Historical and Developmental Changes in Condom Use Among Young Men Who Have Sex with Men Using a Multiple-Cohort, Accelerated Longitudinal Design.

Young men who have sex with men (YMSM) have the highest HIV incidence in the U.S. The last 5 years has seen emergence of new methods for HIV prevention and societal shifts in gay rights. It is important to understand if there have been generational shifts in condom use during the developmental transition from adolescents to young adulthood. To disentangle history from development, we require a multiple-cohort, longitudinal design-a methodology never before applied to study YMSM. We followed three cohorts of YMSM recruited in 2007, 2010, and 2015 (N = 1141) from the ages of 17-26 years and modeled their longitudinal change over time in counts of anal sex acts and the ratio of condomless anal sex (CAS) acts to anal sex acts using latent curve growth modeling. We found that there was no significant developmental change in raw counts of anal sex acts, but there was a significant decline in the ratio of anal sex acts that were condomless. We also found significantly different patterns for ratio of CAS acts for the 2015 cohort. The 2015 cohort reported a significantly lower ratio of CAS acts at age 17, but significantly higher growth in ratio of CAS acts over development. The present study suggests that YMSM recruited in 2015 have very different trajectories of CAS compared to previous cohorts, including lower risk in late adolescence, but with the potential for higher risk after the transition into adulthood.