*BC Centre for Excellence in HIV/AIDS, St. Paul's Hospital, Vancouver, †Department of Infectious Diseases, University of British Columbia, Vancouver
To the Editor:
Improving access to antiretroviral therapy among HIV-infected injection drug users (IDUs) is an urgent international priority,1,2 and several international initiatives, including the WHO's 3 × 5 Initiative,3 are seeking to improve use of antiretroviral therapies among IDUs. In an earlier report from our setting, which considered follow-up until May 2000, it was noted that only the minority of deaths among IDUs were due to HIV infection, and the free availability of highly active antiretroviral therapy (HAART) was posited as a potential explanation for low HIV/AIDS mortality.4
Because the local setting of free HAART provides a somewhat unique opportunity to examine the impact of HIV on mortality where financial barriers to HIV/AIDS care do not exist,5 the present study was conducted to compare updated mortality rates among HIV-infected and HIV-uninfected injection drug users since the local guidelines were changed to restrict all initial antiretroviral regimens to triple therapy.6
Beginning in May 1996, persons who had injected illicit drugs in the previous month were recruited into the Vancouver Injection Drug Users Study (VIDUS).7 As previously described,7 at baseline and then semiannually, a trained nurse-interviewer administers a questionnaire regarding health status and health care utilization. Upon recruitment into the study, IDUs provided a venous blood sample for testing of HIV serology, and a trained research nurse conducted an interviewer-administered questionnaire. The baseline for the present study was restricted to July 1, 1997, because this is the date that the province's therapeutic guidelines were amended to recommend that all antiretroviral regimens consist of triple therapy, rather than the dual therapy regimens that were allowed before this date.6
We calculated the cumulative mortality rates among baseline HIV-infected versus HIV-uninfected participants using Kaplan-Meier methods. As described previously, deaths were determined through a linkage with the province's Vital Statistics agency.1 We also calculated the unadjusted and adjusted relative hazards of mortality using Cox proportional hazards regression. Here, all behavioral variables and HIV status were treated as time-updated covariates based on semiannual follow-up data. For the multivariate model, a fixed model was built that adjusted for those variables that were found to be P < 0.05 in univariate analyses. We considered the following variables: age, gender, ethnicity (Aboriginal vs. other), neighborhood residence, hepatitis C infection, daily cocaine use (yes vs. no), and daily heroin use (yes vs. no). Analyses were conducted using SAS 8.0 (SAS Institute, Cary, NC); the threshold for statistical significance was set at P < 0.05. All P values were 2-sided.
Between July 1, 1997, and November 30, 2005, 1441 individuals were recruited into the VIDUS cohort, among whom 295 were baseline HIV-positive and 136 became HIV-infected during follow-up. Overall, the cumulative mortality was 11.75% by 4 years. As shown in Figure 1, the cumulative mortality rate was 23.29% for HIV-infected individuals and 8.09% for uninfected individuals (log-rank P < 0.001). As also shown here, whereas the pattern of mortality was more similar early during follow-up, in recent years a large differential in mortality has emerged. In Cox regression, HIV infection was associated with elevated mortality in both univariate (relative hazard: 3.54, 95% confidence interval [CI]: 2.75 to 4.55; P < 0.001) and multivariate analyses (relative hazard: 3.63, 95% CI: 2.78 to 4.71; P = 0.001). The final model was adjusted for age (P < 0.001), ethnicity (P = 0.074), neighborhood residence (P = 0.001), and hepatitis C status (P = 0.514).
The generalizability of prospective cohort studies of marginalized populations such as IDUs is limited, in that it is often difficult to know whether the population is similar to the overall community. Prior studies have suggested that the VIDUS cohort is representative of IDUs in the community.4
The present study indicates that a large and growing contribution of HIV to mortality among IDUs has emerged despite the free availability of HAART to all IDUs through a universal health care system. Although mortality rates were more similar between HIV-infected and HIV-uninfected IDUs several years ago in our setting,4 the large difference in mortality that has emerged demonstrates a growing need for interventions to improve access and adherence to HAART among IDUs.
Ryan Blades, BA*
Kathy Li, PhD*
Thomas Kerr, PhD*†
Mark W. Tyndall, MD, ScD, FRCPC*†
Julio S. G. Montaner, MD, FRCPC, FCCP*†
Evan Wood, MD, PhD*†
*BC Centre for Excellence in HIV/AIDS St. Paul's Hospital, Vancouver †Department of Medicine University of British Columbia, Vancouver
The authors wish to thank the participants in the VIDUS study and the VIDUS staff. This study was made possible through support from CANFAR, CIHR, and the U.S. NIH. We thank Deborah Graham and Caitlin Johnston for their research assistance.
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6. Wood E, Hogg RS, Yip B, et al. Effect of medication adherence on survival of HIV-infected adults who start highly active antiretroviral therapy when the CD4+ cell count is 0.200 to 0.350 × 10(9) cells/L. Ann Intern Med
7. Strathdee SA, Patrick DM, Currie SL, et al. Needle exchange is not enough: lessons from the Vancouver injecting drug use study. AIDS