Temporal changes in the rate of progression to death among Italians with known date of HIV seroconversion: Estimates of the population effect of treatment

Objective: To evaluate changes in survival among HIV-positive individuals w ith known date of seroconversion (SC). Design: Prospective cohort study. Methods: Follow-up lasted from SC to death or to the end of 1997. A multiva riate Cox model was applied to estimate relative hazards (RH) of death. The year of SC (as a categoric fixed variable) and calendar year (as a time-de pendent variable) were considered to evaluate, respectively, cohort and pre valent changes in the rate of death. A separate Cox model was used to asses s the association between survival and new combination therapies, using an "intention to treat" approach. Results: The study included 1535 individuals (53.9% injecting drug users, 2 5.3% homosexuals, 19.5% heterosexuals); 75.8% seroconverted between 1980 an d 1991, and 24.2% seroconverted between 1992 and 1997. When adjusting for y ear of SC, the RH of death (and that of AIDS) was significantly lower in 19 97, compared with before 1991 (RH = 0.54; 95% confidence interval, 0.30-0.9 8), Adjusted RHs of death were significantly lower for combination antiretr oviral therapy, compared with no therapy. When combining the two Cox models , the 1997 reduction in risk of death was largely due to antiretroviral the rapies; similar results were obtained when the endpoint was AIDS. Conclusions: A reduction in the risk of death, probably due to combination antiretroviral therapy, was observed in 1997 after having adjusted for age at SC and year of SC.