Determinants of HIV Incidence Disparities Among Young and Older Men Who Have Sex with Men in the United States.

This study sought to determine why young men who have sex with men (MSM) have higher HIV incidence rates than older MSM in the United States. We developed hypotheses that may explain this disparity. Data came from peer-reviewed studies published during 1996-2016. We compared young and older MSM with respect to behavioral, clinical, psychosocial, and structural factors that promote HIV vulnerability. Compared with older MSM, young MSM were more likely to have HIV-discordant condomless receptive intercourse. Young MSM also were more likely to have "any" sexually transmitted infection and gonorrhea. Among HIV-positive MSM, young MSM were less likely to be virally suppressed, use antiretroviral therapy, and be aware of their infection. Moreover, young MSM were more likely than older MSM to experience depression, polysubstance use, low income, decreased health care access, and early ages of sexual expression. These factors likely converge to exacerbate age-associated HIV incidence disparities among MSM.