Objective: The objective of this study is to determine temporal trends in unprotected anal intercourse (UAI) among men who have sex with other men (MSM) participating in the Omega Cohort Study, 1997-2003.
Methods: The Omega Cohort Study was a longitudinal study of HIV-negative MSM aged 16 years or older and living in Montreal. Participants completed self-administered questionnaires and interviews every 6 months. Trend analysis using the generalized estimating equation was done for length of cohort membership (visits) and by calendar time for all visits, per type of sexual partner. Odds ratios (ORs) were calculated to measure the odds of increasing UAI per 6-month period.
Results: Among subjects who were followed for at least 4 years, UAI increased with regular seroconcordant partners (OR, 1.06, 95% CI 1.04-1.09), and any type of partner (OR, 1.05, 95% CI 1.03- 1.07). There was a nonnegligible increase in UAI with casual partners (OR, 1.05; 95% CI, 1.01-1.09). For the analysis by calendar time, there were increases in UAI between with regular seroconcordant partners (OR, 1.04; 95% CI, 1.02-1.05) and any type of partner (OR, 1.03; 95% CI, 1.02-1.04). There were nonnegligible increases in UAI with casual partners (OR, 1.03; 95% CI, 1.00-1.05) and with any type of partner except regular seroconcordant partner from 15.7% to 18.8% (OR, 1.02; 95% CI, 1.00-1.04).
Conclusions: There was a nonnegligible and consistent increase in UAI among Omega participants, between 1997 and 2003. Continuous trend analysis is important because it allows us to closely follow UAI and to implement intervention strategies that may help to stop or reduce the present trend.