Associations between BMI and home, school and route environmental exposures estimated using GPS and GIS: do we see evidence of selective daily mobility bias in children?

Rebecca J Namenek Brouwer,Andy P Jones,Sara E Benjamin Neelon,Thomas Burgoine

doi:10.1186/1476-072x-14-8

Abstract

BackgroundThis study examined whether objective measures of food, physical activity and built environment exposures, in home and non-home settings, contribute to children’s body weight. Further, comparing GPS and GIS measures of environmental exposures along routes to and from school, we tested for evidence of selective daily mobility bias when using GPS data.MethodsThis study is a cross-sectional analysis, using objective assessments of body weight in relation to multiple environmental exposures. Data presented are from a sample of 94 school-aged children, aged 5–11 years. Children’s heights and weights were measured by trained researchers, and used to calculate BMI z-scores. Participants wore a GPS device for one full week. Environmental exposures were estimated within home and school neighbourhoods, and along GIS (modelled) and GPS (actual) routes from home to school. We directly compared associations between BMI and GIS-modelled versus GPS-derived environmental exposures. The study was conducted in Mebane and Mount Airy, North Carolina, USA, in 2011.ResultsIn adjusted regression models, greater school walkability was associated with significantly lower mean BMI. Greater home walkability was associated with increased BMI, as was greater school access to green space. Adjusted associations between BMI and route exposure characteristics were null. The use of GPS-actual route exposures did not appear to confound associations between environmental exposures and BMI in this sample.ConclusionsThis study found few associations between environmental exposures in home, school and commuting domains and body weight in children. However, walkability of the school neighbourhood may be important. Of the other significant associations observed, some were in unexpected directions. Importantly, we found no evidence of selective daily mobility bias in this sample, although our study design is in need of replication in a free-living adult sample.Electronic supplementary materialThe online version of this article (doi:10.1186/1476-072X-14-8) contains supplementary material, which is available to authorized users.

Highlights

This study examined whether objective measures of food, physical activity and built environment exposures, in home and non-home settings, contribute to children’s body weight
We directly address Chaix et al.’s [47] implication of selective daily mobility bias through using Global positioning systems (GPS) data, through a formal comparison of Geographic information systems (GIS) modelled versus GPS actual route environmental exposures
We addressed the potential impact of selective daily mobility bias through a formal comparison of modelled GIS versus actual GPS route environmental exposures

Summary

Introduction

This study examined whether objective measures of food, physical activity and built environment exposures, in home and non-home settings, contribute to children’s body weight. Neighbourhood characteristics linked to health have been recently implicated in design theories such as ‘New Urbanism’, ‘Smart Growth’ and ‘Neotraditonalism’ [4] These describe the importance of walkable, pedestrian-orientated neighbourhoods, with well-connected streets, mixed land uses and good access to local amenities such as stores selling healthy food and green space. Such environmental characteristics have been hypothesised to act either directly (for example through promotion of physical activity), or via a pathway involving increased sense of community and social cohesion on behavioural outcomes and health [5]. We need to better understand the extent to which exposures of this kind contribute to adiposity in children

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