Synthesizing evidence on the social determinants of health for cancer and diabetes outcomes in EU

Abstract Social determinants of health (SDH) contribute significantly to inequalities in the burden and distribution of non-communicable diseases (NCDs), including cardiovascular diseases, cancers, and diabetes. Although progress has been made in reducing socioeconomic inequalities in cardiovascular and cancer mortality in Europe, major challenges remain. Greater efforts are needed to improve measurement and address the wide range of SDH influencing persistent inequalities in NCD outcomes through improved data systems and rigorous evidence synthesis. Umbrella reviews, which synthesize evidence from existing systematic reviews (SRs), provide a robust method for evaluating the strength and quality of evidence on social inequalities in NCDs. We conducted two umbrella reviews examining how social factors, based on the PROGRESS framework, are associated with cancer and diabetes outcomes. Protocols were pre-registered in PROSPERO. Systematic searches were conducted in major databases like Medline, Scopus, and Web of Science and SR repositories like the Cochrane Library without date restrictions (June 17, 2024, for cancer; October 22, 2024, for diabetes). Eligible SRs included cohort or case-control studies on associations between social factors and cancer or diabetes outcomes. For the cancer review, 15,542 records were identified; 7,279 were screened in duplicate by title/abstract and 414 by full text. Data extraction and quality assessment are ongoing for 238 SRs. For the diabetes review, 4,756 records were identified; 2,624 were screened in duplicate by title/abstract and 143 in full text. Data extraction is underway for 34 reviews. We will assess overlap of primary studies using citation matrices and corrected covered area indices. Associations from SRs without meta-analyses will be summarized narratively, and risk estimates pooled using random-effects meta-analyses where possible. Strength of evidence will be evaluated using GRADE. Final results are expected in November 2025.