ABSTRACT Adolescents and young adults living with HIV (AYA-HIV), especially minoritized individuals, face the highest HIV incidence and poorest care outcomes among all age groups of people living with HIV (PWH) in the United States. Mobility has emerged as a critical driver of these disparities, but research in the US context is limited. The convergence of younger age and mobility poses a significant challenge to individual and public health efforts to address care inequities and end the HIV epidemic in the US. Our preliminary work in Tennessee, which includes Memphis/Shelby County, an End-the-Epidemic priority region, found that PWH change addresses nearly four times more often than the general population, with higher frequency among AYA-HIV. Mobile PWH were more likely to be lost from care, and mobility patterns followed recurring spatial pathways suggesting structural determinants. Our central hypothesis is that social and structural determinants of health (SSDOH) are associated with distinct mobility phenotypes among AYA-HIV that differentially impact HIV care outcomes. To build on these critical findings and test this hypothesis, our experienced, multidisciplinary team will assemble a prospective cohort of 300 AYA-HIV in Tennessee. We will use a mixed-methods approach integrating robust individual- and population-level geospatial analyses to accomplish three Aims: 1) Determine patterns of personal mobility and multilevel factors contributing to mobility among AYA-HIV in TN; 2) Evaluate how personal mobility impacts HIV care outcomes among AYA-HIV; 3) Assess the relationship between SSDOH on the prevalence and patterns of residential mobility among all AYA-HIV in TN and the role of mobility as a mediator of the relationship between SSDOH and HIV care outcomes (LTFU, retention and viral suppression). For Aims 1 and 2, we will a) passively monitor personal mobility of cohort members over 18 months via a global positioning system (GPS)-enabled mobile phone application, b) integrate geospatial analyses with data-informed in-depth interviews (IDIs) with AYA-HIV exhibiting potentially distinct mobility patterns (n≤30 every 6 months) to describe mobility phenotypes, and c) utilize qualitative and statistical methods to describe mobility phenotypes, elucidate factors driving personal mobility and assess the relationship between mobility phenotypes and HIV care outcomes. For Aim 3, we will use population-level geospatial methods combined with HIV surveillance and census data from the TN Department of Health to explore neighborhood-level SSDOH as drivers of residential mobility, and the relationship between mobility and HIV care outcomes for all AYA-HIV in the state. This pioneering study will provide a rigorous, multilevel understanding of mobility among AYA-HIV in the US. By elucidating how social and structural factors drive mobility and its downstream impact on health, we will lay the foundation for developing tailored interventions to address this critical barrier to ending the HIV epidemic, with implications for other chronic conditions.

PROJECT NARRATIVE This five-year study aims to understand how social and structural determinants of health influence mobility patterns among adolescents and young adults living with HIV (AYA-HIV) in Tennessee, and how these patterns influence HIV care outcomes. Through a mixed-methods approach – integrating geospatial monitoring, in-depth interviews, population-level data, and clinical data – we will examine how personal and residential mobility affects HIV care outcomes. Elucidating these relationships will inform the development of targeted interventions to address disparities among mobile AYA-HIV and contribute to efforts to end the HIV epidemic.