Greener neighbourhoods, slimmer children? Evidence from 4423 participants aged 6 to 13 years in the Longitudinal Study of Australian children.
OBJECTIVE
There is a growing belief that green space (for example, parks) help prevent obesity. There is evidence of an inverse association between green space and childhood body mass index (BMI); however, the majority of these studies are cross-sectional. Longitudinal studies that track change in BMI across childhood in relation to levels of green space proximity would improve the quality of evidence available for decision making.


METHODS
Objectively measured BMI was obtained every 2 years between 2006 and 2012 for 4423 participants initially aged 6-7 years in the Longitudinal Study of Australian Children (LSAC). The LSAC is a nationally representative study on a range of health and socio-demographic measures. Using Australian Bureau of Statistics mesh block data, which classify small scale land areas based on the main usage, each participant was assigned an objective measure of green space availability within their Statistical Area (level 2) of residence. Gender-stratified multilevel linear regression was used to estimate BMI growth curves across childhood in relation to green space availability. Family income, Australian Indigenous status, mothers' education and language spoken were used to adjust for socio-economic confounding.


RESULTS
Age was found to be an effect modifier of associations between green space and BMI for boys (P=0.005) and girls (P=0.048). As children grew older, an inverse patterning of BMI by green space availability emerged. These findings held after adjustment for socio-economic circumstances for boys (P=0.009), though were less robust for girls after this adjustment (P=0.056).


CONCLUSIONS
A beneficial effect of green space on BMI emerges as children grow older. However, there was little additional benefit after a modest amount of green space was met. Further research is needed to understand whether the drivers of this effect are from age-specific mechanisms, or whether the benefit of living in a greener neighbourhood is accumulated through childhood.
School of Science and Health, University of Western Sydney, Penrith, NSW, Australia.
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Sanders
1] School of Science and Health, University of Western Sydney, Penrith, NSW, Australia [2] School of Health and Society, University of Wollongong, Wollongong, NSW, Australia [3] Menzies Centre for Health Policy, University of Sydney, Sydney, NSW, Australia [4] Boden Institute of Obesity, Nutrition, Exercise and Eating Disorders, University of Sydney, Sydney, NSW, Australia.
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Feng
School of Science and Health, University of Western Sydney, Penrith, NSW, Australia.
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Fahey
Institute for Positive Psychology and Education, Australian Catholic University, Strathfield, NSW, Australia.
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Lonsdale
1] School of Science and Health, University of Western Sydney, Penrith, NSW, Australia [2] School of Geography and Geosciences, University of St Andrews, St Andrews, UK.
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Astell-Burt
D017677:Age Distribution; D001315:Australia / Q000453:epidemiology; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D002648:Child; D004779:Environment Design; D055317:Evidence-Based Practice; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D063766:Pediatric Obesity / Q000453:epidemiology* / Q000209:etiology / Q000517:prevention & control; D011050:Policy Making; D011998:Recreation; D012111:Residence Characteristics; D017678:Sex Distribution; D012959:Socioeconomic Factors; D014504:Urban Health