Leafier Communities, Healthier Hearts: An Australian Cohort Study of 104,725 Adults Tracking Cardiovascular Events and Mortality Across 10 Years of Linked Health Data

Objective: Green space reduces cardiovascular disease (CVD) risk, but few studies examine what types of green space matter, which is an important consideration as cities densify and apartments become more common. Method: Participants were 86,727 in houses and 17,998 in apartments from the 45 and Up Study (Sax Institute) baseline survey with 10 years of linked hospitalisation and death data used to define: (i) all-cause; and (ii) CVD-mortality; (iii) fatal and non-fatal CVD events; and (iv) acute myocardial infarction (AMI). Associations with total green space, tree canopy cover and open grass within 1.6 km buffers were assessed using survival analysis adjusted for potential confounders. Results: Mean percentage green space indicators were all higher among participants in houses than in apartments. Among residents of houses, a 10% increase in total green space was associated with reduced risk of CVD mortality (HR 0.97, 95%CI 0.95–1.00). A 10% increase in tree canopy cover was associated with reduced risks of all-cause mortality (HR 0.97, 95%CI 0.95–0.99), CVD mortality (HR 0.96, 95%CI 0.93–0.98), and fatal or non-fatal AMI (HR 0.93, 95%CI 0.89–0.96). In contrast, a 10% increase in open grass was associated with an increased risk of fatal or non-fatal AMI (HR 1.15, 95%CI 1.09–1.20) in residents of houses. Among residents of apartments, a 10% increase in total green space was associated with increased risk of all-cause mortality (HR 1.04, 95%CI 1.00–1.08) and CVD mortality (HR 1.03, 95%CI 1.00–1.08). Conclusions: Urban reforestation may be a population-level intervention to protect cardiovascular health, especially for people living in houses. The intersection of urban greening and cardiovascular health among residents of apartments warrants further investigation.