Trends in Number and Composition of Sex Partners Among Men Who Have Sex With Men in the United States, National HIV Behavioral Surveillance, 2008-2014

Background: Social and legal acceptance of long-term same-sex partnerships in the United States has increased over the past decade which may impact sexual partnering among men who have sex with men (MSM). Identifying whether and how partnering trends have evolved at a national level could improve understanding of HIV transmission and prevention among MSM partnerships. Methods: We used Centers for Disease Control and Prevention's National HIV Behavioral Surveillance data (2008, 2011, and 2014) to study trends in the number and partner type composition (main/casual) of male sex partners among US MSM. Changes over time were assessed in Poisson regression models with the link function tailored to the count and binary outcomes. Results: The mean total number of partners in the past year increased, while the mean number of main partners remained stable. The percentage of MSM with both main and casual partners increased, and we observed a shift from having >= 1 main and 0 casual partners to having >= 1 main and >= 2 casual partners. Condomless anal sex in the past year increased regardless of partner composition. Discussion: Findings suggest casual partnering among MSM has increased in recent years, including among those with >= 1 main partners. Both partner-based and individual prevention programs remain critical to reaching MSM.