7. PROJECT SUMMARY/ABSTRACT Emerging evidence suggests that sexual and gender minority populations are at increased risk for Alzheimer’s disease and related dementias (ADRD). This may be due, at least in part, to the cumulative impact of minority stress;; related social isolation and loneliness;; and barriers to care and support services. Social support, on the other hand, has emerged as a protective factor in the face of minority stress, and as a predictor of successful cognitive aging among the general population. However, few studies have assessed the social support networks of sexual and gender minorities in detail to determine the specific support characteristics that facilitate cognitive reserve and resilience. The proposed study will fill this gap by comparing the stress, social support networks, and aging-related cognition of a newly recruited sample of sexual and gender minority adults (n = 300, age 25- 85) to those of a matched heterosexual, cisgender sample (n = 300) enrolled in an ongoing longitudinal study of aging and cognitive reserve (the Reference Ability Neural Networks or RANN study). In addition, the proposed study will conduct secondary analysis of MRI data collected in RANN to explore differences in brain features between minority and majority groups, generating hypotheses for future research. The specific aims are: (1) To compare stress (perceived general stress and minority stress related to one or more marginalized identities) and cognitive performance across multiple domains in newly recruited sexual / gender minority adults and matched heterosexual, cisgender adults enrolled in the RANN study;; (2) To compare social network characteristics of sexual / gender minority adults to those of matched heterosexual, cisgender adults, and examine within- and between-group differences in social support based on sexual orientation, gender identity, and age;; (3) Across both identity groups (N = 600), to examine the role of minority stress, social support, resources and wellbeing in development of cognitive reserve and resilience (i.e., how these assets moderate the effects of minority stress and aging on health and cognitive functioning);; and (4) In an exploratory analysis, to evaluate differences between sexual / gender minority (n > 40) and matched heterosexual, cisgender RANN participants in MRI- measured brain features and their relation to stress, social network characteristics, cognitive functioning, and risk for incident ADRD. We expect that understanding differences and similarities in the social networks of minority and majority adults and the relationship of these characteristics to stress and aging-related cognition will enable us to identify modifiable factors associated with cognitive reserve and resilience, informing future inter...