Day-to-day impact of COVID-19 and other factors associated with risk of nonfatal overdose among people who use unregulated drugs in five cities in the United States and Canada

Background: The COVID-19 pandemic has compounded the longstanding drug poisoning crisis in Canada and the United States (US). Research is needed to understand the contributions of COVID-19 and subsequent infection control measures. We sought to estimate the prevalence of and factors associated with nonfatal overdose among participants in nine prospective cohorts of people who use unregulated drugs (PWUD) in Canada and the US. Methods: Data were derived from nine cohorts of PWUD in urban centres in Canada (Vancouver, BC) and the US (Baltimore, MD; Miami, FL; Chicago, IL; Los Angeles, CA) between May, 2020 and April, 2021. Multivariable logistic regression was used to identify factors associated with nonfatal overdose among participants who used unregulated drugs in the past month. Results: Among 885 participants (including 253 females), 41 (4.6 %) experienced a non-fatal overdose in the past month, and 453 (51.2 %) reported being highly impacted day-to-day by the pandemic. In multivariable analyses, people who experienced a non-fatal overdose were more likely to be female (Adjusted Odds Ratio [AOR]=2.18;95 % Confidence Interval [CI]=1.10–4.30); unstably housed/homeless (AOR=2.16;95 % CI=1.11–4.26); engaged in medications for opioid use disorder (AOR=2.45;95 % CI=1.19–4.97); and highly impacted day-to-day (AOR=2.42;95 % CI=1.22–5.10). Conclusion: Our findings may reflect characteristics of participants who experienced a compounding of vulnerabilities during the pandemic and thus are vulnerable to overdose, including women, those unstably housed/homeless, and those who perceived their daily lives were highly impacted by the pandemic. Multi-level interventions are needed to remediate the vulnerabilities and address the main driver of poisoning crisis.