Abstract

Environmental factors increase mortality risk among injection drug users in Tijuana, Mexico

R.A. Pollini¹, R. Lozada², D. Abramovitz¹, A. Vera¹, C. Magis-Rodriguez³, S.A. Strathdee<sup>1

1</sup>University of California San Diego, La Jolla, United States, ²Prevencasa A.C., Tijuana, Mexico, ³Centro Nacional para la Prevencion y Control de SIDA, Mexico City, Mexico

Background: Injection drug users (IDUs) have high mortality rates. We examined individual- and environmental-level predictors of mortality among IDUs in Tijuana, Mexico.
Methods: Beginning in April 2006, IDUs were recruited using respondent driven sampling (RDS) and underwent semi-annual surveys and testing for HIV, TB and syphilis. Mortality was ascertained by witness reports, family member confirmation and/or government mortality databases and confirmed by death certificate when available. Cox regression with RDS adjustment was used to identify predictors of mortality.
Results: Of 1,056 IDUs, 953 (90.2%) had at least one follow-up visit. Of these 953, 48 (5.0%) tested HIV+ at baseline or follow-up and 45 (4.7%) died during follow-up (2.5 per 100 person years; 95% CI: 1.73-3.16). Preliminary data indicate cause of death as follows: 36% overdose, 22% homicide, 13% other injuries, 13% AIDS-related infections, 7% other causes, 7% undetermined. Independent predictors of mortality were HIV infection (adjusted hazard ratio (adjHR) 9.84; 95% CI: 4.18-23.15), number of incarcerations (adjHR: 1.03; 95% CI: 1.01-1.05), injecting drugs in vacant lots (adjHR: 5.89; 95% CI: 1.82- 19.11), injecting heroin powder vs. black tar (adjHR: 11.27; 95% CI: 2.87-44.35), and injecting drug combinations the first time they injected (adjHR: 3.53; 95% CI: 1.35-9.23).
Conclusions: As expected, HIV infection contributed significantly to mortality risk among IDUs in Tijuana. However, environmental factors including incarceration, location of injection and heroin type also increased mortality risk, indicating that structural interventions are needed to reduce IDU mortality. Overdose was the leading cause of death, suggesting that overdose prevention and response interventions should be prioritized in Tijuana.