Factors associated with group sex in heterosexual males and females attending a sexual health clinic in Melbourne, Australia: a cross-sectional survey.

Abstract

There have been limited studies of group sex among heterosexual individuals. This study aimed to explore the factors associated with group sex among heterosexual males and females to improve risk assessment guidelines and inform sexually transmitted infection (STI) screening requirements. A cross-sectional survey was conducted among heterosexual males and females aged ≥16 years attending the Melbourne Sexual Health Centre between March and April 2019. The survey asked about group sex participation, methods used to meet sexual partners, number of casual and/or regular partners, and injection drug use (IDU) 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. 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. 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, p trend =0.010). Meeting partners at sex venues (e.g. brothels) 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 sex, casual and/or regular partners, HIV positivity or IDU. Heterosexual individuals participating in group sex had a six-fold risk of testing positive for STIs. Including group sex in a sexual history is useful to determine STI risk and inform testing practices. Safe sex messages on group sex that are delivered through multiple methods (e.g. at sex venues, social venues and dating apps simultaneously) would be beneficial.