Incidence of Kaposi's sarcoma and HHV-8 seroprevalence among homosexual men with known dates of HIV seroconversion

Objectives: To evaluate temporal trends of Kaposi's sarcoma (KS) and of the KS-related human herpesvirus (HHV-8) among homosexual men who seroconverte d for HIV between 1984 and 1997. Methods: The study participants were 387 homosexual men. Changes over a per iod of time were assessed by estimating KS incidence rates per 1000 person- years for the periods 1984-1989, 1990-1992, 1993-1995, and 1996-1997. The p roportional incidence of KS as the AIDS-defining disease for the same perio ds was also calculated. To evaluate a cohort effect of calendar period, Kap lan-Meier curves were used to estimate the risk of KS by period of HIV sero conversion [i.e. before 1990 (median year of seroconversion) versus later]. Relative hazards for the four periods were estimated using competitive-ris ks models. We also estimated HHV-8 seroprevalence over the study period. Results: Forty-eight participants developed KS. Between 1984 and 1995, the incidence rate of KS per 1000 person-years increased from 3.9 to 32.8, wher eas the proportional incidence decreased from 33.3 to 24.3%. The risk of de veloping KS after HIV seroconversion did not change when comparing the sero conversion periods (i.e. before 1990 versus later). HHV-8 seroprevalence al so remained stable. The rates of KS and the relative hazards dramatically d ecreased after 1995. Conclusions: Although KS incidence rates increased up to 1995, the proporti onal incidence decreased, due to the higher increase in rates of other AIDS -defining diseases. The finding that the risk of developing KS after HIV se roconversion remained stable over time is consistent with the stable trend of HHV-8 seroprevalence. The dramatic decrease in KS incidence rates after 1995 coincides with combined antiretroviral therapy. (C) 2000 Lippincott Wi lliams & Wilkins.