Blackmores Institute

Access to green spaces may be more important than you think with findings of meta-analysis study showing an inverse relationship between people who live surrounded by nature and all-cause mortality. The study authors reported that increasing increments of residential greenness was significantly associated with reducing all-cause mortality over time, suggesting that the more time people can spend in green space the greater the likelihood of better health and wellbeing. 
 
 The researchers used normalised difference vegetation index (NDVI) as a measurement of green spaces. Measurements, usually taken by a satellite and compared over time, include the green spaces around residences, parks, tree cover and canopy density. 
 
 The meta-analysis examined nine studies which included over eight million people from seven countries. Of these, seven studies found a significant inverse relationship between the risk of all-cause mortality and an increase in surrounding greenness per 0.1 NDVI in a zone of 500m or less. “We included studies if their design was longitudinal; the exposure of interest was measured green space; the endpoint of interest was all-cause mortality and; they provided a risk estimate (i.e., a hazard ratio) and the corresponding 95% confidence interval (CI) for the association between green space exposure and all-cause mortality.” 
 
 Analysis showed that the pooled hazards ratio for all-cause mortality per increment of 0.1 NDVI buffer of 500m or less of a participant’s resident was 0.96 (95% CI 0.94- 0.97; I2,95%) with the authors suggesting that increasing increments of residential greenness is significantly associated with reducing all-cause mortality in longitudinal studies. 
 
 “The results of our study are consistent with previous systematic reviews and meta-analyses that had indicated a marked negative association between the amount of nearby green space and mortality and morbidity. Green spaces are associated with more physical activity, physical or mental restoration and reduced stress, higher social capital, and ecosystem services, such as better air quality, less traffic noise, less heat-island effects, and more biodiversity,” the authors said. 
 
 According to the study, there are several possible mechanisms that could explain these results, however, establishing a causal relationship is difficult. “Physical activity has been suggested as an important health determinant associated with green spaces. Green space could be a place where physical activity for leisure can occur and green spaces can also increase active transportation (walking and cycling). 
 
 “Through ecosystem services, green spaces can also confer several health effects. Attenuation of air pollution, noise, and heat-island effects are pathways that have been related to the protective effect of green spaces. Trees and other vegetation can decrease concentrations of air pollutants, and they can reduce atmospheric carbon dioxide through carbon storage and sequestration,” the authors said. 
 
 “Our findings suggest that robust protocols should be used when studying the effects of green spaces on health and future policy interventions related to green spaces should consider the whole range of positive effects that are likely to affect the population, but they also need to be accompanied by regulations to reduce the possible negative effects of increased green space, such as crime and gentrification,” the authors concluded. 
 
 Despite limitations posed by the lack of quality published studies, the authors suggest that the results of their meta-analysis should provide evidence to support development of policy recommendations on having greater green spaces in our lives. Source: Rojas-Rueda D, et.al.: Green spaces and mortality: a systematic review and meta-analysis of cohort studies. The Lancet Planetary Health. DOI: <a href="https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(19)30215-3/fulltext" target="_blank">https://doi.org/10.1016/S2542-5196(19)30215-3</a><a href="https://www.sciencedirect.com/science/article/pii/S2542519619302153" target="_blank">https://www.sciencedirect.com/science/article/pii/S2542519619302153</a>

Covid-19 restrictions have challenged people in numerous ways and highlighted the importance of many things previously taken for granted, such as spending time outdoors. With results of a recent study finding that accessing green spaces can be supportive of health and wellbeing, now, more than ever, is the time to ‘go bush’ - restrictions permitting, of course.

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