AIMS: To measure mortality rates and factors associated with mortality risk among participants in the SuperMIX study, a prospective cohort study of people who inject drugs.

DESIGN: A prospective observational study in Melbourne, Australia. using self-reported behavioural and linked mortality data. A total of 1209 people who inject drugs (67% male) were followed-up between 2008 and 2019 for 6913 person-years (PY).

MEASUREMENTS: We linked participant identifiers from SuperMIX to the Australian National Death Index and estimated all-cause and drug-related mortality rates and standardized mortality ratios (SMRs). We used Cox regression to examine associations between mortality and fixed and time-varying socio-demographic, alcohol and other drug use and health service-related exposures.

FINDINGS: Between 2008 and 2019 there were 76 deaths in the SuperMIX cohort. Of those with a known cause of death (n = 68), 35 (51%) were drug-related, yielding an all-cause mortality rate of 1.1 per 100 PY with an estimated SMR of 16.64 and overall accidental drug-induced mortality rate of 0.5 per 100 PY. Reports of recent use of ambulance services and four or more incarcerations were associated with increased mortality risk.

CONCLUSIONS: In Melbourne, Australia, mortality among people who inject drugs appears to be positively associated with recent ambulance attendance and experience of incarceration.