Mortality risk among individuals who smoke opioids compared with those who inject: A propensity score-matched cohort analysis of United States national treatment data

Background and Aims

Opioid smoking is becoming more common in the United States. The aim of this analysis was to estimate relative mortality risk among those who primarily smoke opioids compared with those who inject.

Design

Retrospective propensity score-matched cohort analysis.

Setting

2006–2021 US treatment episode data from SAMHSA TEDS-D.

Participants

We matched 287 481 individuals in a substance use treatment program reporting smoking opioids as their primary substance use to an equal weighted number of individuals in a substance use treatment program reporting injecting opioids as their primary substance use. The majority of individuals reporting smoking were male (62.6%), 21–29 years old (47.9%), white (65.7%), independently housed (54.3%) and in the West Census Region (70.3%). Cohort characteristics were closely balanced after matching.

Measurements

The outcome of interest was death during a treatment episode. Variables used for matching were year, opioid category, gender, race/ethnicity, age category, census region, housing status, employment status, number of prior treatment admissions, variables associated with opioid use severity (opioid use frequency, treatment setting intensity, age at first opioid use, use of medication-assisted treatment) and other reported substance use (methamphetamine, alcohol, benzodiazepines, cocaine).

Findings

The mortality rate was 6.5 [95% confidence interval (CI) = 5.9–7.1] per 1000 person-years in the smoking cohort and 9.7 (95% CI = 8.8–10.8) per 1000 person-years in the injection cohort, with a mortality rate ratio of 0.67 (95% CI = 0.58–0.77).

Conclusions

Among individuals in substance use treatment in the United States, those who usually smoke opioids appear to have a lower all-cause mortality risk than those who usually inject.