Background
HIV-infected individuals with a history of transmission via injection drug use (IDU) have poorer survival than other risk groups. The extent to which higher rates of hepatitis C (HCV) infection in IDU explain survival differences is unclear.
Methods
Adults who started antiretroviral therapy (ART) between 2000-2009 in 16 European and North American cohorts with >70% complete data on HCV status were followed for 3 years. We estimated unadjusted and adjusted [for age, sex, baseline CD4 count and HIV-1 RNA, AIDS diagnosis prior to ART, and stratified by cohort] mortality hazard ratios (HR) for IDU (versus non-IDU) and for HCV-infected (versus HCV-uninfected).
Results
Of 32,703 patients 3,374 (10%) were IDU; 4,630 (14%) HCV+; 1,116 (3.4%) died. Mortality was higher in IDU compared with non-IDU (adjusted HR 2.71; 95% CI 2.32,3.16) and in HCV+ compared with HCV− (2.65; 2.31,3.04). The effect of IDU was substantially attenuated (1.57; 1.27,1.94) after adjustment for HCV, while attenuation of the effect of HCV was less substantial (2.04; 1.68,2.47) after adjustment for IDU. Both IDU and HCV were strongly associated with liver-related mortality (10.89; 6.47,18.3 for IDU and 14.0; 8.05,24.5 for HCV) with greater attenuation of the effect of IDU (2.43; 1.24,4.78) than for HCV (7.97; 3.83,16.6). Rates of CNS, respiratory and violent deaths remained elevated in IDU after adjustment for HCV.
Conclusions
A substantial proportion of the excess mortality in HIV-infected IDU is explained by HCV co-infection. These findings underscore the potential impact on mortality of new treatments for HCV in HIV-infected people.