P451 Factors associated with group sex in heterosexual males and females attending a sexual health clinic in Melbourne, Australia

Abstract

<h3>Background</h3> Group sex participation carries a higher risk of sexually transmitted infection (STI) transmission. Research on group sex has predominately analysed men who have sex with men, while there have been a small number on heterosexuals. This study aimed to explore the factors associated with group sex among heterosexuals. <h3>Methods</h3> A cross-sectional survey was conducted amongst heterosexuals aged ≥16 years attending the Melbourne Sexual Health Centre between March and April 2019. Participants completed a survey about participation in group sex, methods used to meet partners, casual and/or regular partners, and intravenous drug use (IVDU) in the previous 3 months. HIV and STI (chlamydia, gonorrhoea, syphilis) diagnoses were extracted. A multivariable logistic regression was conducted to identify the factors associated with group sex participation. <h3>Results</h3> A total of 698 participants (325 males, 373 females) were included and 4.7% (33/698) had participated in group sex in the previous 3 months. There was no difference between the proportion of males (6.5%, 21/325) and females (3.2%, 12/373) participating in group sex (p=0.198). The proportion who participated in group sex increased with age (2.1% in 16–24 years, 5.5% in 25–34 years, 7.8% in ≥35 years, ptrend=0.010). Meeting partners at sex-venues (e.g. brothel) was associated with the highest odds of participating in group sex (AOR=5.74, 95%CI:1.20–27.44), followed by dating-apps (AOR=2.99, 95%CI:1.36–6.58), friends/family (AOR=2.99, 95%CI:1.34–6.69) and social-venues (e.g. bar) (AOR=2.73, 95%CI:1.18–6.30). Group sex was strongly associated with STI positivity (AOR=6.24, 95%CI:2.41–16.13). There was no association between group sex and HIV positivity, casual and/or regular partners, or IVDU. <h3>Conclusion</h3> Heterosexuals participating in group sex had a six-fold risk of testing positive for STIs and were most likely to meet sexual partners at sex-venues. Including group sex in a sexual history is useful to determine STI risk. Safe sex messages on group sex at sex-venues would be beneficial.