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BACKGROUND/OBJECTIVES: Recent evidence suggests clustering of human body height. We want to assess the consequences of connectedness in a spatial network on height clustering in an artificial society. SUBJECTS/METHODS: We used an agent-based computer modelling technique (Monte Carlo simulation) and compared simulated height in a spatial network with characteristics of the observed geographic height distribution of three historic cohorts of Swiss military conscripts (conscripted in 1884-1891;1908-1910;and 2004-2009). RESULTS: Conscript height shows several characteristic features: (1) height distributions are overdispersed. (2) Conscripts from districts with direct inter-district road connections tend to be similar in height. (3) Clusters of tall and clusters of short stature districts vary over time. Autocorrelations in height between late 19th and early 21st century districts are low. (4) Mean district height depends on the number of connecting roads and on the number of conscripts per district. Using Monte Carlo simulation, we were able to generate these natural characteristics in an artificial society. Already 5% height information from directly connected districts is sufficient to simulate the characteristics of natural height distribution. Very similar observations in regular rectangular networks indicate that the characteristics of Swiss conscript height distributions do not so much result from the particular Swiss geography but rather appear to be general features of spatial networks. CONCLUSIONS: Spatial connectedness can affect height clustering in an artificial society, similar to that seen in natural cohorts of military conscripts, and strengthen the concept of connectedness being involved in the regulation of human height. European Journal of Clinical Nutrition (2016) 70, 671-678;doi:10.1038/ejcn.2016.45; published online 6 April 2016, INTRODUCTION Humans are social. They dwell in groups, they communicate and similar individuals tend to cluster as the old ones say: Birds of a feather flock together. However, do those [...]

BACKGROUND/OBJECTIVES: Given the availability of large longitudinal data sets on human height and weight, different modelling approaches are at hand to access quantities of interest relating to important diagnostic aims. SUBJECTS/METHODS: Statistical modelling frameworks for longitudinal data on human height and weight have to consider the issues of individual heterogeneity and time dependence to provide an accurate statistical characterisation. Further, missing values inevitably occurring within longitudinal data sets have to be addressed adequately to allow for valid inference. The Bayesian framework is illustrated to facilitate stringent comparison of available non-nested model frameworks addressing these issues using simulated and empirical data sets. RESULTS: Comparing random-effects and fixed-effects modelling approaches with the Preece-Baines (PB) model reveals that, for simulated data, the Bayesian approach towards model comparison is effective in discriminating between different model specifications. With regard to analysis of 14 longitudinal data sets, the implicit trade-off between model fit, that is, description of the data, and a parsimonious parameterisation favouring prediction is often best addressed via the PB model. CONCLUSIONS: The Bayesian approach is illustrated to allow for effective comparison in case model specifications for longitudinal data are not linked directly via parametric restrictions. European Journal of Clinical Nutrition (2016) 70, 656-661; doi: 10.1038/ejcn.2016.23; published online 30 March 2016, INTRODUCTION Human growth charts serve as well-accepted indicators for measuring the population and in particular the health status of children. (1) Therefore, several statistical approaches were developed to model these [...]

BACKGROUND/OBJECTIVES: Besides large efforts regarding field work, provision of valid databases requires statistical and informational infrastructure to enable long-term access to longitudinal data sets on height, weight and related issues. SUBJECTS/METHODS: To foster use of longitudinal data sets within the scientific community, provision of valid databases has to address data-protection regulations. It is, therefore, of major importance to hinder identifiability of individuals from publicly available databases. To reach this goal, one possible strategy is to provide a synthetic database to the public allowing for pretesting strategies for data analysis. The synthetic databases can be established using multiple imputation tools. Given the approval of the strategy, verification is based on the original data. RESULTS: Multiple imputation by chained equations is illustrated to facilitate provision of synthetic databases as it allows for capturing a wide range of statistical interdependencies. Also missing values, typically occurring within longitudinal databases for reasons of item non-response, can be addressed via multiple imputation when providing databases. CONCLUSIONS: The provision of synthetic databases using multiple imputation techniques is one possible strategy to ensure data protection, increase visibility of longitudinal databases and enhance the analytical potential. European Journal of Clinical Nutrition (2016) 70, 653-655; doi:10.1038/ejcn.2016.22; published online 9 March 2016, INTRODUCTION Collecting longitudinal data sets is typically very costly. Tremendous efforts in field work ensure the highest possible quality in measurements. However, missing values inevitably occur for various reasons. Providing [...]

Aim: National European growth references differ. We aimed to convert (harmonize) currently used charts into a single unified interchangeable LMS format for each European nation.Methods: Nine currently used national European growth references from Belgium (2009), France (1979), Poland (2001), Sweden (2002), Switzerland (1989), the UK (1990), Italy (2006) and Germany (1979 and 1997) were harmonized and compared with the international WHO child growth standards and WHO growth reference data for 5-19 years.Results: European growth charts can be harmonized. The approach appears useful as height, and body mass index (BMI) is inappropriately represented by WHO references. European height references exhibit warping when plotted against the WHO reference. The French appears too short, the other Europeans too tall. Also, the BMI is not appropriately represented by the WHO references.Conclusions: Harmonizing references is a novel, convenient and cost-effective approach for converting historic and/or incomplete local or national growth reference charts into a unified interchangeable LMS format. Harmonizing facilitates producing growth references 'on demand', for limited regional purposes, for ethnically, socio-economically or politically defined minorities, but also for matching geographically different groups of children and adolescents for international growth and registry studies. [ABSTRACT FROM AUTHOR]