Is Partner Age Associated with Unprotected Anal Sex Risk Behavior for HIV/STI Transmission in a Diverse Sample of Substance-Using MSM?

Background:  Research, although limited, suggests that relative partner age may be a particularly important mixing factor to consider in HIV/STI transmission risk among MSM, who are at hightened risk for HIV transmission.

Objectives:  To better understand relative age-related sexual mixing by respondent HIV status among high-risk, substance-using MSM, and whether having a >10 year younger or older casual sex partner may be linked to heightened HIV/STI risk.

Methods:  A convenience sample of substance-using MSM was enrolled in Chicago, Los Angeles, New York City, and San Francisco (n=2039). Partner age groupings were:  >10 years ”Younger”, >10 years “Older”, and <10 years (“Similar”) age relative to the respondent.  Multivariate models analyzed demographic factors (including partner age; Similar age as referent) associated with sexual risk behavior, stratified by respondent HIV status.  

Results:  23% (n=471), 16% (n=332), and 61% (n=1236) of respondents reported on risk behavior with a recent Younger, Older, and Similar age partner, respectively. Among HIV-negative respondents:  In multivariate analysis, respondents who had a Younger (vs. Similar) age partner were less likely to report having unprotected receptive anal sex with that partner (OR=0.6, 95% CI=0.3-0.9). Relative partner age was not associated with respondent unprotected insertive anal sex. Among HIV-positive respondents:  Respondents who had a Younger (vs. Similar) age partner were more likely to report unprotected insertive anal sex with that partner (OR=1.9, CI=1.2-2.9); relative partner age was not associated with unprotected receptive anal sex.

Conclusions:  Associations between age-related sexual mixing and risk behavior vary by HIV-status, reflecting differential risk for HIV/STI transmission, particularly for HIV-positive men with younger partners. Efforts to curb HIV/STI infection should address all partner age groups of HIV-negative and -positive men.

Implications for Programs, Policy, and Research:  Sexual age mixing behavior requires more research, and strategies should be targeted to address mixing dynamics that facilitate HIV/STI transmission.