EFFECT OF AGE AND EXPOSURE GROUP ON THE ONSET OF AIDS IN HETEROSEXUALAND HOMOSEXUAL HIV-INFECTED PATIENTS

Objective: To analyse the influence of age at seroconversion and sexua l exposure group on the progression of HIV disease. Design: This multi centre prospective cohort study involved 443 subjects whose date of HI V infection was known to within +/- 1 year. Individuals whose sexual b ehaviour was exclusively heterosexual after HIV infection constituted the heterosexual group (n=131). AIDS-free survival was compared with t hat of men (n=312) infected through homosexual sex and who continued h omosexual activity after HIV infection. They constituted the homosexua l group. Methods: The end-point was the onset of an AIDS-defining illn ess listed in the 1987 revised Centers for Disease Control and Prevent ion (CDC) criteria. Using the Kaplan-Meier method, AIDS-free survival curves were plotted for three age categories (<20, 20-39, greater than or equal to 40 years). A Cox model was used to quantify the effect of age and to assess the influence of exposure group on AIDS onset after adjustment for age. Because of the high incidence of Kaposi's sarcoma (KS) among homosexual men, a disease that can be an early AIDS-defini ng illness, multivariate analysis was performed with and without consi deration of the occurrence of KS. Results: Patients aged greater than or equal to 40 years at seroconversion progressed more rapidly to AIDS than younger patients (P<0.006). When age was fitted as a continuous variable and adjusted for exposure group, the relative risk of develop ing AIDS by any time after seroconversion was 1.34 for a 10-year incre ase difference [P-0.03; 95% confidence interval (Cl), 1.03-1.77]. Afte r adjustment for age, the relative risk of developing AIDS (CDC criter ia) was 2.42 (P=0.008; 95% Cl, 1.18-4.97) among the homosexual men (AI DS cases, n=56). All cases of KS (n=19) involved the homosexual group. Excluding KS as a first manifestation of AIDS, homosexual or bisexual subjects had a risk of AIDS of 1.92 (P=0.07; 95% Cl, 0.92-4.03) compa red with heterosexual subjects. Conclusions: The risk of AIDS increase s with age at seroconversion. The more rapid progression towards AIDS in the homosexual group than in the heterosexual group persisted after adjustment for age. Further studies are required to determine the pos sible role of repeated exposure to HIV or other pathogens acquired sex ually.