No association between HIV status and risk of non-fatal overdose among people who inject drugs in Vancouver, Canada

Background: The evidence to date on whether HIV infection increases the risk of accidental drug overdose among people who inject drugs (PWID) is equivocal. Thus, we sought to estimate the effect of HIV infection on risk of non-fatal overdose among two parallel cohorts of HIV-positive and -negative PWID. Methods: Data were collected from a prospective cohort of PWID in Vancouver, Canada between 2006 and 2013. During biannual follow-up assessments, non-fatal overdose within the previous 6 months was assessed. Bivariable and multivariable generalized mixed-effects regression models were used to determine the unadjusted and adjusted associations between HIV status, plasma HIV-1 RNA viral load, and likelihood of non-fatal overdose. Results: A total of 1760 eligible participants (67% male, median age = 42, and 42% HIV-positive at baseline) were included. Among 15,070 unique observations, 649 (4.3%) included a report of a non-fatal overdose within the previous 6 months (4.4% among seropositive and 43% among seronegative individuals). We did not observe a difference in the likelihood of overdose by HIV serostatus in crude (odds ratio [OR]: 1.05, p = 0.853) analyses or analyses adjusted for known overdose risk factors (adjusted OR [AOR]: 1.19, p = 0.474). In a secondary analysis, among HIV-positive PWID, we did not observe an association between having a detectable viral load and overdose (AOR: 1.03, p = 0.862). Conclusions: Despite the evidence that HIV infection is a risk factor for fatal overdose, we found no evidence for a relationship between HIV disease and non-fatal overdose. However, overdose remains high among PWID, indicating the need for ongoing policy addressing this problem, and research into understanding modifiable risk factors that predict non-fatal overdose. (C) 2016 Elsevier Ltd. All rights reserved.