Abstract
Social vulnerability indices (SVIs) have the potential to guide risk stratification and support socially differentiated interventions to improve healthcare equity. However, their applicability in clinical settings remains uncertain. This systematic review synthesizes evidence from individual-level SVIs, focusing on (1) how social vulnerability is defined, (2) the domains and items covered, and (3) their ability to predict poor health outcomes. We searched the Medline, PsycInfo, Embase, and Web of Science databases from inception to 31 January 2024 for studies linking individual-based SVIs with poor health outcomes in adult populations in Europe, North America, and Australasia. Data were extracted independently by two authors, and the certainty of evidence was assessed using the GRADE approach. A narrative synthesis addressed the review's aims, with thematic synthesis for the first two and a vote-counting approach for the third. Most SVIs included domains like income, social support, living situation, and educational attainment, with over 50% covering these factors. A consistent association was found between higher social vulnerability and poorer health outcomes. However, none of the identified SVIs were prospectively tested in clinical settings. The overall certainty of evidence was assessed as low due to retrospective study designs and significant heterogeneity. This review highlights the potential of SVIs to predict poor health outcomes, though their lack of prospective validation limits current use. Future research should focus on adapting and testing SVIs that prioritize key socioeconomic and social support domains while adopting a simple and pragmatic approach.