Quality of Urban Green and Blue Spaces with a Specific Focus on Public Health Outcomes: An Umbrella Review

Research on the relationship between the quality of Urban Green and Blue Spaces (UGBS) and health is a growing field, but the overall understanding of current evidence remains unclear. Therefore, this study was conducted to review the current conceptualisations, progress, methodologies, and gaps in this area. From a database search (PubMed, Web of Science, Embase, and Scopus) of 2514 articles up to April 22, 2026, we included 28 systematic reviews for further interpretation. An overlap analysis and a supplementary qualitative sensitivity analysis were conducted to ensure evidence accuracy and the robustness of the main findings. In health research, UGBS's quality involved 8 quality domains across extrinsic and intrinsic dimensions, which could be assessed objectively and subjectively by 67 distinct metrics and 31 existing tools. Beneficial associations of UGBS's quality with 18 general, physical, and mental health outcomes were observed via varying mechanisms (direct or mediating pathways). Our findings provide a conceptual framework for the pathways from UGBS's qualities to broad public health outcomes and outline concrete directions for future primary and secondary research as well as policy and practice.