Sexual Identity and Condomless Sex Among Mexican MSM: The Overlooked Role of Heterosexual-Identified MSM

HIV prevention efforts in Mexico often overlook heterosexual-identified men who have sex with men (H-MSM), a subgroup at elevated risk for HIV. Using data from the 2021-2022 National Survey on Sexual and Gender Diversity (ENDISEG), we examined condomless sex among cisgender MSM, categorizing participants by sexual identity (heterosexual vs. gay, bisexual, or other non-heterosexual), sexual behavior (only male partners vs. both male and female), and their combinations: H-MSM, H-MSMW, GB+MSM, and GB+MSMW. Among cisgender men, 3.9% (<i>n</i> = 775) reported a male sexual partner in the past year, and 41% of them identified as heterosexual. Condomless sex was reported by 63.8% of MSM overall and was most common among H-MSM (74.4%). Probit regression analysis showed significantly lower probabilities of condomless sex among H-MSMW (-19.8%), GB+MSM (-14.8%), and GB+MSMW (-15.9%) compared to H-MSM. Additional risk factors included older age, lower education, and depression. These findings underscore the limitations of considering MSM as one group and reveal a sizable, high-risk subgroup that may be missed by current HIV programs. Effective prevention strategies must integrate sexual identity and behavior and be adapted to Mexico's sociocultural context. Identity-sensitive approaches, particularly for H-MSM and H-MSMW, are essential to reduce HIV transmission in this population.