1. Trends in HIV incidence and sexual behaviour among a cohort of men who have sex with men (MSM) in Montreal:
Robert S. Remis, Michel Alary, Joanne Otis, Benoit Mâsse, Eric Demers, Clemon George, Jean Vincelette, Bruno Turmel, René Lavoie, Roger LeClerc, Raymond Parent and the Omega Study Group
XIV International Conference on AIDS
Barcelona, Spain, July 9, 2002

2. Background MSM in Montreal seriously affected by the HIV epidemic
Omega is a cohort study of 2,000 seronegative gay men whom we are following to better understand HIV transmission in Montreal
First subject recruited October 1996

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
Attempt 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 analysis, trends 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. Characteristics of participants (n=1,787)
Age Median 31, 80% 21 – 47
Education College/university 69%
Residence Montreal Island 88%
Place of Birth Quebec 71%, Canada other 12%
Language French only 79%, English only 12%

8. HIV prevalence at baseline by age

9. HIV prevalence at baseline by education
p-value
Education
< Secondary
Secondary/College
Higher
112
700
699
7.4%
1.4%
0.86%
0.001

10. HIV prevalence at baseline by drug injection

11. HIV prevalence at baseline by sexual history
p-value
Age at first homosexual sex
<15
15-20
20+
395
486
316
3.3%
1.2%
0.00%
0.002  
Number of casual partners, lifetime
0-5
6-49
50+
379
710
585
0.79%
1.3%
2.8%
0.03

12. Incidence density among subjects with two or more visits (n=1,436)
Age
Sero- conversions
Person-years
Incidence density (95% CI)
<30
30+ 11 12
1,493
2,549
0.74 (0.37, 1.3)
0.47 (0.20, 0.74)
Total 23
4,041
0.57 (0.34, 0.80)

13. HIV incidence by age group and period of study

14. Unprotected anal sex among subjects by sexual partner type and calendar time
04-09/97
10/98-03/99
04-09/00
10/01- 03/02
p-value
p-value, adjusted
Relationship %
Casual partner
8.2
10.4
11.1
11.5
0.02 NS
Regular HIV-
21.4
23.0
23.2
24.2
0.09
All except
regular HIV-
15.7
16.6
18.9
19.4
0.005
Regular HIV+
0.6
1.3
1.4
1.0
Regular HIV?
8.8
7.7
9.0
9.8
0.004
Any partner
34.1
36.4
37.5
40.9
0.0003

15. Unprotected anal sex among subjects <30 years by sexual partner type and calendar time
04-09/97
10/98-03/99
04-09/00
10/01- 03/02
p-value
p-value, adjusted
Relationship %
Casual partner
4.4
12.0
10.1
13.4
0.01 NS
Regular HIV-
22.1
23.7
27.3
32.3
0.08
All except
regular HIV-
18.8
20.3
21.2
23.4
0.06
Regular HIV+
0.9
0.4
1.1
0.5
Regular HIV?
15.2
11.0
13.0
12.9
Any partner
36.7
40.9
43.9
52.0
0.006

16. Unprotected anal sex among subjects 30+ years by sexual partner type and calendar time
04-09/97
10/98-03/99
04-09/00
10/01- 03/02
p-value
p-value, adjusted
Relationship %
Casual Partner
10.0
9.3
11.6
10.8 NS
Regular HIV-
21.0
22.5
21.2
20.9
All except
regular HIV-
14.4
14.0
17.8
0.02
Regular HIV+
0.4
1.9
1.6
1.2
Regular HIV?
5.9
5.3
7.0
8.7
0.09
0.01
Any partner
32.9
33.2
34.4
36.5
0.002

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,
drug injection and age at first homosexual sex
Trends in HIV incidence differ in younger versus older MSM
Overall, HIV incidence relatively low and stable
Reasons are not clear; organization dedicated to HIV prevention in MSM may in part be responsible
Increase in may be real, given increasing risky sexual behaviour

19. 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