20th International AIDS Conference - Melbourne, Australia


PUB096 - Publication Only

Are interactions between substance use and place associated with sexual risk? An analysis of new partner encounters in a sample of MSM in England

G.J. Melendez-Torres1,2, F. Hickson3, D. Reid3, P. Weatherburn3, C. Bonell2

1Centre for Evidence-Based Intervention, Department of Social Policy and Intervention, University of Oxford, Oxford, United Kingdom, 2Social Science Research Unit, Institute of Education, University of London, London, United Kingdom, 3Sigma Research, London School of Hygiene and Tropical Medicine, London, United Kingdom

Background: Sexual encounter-level analyses examining relationships between substance use and sexual risk in men who have sex with men (MSM) have inadequately considered how this relationship may be moderated by situational characteristics. Yet quantitative and qualitative evidence documents the different sexual contexts associated with distinct substance use patterns among MSM. Little event-level evidence examining substance use and sexual risk exists for MSM populations in England. Finally, event-level analyses may be confounded by not distinguishing between partners. This study investigates event-level relationships between substance use, place of sex, and unprotected anal intercourse (UAI) in a sample of sexual encounters with new partners reported by MSM in England.
Methods: In early 2011, MSM in England were invited to take part in a web-based survey to report their two last single-partner sexual encounters with new male partners. Generalised estimating equations with exchangeable correlation matrices and logit link tested whether respondent substance use (binary for any substance use, and number of substances used) and place of sex (private, sex-on-premises venue, or cruising venue) were associated with UAI. Interactions between substance use and place of sex were then tested in a new model.
Results: 1,879 MSM reported 2,913 eligible encounters. In univariate analyses, respondent substance use (OR=1.57, p< 0.001) and number of substances used (OR=1.32, p< 0.001) were associated with UAI, as were sex-on-premises venues (OR=0.69, p< 0.01), but not cruising locations (OR=0.99, p>0.05), when compared to private venues. Interactions between any substance use and location revealed a statistically significant interaction with sex-on-premises venues (OR=2.23, p< 0.05), but not cruising locations (OR=0.73, p>0.05). Main effects in the interaction model for substance use (OR=1.47, p< 0.001) and for venue (sex-on-premises OR=0.43, p< 0.01; cruising OR=1.21, p>0.05) were similar to univariate models. Interactions between number of substances used and sex venue were statistically non-significant (p>0.05).
Conclusions: This event-level analysis focuses on a specific, understudied class of sexual encounters where risk for HIV transmission may be high. It suggests that place of sex may moderate the relationship between substance use and place of sex, with substance use in sex-on-premises venues?saunas, sex clubs, and porn cinemas, for example?more strongly associated with UAI.

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