title: Comparison of sexual behaviors, unprotected sex, and substance use between two independent cohorts of gay and bisexual men.
abstract: OBJECTIVE
  To compare demographic characteristics, sexual practices, unprotected receptive and insertive anal intercourse, substance use and rates of HIV-1 seroconversion between two prospective cohorts of HIV-negative men who have sex with men.
  
  
  METHODS
  Comparative analysis of two independent cohorts.
  
  
  METHODS
  Between May 1995 and April 1996, 235 HIV-negative Vanguard Project (VP) participants were enrolled and between January and December 1985, 263 HIV-negative participants in the Vancouver Lymphadenopathy AIDS Study (VLAS) completed a follow-up visit. The VP participants were compared with VLAS participants with respect to self-reported demographic variables, sexual behaviors, unprotected sex, substance use and rates of HIV-1 seroconversion during follow-up.
  
  
  RESULTS
  In comparison with the VLAS participants the VP participants were younger (median age, 26 versus 34 years; P< 0.001), more likely to be non-Caucasian (75 versus 97%; P< 0.001), and were less likely to have attended university/college (35 versus 46%; P = 0.014). The VP participants reported a higher mean number of male sex partners in the previous year (15 versus 12; P= 0.026) and a higher mean number of regular partners (1.7 versus 0.6; P < 0.001). The VP participants were more likely to report engaging in receptive (92 versus 60%; P< 0.001) and insertive (90 versus 69%; P < 0.001) anal intercourse with regular partners and receptive anal intercourse with casual partners (62 versus 38%; P< 0.001). The VLAS participants were more likely to report never using condoms during insertive and receptive anal intercourse with both regular and casual partners. The VP participants were less likely to report using nitrite inhalants (34 versus 43%; P= 0.033), but more likely to report the use of cocaine (30 versus 8%; P< 0.001), LSD (21 versus 3%; P < 0.001), amphetamine (11 versus 1%; P< 0.001), heroin (3 versus 0%; P= 0.010) and methyldiamphetamine (17 versus 10%; P= 0.034). The VLAS participants were nine times more likely to report high-risk sexual behavior, after controlling for differences in age, ethnicity, substance use, and method of recruitment between cohort members. After adjustment for differences in demographics, sexual behaviors, and level of substance use, the risk ratio for seroconversion among VLAS participants remained significantly elevated compared with VP participants.
  
  
  CONCLUSIONS
  These data provide evidence that men who have sex with men who were enrolled in the VP were more sexually active than their VLAS counterparts were 10 years ago as measured by self-reported numbers of regular and casual partners and frequency of anal intercourse with these partners. However, condom use appears to be significantly higher among VP participants, which has contributed to a lower rate of HIV-1 infection.
authors.affiliation: British Columbia Centre for Excellence in HIV/AIDS, St Paul's Hospital, Vancouver, Canada.
authors.forename: K J
authors.initials: KJ
authors.lastname: Craib
authors.forename: A C
authors.initials: AC
authors.lastname: Weber
authors.forename: P G
authors.initials: PG
authors.lastname: Cornelisse
authors.forename: S L
authors.initials: SL
authors.lastname: Martindale
authors.forename: M L
authors.initials: ML
authors.lastname: Miller
authors.forename: M T
authors.initials: MT
authors.lastname: Schechter
authors.forename: S A
authors.initials: SA
authors.lastname: Strathdee
authors.forename: A
authors.initials: A
authors.lastname: Schilder
authors.forename: R S
authors.initials: RS
authors.lastname: Hogg
mesh_terms: D000293:Adolescent; D000328:Adult; D001727:Bisexuality; D001955:British Columbia / Q000453:epidemiology; D015331:Cohort Studies; D017280:Condoms; D003710:Demography; D015658:HIV Infections / Q000453:epidemiology; D018451:Homosexuality, Male; D006801:Humans; D015994:Incidence; D008297:Male; D015999:Multivariate Analysis; D011446:Prospective Studies; D012747:Sexual Partners; D019966:Substance-Related Disorders / Q000453:epidemiology*