Group sex among men who have sex with men in the era of PrEP: A cross-sectional study.

BACKGROUND Group sex has been commonly reported among gay and bisexual men who have sex with men (GBMSM), however there are limited studies on the factors associated with participating in group sex. SETTING A cross-sectional study among GBMSM attending a sexual health clinic in Melbourne, Australia. METHODS Univariable and multivariable logistic regression were performed to examine the association between GBMSM participating in group sex in the previous three months and their demographic characteristics, including age, pre-exposure prophylaxis (PrEP) use, HIV status, any STI (gonorrhoea, chlamydia, syphilis) diagnosis on the day and method of seeking partners. RESULTS There were 357 GBMSM who participated in the survey and their mean age was 32.9 years (SD=10.9). Almost a third (n=115; 32.2%) had participated in group sex in the previous three months. GBMSM who sought sex partners at sex on premises venues (aOR 5.83; 95% CI: 3.23 - 10.53) had the highest odds of group sex participation after adjusting for other potential confounders. Compared with GBMSM not living with HIV and not taking PrEP, GBMSM taking PrEP had higher odds of group sex participation (aOR 2.09; 95% CI: 1.05 - 4.15) but GBMSM living with HIV did not (aOR 0.93; 95% CI: 0.23 - 3.68).Recent group sex participation was not associated with being diagnosed with any STI (chlamydia, syphilis or gonorrhoea) on the day in the adjusted analyses. CONCLUSION PrEP users and MSM attending SOPVs are more likely to participate in group sex. SOPV could be important venues for future public health campaigns.