Novel green space measures and birthweight in Queensland, Australia

Abstract

IntroductionEnvironmental exposures can contribute both benefits and risks to human health. Green space represents an environmental exposure that may confer benefits to human health. There are several proposed benefits to green space exposure, such as improving mental wellbeing, increasing physical activity, improving the social cohesion of local neighbourhoods, reducing the negative effect of environmental risk factors, and improving exposure to beneficial microbiota. One of the proposed health benefits is an improvement in the health outcomes of neonates. Maternal exposure to green space has been associated with improvements in birthweight, among other birth outcomes. The developmental origins of health and disease hypothesis suggests that investing in healthy foetal development in Utero confers benefits across the life span. This makes an assessment of the potential impacts of environmental exposures on foetal development an important undertaking in population health. The current body of evidence on birthweight and maternal green space exposure is limited to a handful of exposure measures and coarse allocation of exposure. Newer measures of green space have been developed, which allows for an exploration of the effect of different ground covers (green, dry and bare earth), as well as measures of biodiversity, on health. This thesis explores the association of these novel green space measures with birthweight in a large birth cohort in Queensland, Australia. ObjectivesThis study has several objectives: 1) to examine the maternal and socio-demographic characteristics associated with birthweight; 2) to test for an association between green space, dry cover and bare earth and birthweight outcomes, controlling for the maternal and social factors; 3) to test whether foliage projective cover, a measure of crown canopy shading, is associated with birthweight outcomes; 4) to explore whether effects of green space differ between rural and urban communities; 5) to explore the interaction of green space with other environmental variables, namely air pollution and ambient temperature; and 6) to explore whether biodiversity is associated with birthweight outcomes. MethodsSeveral data sets were acquired and merged to create the data set used in this study. The outcome was birthweight (in grams and age-standardised), and this was acquired along with maternal covariates from the routine health records available for all births in Queensland, Australia. Social and neighbourhood variables were acquired from the Australian Bureau of Statistics. The exposures of interest to this study were green space (fractional cover, biodiversity and foliage projective iii cover), ambient temperature and air pollution. Directed acyclic graphs were developed to guide variable selection in all analyses. Mixed-effects linear regression and generalised linear mixedeffects models were developed, with random intercepts for maternal residential locality and year of birth. Results are presented as standardised beta coefficients or odds ratios, with 95% ...