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The association between green space and cause-specific mortality in urban New Zealand: an ecological analysis of green space utility.

Richardson E, Pearce J, Mitchell R, Day P, Kingham S - BMC Public Health (2010)

Bottom Line: No significant associations between usable or total green space and mortality were observed after adjustment for confounders.Our inability to adjust for individual-level factors with a significant influence on cardiovascular disease and lung cancer mortality risk (e.g., diet and alcohol consumption) will have limited the ability of the analyses to detect green space effects, if present.Additionally, green space variation may have lesser relevance for health in New Zealand because green space is generally more abundant and there is less social and spatial variation in its availability than found in other contexts.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of GeoSciences, The University of Edinburgh, Edinburgh, UK.

ABSTRACT

Background: There is mounting international evidence that exposure to green environments is associated with health benefits, including lower mortality rates. Consequently, it has been suggested that the uneven distribution of such environments may contribute to health inequalities. Possible causative mechanisms behind the green space and health relationship include the provision of physical activity opportunities, facilitation of social contact and the restorative effects of nature. In the New Zealand context we investigated whether there was a socioeconomic gradient in green space exposure and whether green space exposure was associated with cause-specific mortality (cardiovascular disease and lung cancer). We subsequently asked what is the mechanism(s) by which green space availability may influence mortality outcomes, by contrasting health associations for different types of green space.

Methods: This was an observational study on a population of 1,546,405 living in 1009 small urban areas in New Zealand. A neighbourhood-level classification was developed to distinguish between usable (i.e., visitable) and non-usable green space (i.e., visible but not visitable) in the urban areas. Negative binomial regression models were fitted to examine the association between quartiles of area-level green space availability and risk of mortality from cardiovascular disease (n = 9,484; 1996 - 2005) and from lung cancer (n = 2,603; 1996 - 2005), after control for age, sex, socio-economic deprivation, smoking, air pollution and population density.

Results: Deprived neighbourhoods were relatively disadvantaged in total green space availability (11% less total green space for a one standard deviation increase in NZDep2001 deprivation score, p < 0.001), but had marginally more usable green space (2% more for a one standard deviation increase in deprivation score, p = 0.002). No significant associations between usable or total green space and mortality were observed after adjustment for confounders.

Conclusion: Contrary to expectations we found no evidence that green space influenced cardiovascular disease mortality in New Zealand, suggesting that green space and health relationships may vary according to national, societal or environmental context. Hence we were unable to infer the mechanism in the relationship. Our inability to adjust for individual-level factors with a significant influence on cardiovascular disease and lung cancer mortality risk (e.g., diet and alcohol consumption) will have limited the ability of the analyses to detect green space effects, if present. Additionally, green space variation may have lesser relevance for health in New Zealand because green space is generally more abundant and there is less social and spatial variation in its availability than found in other contexts.

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Flowchart illustration of usable and non-usable green space classification system.
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Figure 1: Flowchart illustration of usable and non-usable green space classification system.

Mentions: Spatial land cover data sets for New Zealand were sought and processed using ArcMap GIS software (ESRI, Redlands, CA) to produce the green space classification. For the purposes of distinguishing usable and non-usable green space across the country we required data with both a good level of attribute information and national coverage. Three New Zealand-wide spatial data sets (with land areas represented as polygons) were obtained and integrated (Table 1). The Land Cover Data Base (LCDB2) data set gave contiguous national coverage but had the lowest resolution and provided the least attribute information; hence we augmented this data set with two more detailed but less contiguous data sets from the Department of Conservation (DOC) and Land Information New Zealand (LINZ). Our definition of green space included natural areas (e.g., parks, beaches, and fields) but excluded aquatic areas (e.g., lakes and the sea) as these are not generally treated as green space in the literature. The decision tree developed to produce our green space classification is shown in Figure 1.


The association between green space and cause-specific mortality in urban New Zealand: an ecological analysis of green space utility.

Richardson E, Pearce J, Mitchell R, Day P, Kingham S - BMC Public Health (2010)

Flowchart illustration of usable and non-usable green space classification system.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2875209&req=5

Figure 1: Flowchart illustration of usable and non-usable green space classification system.
Mentions: Spatial land cover data sets for New Zealand were sought and processed using ArcMap GIS software (ESRI, Redlands, CA) to produce the green space classification. For the purposes of distinguishing usable and non-usable green space across the country we required data with both a good level of attribute information and national coverage. Three New Zealand-wide spatial data sets (with land areas represented as polygons) were obtained and integrated (Table 1). The Land Cover Data Base (LCDB2) data set gave contiguous national coverage but had the lowest resolution and provided the least attribute information; hence we augmented this data set with two more detailed but less contiguous data sets from the Department of Conservation (DOC) and Land Information New Zealand (LINZ). Our definition of green space included natural areas (e.g., parks, beaches, and fields) but excluded aquatic areas (e.g., lakes and the sea) as these are not generally treated as green space in the literature. The decision tree developed to produce our green space classification is shown in Figure 1.

Bottom Line: No significant associations between usable or total green space and mortality were observed after adjustment for confounders.Our inability to adjust for individual-level factors with a significant influence on cardiovascular disease and lung cancer mortality risk (e.g., diet and alcohol consumption) will have limited the ability of the analyses to detect green space effects, if present.Additionally, green space variation may have lesser relevance for health in New Zealand because green space is generally more abundant and there is less social and spatial variation in its availability than found in other contexts.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of GeoSciences, The University of Edinburgh, Edinburgh, UK.

ABSTRACT

Background: There is mounting international evidence that exposure to green environments is associated with health benefits, including lower mortality rates. Consequently, it has been suggested that the uneven distribution of such environments may contribute to health inequalities. Possible causative mechanisms behind the green space and health relationship include the provision of physical activity opportunities, facilitation of social contact and the restorative effects of nature. In the New Zealand context we investigated whether there was a socioeconomic gradient in green space exposure and whether green space exposure was associated with cause-specific mortality (cardiovascular disease and lung cancer). We subsequently asked what is the mechanism(s) by which green space availability may influence mortality outcomes, by contrasting health associations for different types of green space.

Methods: This was an observational study on a population of 1,546,405 living in 1009 small urban areas in New Zealand. A neighbourhood-level classification was developed to distinguish between usable (i.e., visitable) and non-usable green space (i.e., visible but not visitable) in the urban areas. Negative binomial regression models were fitted to examine the association between quartiles of area-level green space availability and risk of mortality from cardiovascular disease (n = 9,484; 1996 - 2005) and from lung cancer (n = 2,603; 1996 - 2005), after control for age, sex, socio-economic deprivation, smoking, air pollution and population density.

Results: Deprived neighbourhoods were relatively disadvantaged in total green space availability (11% less total green space for a one standard deviation increase in NZDep2001 deprivation score, p < 0.001), but had marginally more usable green space (2% more for a one standard deviation increase in deprivation score, p = 0.002). No significant associations between usable or total green space and mortality were observed after adjustment for confounders.

Conclusion: Contrary to expectations we found no evidence that green space influenced cardiovascular disease mortality in New Zealand, suggesting that green space and health relationships may vary according to national, societal or environmental context. Hence we were unable to infer the mechanism in the relationship. Our inability to adjust for individual-level factors with a significant influence on cardiovascular disease and lung cancer mortality risk (e.g., diet and alcohol consumption) will have limited the ability of the analyses to detect green space effects, if present. Additionally, green space variation may have lesser relevance for health in New Zealand because green space is generally more abundant and there is less social and spatial variation in its availability than found in other contexts.

Show MeSH
Related in: MedlinePlus