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EFFECT OF HEPATITIS C VIRUS (HCV) AND HUMAN IMMUNODEFICIENCY VIRUS (HIV) INFECTIONS ON MORTALITY AMONG ILLICIT DRUG USERS

J Grebely¹, J Raffa ², B Conway¹, C Lai³, M Krajden⁴, MW Tyndall³
¹Department of Pharmacology and Therapeutics, ²Department of Statistics, University of British Columbia; ³BC Centre for Excellence in HIV/AIDS; ⁴BC Centre for Disease Control, Vancouver, British Columbia

There are little data evaluating the impact of HCV infection on mortality in illicit drug users. With this in mind, we sought to evaluate the impact of HCV and HIV infections on mortality in illicit drug users.
CHASE is a cohort study of inner city residents recruited from 01/03-06/04. HIV and HCV status were determined through linkage with provincial databases. Mortality data were derived from the BC Vital Statistics registry (2003-2005). Reported ICD-10 codes determined the underlying cause of death. In each category (HIV-/HCV-, HIV-/HCV+, HIV+/HCV-, HIV+/HCV+), natural cause mortality rates and mortality due to HIV and HCV were calculated.
Of 2,069 participants, we identified 721 HCV-/HIV-, 962 HCV+/HIV-, 33 HCV-/HIV+, 353 HCV+/HIV+ subjects. Among 82 deaths, common causes of death were HIV infection (25.6%) and unnatural causes (19.5%). The natural cause mortality rate was 15.5 deaths/1000 p-yrs overall (n=66), 9.6 deaths/1000 p-yrs for HCV-/HIV- (n=15), 11.0 deaths/1000 p-yrs for HCV+/HIV- (n=28), 30.4 deaths/1000 p-yrs for HCV-/HIV+ (n=2) and 37.8 deaths/1000 p-yrs for HCV+/HIV+ subjects (n=37). Among HCV-/HIV+ and HCV+/HIV- subjects, mortality attributed to HIV and HCV was 15.2 and 2.0 deaths/1000 p-yrs. In HCV+/HIV+ subjects, mortality attributed to HIV and HCV were 25.6 and 1.3 deaths/1000 p-yrs. Overall, Cox proportional hazards analyses demonstrated that natural cause mortality was associated with HIV infection (adjusted HR 5.3; 3.0-9.7, p<0.001), age (HR 1.8/10 year increase; 1.3-2.4, p<0.001) and Aboriginal ethnicity (HR 1.7; 0.96-3.0, p=0.07) and not associated with HCV infection (HR 1.0; 0.50-2.0, p=0.99).
In this large retrospective analysis, mortality rates in illicit drug users were high, with HIV infection leading to a five-fold increase in risk of mortality. Due to the timing of the HCV epidemic in this population, there has been little impact of HCV on mortality to date. However, without programs to treat HCV in this group, we expect a significant increase in mortality attributable to HCV infection.

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