The effect of injecting drug use history on disease progression and death among HIV-positive individuals initiating combination antiretroviral therapy: collaborative cohort analysis

Abstract

Background: We examined whether determinants of disease progression and causes of death differ between injecting drug users (IDUs) and non-IDUs who initiate combination antiretroviral therapy (cART).

Methods: The ART Cohort Collaboration combines data from participating cohort studies on cART-naïve adults from cART initiation. We used Cox models to estimate hazard ratios for death and AIDS among IDUs and non-IDUs. The cumulative incidence of specific causes of death was calculated and compared using methods that allow for competing risks.

Results: Data on 6269 IDUs and 37 774 non-IDUs were analysed. Compared with non-IDUs, a lower proportion of IDUs initiated cART with a CD4 cell count <200 cells/μL or had a prior diagnosis of AIDS. Mortality rates were higher in IDUs than in non-IDUs (2.08 vs. 1.04 per 100 person-years, respectively; P<0.001). Lower baseline CD4 cell count, higher baseline HIV viral load, clinical AIDS at baseline, and later year of cART initiation were associated with disease progression in both groups. However, the inverse association of baseline CD4 cell count with AIDS and death appeared stronger in non-IDUs than in IDUs. The risk of death from each specific cause was higher in IDUs than non-IDUs, with particularly marked increases in risk for liver-related deaths, and those from violence and non-AIDS infection.

Conclusion: While liver-related deaths and deaths from direct effects of substance abuse appear to explain much of the excess mortality in IDUs, they are at increased risk for many other causes of death, which may relate to suboptimal management of HIV disease in these individuals.

© 2011 British HIV Association.

Figures

Fig. 1

Numbers (below graph) and percentages (above bars) of specific causes of death in patients who were and were not infected via injecting drug use (IDU). Liver-related deaths include hepatitis and liver failure; violent deaths include accident, suicide and overdose; cardiovascular disease (CVD) includes myocardial infarction, ischaemic heart disease, stroke, heart failure/unspecified and other heart disease; ‘Other’ includes causes with fewer than 20 deaths overall. Unknown deaths are those for which there was insufficient information to assign a cause of death.

Fig. 2

Total cumulative mortality from the start of combination antiretroviral therapy (cART) in patients who were (a) and were not (b) infected by injecting drug use (IDU), partitioned by cause of death grouped as AIDS, liver-related, violent and other.