Investigating associations between neighbourhood green space and weight status : a longitudinal study of Australian Children aged 4 to 13 years old

Abstract

Background: There is a growing belief that increasing exposure to neighbourhood green space (e.g., parks) may help to prevent obesity in children. While evidence of an inverse association has previously been found (i.e., more green space has been associated with lower BMI), much of the evidence to date has been cross-sectional. Further, the mechanisms by which green space may influence weight status, such as through changes in physical activity behaviour, are under-researched. To assist urban planning, decision-makers need evidence based on longitudinal studies, which tracks children's weight status and behaviour across childhood in relation to levels of exposure to green space. Aim: The primary aim of this thesis was to investigate the longitudinal relationship between residential neighbourhood green space and children's weight status. The secondary aim was to investigate potential mechanisms for green space and children's weight status through mediation pathways and effect measure modification. Methods: Data for this thesis came from the Longitudinal Study of Australian Children (LSAC), a large-scale government project which collects data on a range of health, social, and demographic variables. Children's (n=4,983) anthropometry, physical activity behaviour, and socio-demographic information were provided biennially at five data collection points between 2004 (aged 4-5 years) and 2012 (aged 12-13 years). A measure of residential green space was derived from Australian Bureau of Statistics mesh block data, which classify small-scale land parcels based on their primary use. The percentage of area designated as parkland was derived for each Statistical Area (level 2) that children of the LSAC resided in. Multilevel regression analyses formed the basis of much of the statistical analyses conducted. Results: Green space was related to children's BMI, waist circumferences, and waist-to-height ratios, although associations for girls were mostly explained by socioeconomic status. For boys, differences by quantity of green space were largest as boys grow older. Green space was also associated with boys', but not girls', physical activity and screen time, such that more green space was associated with more time spent physical active, and less time was spent engaging in screen time behaviours. Green space also positively predicted parents' feelings of safety, which in turn acted as an effect modifier in the relationship between neighbourhood green space and boys' BMI. Despite regularly being hypothesised to act a mediator, there was no evidence that physical activity mediated the relationship between green space and children's weight status. These findings suggest that policy makers should ensure that a minimum level of green space is established, to contribute to healthy neighbourhoods for children to live in.

Date of Award	2016
Original language	English