Abstract
Introduction: There is evidence that urban design characteristics, including greater green space provision, have positive effects on health. Possible mechanisms include more opportunity for exercise, better air quality, smaller urban heat island effects, and lowered stress levels. Only a few previous studies have examined associations between green space and mortality and they have given inconsistent results. We conducted an ecological study relating green space to mortality in Hong Kong from 2006-2011. Methods: Normalized Difference Vegetation Index (NDVI), a measure of green space coverage, was measured for 199 small geographic areas in Hong Kong. Negative Binomial Regression Models were fit for each mortality outcome with NDVI as a covariate, and age, gender, population density, and area-level measures of socioeconomic status controlled as confounders, with Generalized Estimating Equations used to control for within-area correlation. Results: There were 236734, 58854, 21422, 11744, and 2964 deaths from all natural causes, cardiovascular diseases (CVD), lung cancer, chronic respiratory diseases (CRD), and diabetes, respectively. An increase of 0.44 units in NDVI, equivalent to it’s observed interquartile range, was significantly associated with lower CVD (relative risk (RR) = 0.88, 95% confidence interval (CI) = 0.80, 0.98) and diabetes (RR = 0.72, 95% CI = 0.60, 0.92) mortality, and marginally significantly associated with lower CRD mortality (RR = 0.90, 95% CI = 0.79, 1.02). These associations were stronger for males and residents of low-income areas. Lung cancer mortality had no significant association with green space. Conclusions: Better provision of green space in urban areas, particularly in low income areas, seems to have potential to reduce mortality in densely populated Asian cities. Policy makers involved in urban planning should consider these findings when making difficult decisions concerning land use in an era of rapid urban population growth.
Highlights
Green space is defined as areas of grass, trees, or other vegetation set apart for recreational or aesthetic purposes [1], and examples of green space include national parks, forests, recreation areas, community gardens, green belts, and city parks
Hong Kong is a high-income country, it has a very high level of income inequality [20], and is one of the most densely populated places in the world [21]. In this Hong Kong-based ecological study, we examined the association between area-level green space, population density, and several socioeconomic indicators, with all non-accidental causes of mortality and cause-specific mortality from cardiovascular diseases, chronic respiratory diseases, diabetes, and lung cancer
The results show that the protective association between Normalized Difference Vegetation Index (NDVI) was considerably stronger for males than for females for all-natural and CVD mortality, and slightly stronger for diabetes and chronic respiratory mortality
Summary
Green space is defined as areas of grass, trees, or other vegetation set apart for recreational or aesthetic purposes [1], and examples of green space include national parks, forests, recreation areas, community gardens, green belts, and city parks. Hong Kong is a very densely populated city with over seven million people and limited land availability. Longevity in a densely populated city [13] and is associated with a lower odds of having any form of impaired glucose regulation [14]. The few studies examining associations between area-level green space and mortality have given inconsistent results. There are many factors that could influence these results and explain the inconsistencies between studies including differences in local climate, nature, accessibility of green space, and individual characteristics of the populations, such as socioeconomic status and personal habits. Two studies from the United Kingdom found that living in areas with more green space was associated with health and lower mortality for all cause [4], circulatory [4,15], and respiratory mortality [15], but not lung cancer mortality [15], while a similar study from New
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