Longitudinal polysubstance use patterns and non-fatal overdose: A repeated measures latent class analysis

Area of Science:

• Public Health
• Epidemiology
• Addiction Science

Background:

• Polysubstance use (PSU) is prevalent among people who use opioids (PWUO).
• PSU is associated with increased drug-related harms and overdose risks.
• Understanding longitudinal PSU patterns is crucial for harm reduction.

Purpose of the Study:

• To identify distinct latent longitudinal classes of polysubstance use among PWUO.
• To characterize the association between these PSU classes and non-fatal overdose risk over time.

Main Methods:

• Utilized longitudinal data from prospective cohorts of PWUO in Vancouver (2005-2018).
• Employed repeated measures latent class analysis (RMLCA) to identify PSU patterns.
• Used generalized estimating equations to assess non-fatal overdose risk across PSU classes, adjusting for confounders.

Main Results:

• Five latent longitudinal PSU classes were identified among 2627 PWUO.
• Classes included low/infrequent use, opioid/methamphetamine use, cannabis use, opioid/crack use, and frequent PSU.
• Compared to low use, opioid/methamphetamine, opioid/crack, and frequent PSU classes showed significantly increased odds of non-fatal overdose.

Conclusions:

• PWUO exhibit heterogeneous PSU patterns associated with varying non-fatal overdose risks.
• The diverse nature of PSU necessitates tailored approaches in substance use treatment and care.
• Recognizing specific substance combinations and usage frequency is key to mitigating overdose risk.