Residential Green and Mortality in Switzerland

Abstract

Background/Aim: Residential green, i.e. greenspaces or greenness, may improve health and decrease mortality by promoting physical activity and enabling stress recovery. We investigated the association between residential green and specific causes of death. Methods: We used Cox proportional hazard models to study the association for all natural cause, all respiratory, all cardiovascular disease (CVD), ischemic heart disease, stroke and blood-pressure related mortality in the adult population of Switzerland using the Swiss National Cohort. Satellite-based normalised difference vegetation index (NDVI: greenness) and spatially resolved land use data (SwissTLM: greenspace) were used to model address-level exposure in the immediate surrounding and local neighbourhood. Hazard ratios (HR) were adjusted for sex, civil status, region, urbanity, job position, education, neighbourhood socio-economic position (SEP), and incrementally for NO2, total transportation noise and altitude. Results: With 4.2 million adults and 7.8 years of follow-up, we respectively accrued >363,000, >85,000 and >232,000 natural cause, respiratory and CVD deaths. In adjusted models, we found statistically significant protective effects for all outcomes with residential green. HR (95% confidence intervals) for NDVI [and SwissTLM] per IQR within 500m were: 0.94 (0.93 – 0.95) [0.94 (0.93 – 0.95)] for natural cause; 0.93 (0.91 – 0.95) [0.93 (0.91 – 0.96)] for respiratory; and 0.94 (0.93 – 0.95) [0.96 (0.94 – 0.97)] for CVD mortality. We found a stronger protective effect in younger individuals, and greater benefit for females. The protective effect of residential green was stronger in urban communities compared to rural and in the highest versus lowest SEP quartile. Incremental adjustment for NO2, noise and altitude did not substantially change the HRs. Conclusions: Residential green consistently and independently reduced the risk of all natural cause, respiratory and CVD death. The impact of residential green on health may go beyond the lack of noise, air pollution and other environmental hazards.