Green space exposure on mortality and cardiovascular outcomes in older adults: a systematic review and meta-analysis of observational studies

Background With the launch of the "Global Age-Friendly Cities project", increasing emphasis has been placed on the effects of green spaces on health in the elderly. The previous literature has shown that green spaces are beneficial to a range of health-related outcomes in adults. However, associations of greenness with mortality and cardiovascular outcomes are less certain, which may differ depending on the age class. This review aimed to synthesize current evidence from observational studies to assess relationships of green space exposure with mortality and cardiovascular outcomes in older individuals. Methods Five databases were searched. Qualitative evaluation and meta-analyses of included studies were conducted. This review is registered with PROSPERO, CRD42020160366. Results Of the 8,143 records identified, we finally included 22 studies. In a narrative systematic review, we observed that the majority of studies showed reductions in the risk of all-cause mortality and total cardiovascular disease. Further meta-analyses which included eight cohort studies, indicated that greater greenness exposure (per 0.1 unit increase of normalized difference vegetation index (NDVI)) was associated with a reduced risk of all-cause mortality (pooled hazard ratios (HR) (95% confidence interval (CI) = 0.99 (0.97, 1.00)) and stroke mortality (pooled HR (95% CI) = 0.77 (0.59, 1.00)) in older individuals. Conclusions This review supports increasing green space exposure in terms of the prevention of death and cardiovascular outcomes in older individuals. Effective measures to increase or preserve greenspaces should therefore be considered as important public health interventions.