Opioid overdose survivors face elevated mortality risk within one year

After an emergency department visit for an opioid overdose, 9 per cent of individuals died and 21 per cent experienced a repeat opioid overdose in the following year, according to a new study from ICES and the Centre for Addiction and Mental Health (CAMH). 

The risks were particularly high within seven and thirty days after being discharged from an emergency department. The mortality estimates were higher than in previous studies, which found non-fatal opioid overdoses to be approximately 6 per cent. 

"Most older studies were conducted before the introduction of fentanyl into the unregulated drug supply," says lead author Robert Kleinman, a scientist with the Institute for Mental Health Policy Research at CAMH and an assistant professor in the Department of Psychiatry at the University of Toronto. "The current fentanyl supply is highly toxic and associated with a greater risk of overdose or death." 

The researchers evaluated one-year mortality among 28,488 opioid overdose survivors in Ontario, Canada, using linked administrative data held at ICES. Individuals aged 15 to 105 years were included if they visited the emergency department between 2017 and 2023 for a non-fatal opioid overdose. 

Within seven days of discharge, 0.6 per cent of individuals died and 2 per cent experienced a repeat opioid overdose. Within 30 days, 2 per cent of individuals died and 6 per cent experienced another overdose. People with additional prior overdose experiences were at an increased risk of death. 

"These elevated risks after leaving the hospital highlight the importance of ensuring that interventions such as opioid agonist treatments and take-home naloxone are available and accessible for opioid overdose survivors," says Kleinman. 

One limitation is that non-fatal opioid overdoses that didn't result in an emergency department visit were not captured in the study. This means that rates of opioid overdoses during the subsequent year were likely underestimated, and further research is needed to explore overdoses within the community. 

"The elevated mortality risk observed in this study is highly concerning. The development of evidence-based care pathways for when individuals with opioid use disorders show up to an Emergency Department with an overdose or in withdrawal may help to both reduce the high mortality rate and help people access treatment," says Paul Kurdyak, a senior scientist with ICES and CAMH.