Four-year follow-up of school-based intervention on overweight children: the KOPS study

Objective: To evaluate the 4‐year outcome of a school‐based health promotion on weight status as part of the Kiel Obesity Prevention Study (KOPS). Research Methods and Procedures: Within a cluster‐sampled quasi‐randomized controlled trial, 1764 children at 6 and 10 years of age were assessed between 1996 and 2005 in 32 primary schools in Kiel, North Germany. Six nutrition units followed by 20‐minute running games were performed within the first year at school. Prevalence, incidence, and remission of overweight were main outcome measures. Results: The 4‐year change in BMI was +11.6%, with increases in prevalence of overweight and obesity from 5.2% to 11.1% and 3.9% to 5.1%, respectively. Cumulative 4‐year incidence of overweight and obesity was 9.2% and 3.1%, respectively. Intervention had no effect on mean BMI. The effect on prevalence was significant in children from families with high socioeconomic status [odds ratio (OR), 0.35; 95% confidence interval (CI), 0.14 to 0.91] and marginally significant in children of normal‐weight mothers (OR, 0.57; 95% CI, 0.33 to 1.00). Cumulative 4‐year incidence of overweight was lower only in intervention children from families with high socioeconomic status (OR, 0.26; 95% CI, 0.07 to 0.87). Remission of overweight was most pronounced in children of normal‐weight mothers (OR, 5.43; 95% CI, 1.28 to 23.01). Prevalence of underweight was unchanged. The intervention had minor but favorable effects on lifestyle. Discussion: A school‐based health promotion has sustainable effects on remission and incidence of overweight; it was most pronounced in children of normal‐weight mothers and children from families with high socioeconomic status. There was no effect on obesity. The data argue in favor of additional measures of prevention.     

High-level medium-chain triglyceride feeding and energy expenditure in normal-weight women

The objective of this study was to assess how short-term feeding of high levels of dietary medium-chain triglyceride (MCT) affect energy expenditure and postprandial substrate oxidation rates in normal-weight, premenopausal women. Eight healthy women were fed both a MCT-rich and an isocaloric long-chain triglyceride (LCT)-rich diet for two 1-week periods separated by a minimum of 21 days. The energy intake in each diet was 45% carbohydrates, 40% fat, and 15% protein. The 2 diets had either 60.81% or 1.11% of total fat energy from MCT with the remaining fat energy intake from LCT. On days 1 and 7 of each diet, resting metabolic rate and postprandial energy expenditure (EE) were measured by indirect calorimetry with a ventilated hood. Results indicated on days 1 and 7, there were no significant differences between diets for resting metabolic rate or mean postprandial EE. On both days 1 and 7, fat oxidation for the MCT-rich diet was significantly greater (0.0001 相似文献   

中国小麦燃料乙醇的能量收益

分析了燃料乙醇能量收益问题提出的背景,国外有关燃料乙醇能量收益研究的最新进展及国内研究现状,采用全生命周期分析方法,计算了小麦燃料乙醇净能量值和能量产投比,对中国小麦燃料乙醇的能量收益进行了评价。主要结论有:如不考虑副产品能量价值,旧工艺和新工艺的NEV分别为-17022MJ/t燃料乙醇和-11778MJ/t燃料乙醇,R值分别是0.64和0.72;如考虑副产品能量价值,旧工艺和新工艺的NEV值分别为2271MJ/t燃料乙醇和11249MJ/t燃料乙醇,R值分别是1.05和1.27,从能源经济性角度看,旧工艺和新工艺的能量收益已是正效益,且新工艺的能量收益显著提高;与美国玉米燃料乙醇生产相比,如考虑副产品能量价值,新工艺和美国玉米燃料乙醇的NEV分别为11249MJ/t燃料乙醇和7457MJ/t燃料乙醇,R值分别是1.27和1.34。由于小麦转化率要低于玉米,因而小麦燃料乙醇的R值会低于玉米燃料乙醇。中国小麦燃料乙醇生产(新工艺)NEV大于美国玉米燃料乙醇的原因在于:中国小麦燃料乙醇副产品综合利用水平(23027MJ/t燃料乙醇)已明显优于美国玉米燃料乙醇(5078MJ/t燃料乙醇)。     

Anthropometric data, proportion and form in children 2 to 5 years old--a longitudinal study

A longitudinal anthropometric study with integrated picture documentation was made in the German administrative district of Potsdam-Mittelmark from April 2002 until April 2003. During that time 183 children aged between 2 to 5 years were measured. The results of the study show, that with the help of the calculation method for pictures, presented here for the first time, additional information about the changes of proportions and body shape can be gained and made measurable. The aim of the study is to make use of the measureable individual changes in body shape for an objective estimation of the biological age. Being able to calculate the age of a child may be useful when investigating a crime, e. g. in case of an abused child, whose chronological age is unknown at the time of the incident, and the only possibility for an age-estimation depends on a picture.     

Stability of exploratory multivariate data modeling in longitudinal data

Exploratory data-driven multivariate analysis provides a means of investigating underlying structure in complex data. To explore the stability of multivariate data modeling, we have applied a common method of multivariate modeling (factor analysis) to the Genetic Analysis Workshop 13 (GAW13) Framingham Heart Study data. Given the longitudinal nature of the data, multivariate models were generated independently for a number of different time points (corresponding to cross-sectional clinic visits for the two cohorts), and compared. In addition, each multivariate model was used to generate factor scores, which were then used as a quantitative trait in variance component-based linkage analysis to investigate the stability of linkage signals over time. We found surprisingly good correlation between factor models (i.e., predicted factor structures), maximum LOD scores, and locations of maximum LOD scores (0.81< rho <0.94 for factor scores; rho >0.99 for peak locations; and 0.67< rho <0.93 for peak LOD scores). Furthermore, the regions implicated by linkage analysis with these factor scores have also been observed in other studies, further validating our exploratory modeling.     

Bridging the gap between theory and data in ecological models

In September 2011, the University of Essex, UK, hosted an interdisciplinary conference, Mathematical and Theoretical Ecology 2011 (MATE 2011), with the theme of ‘Linking models with ecological processes’. The aim of the meeting was to create discussion and debate between modellers and empiricists working in ecology. A wide range of topics were discussed at the meeting including evolutionary and community models of ecosystem structure, epidemiological models, non-linear models of population dynamics, spatiotemporal models, individual and collective movement behaviour, and applications of ecological models to engineering problems. In this introductory article, we provide a report of the MATE 2011 meeting, and briefly review the most recent relevant research in the fields of mathematical and theoretical ecology. We introduce and summarise the eight contributed articles that were selected for this special issue. The diverse range of topics and the wide range of mathematical, statistical and computational tools used illustrate the broad appeal and depth of research in the rich field of mathematical and theoretical ecology.     

Characterization of the diurnal rhythm of peptide YY and its association with energy balance parameters in normal-weight premenopausal women

PYY may play a role in modulating satiety and energy expenditure; increasing PYY postprandially has been studied largely in single-meal responses. The diurnal rhythm of PYY and its role in energy balance have not been fully characterized. The purpose of our study was to characterize features of the diurnal rhythm of PYY and determine its role in regulating energy balance. This study was a cross-sectional analysis of 11 subjects in whom 24-h repeated blood sampling was conducted at baseline of a larger prospective study. Breakfast (B), lunch (L), dinner (D), and a snack (S) occurred between 0900 and 1900. Total PYY was assayed every hour from 0800 to 1000, every 20 min from 1000 to 2000, and every hour from 2000 to 0800. PYY variables included total AUC, postprandial peaks, and 24-h mean. Energy balance variables included energy intake, RMR, RQ, and NEAT. PYY postprandial peaks were significantly higher than fasting (P < 0.05). Twenty-four-hour peak PYY occurred after L and was significantly higher than all other peaks (P < 0.05). A cubic curve function accounted for most of the variance in PYY (r(2) = 69.9%, P < 0.01). Fasting PYY (0800) correlated with postprandial peaks at B (r = 0.77, P = 0.01), L (r = 0.71, P = 0.01), and D (r = 0.65, P = 0.03). The only significant association between PYY and energy expenditure was that RMR (kcal/24 h) correlated with 24-h mean PYY (r = 0.71, P = 0.013) and total AUC (r = 0.69, P = 0.019). We conclude that PYY displays a meal-driven diurnal rhythm and is correlated to RMR, a major contributor to energy expenditure. Thus, PYY varies in accordance with energy content and RMR, supporting a role for PYY in energy balance modulation.     

Genetic markers of obesity risk: stronger associations with body composition in overweight compared to normal-weight children

Background

Genetic factors are important determinants of overweight. We examined whether there are differential effect sizes depending on children''s body composition.

Methods

We analysed data of n = 4,837 children recorded in the Avon Longitudinal Study of Parents and Children (ALSPAC), applying quantile regression with sex- and age-specific standard deviation scores (SDS) of body mass index (BMI) or with body fat mass index and fat-free mass index at 9 years as outcome variables and an “obesity-risk-allele score” based on eight genetic variants known to be associated with childhood BMI as the explanatory variable.

Results

The quantile regression coefficients increased with increasing child''s BMI-SDS and fat mass index percentiles, indicating larger effects of the genetic factors at higher percentiles. While the associations with BMI-SDS were of similar size in medium and high BMI quantiles (40th percentile and above), effect sizes with fat mass index increased over the whole fat mass index distribution. For example, the fat mass index of a normal-weight (50th percentile) child was increased by 0.13 kg/m² (95% confidence interval (CI): 0.09, 0.16) per additional allele, compared to 0.24 kg/m² per allele (95% CI: 0.15, 0.32) in children at the 90th percentile. The genetic associations with fat-free mass index were weaker and the quantile regression effects less pronounced than those on fat mass index.

Conclusions

Genetic risk factors for childhood overweight appear to have greater effects on fatter children. Interaction of known genetic factors with environmental or unknown genetic factors might provide a potential explanation of these findings.     

Reproducibility of anthropometric measurements in children: a longitudinal study

The purpose of this study was to establish the reproducibility of a series of anthropometric measures performed twice during one week during a three year period in boys and girls. The subjects of this investigation were 39 children (21 boys and 18 girls), 9-10 year of age at the beginning of the study. Children were measured three times with one year interval. Children were classified by Tanner stage 1-2 during the first measurements, stage 1-3 during the second measurements and stage 1-4 during the third measurements. Body height and weight were measured and BMI calculated. All anthropometric parameters were measured according to the protocol recommended by the International Society for the Advancement of Kinanthropometry (Norton & Olds 1996). Nine skinfolds, 13 girths, eight lengths and eight breadths/lengths were measured. The reproducibility of body height (r = 0.995-0.999), body weight (r = 0.990-0.999) and BMI (r = 0.969-0.999) was very high in boys and girls. The intraclass correlations (ICC), technical errors (TE) and coefficients of variation (CV) were quite different depending on the measurement site of the skinfold thickness. It was surprising that the ICCs were highest and TEs and CVs were lowest during the second year of the measurement. The computed ICC was high, and TE and CV values were quite similar and relatively low in girth, length and breadth/length measurements. It was concluded that the reproducibility of girths, lengths and breadths/lengths in children is very high and the reproducibility of skinfolds is high. Specifically, the reproducibility is very high immediately before puberty in boys and girls.     

Proton channel models: Filling the gap between experimental data and the structural rationale

Voltage-gated proton channels are integral membrane proteins with the capacity to permeate elementary particles in a voltage and pH dependent manner. These proteins have been found in several species and are involved in various physiological processes. Although their primary topology is known, lack of details regarding their structures in the open conformation has limited analyses toward a deeper understanding of the molecular determinants of their function and regulation. Consequently, the function-structure relationships have been inferred based on homology models. In the present work, we review the existing proton channel models, their assumptions, predictions and the experimental facts that support them. Modeling proton channels is not a trivial task due to the lack of a close homolog template. Hence, there are important differences between published models. This work attempts to critically review existing proton channel models toward the aim of contributing to a better understanding of the structural features of these proteins.     

Model of hidden heterogeneity in longitudinal data

Variables measured in longitudinal studies of aging and longevity do not exhaust the list of all factors affecting health and mortality transitions. Unobserved factors generate hidden variability in susceptibility to diseases and death in populations and in age trajectories of longitudinally measured indices. Effects of such heterogeneity can be manifested not only in observed hazard rates but also in average trajectories of measured indices. Although effects of hidden heterogeneity on observed mortality rates are widely discussed, their role in forming age patterns of other aging-related characteristics (average trajectories of physiological state, stress resistance, etc.) is less clear. We propose a model of hidden heterogeneity to analyze its effects in longitudinal data. The approach takes the presence of hidden heterogeneity into account and incorporates several major concepts currently developing in aging research (allostatic load, aging-associated decline in adaptive capacity and stress-resistance, age-dependent physiological norms). Simulation experiments confirm identifiability of model's parameters.     

Cross-platform analysis of longitudinal data in metabolomics

Metabolic profiling is considered to be a very promising tool for diagnostic purposes, for assessing nutritional status and response to drugs. However, it is also evident that human metabolic profiles have a complex nature, influenced by many external factors. This, together with the understanding of the difficulty to assign people to distinct groups and a general move in clinical science towards personalized medicine, raises the interest to explore individual and variable metabolic features for each individual separately in longitudinal study design. In the current paper we have analyzed a set of metabolic profiles of a selection of six urine samples per person from a set of healthy individuals by (1)H NMR and reversed-phase UPLC-MS. We have demonstrated that the method for recovery of individual metabolic phenotypes can give complementary information to another established method for analysis of longitudinal data--multilevel component analysis. We also show that individual metabolic signatures can be found not only in (1)H NMR data, as has been demonstrated before, but also even more strongly in LC-MS data.     

Parasite interactions in natural populations: insights from longitudinal data

The physiological and immunological state of an animal can be influenced by current infections and infection history. Consequently, both ongoing and previous infections can affect host susceptibility to another parasite, the biology of the subsequent infection (e.g. infection length) and the impact of infection on host morbidity (pathology). In natural populations, most animals will be infected by a succession of different parasites throughout the course of their lives, with probably frequent concomitant infections. The relative timing of different infections experienced by a host (i.e. the sequence of infection events), and the effects on factors such as host susceptibility and host survival, can only be derived from longitudinal data on individual hosts. Here we review some of the evidence for the impact of co-infection on host susceptibility, infection biology and pathology focusing on insights obtained from both longitudinal studies in humans and experiments that explicitly consider the sequence of infection. We then consider the challenges posed by longitudinal infection data collected from natural populations of animals. We illustrate their usefulness using our data of microparasite infections associated with field vole (Microtus agrestis) populations to examine impacts on susceptibility and infection length. Our primary aim is to describe an analytical approach that can be used on such data to identify interactions among the parasites. The preliminary analyses presented here indicate both synergistic and antagonistic interactions between microparasites within this community and emphasise that such interactions could have significant impacts on host-parasite fitness and dynamics.     

Towards representative energy data: the Machiguenga study

Representative energy data for a human population can be produced by combining randomly sampled time allocation observations with activity-specific energy expenditure measurements. Research to produce representative energy data for adults of a population of Machiguenga Indians has recently been conducted in lowland, southeastern Peru. Marked contrast was found between the sexes for average married adults in energy expended on an average day. Men spent about 3,200 kcals and women, about 1,925; ratio: 1.66 to 1. In general, men tended to work at somewhat more energetic activities and for longer periods than did women. In addition to sex-role-related task differences were contrasts in uses of technological items and in respective work settings. These representative behavior data permit direct estimates of population-level energy requirements for average days, seasons, or for 1 year.     

Joint modeling of survival and longitudinal data: likelihood approach revisited

The maximum likelihood approach to jointly model the survival time and its longitudinal covariates has been successful to model both processes in longitudinal studies. Random effects in the longitudinal process are often used to model the survival times through a proportional hazards model, and this invokes an EM algorithm to search for the maximum likelihood estimates (MLEs). Several intriguing issues are examined here, including the robustness of the MLEs against departure from the normal random effects assumption, and difficulties with the profile likelihood approach to provide reliable estimates for the standard error of the MLEs. We provide insights into the robustness property and suggest to overcome the difficulty of reliable estimates for the standard errors by using bootstrap procedures. Numerical studies and data analysis illustrate our points.     

VEP's in normal full-term and premature neonates: longitudinal versus cross-sectional data

VEPs have been shown to change with CNS maturation in children, yet few studies had documented maturational changes in the premature infant. Using LED goggles, VEPs were studied in 75 neurologically normal infants of 22–42 weeks gestational age (GA) within the first 3 days of life. Twenty of these (22–32 weeks GA) were also followed longitudinally.The 22–23 week GA neonates had no identifiable waves. In all infants >24 weeks a large negative wave is seen with a latency around 300 msec (N300). After 27 weeks GA a late positive wave was present (P400), but with more variable latency and morphology. Between 30 and 35 weeks GA a small positive wave (P200) was seen in over one-third of the neonates; this component was present in all infants > 36 weeks GA.The consistency of the N300 across the ages studied suggests that it might arise from the basilar dendrites in the visual cortex, which are well developed by 24 weeks GA and undergo relatively little further development between 24 weeks and term. The P200 is suggested to arise from the apical dendrites which develop in the last trimester, explaining the emergence of P200 after 30 weeks GA.The infants followed longitudinally showed the same components, emerging in the same order, but with more rapid development (particularly of P200) compared to the cross-sectional studies. These data suggest that there are differences in the maturation of the visual system in the extrauterine versus intrauterine environment.     

Spatio-temporal gap analysis of OBIS-SEAMAP project data: assessment and way forward

The OBIS-SEAMAP project has acquired and served high-quality marine mammal, seabird, and sea turtle data to the public since its inception in 2002. As data accumulated, spatial and temporal biases resulted and a comprehensive gap analysis was needed in order to assess coverage to direct data acquisition for the OBIS-SEAMAP project and for taxa researchers should true gaps in knowledge exist. All datasets published on OBIS-SEAMAP up to February 2009 were summarized spatially and temporally. Seabirds comprised the greatest number of records, compared to the other two taxa, and most records were from shipboard surveys, compared to the other three platforms. Many of the point observations and polyline tracklines were located in northern and central Atlantic and the northeastern and central-eastern Pacific. The Southern Hemisphere generally had the lowest representation of data, with the least number of records in the southern Atlantic and western Pacific regions. Temporally, records of observations for all taxa were the lowest in fall although the number of animals sighted was lowest in the winter. Oceanographic coverage of observations varied by platform for each taxa, which showed that using two or more platforms represented habitat ranges better than using only one alone. Accessible and published datasets not already incorporated do exist within spatial and temporal gaps identified. Other related open-source data portals also contain data that fill gaps, emphasizing the importance of dedicated data exchange. Temporal and spatial gaps were mostly a result of data acquisition effort, development of regional partnerships and collaborations, and ease of field data collection. Future directions should include fostering partnerships with researchers in the Southern Hemisphere while targeting datasets containing species with limited representation. These results can facilitate prioritizing datasets needed to be represented and for planning research for true gaps in space and time.