Green Space and Cardiovascular Disease: A Systematic Review with Meta-Analysis

Background: Exposure to greenspace has been proposed to be beneficially associated with cardiovascular morbidity and mortality. Many studies have explored this topic, but the results remain conflicting. We aimed to evaluate the epidemiological evidence on this topic by performing a systematic review with meta-analysis. Methods: We searched PubMed, Web of Science and Embase for studies on the green space-cardiovascular disease (CVD) relationship that were published till May 12th, 2021. Two authors independently performed study selection, data extraction, quality assessment, and risk of bias assessment. For studies providing detailed numeric data, we conducted quantitative meta-analyses and calculated the pooled odd ratios (ORs) for associations between the most commonly used greenspace exposure (normalized difference vegetative index [NDVI]) and six CVD events: CVD mortality, ischemic heart disease (IHD) mortality, stroke incidence/prevalence, and coronary heart disease (CHD) incidence/prevalence. Sensitivity analyses and publication bias tests were also conducted. Findings: Of the 6229 records identified, 48 studies were eligible for inclusion. These studies covered 18 countries and included data from more than 100 million persons. Meta-analyses showed that a 0∙1 increase in NDVI was associated with 2-13% lower odds of CVD mortality (OR 0∙97, 95% CI 0∙96-0∙99, I2 95∙8%), IHD mortality (OR 0∙98, 95% CI 0∙96-1∙00, I2 90∙7%), stroke incidence/prevalence (OR 0∙97, 95% CI 0∙96-0∙99, I2 29∙6%), and CHD incidence/prevalence (OR 0∙87, 95% CI 0∙83-0∙91, I2 0∙0%). The pooled estimates were not substantially different in sensitive analyses. No evidence of publication bias was detected. Interpretation: We provide strong and robust evidence for beneficial effects of greenspace exposure on cardiovascular health. More prospective studies and mechanistic studies are needed. Funding: The Natural Science Foundation of the Xinjiang Uyghur Autonomous Region, China; the National Natural Science Foundation of China. Declaration of Interests: We declare no competing interests.