Objectives:

To determine the protective efficacy of highly active antiretroviral therapy (HAART) against AIDS dementia complex (ADC) relative to other initial AIDS-defining illnesses (ADIs), Australian AIDS notification data over recent years were examined.

Methods:

All initial ADIs in Australia over the period 1992-1997 were included. Three initial ADI groups were established: ADC; other predominantly central nervous system (CNS) ADIs (toxoplasmosis and cryptococcosis); and non-CNS ADIs. For each ADI grouping, the proportion of total ADIs, and median CD4 cell count in the pre-HAART era (1992-1995) were compared with the HAART era (1996 and 1997).

Results:

Initial ADIs peaked in Australia in 1994 (n= 1049), with a gradual decline to 1996 (n= 722), and a marked decline in 1997 (n= 367). ADC constituted 4.4% of initial ADIs over the period 1992-1995, but increased after the introduction of HAART to 6.0% in 1996 and 6.5% in 1997 (P= 0.02). In contrast, the proportion of other CNS ADIs (1992-1995, 8.1%; 1996, 6.0%; 1997, 8.2%; P= 0.41) was stable over the period 1992-1997. The median CD4 cell count at ADC diagnosis increased from 70/mm 3 in 1992-1995 to 120/mm 3 in 1996 and 170/mm 3 in 1997 (P= 0.04). Although the median CD4 cell count also increased significantly over this period for both other CNS ADIs (40-60/mm 3; P= 0.02), and non-CNS ADIs (60-70/mm 3; P= 0.02), the increase was small.

Conclusion:

A proportional increase in ADC compared with other ADIs and a marked increase in the median CD4 cell count at ADC diagnosis have occurred since the introduction of HAART in Australia. These changes suggest that HAART has a lesser impact on ADC than on other ADIs, with the poor CNS penetration of many antiretroviral agents a possible explanation.