Objective: To estimate the effects of alcohol consumption and number of unprotected receptive anal intercourse partners on HIV seroconversion while appropriately accounting for time-varying confounding.
Design: Prospective cohort of 3725 HIV-seronegative men in the Multicenter AIDS Cohort Study between 1984 and 2008.
Methods: Marginal structural models were used to estimate the joint effects of alcohol consumption and number of unprotected receptive anal intercourse partners on HIV seroconversion.
Results: Baseline self-reported alcohol consumption was a median 8 drinks/week (quartiles: 2, 16), and 30% of participants reported multiple unprotected receptive anal intercourse partners in the prior 2 years. Five hundred and twenty-nine HIV seroconversions occurred over 35 870 person-years of follow-up. After accounting for several measured confounders using a joint marginal structural Cox proportional hazards model, the hazard ratio for seroconversion associated with moderate drinking (1–14 drinks/week) compared with abstention was 1.10 [95% confidence limits: 0.78, 1.54] and for heavy drinking (>14 drinks/week) was 1.61 (95% confidence limits: 1.12, 2.29) (P for trend <0.001). The hazard ratios for heavy drinking compared with abstention for participants with 0–1 or more than 1 unprotected receptive anal intercourse partner were 1.37 (95% confidence limits: 0.88, 2.16) and 1.96 (95% confidence limits: 1.03, 3.72), respectively (P for interaction = 0.42).
Conclusion: These findings suggest that alcohol interventions to reduce heavy drinking among men who have sex with men should be integrated into existing HIV prevention activities.
aDepartment of Epidemiology, University of North Carolina Gillings School of Global Public Health, Chapel Hill, North Carolina
bDepartment of Behavioral and Community Health Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania
cDepartment of Epidemiology, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, Maryland
dDivision of Infectious Diseases
eDepartment of Psychiatry, School of Medicine, University of North Carolina, Chapel Hill, North Carolina
fDepartment of Molecular Microbiology and Immunology, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, Maryland
gLos Angeles Gay & Lesbian Center, Los Angeles, California
hOgburn-Stouffer Center for Social Organization Research at the National Opinion Research Center, University of Chicago, Chicago, Illinois, USA.
Correspondence to Stephen R. Cole, UNC CB#7435, Chapel Hill, NC 27599-7435 USA. Tel: +1 919 966 7415; fax: +1 919 966 2089; e-mail: firstname.lastname@example.org
Received 17 July, 2012
Revised 14 November, 2012
Accepted 23 November, 2012
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