Urban blue spaces and human health : a systematic review and meta-analysis of quantitative studies

Blue spaces, defined as all forms of natural and manmade surface water, are an integral part of cities. This is the first quantitative synthesis of the health impacts of urban blue spaces. Research exploring the health benefits of blue spaces in urban contexts is emergent and, thus, a systematic review and meta-analysis of the evidence is deemed timely. We searched seven databases from inception to August 2019. From 4493 screened citations, 25 eligible studies were identified. Fourteen of these were included in a quantitative synthesis. We found a beneficial association between urban blue space and obesity (beta = -0.34, 95% CI [-0.19, -0.09], p < 0.001), all-cause mortality (HR = 0.99, 95% CI [0.97, 1.00], p = 0.038), general health (Cohen's d = -0.09, 95% CI [-0.10, -0.08], p < 0.001) and self-reported mental health and wellbeing (Cohen's d = -0.25, 95% CI [-0.44, -0.07], p < 0.001). Effect sizes were small but statistically significant and the overall quality of evidence was good. Evidence for all other health outcomes was incommensurable, and so we provide a narrative description of study results for those outcomes. Although evidence is growing within the field of urban blue space and health, the body of evidence remains small and heterogeneous. More research is required to further understand and harness the benefits of urban blue spaces for public health and guide urban blue space management and development