How does social health impact cognitive function and brain reserve? Findings from the SHARED Consortium

Social health is increasingly recognised as an important factor influencing cognitive ageing and experiences of dementia. Yet definitions and measurement remain inconsistent, and evidence on how social health relates to cognitive outcomes remains limited. This narrative review presents the conceptual framework and synthesises the empirical findings from the Social Health and Reserve in the Dementia Patient Journey (SHARED) consortium, established to advance understanding of social health across the continuum from preclinical cognitive change to dementia, with a central aim to develop a comprehensive social health framework. SHARED combined conceptual framework development, global qualitative and quantitative studies, coordinated analyses across more than 40 cohorts (~150,000 participants) and investigations of pathways underlying cognitive resilience. We refined the conceptualisation of social health by integrating individual capacities with features of the social environment. Qualitative interviews further identified novel and often unmeasured dimensions, informing refinement of the framework. Across multiple global cohorts, better social health was associated with higher cognitive performance, slower decline, and reduced risks of mild cognitive impairment and dementia, although associations varied across markers, domains, and contexts. Mechanistic analyses linked social health to markers of brain reserve, including total brain volume and white matter microstructure, and showed that depressive symptoms partially mediated social support–cognition associations. SHARED delivers a comprehensive, multidimensional framework for social health and provides strong multi-cohort evidence of its importance for cognitive ageing and dementia. Findings highlight the need for improved social health measurement and further work to disentangle its mechanisms and bidirectional links with cognitive ageing and dementia. • Social health is a key determinant of cognitive health throughout the dementia journey • SHARED developed a new framework to strengthen research on social health in cognitive ageing • Better social health links to slower cognitive decline and reduced dementia risk • Mixed methods revealed and validated novel social health markers, refining the framework • Brain reserve and depressive symptoms emerged as pivotal mechanisms