Greenspace exposure and associated health outcomes: a systematic review of reviews

Background Numerous systematic reviews and meta-analyses have sought to clarify the relationship between greenspace exposure and health outcomes, but the results are inconsistent. We aimed to synthesise all relevant systematic reviews and meta-analyses on this association. Methods We searched five databases (PubMed, Embase, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), Scopus, and the Cochrane Database of Systematic Reviews) and conducted a manual reference search for systematic reviews and meta-analyses written in English and published in peer-reviewed journals that used clearly defined measures of greenspace exposure and reported health outcomes directly attributable to greenspace exposure. A total of 36 systematic reviews published between January 2010 and December 2020 were identified for inclusion in this systematic review of reviews (PROSPERO: CRD42021227422). An updated review is underway, and the protocol is published in PROSPERO (CRD42022383421). The methodological quality and risk of bias of included systematic reviews were evaluated using the AMSTAR-2 and ROBIS tools, respectively. Results Beneficial effects of greenspace exposure were observed for all-cause and cardiovascular disease mortality, and mental health and cognitive function. Ambivalent results were found for cardiovascular and metabolic health, general health and quality of life (QOL), and respiratory health and allergies. Most of the systematic reviews included in the current umbrella review had a low to moderate methodological quality and a high risk of bias. Conclusions This umbrella review highlights the link between greenspaces and a variety of health outcomes, emphasising the importance of preserving existing greenspaces and integrating additional vegetation into urban areas to maintain public health.