Longitudinal Analysis of Substance Use as a Predictor PrEP Use and Adherence Among Young Transgender Women and Nonbinary Individuals

Previous research on the influence of substance use on PrEP uptake and adherence among transgender women has either relied on cross-sectional analyses or on combined samples of cisgender men who have sex with men and a much smaller subsample of transgender women. To the best of our knowledge, no longitudinal study has examined the relationship of substance use and PrEP use/adherence among young transgender women and nonbinary people assigned male at birth (TNBY). We sought to understand whether substance use (i.e., binge drinking, marijuana use, and illicit drug use) predicts PrEP uptake and adherence for TNBY over time. Using a sample of 242 young and racially/ethnically diverse TNBY from the RADAR cohort study, we performed bivariate and multivariate generalized estimating equations binary logistic regression to assess whether substance use predicted PrEP use and adherence and latent growth curve modeling to examine trends in self-reported PrEP use over time. There were no significant differences in PrEP use or adherence by race/ethnicity, gender or educational attainment. In multivariable models, binge drinking (OR 1.37, 95% CI 1.08-1.74), number of condomless sex partners (OR 1.08, 95% CI 1.04-1.13), and HIV/STI testing (OR 2.20, 95% CI 1.65-2.92) were all significantly positively associated with PrEP use in the past 6 months. Binge drinking (OR 1.27, 95% CI 0.97-1.67), number of condomless sex partners (OR 1.09, 95% CI 1.04-1.13), and HIV/STI testing (OR 1.85, 95% CI 1.35-2.53) were significantly positively associated with current PrEP use. Both age (OR 1.25, 95% CI 1.02-1.54) and binge drinking (OR 8.66, 95% CI 2.12-35.30) were significantly positively associated with PrEP adherence. Cannabis use was significantly negatively associated with PrEP adherence (OR 0.89, 95% CI 0.82-0.97). Latent growth curve modeling detailed that the proportion of participants using PrEP significantly increased over time across age, reducing initial differences in PrEP use by age. These findings provide valuable insights into the relationship between substance use and PrEP use and adherence, showing the different effects of binge drinking and problematic cannabis consumption on PrEP outcomes. These findings emphasize the importance of nuanced and intersectional approaches to HIV prevention, considering both demographic variability and behavioral health factors.