Abstract

Health services research methods, including in HIV epidemiology, have long labeled people who cycle in and out of treatment as “non-adherent,” a deficit-based view that masks the strength required to re-engage in care. Rising syphilis rates in the US, especially among people who use drugs, underscore the need for approaches that reflect the realities of cyclical engagement. Using national insurance claims from 33,000 people diagnosed with syphilis, we will characterize HIV testing, prevention, and treatment patterns and assess how substance use and mental health disorders shape these trajectories. Applying a multistate, day-level analytic framework, we will map transitions between engagement, disengagement, and return to care, quantifying both interruptions and re-entry, and identifying predictors of renewed engagement—recognizing interruptions as expected in SUD care. Guided by a diverse investigative team and community partners, this work will pinpoint actionable intervention opportunities and inform future studies aligned with NIH OAR HIV/AIDS priorities.