Mortality in the SuperMIX cohort of people who inject drugs in Melbourne, Australia: a prospective observational study.

ABSTRACT

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 using self-reported behavioural and linked mortality data. SETTING: Melbourne, Australia. PARTICIPANTS/CASES A total of 1209 people who inject drugs (67% male) 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 [95% confidence interval (CI) = 0.88-1.37] with an estimated SMR of 16.64 (95% CI = 13.29-20.83) and overall accidental drug-induced mortality rate of 0.5 per 100 PY (95% CI = 0.36-0.71). Reports of recent use of ambulance services [adjusted hazard ratio (aHR) = 3.77, 95% CI =1.78-7.97] and four or more incarcerations (aHR = 2.78, 95% CI = 1.55-4.99) 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.