especially 'face-to-face' support for practical issues; and recognising and supporting mothers who are struggling with mental health challenges or other aspects of their health. The effectiveness of online versus face-to-face contact is currently uncertain, and requires further evaluation.

Filling the weight gap: Estimating body weight and BMI using height, chest and upper arm circumference of Swiss conscripts in the first half of the 20th century

We estimate weight and BMI values based on height, chest circumference, and mid upper arm circumference measures of Swiss conscripts in the city of Zurich for each year between 1904 and 1932. Height, chest circumference, and mid upper arm circumference were measured each year from 1904 to 1951. Body weight is available from 1933 to 1951. We used prediction equations from the literature, and also developed our own equations, which we tested and validated on the dataset from 1933 to 1951. We used a representative sample of usually 19-year-old Swiss males (N = 88,792, coverage > 88 %). There was an increase in average height and chest circumference between 1904 and 1951. During both world wars, chest circumference, mid upper arm circumference, weight, and BMI decreased, while height stagnated. Overall mean weight and BMI increased from 1904 to 1951, but decreased during the Great Depression. After World War II, weight quickly returned to the pre-war and pre-Great Depression level, while BMI had not reached the 1933 level by 1951. Average weights of the lower and middle socioeconomic groups were catching up with average weight of the upper socioeconomic group from 1904 to 1951. The convergence in height is less pronounced. Finally, we show that it is possible to accurately predict mean weight and BMI from other anthropometric measurements. We suggest that our estimation approach could be replicated for other historical populations to obtain more information on how nutritional status changed over time.

Utility of specific bioelectrical impedance vector analysis for the assessment of body composition in children

Background & aims

Bioelectrical impedance analysis (BIA) is widely considered a body composition technique suitable for routine application. However, its utility in sick or malnourished children is complicated by variability in hydration. A BIA variant termed vector analysis (BIVA) aims to resolve this, by differentiating hydration from cell mass. However, the model was only partially supported by children's data. To improve accuracy, further adjustment for body shape variability has been proposed, known as specific BIVA (BIVA_specific).

Methods

We re-analysed body composition data from 281 children and adolescents (46% male) aged 4–20 years of European ancestry. Measurements included anthropometry, conventional BIA, BIVA outcomes adjusted either for height (BIVA_conventional), or for height and body cross-sectional area (BIVA_specific), and fat-free mass (FFM) and fat mass (FM) by the criterion 4-component model. Graphic analysis and regression analysis were used to evaluate different BIA models for predicting FFM and FM.

Results

Age was strongly correlated with BIVA_conventional parameters, but weakly with BIVA_specific parameters. FFM correlated more strongly with BIVA_conventional than with BIVA_specific parameters, whereas the opposite pattern was found for FM. In multiple regression analyses, the best prediction models combined conventional BIA with BIVA_specific parameters, explaining 97.0% and 89.8% of the variance in FFM and FM respectively. These models could be further improved by incorporating body weight.

Conclusions

The prediction of body composition can be improved by combining two different theoretical models, each of which appears to provide different information about the two components FFM and FM. Further work should test the utility of this approach in pediatric patients.

Utility of bio-electrical impedance vector analysis for monitoring treatment of severe acute malnutrition in children

BACKGROUND & AIMS

Change in hydration is common in children with severe acute malnutrition (SAM) including during treatment, but is difficult to assess. We investigated the utility of bio-electrical impedance vector analysis (BIVA), a quick non-invasive method, for indexing hydration during treatment.

METHODS

We studied 350 children 0·5-14 years of age with SAM (mid-upper arm circumference <11·0 cm or weight-for-height <70% of median, and/or nutritional oedema) admitted to a hospital nutrition unit, but excluded medically unstable patients. Weight, height (H), resistance (R), reactance (Xc) and phase angle (PA) were measured and oedema assessed. Similar data were collected from 120 healthy infants and preschool/school children for comparison. Means of height-adjusted vectors (R/H, Xc/H) from SAM children were interpreted using tolerance and confidence ellipses of corresponding parameters from the healthy children.

RESULTS

SAM children with oedema were less wasted than those without (p < 0·001), but had BIVA parameters that differed more from those of healthy children (P < 0·05) than those non-oedematous. Initially, both oedematous and non-oedematous SAM children had mean vectors outside the reference 95% tolerance ellipse. During treatment, mean vectors migrated differently in the two SAM groups, indicating fluid loss in oedematous patients, and tissue accretion in non-oedematous patients. At admission, R/H was lower (oedematous) or higher (non-oedematous) among children who died than those who exited the hospital alive.

CONCLUSIONS

BIVA can be used in children with SAM to distinguish tissue-vs. hydration-related weight changes during treatment, and also identify children at high risk of death enabling early clinical interventions.

Bioelectric impedance vector analysis (BIVA) in hospitalised children; predictors and associations with clinical outcomes

BACKGROUND

Clinical use of bioelectric impedance is limited by variability in hydration. Analysis of raw bioelectric impedance vectors (BIVA), resistance (R), reactance (Xc) and phase angle (PA) may be an alternative for monitoring disease progression/treatment. Clinical experience of BIVA in children is limited. We investigated predictors of BIVA and their ability to predict clinical outcomes in children with complex diagnoses.

METHODS

R, Xc and PA were measured (BODYSTAT Quadscan 4000) on admission in 108 patients (4.6-16.8 years, mean 10.0). R and Xc were indexed by height (H) and BIVA-SDS for age and sex calculated using data from healthy children. Potential predictors and clinical outcomes (greater-than-expected length-of-stay (LOS), complications) were recorded.

RESULTS

Mean R/H-SDS was significantly higher (0.99 (SD 1.32)) and PA-SDS lower (-1.22 (1.68))) than expected, with a wide range for all parameters. In multivariate models, the Strongkids risk category predicted R/H-SDS (adjusted mean for low, medium and high risk = 0.49, 1.28, 2.17, p = 0.009) and PA-SDS (adjusted mean -0.52, -1.53, -2.36, p = 0.01). BIVA-SDS were not significantly different in patients with or without adverse outcomes.

CONCLUSIONS

These complex patients had abnormal mean BIVA-SDS suggestive of reduced hydration and poor cellular health according to conventional interpretation. R/H-SDS was higher and PA-SDS lower in those classified as higher malnutrition risk by the StrongKids tool. Further investigation in specific patient groups, including those with acute fluid shifts and using disease-specific outcomes, may better define the clinical role of BIV.

Real-world outcomes of nivolumab and cabozantinib in metastatic renal cell carcinoma: results from the International Metastatic Renal Cell Carcinoma Database Consortium

Objectives

In the present study, we explored the real-world efficacy of the immuno-oncology checkpoint inhibitor nivolumab and the tyrosine kinase inhibitor cabozantinib in the second-line setting.

Methods

Using the International Metastatic Renal Cell Carcinoma Database Consortium (imdc) dataset, a retrospective analysis of patients with metastatic renal cell carcinoma (mrcc) treated with nivolumab or cabozantinib in the second line after prior therapy targeted to the vascular endothelial growth factor receptor (vegfr) was performed. Baseline characteristics and imdc risk factors were collected. Overall survival (os) and time to treatment failure (ttf) were calculated using Kaplan-Meier curves. Overall response rates (orrs) were determined for each therapy. Multivariable Cox regression analysis was performed to determine survival differences between cabozantinib and nivolumab treatment.

Results

The analysis included 225 patients treated with nivolumab and 53 treated with cabozantinib. No significant difference in median os was observed: 22.10 months [95% confidence interval (ci): 17.18 months to not reached] with nivolumab and 23.70 months (95% ci: 15.52 months to not reached) with cabozantinib (p = 0.61). The ttf was also similar at 6.90 months (95% ci: 4.60 months to 9.20 months) with nivolumab and 7.39 months (95% ci: 5.52 months to 12.85 months) with cabozantinib (p = 0.20). The adjusted hazard ratio (hr) for nivolumab compared with cabozantinib was 1.30 (95% ci: 0.73 to 2.3), p = 0.38. When adjusted by imdc criteria and age, the hr was 1.32 (95% ci: 0.74 to 2.38), p = 0.35.

Conclusions

Real-world imdc data indicate comparable os and ttf for nivolumab and cabozantinib. Both agents are reasonable therapeutic options for patients progressing after initial first-line vegfr-targeted therapy.

Weight centile crossing in infancy: correlations between successive months show evidence of growth feedback and an infant-child growth transition

BACKGROUND

Early rapid weight gain is associated with later overweight, which implies that weight centile crossing tracks over time.

OBJECTIVE

Centile crossing is defined in terms of the change or deviation in weight z score during 1 mo, and the correlations between successive deviations are explored at different ages.

DESIGN

Two Cambridge (United Kingdom) growth cohorts were used: Widdowson (1094 infants born during 1959-1965) and the Cambridge Infant Growth Study (CIGS; 255 infants born during 1984-1987), each with weights measured monthly in the first year. Weights were converted to WHO age- and sex-adjusted z scores, deviations were calculated as the change in z score between adjacent measurement occasions, and the correlations between deviations were studied.

RESULTS

In both cohorts, the correlations between successive monthly deviations were positive in the first 6 mo and highest at ages 3-4 mo (r = 0.3, P < 0.0001), whereas after 6 mo they were negative and were lowest at ages 10-11 mo (r = -0.3, P < 0.0001), with the correlation decreasing linearly with age between these extremes. Thus, during the first 6 mo of age, infants crossing centiles in 1 mo tended to continue crossing centiles in the same direction the following month, whereas after 6 mo they tended to cross back again. This represents positive and negative feedback, respectively. At age 12 mo, the correlation was close to zero, which suggests an infant-child transition in growth.

CONCLUSIONS

The results confirm that weight centile crossing tracks over time, with the correlations between successive periods that change with age suggesting a complex feedback mechanism underlying infant growth. This may throw light on the link between early rapid weight gain and later overweight. Clinically, the correlations indicate that when predicting future weight from current weight, recent centile crossing affects the prediction in an age-dependent manner.

Body composition, leg length and blood pressure in a rural Italian population: a test of the capacity-load model

BACKGROUND AND AIMS

Whereas adult weight or body mass index (BMI) are directly associated with blood pressure (BP), birth weight is inversely associated with BP. The scenario for height is more complex, as both tall and short stature have been associated with higher BP. We used a theoretical model treating sitting height (SH) and tissue masses (fat mass, lean mass) as components of metabolic load, and leg length (LL) as a marker of homeostatic metabolic capacity. We predicted that decreased capacity and increased load would be independently associated with increased BP..

METHODS AND RESULTS

Anthropometry, body composition (bio-electrical impedance analysis) and BP were measured in 601 adults (228 male) aged 20-91 years from three hill villages in southern Italy. Multiple regression analysis was used to investigate associations of body composition and anthropometry with BP. Adjusting for age, systolic BP (SBP) was associated with lean mass in males, and with adiposity in females, whereas diastolic BP (DBP) was associated with fat mass in both sexes. Associations of LL and SH with BP were in opposite directions. LL was inversely associated with SBP and DBP in males, with a similar trend evident in females. SH was directly associated with SBP and DBP in females, and with DBP in males.

CONCLUSIONS

Consistent with our theoretical model, metabolic load is associated with increased BP, though differently between the sexes, whereas metabolic capacity is independently associated with lower BP. Our findings suggest that early growth improves hemodynamic tolerance of high metabolic load in adulthood..

Body composition assessed by the 4-component model and association with lung function in 6-12-y-old children with cystic fibrosis

BACKGROUND

Malnutrition is an indicator of a poor prognosis in patients with cystic fibrosis (CF). Previous body-composition (BC) studies in children with CF used 2-component models (2CMs) to assess fat mass (FM) and fat-free mass (FFM), but to our knowledge no study has used the gold-standard 4-component model (4CM), which allows for a more accurate evaluation of the nature of both elements.

OBJECTIVE

We measured BC by using the 4CM in 6-12-y-old children with CF to 1) compare findings with those of healthy, matched control children and reference data; 2) relate BC to lung spirometry [forced expired volume in 1 s (FEV₁)]; and 3) compare findings with those from more commonly used 2CM techniques.

DESIGN

One hundred clinically stable children with CF (57% girls) aged 6-12 y were measured by using the 4CM. Children with CF underwent spirometry (FEV₁).

RESULTS

Girls with CF had significantly less FM than did healthy girls, even after adjustment for height and pubertal status; boys with CF had higher body mass index SD scores than did healthy boys. FM in girls was positively associated with the FEV₁ percentage predicted. The 2CM FM was significantly different from the 4CM FM, with differences dependent on sex and condition, although most techniques identified a relation between FM and FEV₁ in girls.

CONCLUSIONS

Although shorter than healthy children, boys with CF were heavier and had a BC within the normal range; however, girls with CF had lower FM than did healthy girls, and this was associated with poorer lung function. Given the worse prognosis in girls, this finding merits more attention. The reliability of 2CM techniques varied with sex and health status.

Infant growth and later body composition: evidence from the 4-component model

BACKGROUND

Rapid weight gain in infancy is associated with higher body mass index in later life, but its relation with individual body-composition components remains unclear.

OBJECTIVE

We aimed to investigate associations between weight gain during different periods in infancy and later fat mass (FM) and fat-free mass (FFM).

DESIGN

Body composition was assessed by using the 4-component model, dual-energy X-ray absorptiometry, and anthropometry in 234 healthy UK children and adolescents (105 boys; x +/- SD age: 11.4 +/- 3.8 y). Early growth measurements were prospective in 52 subjects and retrospective in 182. Relative weight gain was calculated as change in SD score (SDS) during different periods.

RESULTS

Relative weight gain from 0 to 3 mo and from 3 to 6 mo showed positive relations with childhood FM, waist circumference, and trunk FM that were equivalent to increases in FMI (FM/height(2)) of 0.24 SDS (95% CI: 0.04, 0.44) and 0.50 SDS (0.25, 0.75) per 1-SDS increase in early weight and that were comparable to the effect of current obesity risk factors. Relative weight gain from 0 to 3 mo was also positively associated with later FFMI (FFM/height(2)). Relative weight gain from 6 to 12 mo was not associated with later body composition. Associations were independent of birth weight, sex, puberty, physical activity, socioeconomic class, ethnicity, and parental body mass index.

CONCLUSIONS

In this Western population, greater relative weight gain during early infancy was positively associated with later FM and central fat distribution and with FFM. Rapid weight gain in infancy may be a risk factor for later adiposity. Early infancy may provide an opportunity for interventions aimed at reducing later obesity risk.

Multiscale simulations of carbon nanotube nucleation and growth: electronic structure calculations

Several first-principles surface and bulk electronic structure calculations relating to the nucleation and growth of single-wall carbon nanotubes are described. Density-functional theory in various forms is used throughout. In the surface-related calculations, a 38-atom Ni cluster and several low-index Ni surfaces are investigated using pseudopotentials and plane-wave expansions. The energetic ordering of the sites for C atom adsorption is found to be the same, with the Ni(100) facet favored. The bulk diffusion coefficient of C in Ni as a function of cluster size and temperature is calculated from various molecular dynamics approaches. In another group of bulk-related calculations, Gaussian orbital basis sets are used to study a cluster or "flake" containing 14 C atoms. The flake is a segment of three hexagons from an "unrolled" carbon nanotube, with an armchair termination. The binding energies of C, Ni, Co, Fe, Cu, and Au atoms to it were calculated in an effort to gain insight into the mechanism for the high catalytic activity of Ni, Co, and Fe and the lack of it in Cu and Au. The binding energies of Cu and Au are about 1 eV less than those of the three catalytic elements. Similar methods are used to study the initial stages of nanotube growth within the context of classical nucleation theory. Finally, issues relating to the establishment of a fundamental catalytic mechanism are addressed.

Body composition in early onset eating disorders

BACKGROUND

Body mass index (BMI) or equivalent weight for height indices are the most widely used measures of body composition in early onset and adolescent eating disorders. Although of value as screening instruments the limitation in disease states is their inability to discriminate fat and fat-free components of body weight.

OBJECTIVE

To compare height-adjusted fat and fat-free components of body composition in children and young adolescents with different types of eating disorders with those of age matched reference children.

DESIGN

Weight, height, triceps and subscapular skinfold thickness were measured in 172 children (aged 7-16 y) with eating disorders receiving specialist treatment. Fat mass index (FMI) and fat-free mass index (FFMI) were calculated using Slaughter's and Deurenberg's equations and normalisation for height. Using data from 157 normal children, representative of the UK 1990 growth reference data, reference curves for FMI and FFMI+/-2 s.d. were derived. Results for patient groups were superimposed on these reference curves.

RESULTS

FMI and FFMI were both reduced in eating disorders associated with malnutrition, including anorexia nervosa (AN). AN subjects did not differ from other subjects with comparable degrees of malnutrition. Children with eating disorders of normal weight, such as bulimia nervosa and selective eating, did not differ significantly from reference children in their relative FM and FFM.

CONCLUSIONS

FM and FFM merit independent consideration in disorders of malnutrition in children, rather than expressing data as percentage body fat or percentage BMI. The implications of loss of FFM on growth and development merit further investigation.

The potential of near infra-red interactance for predicting body composition in children

OBJECTIVE

To establish whether near infra-red interactance (NIRI) has potential for use instead of skinfold thickness (SFT) measurements in the assessment of body composition in young children.

DESIGN

Strengths of relationships were established between NIRI or SFT measurements and four-component model (4-CM) assessments of body composition.

SUBJECTS

Nineteen boys and 19 girls, aged 8-12 y.

MEASUREMENTS

4-CM estimates of body composition were obtained from measurements of body weight, body volume, bone mineral content and total body water. SFT and NIRI were measured at the same four recognized sites (biceps, triceps, subscapular and suprailiac).

RESULTS

All children subjectively expressed a preference for NIRI rather than SFT calipers. Although SFTs were slightly more strongly and consistently related to 4-CM estimates, NIRI measurements at the biceps, subscapular and sum of four sites were significantly related to body composition indices. Subscapular NIRI measurements were as successful as subscapular SFTs in ranking subjects relative to 4-CM fatness, both techniques being most successful at lower levels of fatness.

CONCLUSION

NIRI has potential for use instead of SFT for estimating body composition in young children. Its contribution may prove to be greatest in sick children in whom SFT measurements may be unwelcome, and weight-for-height indices of little value due to abnormalities of water distribution. However, greater numbers are required to develop child-specific prediction equations and the viability and validity of NIRI in pediatric patients is still to be evaluated.

Precision of measurement and body size in whole-body air-displacement plethysmography

OBJECTIVE

To investigate methodological and biological precision for air-displacement plethysmography (ADP) across a wide range of body size.

DESIGN

Repeated measurements of body volume (BV) and body weight (WT), and derived estimates of density (BD) and indices of fat mass (FM) and fat-free mass (FFM).

SUBJECTS

Sixteen men, aged 22--48 y; 12 women, aged 24--42 y; 13 boys, aged 5--14 y; 17 girls, aged 5--16 y.

MEASUREMENTS

BV and WT were measured using the Bodpod ADP system from which estimates of BD, FM and FFM were derived. FM and FFM were further adjusted for height to give fat mass index (FMI) and fat-free mass index (FFMI).

RESULTS

ADP is very precise for measuring both BV and BD (between 0.16 and 0.44% of the mean). After removing two outliers from the database, and converting BD to body composition, precision of FMI was <6% in adults and within 8% in children, while precision of FFMI was within 1.5% for both age groups.

CONCLUSION

ADP shows good precision for BV and BD across a wide range of body size, subject to biological artefacts. If aberrant values can be identified and rejected, precision of body composition is also good. Aberrant values can be identified by using pairs of ADP procedures, allowing the rejection of data where successive BD values differed by >0.007 kg/l. Precision of FMI obtained using pairs of procedures improves to <4.5% in adults and <5.5% in children.

A critique of the expression of paediatric body composition data

There is increasing interest in body composition in paediatric research, as distinct from growth and nutritional status, as almost all diseases have adverse effects on either fatness or the fat-free mass. However, the approaches used to assess growth and nutritional status are not appropriate for separate evaluations of body fatness and lean mass. Traditional measurements such as body mass index and skinfold thickness do not measure fat in accurate quantitative terms. Various techniques have been used in recent years which divide body weight into fat mass and fat-free mass; however, the data tend not to be appropriately expressed. Body fatness is generally expressed as a percentage of weight, while fat-free mass typically remains unadjusted for size. A more appropriate approach is to normalise both body fatness and fat-free mass for height. This recommendation is relevant both to studies comparing patients with controls and to the expression of new reference data on body composition which are needed to allow informative comparisons. The same approach is appropriate for the classification of childhood obesity.

Evaluation of a model for total body protein mass based on dual-energy X-ray absorptiometry: comparison with a reference four-component model

The aim of the present study was to evaluate a model of body composition for assessing total body protein (TBP) mass using dual-energy X-ray absorptiometry (DXA), with either measured or assumed total body water (TBW); it was intended to provide a less complex or demanding alternative technique to, for example, the four-component model (4-CM). The following measurements were obtained in healthy adults (n 46) aged 18--62 years, and children (n 30) aged 8--12 years: body weight (BWt), body volume (BV; under-water weighing), TBW ((2)H-dilution space or predicted using an assumed hydration fraction of fat-free mass (HF(ffm))), bone mineral content (BMC; DXA) and fat-free soft tissue (FFST; DXA). TBP was calculated using the 4-CM (TBP = 3.05BWt -- 0.290TBW -- 2.734BMC -- 2.74BV) and the DXA model (TBP = FFST -- 0.2302BMC -- TBW). DXA measurements were obtained using the Lunar DPX (Lunar Radiation Corporation, Madison, WI, USA) or Hologic QDR 1000/W (Hologic, Waltham, MA, USA). Precision of the DXA model for TBP with measured TBW (4.6--6.8 % mean TBP) was slightly worse than the 4-CM (4.0--5.4 %), whereas that modelled with assumed HF(ffm) was more precise (2.4--5.2 %) because it obviated imprecision associated with measuring TBW. Agreement between the 4-CM and DXA model with measured TBW was also worse (e.g. bias, 15 % of the mean; 95 % limits of agreement up to +/-39 % for adults measured on the Lunar DPX) than when a constant for HF(ffm) was assumed (3.7 % and +/-21 % respectively). Most of the variability in agreement between these various models was due to interpretation of biological factors, rather than to measurement imprecision. Therefore, the DXA model, which is less complex and demanding than the 4-CM, is of value for assessing TBP in groups of healthy subjects, but is of less value for individuals in whom there may be substantial differences from reference 4-CM estimates.

Physical activity at 9-12 months and fatness at 2 years of age

Previous research has shown that physical activity in early infancy does not predict later fatness, whereas in preschool children, such a relationship is found. The objective of this study was to investigate whether total energy expenditure (TEE) and behavior in late infancy are related to subcutaneous and total fatness in early childhood. Twenty-six infants were studied at 9-12 months and followed up at 2 years of age. Anthropometry, body composition, TEE, and behavior were measured in late infancy; skinfold thicknesses and total body fat were measured at 2 years of age. Infant TEE adjusted for fat-free mass was not related to later fatness. Infant behavior was related to later subcutaneous fatness, but not to total body fatness. Lower levels of infant activity were associated with greater skinfold thicknesses in childhood. Thus, by late infancy, physical activity level is related to subsequent skinfold thickness. Particular aspects of infant behavior appear to be more important than the sum of energy expended on activity. However, the relationship did not extend to total body fat.

Feeding preterm infants after hospital discharge: growth and development at 18 months of age

We have shown that preterm infants fed a preterm formula grow better than those fed a standard term infant formula after hospital discharge. The purpose of this follow-up study was to determine whether improved early growth was associated with later growth and development. Preterm infants (< or =1750 g birth weight, < or =34 wk gestation) were randomized to be fed either a preterm infant formula (discharge to 6 mo corrected age), or a term formula (discharge to 6 mo), or the preterm (discharge to term) and the term formula (term to 6 mo). Anthropometry was performed at 12 wk and 6, 12, and 18 mo. Mental and psychomotor development were assessed using the Bayley Scales of Infant Development II at 18 mo. Differences in growth observed at 12 wk were maintained at 18 mo. At 18 mo, boys fed the preterm formula were 1.0 kg heavier, 2 cm longer, and had a 1.0 cm greater occipitofrontal circumference than boys fed the term formula. Boys fed the preterm formula were also 600 g heavier and 2 cm longer than girls fed the preterm formula. However, no differences were noted in MDI or PDI between boys fed the preterm formula and boys fed the term formula or between the boys fed preterm formula and girls fed the preterm formula. Overall, boys had significantly lower MDI than girls (mean difference, 6.0; p < 0.01), primarily reflecting lower scores in boys fed the term formula. Thus, early diet has long-term effects on growth but not development at 18 mo of age. Sex remains an important confounding variable when assessing growth and developmental outcome in these high-risk infants.

Validation of food diary method for assessment of dietary energy and macronutrient intake in infants and children aged 6-24 months

OBJECTIVES

To compare the estimated food diary record (ED) method against weighed intake record method (WI) for assessing dietary intake in infants and children aged 6-24 months; additionally, to compare WI with metabolisable energy intake (ME) measured by doubly labelled water (DLW) in infants aged 6 12 months.

DESIGN

Cross-over study of 5 day WI vs 5 day ED.

SUBJECTS

Seventy-two children aged 6-24 months.

METHODS

Subjects were randomly assigned to one method during week 1 crossing over to the alternative method in week 2. Data were coded and translated into daily nutrient intakes using COMP-EAT version 5 nutritional analysis software. The analysis compared energy, protein, fat and carbohydrate. Twenty-one infants were dosed with DLW for measurement of total energy expenditure (TEE) and ME.

RESULTS

Mean energy intake calculated from WI and ED was 3,782 and 3,920 kJ/day, respectively. There was no significant difference between these values. Using WI as a reference, ED showed a mean bias of 138 kJ/day, equivalent to 3.6% of mean energy intake. Limits of agreement (+/- 2 s.d. of the bias) were wide at +/- 1,385 kJ/day. There were no significant differences between methods for any of the nutrient sub-classes. Using DLW as a reference, WI showed a mean bias of 243 kJ/day, equivalent to 7.3% of mean energy intake, limits of agreement were wide at +/- 1686 kJ/day.

CONCLUSION

There is no evidence from the present analysis that ED is less accurate than WI for assessing energy and nutrient sub-class intakes in groups of this age but this good agreement between methods in groups does not extend to individuals.

A novel infant formula milk with added long-chain polyunsaturated fatty acids from single-cell sources: a study of growth, satisfaction and health

OBJECTIVE

To evaluate the growth, feeding and health of babies fed a novel infant formula milk with added long chain polyunsaturated fatty acids (LCPs) produced from single-cell sources, at concentrations similar to those found in mature breast milk.

DESIGN

Randomized double-blind control trial.

SUBJECTS

One-hundred and forty healthy, full-term infants of birth weight 2.5-4.5 kg born at the Maternity Department, East Glamorgan General Hospital, Wales, whose mothers had already decided to bottle feed.

INTERVENTIONS

Subjects were randomized to two groups; one (control group) to receive a standard formula milk and the other to receive the trial milk with added LCPs. Milks were supplied in a double-blind fashion and given for the first 12 weeks of life. Anthropometric measurements were made at recruitment, 3 months, 6 months and 1 y. Feeding diaries were completed at 6 weeks and 3 months, and a parental record was kept of any ill health suffered by the subjects during the first year of life.

RESULTS

Of 140 infants recruited, 31 did not complete the protocol. Small but statistically significant differences were found only in the subscapular skinfold thickness at 6 weeks and 3 months, that in the trial group being slightly higher, but unlikely to be of any clinical importance. No differences were found in the feeding patterns of the infants in the two groups. Stool patterns were similar, as were the frequencies of illness and allergy.

CONCLUSIONS

This study supports the view that LCPs from single-cell sources do not have detrimental effects on the growth, feeding and general health of infants.

Environmental temperature and human growth in early life

A link between adult human body size and environmental temperature, evolved through adaptation to heat stress, was first recognized a century ago and is now well accepted in human biology. Increasing heat stress favours smaller body size and an increased ratio of surface area to mass. However, possible effects of temperature on growth in early life have not been considered. Many developing country populations inhabit relatively hot environments compared to industrialized populations, but growth faltering in developing countries is invariably attributed to the combination of poor nutrition and infection. The aim of this study was to model the theoretical effect of growth faltering on cooling capacity in early life. Data on weight, length and total energy expenditure were selected from the literature. Three types of growth (normal growth, stunting and wasting) were considered, and the relationship between body size and heat production investigated. Relative to normal growth, stunting causes little increase in the area-to-mass ratio until 2 years of age, and results in little increase in cooling capacity during infancy. Wasting increases the area-to-mass ratio by > 15% in early infancy, and by 10% thereafter, equivalent to a similar increase in cooling capacity. These findings demonstrate theoretically that growth faltering can relieve heat stress in both infancy and childhood. The hypothesis that heat stress plays a role in human growth faltering in hot environments therefore merits empirical investigation.

Assessment of body volume using three-dimensional photonic scanning

Measurement of body volume (BV) can be used to estimate body composition using two- or multicomponent models. The traditional approach, underwater weighing (UWW), is awkward and unsuitable for many subjects. A newer alternative, whole body air displacement plethysmography (ADP), is less demanding but still unsuitable for young children, who may not remain still during the measurement. We have, therefore, considered whether a novel approach, three-dimensional photonic scanning, is a viable alternative. Duplicate measurements of body volume were obtained in 22 adults (11 of each sex; mean [SD] BMI, 21.8 [2.5] kg/m2) by UWW, ADP, and a Hamamatsu Bodyline Scanner (HBS) (Hamamatsu, Japan). Subjects wore a tight-fitting swimming costume for all three measurements, which were performed within one day of each other. Scans lasted 10 seconds, with the subject standing in a predefined position. The body surface skin was reconstructed using a B-spline-fitting model. In UWW, lung volume (LV) was measured simultaneously with underwater weight. In ADP and HBS, LV was predicted from weight and height. Results were compared using correlation and Bland and Altman analysis. Correlation analysis indicated that the scanner successfully ranked subjects in terms of BV. However, Bland and Altman analysis demonstrated that, relative to both UWW and ADP, HBS measured BV without bias but with limits of agreement between individuals of > 2 liters, equivalent to approximately 20% fat. Scan precision was 0.57 liter, or 4.1% fat. Although HBS cannot yet measure BV with sufficient accuracy to predict fatness, much of the error is probably due to difficulties in standardizing LV during the scan. Simultaneous measurement of LV with volume by HBS is expected to improve limits of agreement substantially. Occlusion is also an important source of error. The method offers many advantages over alternative techniques, because the measurement is brief, noninvasive, and suitable for repeat measurements.

A Hattori chart analysis of body mass index in infants and children

BACKGROUND

Body mass index (BMI) is widely used as an index of fatness in paediatrics, but previous analysis of the BMI-fatness relationship has been insufficient.

OBJECTIVE

To consider the effects of variation in fat-free mass (FFM) and fat mass (FM) on BMI in infants, children and Fomon's reference child (Am J Clin Nutr 1982; 35: 1169-1175).

SUBJECTS

42 infants aged 12 weeks; 64 children aged 8-12 y; Fomon's reference child.

METHODS

FFM was measured by deuterium dilution. FFM index (FFMI) and FM index (FMI) were calculated. The effects of variation in FFM and FM on BMI were explored using Hattori's body composition chart (Am J Hum Biol 1997; 9: 573-578).

RESULTS

In both infancy and childhood, a given BMI can embrace a wide range of percentage body fat. At both time points, the s.d. of FFMI was > 60% of the s.d. of FMI. Graphic analysis differentiated the effects of lean tissue and fat deposition on BMI with age in the reference child.

CONCLUSION

Although valuable for assessing short-term changes in nutritional status in individuals, and for comparing mean relative weight between populations, BMI is of limited use as a measure of body fatness in individuals in both infancy and childhood. The development of BMI with age may be disproportionately due to either FFM and FM at different time points.

Whole body air displacement plethysmography compared with hydrodensitometry for body composition analysis

AIMS

To assess the acceptability and feasibility of whole body air displacement plethysmography in children and to determine its precision and agreement with hydrodensitometry, an appropriate reference method.

METHODS

Age specific two component model equations were used to predict fat mass from body density in 22 children aged 8-12 years and in 10 adults for comparison of methods. Precision for each method was established from duplicate measurements.

RESULTS

Plethysmography was accepted more readily than hydrodensitometry (100% v 69% provided duplicate measurements). Precision for fat mass in children was 0.38 kg by plethysmography and 0.68 kg by hydrodensitometry, and results were similar in adults. The mean (SD) fat mass in children was 6.9 kg (4.0) and 6.7 kg (4. 2) by plethysmography and hydrodensitometry, respectively, but 95% limits of agreement between methods were large (-4.1 kg to 3.5 kg fat).

CONCLUSION

Plethysmography was more readily accepted and had better precision than hydrodensitometry. It also provided similar body composition results for the group but not for all individual children.

Natural selection and sex differences in morbidity and mortality in early life

Both morbidity and mortality are consistently reported to be higher in males than in females in early life, but no explanation for these findings has been offered. This paper argues that the sex difference in early vulnerability can be attributed to the natural selection of optimal maternal strategies for maximizing lifetime reproductive success, as modelled previously by Trivers and Willard. These authors theorized that males and females offer different returns on parental investment depending on the state of the environment. Natural selection has therefore favoured maternal ability to manipulate offspring sex in response to environmental conditions in early life, as shown in variation in the sex ratio at birth. This argument can be extended to the whole period of parental investment until weaning. Male vulnerability in response to environmental stress in early life is predicted to have been favoured by natural selection. This vulnerability is most evident in the harsh conditions resulting from pre-term birth, but can also be seen in term infants, and manifests as greater morbidity and mortality persisting into early childhood. Malnutrition, interacting with infection after birth, is suggested as the fundamental trigger mechanism. The model suggests that whatever improvements are made in medical care, any environmental stress will always affect males more severely than females in early life.

Can body size predict infant energy requirements?

Traditionally, infant energy requirements have been predicted from body size or age, whereas in older children and adults, physical activity is also taken into account. However, the extent to which body size determines energy use in individual infants has not been considered. Data on 232 measurements of total energy expenditure obtained in 124 infants aged 1.5 to 12 months were used to assess the relation between body size and energy use in individuals. Age, weight, and fat free mass consistently predicted total energy expenditure with an error of 21-23%. This contrasts greatly with the error of 10% with which infant basal metabolism can be predicted from anthropometry. Body size is a poor index of the total energy requirements of individual infants, and predictive equations generated from data on healthy infants will be inappropriate for disease states where physical activity or growth is altered.

Double-blind, randomized trial of a synthetic triacylglycerol in formula-fed term infants: effects on stool biochemistry, stool characteristics, and bone mineralization

BACKGROUND

The low sn-2 palmitate content of infant formulas results in formation of fatty acid calcium soaps in the stools and reduced calcium absorption.

OBJECTIVE

Our objective was to test the hypotheses that increasing the proportion of sn-2 palmitate in formula for term infants would result in greater skeletal mineral deposition and reduced stool hardness.

DESIGN

Healthy term neonates were randomly assigned to receive standard formula (n = 103) or formula containing 50% sn-2 palmitate (high-sn-2 formula; n = 100) for 12 wk. One hundred twenty breast-fed infants were also studied. The main outcome measures were 1) radial (single-photon absorptiometry) and whole-body (dual-energy X-ray absorptiometry) bone mineral content (WBBMC) at 12 wk and 2) stool frequency, volume, and consistency at 6 and 12 wk. Secondary outcome measures included stool fatty acid content.

RESULTS

Infants receiving high-sn-2 formula had higher WBBMC (128.1 +/- 9.7 compared with 122.7 +/- 10.1 g, adjusted for size and sex), softer stools at 6 and 12 wk, and a lower proportion of stool soap fatty acids than did infants receiving the control formula. Breast-fed infants had adjusted WBBMC values (128.3 +/- 9.1 g) similar to those of infants fed high-sn-2 formula and significantly higher than those of infants fed the control formula.

CONCLUSIONS

Changing the stereoisomeric structure of palmitate in infant formula resulted in higher WBBMC, reduced stool soap fatty acids, and softer stools more like those of breast-fed infants. The greater bone mass measured could be important if it persists beyond the trial period; this merits further investigation.

Feeding preterm infants after hospital discharge: effect of diet on body composition

Our purpose in this study was to examine whole body composition, using dual energy x-ray absorptiometry (DEXA) during dietary intervention in preterm infants (< or = 1750 g birthweight, < or = 34 wk gestation). At discharge, infants were randomized to be fed either a preterm infant formula (discharge-6 mo; group A) or a term formula (discharge-6 mo; group B), or the preterm formula (discharge-term) and the term formula (term-6 mo; group C). Nutrient intake was measured between each clinic visit. To measure body composition, DEXA was used at discharge, term, 12 wk, 6 mo, and 12 mo corrected age. The data were analyzed by ANOVA. At discharge, no differences were noted in patient characteristics between groups A, B, and C. Although energy intakes were similar, protein and mineral intakes differed between groups (A > C > B; p < 0.0001). During the study, weight gain and LM gain were greater in group A than B. At 12 mo, weight, LM, FM, and BMM but not % FM or BMD were greater in group A than B. However, the effects of diet were confined to boys, with no lasting effects seen in girls. In summary, therefore, DEXA was precise enough to detect differences in whole body composition during dietary intervention. Increased weight gain primarily reflected an increase in LM and is consistent with the idea that the preterm formula more closely met protein and/or protein-energy needs in rapidly growing preterm male infants.

Body composition of preterm infants during infancy

AIMS

To examine body composition in preterm infants.

METHODS

Body composition was measured by dual energy x-ray absorptiometry (DEXA) at hospital discharge, term, 12 weeks, and at 6 and 12 months corrected age in 125 infants (birthweight < or = 1750 g, gestational age < or = 34 weeks).

RESULTS

Body weight derived by DEXA accurately predicted that determined by conventional scales. In both sexes lean mass (LM), fat mass (FM), %FM, bone area (BA), bone mineral mass (BMM), and bone mineral density (BMD) increased rapidly during the study; significant changes were detectable between discharge and term. At 12 months, LM, BA, and BMM, but not FM, %FM, or BMD were greater in boys than in girls. Corrected for age, LM was less than those of the reference term infant; FM and %FM were similar; BMM was greater. Corrected for weight, LM was similar to those of the reference infant, while the FM and %FM of study infants were slightly greater.

CONCLUSIONS

DEXA accurately measures body mass. Body composition in preterm boys and girls differs. Interpretation of DEXA values may depend on whether age or body weight are regarded as the appropriate reference.

Four-component model of body composition in children: density and hydration of fat-free mass and comparison with simpler models

BACKGROUND

Body composition in children is generally measured by 2-component (2C) models, which are subject to error arising from variation in fat-free mass (FFM) composition. The 4-component (4C) model, which divides body weight into fat, water, mineral, and protein, can overcome these limitations.

OBJECTIVE

The aims of our study were to 1) describe 4C model data for children aged 8-12 y; 2) evaluate interindividual variability in the hydration, bone mineral content, and density of FFM; 3) evaluate the success with which 2C models and bedside techniques measure body composition in this age group with use of the 4C model as a reference.

DESIGN

Dual-energy X-ray absorptiometry, underwater weighing, deuterium dilution, bioelectrical impedance analysis, and anthropometry were used to determine body composition in 30 children. The contribution of methodologic error to the observed variability in the hydration and density of FFM was evaluated by using propagation of error.

RESULTS

Mean (+/-SD) FFM density and hydration were 1.0864+/-0.0074 kg/L and 75.3+/-2.2%, respectively, and were significantly different from adult values (P < 0.02). Relative to the 4C model, deuterium dilution and dual-energy X-ray absorptiometry showed no mean bias for fatness, whereas underwater weighing underestimated fatness (P < 0.025). Fatness determined by using skinfold-thickness and bioelectrical impedance analysis measurements along with published equations showed poor agreement with 4C model data.

CONCLUSIONS

Biological variability and methodologic error contribute equally to the variability of FFM composition. Our findings have major implications for bedside prediction methods used for children, traditionally developed in relation to underwater weighing.

Dementing illnesses in rural populations: the need for research and challenges confronting investigators

Expansion of the world's elderly populations has increased concerns about aging-related medical disorders like Alzheimer's disease and other dementias. In the United States, one fourth of those older than age 65 and at greatest risk for developing dementia live in rural environments that may influence its manifestation. The objectives of this study were to determine the need for and potential benefits of further epidemiological research concerning dementia and similar disorders in rural U.S. populations and to identify pertinent methodological issues related to rural dementia research. This study employed a National Library of Medicine (MEDLINE) document search based on the key words "cognitive disorders," "dementia," "Alzheimer's disease," and "rural," followed by recovery of literature resources references in the bibliographies of selected articles. Nineteen studies focusing on dementia or related disorders in rural settings have been reported from around the world. While four of these were conducted in the United States, only one rural dementia prevalence study has been undertaken in this country. Because of methodological variability, comparisons of prevalence estimates between these rural studies, as well as with those from urban investigations, is difficult. Nonetheless, there is reason to believe that certain potentially dementing illnesses are more common in rural populations. There is also evidence to suggest that the screening instruments commonly used in such studies tend to misclassify rural elders as "false positive" dementia cases. Information regarding dementing disorders, particularly Alzheimer's disease, in rural populations is scarce. Preliminary observations that dementia may be more common in rural settings and that rural families are more likely to maintain their dementing elders in the community imply that further rural dementia research could yield important insights into the risk factors for these illnesses, the variables influencing their course, and the methods by which they can be more effectively managed. A determination of the reliability and validity of commonly used dementia screening instruments in rural populations would represent an important advancement in this area of research.

Energy metabolism in infants and children

Energy is used continuously in the body and is fundamental to physiologic processes. Requirements of individuals vary in relation to a wide variety of factors, making energy metabolism an issue of great importance to the pediatrician. Techniques are available for short- and long-term measurements of energy expenditure, which serve different purposes. The principal techniques are suitable for the age range from birth to adolescence. The theory of energy metabolism is briefly discussed, including a summary of the different working definitions. The principles and practicalities of classical indirect calorimetry, the doubly labeled water method, the bicarbonate method, and heart rate monitoring are then described.

Precision and accuracy in a metabolic monitor for indirect calorimetry

OBJECTIVE

To determine within-machine and between-machine precision (reproducibility) and accuracy, of the Deltatrac Mk 1 Metabolic Monitor.

DESIGN

Within-machine and between-machine comparison for gas exchange (VO2 and VCO2), respiratory quotient (RQ) and energy expenditure (EE).

SUBJECTS

3 Deltatrac Mk 1 Metabolic Monitors.

METHODS

Within-machine and between-machine reproducibility were assessed by five successive 10 min gas infusion tests in each machine. Accuracy was assessed by measuring independently the gas content of the infusion mixture. The Deltatrac flowmeters were evaluated by further infusion tests.

RESULTS

Within-study reproducibility was < 1 ml/min for VCO2, < 2.5 ml/min for VO2, < 5 kcal/d for EE and < 0.01 for RQ. Between-study reproducibility was < 0.2% for RQ, < 1% for VCO2 and < 2% for VO2 and EE. Between-machine reproducibility was < 0.1% for RQ and < 1% for VO2, VCO2 and EE. Accuracy in all three machines was within 3% for VO2, VCO2 and EE, and within 0.2% for RQ.

CONCLUSIONS

The Deltatrac Mk 1 is a very precise metabolic monitor, and is accurate within 3% for gas exchange and EE. RQ is measured with greatest reproducibility and accuracy (within 0.2%), making the monitor particularly suitable for studies of substrate utilisation.

Energy intake in early infancy and childhood fatness

OBJECTIVE

To investigate whether aspects of infant energy intake are related to fatness in early childhood.

DESIGN

Longitudinal investigation of infants studied at 12 weeks and 2-3.5 y.

SUBJECTS

20 healthy infants, breast-fed or formula-fed, from the general population.

MEASUREMENTS

Milk volume intake (MVI) by deuterium turnover, estimated energy intake, weaning status and body composition in infancy, body composition in childhood.

RESULTS

MVI was not related to infant skinfolds or percentage fat. Weaning was inversely related to MVI (P < 0.04) at 12 weeks, and inversely related to skinfolds (P = 0.055) and fat mass (P = 0.020) in childhood. MVI and total energy intake were not related to childhood fatness.

CONCLUSIONS

Early weaning was associated with a moderate reduction in childhood fatness. Two possible mechanisms are discussed. However, early infant energy intake was not an important determinant of later fatness in this population.

Factors affecting the 2H to 18O dilution space ratio in infants

In the doubly labeled water (DLW) method, for measurement of energy expenditure in humans, calculation of carbon dioxide production rate is influenced by the ratio (R) of the dilution spaces of the tracer isotopes 2H and 18O. Recent publications have recommended use of a fixed value for R, using a mean population value (meanR) rather than individually derived experimental values. However, most of the data considered previously were derived from adults. Infants are characterized by rapid rates of energy deposition and high body water content, either of which could influence isotope kinetics. We have considered whether use of a fixed R value is suitable for DLW studies of infants, and whether the adult (meanR) value is appropriate. Data from 281 DLW measurements in healthy infants aged 6 wk to 12 mo were analyzed. Mean R of all measurements was 1.036 (SD 0.019), very similar to (meanR) values recommended for adults. We found analytical precision could account for almost all between-subject variation at a single time point. However, we also found relationships between R and age and weight gain, indicating that physiology does influence the space ratio. The effect of weight gain on R was negligible, but changes of (meanR) with age, reflecting changes in percentage body water during infancy, were of sufficient magnitude to affect calculation of energy expenditure significantly. Our analysis suggests that use of a fixed ratio at a single time point in infancy is acceptable, but that the appropriate value of (meanR) changes over the first year of life.