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Background

Trends in HIV incidence and sexual behaviour in a cohort of men who have sex with men (MSM) in Montreal, 1996-2003.

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  1. Trends in HIV incidence and sexual behaviour in a cohort of men who have sex with men (MSM) in Montreal, 1996-2003 Robert S. Remis, Michel Alary, Joanne Otis, Eric Demers, Benoit Mâsse, Clemon George, Jean Vincelette, Bruno Turmel, René Lavoie, Roger LeClerc, Raymond Parent and the Omega Study Group Canadian Association of HIV/AIDS Research 13th Scientific Conference Montreal, Quebec, May 13-16, 2002

  2. Background • MSM in Montreal seriously affected by the HIV epidemic • Omega was a cohort study of over 1,800 seronegative MSM to monitor and characterize HIV transmission in Montreal • First subject recruited October 1996 • Study ended in June 2003 (6.7 years)

  3. Study objectives • Estimate HIV incidence and identify risk factors associated with seroconversion among Montreal MSM • Monitor and characterize trends in sexual behaviour • Facilitate transfer of knowledge to community groups for HIV prevention

  4. Recruitment and follow-up • MSM HIV-negative or unknown serostatus • Recruited from community and clinical sites • Follow-up visit every 6 months • Continuous recruitment to replace those lost to follow-up • Attempted to oversample younger (<30 years) and marginalized MSM and those from ethnic minorities

  5. Data and specimen collection • Self-administered and interviewer administered questionnaires on: • Demographic characteristics • Sexual behaviours, lifetime and previous 6 months • Psychosocial data • HIV and syphilis test at each visit

  6. Statistical analysisTrends in sexual behaviour • Calendar time divided into six-month periods • Each subject presenting at a particular calendar visit included • Trend analysis: General estimating equation (GEE) to control for multiple visits by the same subject

  7. Statistical analysisAnalysis of HIV incidence • HIV incidence calculated by year • Trends in HIV incidence using “bootstrap” • Analyzed risk factors for HIV seroconversion with Cox proportional hazards regression model

  8. Characteristics of participants (n=1,892) Age Median 31, IQR 25–38 years Education College/university 67% Residence Montreal Island 89% Place of Birth Quebec 71%, Canada other 12% Language French only 78%, English only 12%

  9. HIV prevalence at baseline by age

  10. HIV prevalence at baseline by education

  11. HIV prevalence at baseline by drug injection

  12. Incidence density among subjects with two or more visits (n=1,592)

  13. HIV incidence by age group and study year

  14. Risk Factor Univariate Analyses Multivariate Analyses RR P-value RR 95% CI UAS exc HIV-neg regular partners 8.4 <0.001 5.1 2.3-11.3 > 5 casual partners 4.2 <0.001 2.4 1.1-5.1 Risky oral sex 3.9 <0.001 2.0 0.96-4.3 Frequent use of drugs or alcohol before sex 3.2 0.002 1.6 0.73-3.5 Risk factors for HIV seroconversion, Cox proportional hazards regression model

  15. Proportion UAS by type of partner, 584 subjects followed to T8

  16. Proportion of UAS by partner type,all participants, by 6-month period

  17. Limitations • Data on behaviours self-reported • Subjects not necessarily representative of MSM in Montreal • Selective attrition may introduce bias

  18. Conclusions • HIV prevalence at baseline related to age and drug injection • HIV incidence remains relatively low (<1.0 per 100 p-y) though non-negligible, among MSM in Montreal (estimated 300-400 annual infections) • Unprotected anal sex remains the main risk factor for HIV acquisition, though also associated with number of casual partners • Role of risky receptive oral somewhat unclear; may be due to a classification bias

  19. Conclusions (continued) • Though relatively modest, the increased frequency of unprotected anal sex is concerning • Though not statistically significant, HIV incidence has increased steadily since 2000 • HIV incidence must be closely monitored since increase in risky behaviours may precede increase in HIV incidence • Need to reinforce preventive interventions aimed at reversing trends

  20. Acknowledgements • Gay and HIV-related community organizations • Staff, volunteers and Steering Committee members • Funding agencies who supported the study: • Canadian Institutes for Health Research • Centre québécois de coordination du sida • Fonds de la recherche en santé du Québec • Men who contributed their time and energy by participating in the study

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