COMPARISON OF PROGRESSION AND NON-PROGRESSION IN INJECTING DRUG-USERSAND HOMOSEXUAL MEN WITH DOCUMENTED DATES OF HIV-1 SEROCONVERSION

Objective: To compare the progression and non-progression of HIV infec tion among 418 injecting drug users (IDU) and 422 homosexual men with documented dates of HIV seroconversion from 12 cohorts. Methods: Seroc onversion dates were calculated for each subject using a cohort-specif ic estimate of the cumulative HIV seroincidence over calendar time. In survival analysis, we studied the progression from seroconversion to AIDS and death by risk group. We compared non-progression between both risk groups by evaluating annual CD4 decline over the 7 years followi ng seroconversion among AIDS-free subjects. Results: The relative haza rd (RH) of AIDS for homosexual men compared with IDU was 1.54 before, and 1.21 after, adjusting for age at seroconversion and year of seroco nversion. The risk of death from any cause for homosexual men compared with IDU increased over time since seroconversion. Fifty IDU died pri or to AIDS, compared with seven homosexual men (unadjusted RH for homo sexual men 0.10). Ignoring this pre-AIDS mortality, the crude RH of de ath for homosexual men compared with IDU was 2.05. After adjusting for age at seroconversion and year of seroconversion in multivariate anal ysis, the RH became 1.42. No differences in progression between subgro ups aged 24 years or older could be demonstrated, but subjects < 24 ye ars were found to be at a decreased risk. Proportions of nonprogressor s based on CD4 slope greater than or equal to 0 at 7 years following s eroconversion were higher for IDU than for homosexual men. No differen ces were found in the proportion (approximate to 5%) classified as non -progressors by criteria of both slope greater than or equal to 0 and absolute CD4 counts > 500 cells x 10(6)/l, even if pre-AIDS deaths and losses to follow-up were included. Conclusions: We found little evide nce for an effect of risk group on progression and non-progression. Pr e-AIDS mortality was much higher among IDU than homosexual men. Pre-AI DS mortality and a nonlinear age effect should be considered in planni ng interventions as well as studies comparing risk groups and modellin g the epidemic.