TRENDS IN INCIDENCE OF AIDS ILLNESSES IN AUSTRALIA FROM 1983 TO 1994 - THE AUSTRALIAN AIDS COHORT

To assess time trends in incidence of AIDS illnesses in Australia, a r etrospective cohort of people diagnosed with AIDS from January 1, 1983 to December 31, 1994 in three HIV medicine units in Sydney, Melbourne , and Perth was established. Data on initial and subsequent AIDS illne sses were available for 2580 AIDS cases, or 45% of Australian AIDS not ifications over the study period. Males represented 97.2% of the cohor t, and HIV exposure category was homosexual contact for 89.9%. Subcoho rts were formed by interval of AIDS diagnosis: 1983 through 1987, 1988 through 1990, and 1991 through 1994, with estimation of cumulative ri sk for each AIDS illness by the Kaplan-Meier method. The cumulative ri sk declined for Pneumocystis carinii pneumonia (PCP) (p < 0.0001) and for Kaposi's sarcoma (KS) (p < 0.0001); PCP cumulative risk estimates 2 years following AIDS diagnosis were 70% for people diagnosed with AI DS in 1983 through 1987 and 48% in 1991 through 1994, and KS cumulativ e risk estimates 2 years following AIDS diagnosis were 44% in 1983 thr ough 1987 and 32% in 1991 through 1994. In contrast, cumulative risk i ncreased from 34% to 40% for cytomegalovirus (CMV) disease (p = 0.005) , from 47% to 50% for Mycobacterium avium complex (MAC) (P < 0.0001), and from 26% to 33% for esophageal candidiasis (p < 0.0001). Correspon ding to this changing spectrum of AIDS illness has been an increase in severity of immunodeficiency at AIDS, with median CD4 cell count decl ining from 54 cells/mm(3) in 1983 through 1987 to 34/mm(3) in 1991 thr ough 1994 (p = 0.002).