”Sexual Age” and Sexual Risk Behaviors Among Men Who Have Sex with Men

Background:  Men who have sex with men (MSM) in the United States (US) are particularly vulnerable to HIV and other sexually transmitted infections (STI). While age is frequently examined as a potential predictor of behavior and HIV/STI risk, “sexual age” (SA) or time since first having sex with men may be more predictive of behavioral patterns than chronological age.

Methods:  We analyzed survey data from 17,949 men (82% white; 81% gay; median age=33) recruited from a US website for men seeking social or sexual interactions with other MSM. SA was defined as the time in years since first oral or anal sex with a male partner (median SA=13 years). We used the time-varying effect model (TVEM) to flexibly estimate the rates of anal sex, enema use, and group sex as a nonparametric function of SA. To better understand the impact of SA among men of different ages, models were run separately for three age groups (18-30, 31-50, 51+). 

Results:  For all age groups, the rate of engagement in anal sex was highest in the first year after a man’s first same-sex sexual experience.  Among men aged 18-30, the rate of anal sex was highest initially then declined steeply in the first three years. In contrast, enema use among men increased steadily as a function of SA for all age groups. Among younger men, the rate of engaging in group sex increased gradually across SA; men over 50 with young SA had significantly higher rates of group sex.

Conclusions:  These findings suggest that sexual age may be an important predictor of sexual behaviors and, potentially, HIV/STI acquisition. Further study is needed to understand the trajectory of sexual behavior that occurs after first same-sex sexual experience among MSM.