A CASE-CONTROL STUDY OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 SEROCONVERSION AND RISK-RELATED BEHAVIORS IN THE CHICAGO MACS CCS COHORT, 1984-1992/

This paper focuses on 76 human immunodeficiency virus type 1 (HIV-1) s eroconverters who concurrently participated in the Chicago, Illinois, component of the Multicenter AIDS Cohort Study (MACS) and the Coping a nd Change Study (CCS) of homosexual/bisexual men between 1984 and 1992 . A nested case-control analysis was performed to assess the critical behavioral risk factors associated with incident HIV-1 infection and t he consistency of these relations in early (1984-1988) versus later (1 989-1999) phases of the study. Univariate results revealed strong earl y period associations between seroconversion and various measures of r eceptive anal intercourse (RAI) that became considerably weaker in the study's later period. The weaker associations reflected the overall d ecline in levels of RAI among the cohort during the 9 years of observa tion. In contrast, univariate results revealed stronger later period a ssociations between seroconversion and measures of receptive oral inte rcourse and insertive anal intercourse. Subsequent multivariate testin g did not support the hypothesis that receptive oral intercourse and/o r insertive anal intercourse have replaced unprotected RAI as importan t risk behaviors in the homosexual transmission of HIV-1. In condition al logistic regression models combining intercourse measures with indi ces of drug and condom use, only the latter variables were consistentl y associated with HIV-I seroconversion in both early and later study p eriods. Adjusted odds ratios (ORs) for nonuse of condoms during RAI we re consistently significant throughout the study (ORs = 3.7-4.8), whil e adjusted odds ratios for recreational drug use variables rose dramat ically during the latter half of the study (e.g., for use of cocaine, OR = 81.3 (95% confidence interval 0-824), and for use of nitrite ''po ppers,'' OR = 9.1 (95% confidence interval 1.8-45.5)). The behavioral intervention applications of these findings, as well as their relation to data from other recent cohort studies of HIV-1 seroconversion amon g homosexual/bisexual men, are discussed.