Natural Outdoor Environments and Mortality in Perth, Western Australia

Background/Aim: Natural outdoor environments may mitigate harmful environmental factors associated with city living. We studied the longitudinal relationship between natural (‘green and blue’) outdoor environments and all-cause mortality in a cohort of men residing in Perth, Western Australia. Methods: We used data from 9200 men aged 65 years and older from the Health In Men Study. Participants were recruited in 1996-99 and followed until 2014, during which 5872 deaths were observed. Time-varying surrounding greenness based on the Normalized Difference Vegetation Index around the residences and distance to waterbodies were defined to characterize the natural outdoor environments. All cause non-accidental mortality was ascertained with the Linked Data System in Western Australia. Results: Preliminary analyses showed an 8% lower rate of all-cause non-accidental mortality (95% confidence interval 0.85, 0.99) for men living in the highest quartile of cumulative average surrounding greenness in 300m around their residence compared to those living in the lowest quartile, while adjusting for age. After further adjustments for marital status, country of birth, education, area-level socio-economic status, and smoking, associations attenuated and were no longer significant. Men living further away from waterbodies had a 9.6% higher rate of all-cause non-accidental mortality (95% confidence interval 1.02, 1.18) compared to those living closer (quartile 2 vs. 1), while adjusting for age, marital status, country of birth, highest education, area-level socio-economic status, and smoking. Conclusions: We observed some evidence for higher surrounding greenness and shorter distance to waterbodies to be associated with a decreased risk of mortality. Living in areas with natural features may reduce mortality risk and may provide opportunities for the planning of healthy cities.