Mortality in the Melbourne injecting drug user cohort study (MIX)

Dhanya Nambiar, Paul A. Agius, Mark Stoové, Matthew Hickman, Paul Dietze

There are few studies of mortality amongst people who inject drugs (PWID) in Australia. In this study, we estimate mortality in a cohort of PWID in Melbourne and examine predictors of mortality including health service use, demographic characteristics, drug use and personal wellbeing. We linked identifiers from the Melbourne injecting drug use cohort study (MIX; n = 655) to the National Death Index from 2008 to 2012 to estimate standardised mortality ratios (SMRs). Cox regression was used to examine the bivariate relationship between exposures determined at baseline and subsequent mortality. There were 24 (3.6 %) deaths over the study period. The mortality rate in the cohort was 1.0 per 100 PY (95 % CI 0.71-1.57), with an SMR of 17.3 (95 % CI 11.6-25.8). Baseline reports of four or more lifetime incarcerations (HR 3.65, 95 % CI 1.16-11.52), past month ambulance attendance (HR 4.43, 95 % CI 1.76-11.17), past month emergency department presentation (HR 3.44, 95 % CI 1.47-8.03) and past 6-month self-reported heroin overdose (HR 3.14, 95 % CI 1.24-7.96) were associated with increased mortality risk. Contact with emergency services, particularly for drug overdose, remains a lost opportunity to provide referrals for harm reduction and naloxone training programmes to PWID at greater risk of mortality.