PROJECT SUMMARY/ABSTRACT There are currently over 100,000 older (ages 50+ years) women living with HIV/AIDs (WLWH) in the United States. Advances in antiretroviral therapy treatment have led to a decline in mortality caused by HIV/AIDS, however, experiences of HIV-related and gender-based stigma continue to adversely impact health outcomes in this population. People living with HIV who experience HIV stigma are more likely to delay seeking care and have depressive symptoms and lower quality of life. Yet, older adult women are understudied in research on stigma and HIV. The purpose of this proposed study is to examine the cross-sectional and longitudinal impacts of HIV stigma and gender-based stigma on cognitive function among older WLWH and identify whether social support is protective against the adverse impacts of stigma on cognitive function. We will use data from the Women's Interagency Study (WIHS), a longitudinal, prospective cohort of WLWH in the United States. WIHS was established in 1993 and has enrolled almost 5,000 WLWH to date. Cognitive function was assessed using multiple standardized and validated neurocognitive assessments. Stigma and social support were also assessed using validated survey scales. For the proposed study, we will include all participants who have completed baseline stigma and social support questionnaires before the age of 50 and at least one (cross- sectional analysis) or two (longitudinal analysis) cognitive assessments. The proposed work will test whether HIV stigma and gender-based stigma are independently associated with current cognitive function and change in cognitive decline, and whether there are interaction effects between HIV and gender-related stigma. We will also examine whether social support is protective of cognitive decline despite experiences of stigma. We hypothesize that 1) self-reported HIV stigma or gender-based stigma will be associated with worse cognitive performance and greater cognitive decline; 2) experiences of both types of stigma will be associated with worse cognitive performance and a greater cognitive decline compared to experiencing either type alone, and 3) among those who experienced high levels of stigma, those who report higher levels of social support will have better cognitive performance and lower cognitive decline compared to those who report low levels of social support. These analyses will be done using mixed-effects cross-sectional and longitudinal regression models adjusting for known risk factors for cognitive decline. Findings from this study will provide much needed information about the extent to which individual and compounding effects of stigmatizing experiences should be considered in health promotion interventions for older WLWH, as well as insight into a potential protective factor (social support) that could be leveraged to improve health outcomes in this population.