Social factors have been linked to cognitive decline and risk of dementia. However, our understanding of their impact on cognition in the context of Alzheimer’s disease (AD) pathology is still limited.

This study examined whether two structural social factors, relationship status (RS) and living situation (LS), modify the association between AD pathology and cognition.

Observational, analysis of existing cohort data.

Data were obtained from the National Alzheimer's Coordinating Center (NACC) and the Imaging Dementia–Evidence for Amyloid Scanning (IDEAS) study.

Participants with available data on cognitive performance, AD pathology, and structural social factors.

We used the Mini-Mental State Examination (MMSE), a widely used brief screening measure of global cognitive status. For the description of AD, postmortem neuropathology (NACC) reports, or amyloid PET (IDEAS) were used. RS and LS were coded according to the respective datasets. Group comparisons and regression models were used to evaluate interactions between RS or LS with AD pathology on cognition.

Across cohorts, up to 31% of individuals were not in a relationship, and up to 22% lived alone. Individuals in a relationship (RS+) or those who lived with someone (LS+) showed poorer cognitive performance than those not in a relationship (RS-) or living alone (LS-) at comparable levels of AD pathology. Interaction analyses indicated that the association between AD pathology and MMSE differed by LS, with LS+ being associated with slightly lower MMSE scores across pathology levels, an effect primarily driven by participants living with someone who is not a partner. In contrast, within the NACC cohort, RS+ individuals showed overall lower MMSE scores, while the association between AD pathology and MMSE was weaker compared to RS− individuals.

LS and RS showed differences in how AD pathology related to global cognitive status. Being in a relationship was linked to a weaker association between AD pathology and global cognitive status, whereas living with someone was associated with a lower global cognitive status at comparable levels of pathology. While the direction of these associations remains unclear, our findings suggest that the relationship between AD pathology and cognitive status may vary across different structural social contexts.