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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