Unhoused trauma patients present with unique injury patterns and comorbidities. While this population has a higher prevalence of substance use, the existing literature does not characterize rates of polysubstance use. This study aims to evaluate differences in substance use in housed and unhoused trauma patients at a national scale, particularly for rates of polysubstance use.

Methods All patients included from 1/1/2021 to 12/31/2021 in the National Trauma Database (NTDB) were retrospectively sorted into housed and unhoused groups, and their drug and alcohol screening results were collected. The NTDB reports the screening of alcohol and 13 types of drugs, of which tricyclic antidepressants were excluded. A BAC greater than or equal to 0.08% was considered alcohol positive. Polysubstance use was defined as positive screening results of 2 or more substances (drugs and/or alcohol). All statistical analyses were performed in R4.4.0.

The NTDB 2021 dataset contains a total of 1,209,097 patients, of which 9537 (0.79%) identified as unhoused. 82.64% of unhoused patients were male compared to 57.98% of housed patients.

Unhoused patients underwent alcohol testing more frequently than housed patients (RR=1.80, 95% CI 1.78, 1.82). Of those screened for alcohol, the unhoused had a higher likelihood of positive test results (RR=1.36, 95% CI 1.31,1.41). Unhoused patients were also more likely to be drug tested than housed patients (RR=2.12, 95% CI 2.08, 2.15). Of those screened for drugs, unhoused patients were more than twice as likely to test positive (RR=1.73, 95% CI 1.70,1.76).

Compared to housed patients, unhoused patients were more likely to be screened for both drugs and alcohol (RR=2.21, 95% CI 2.17, 2.26). In patients screened for both drugs and alcohol, a positive drug and alcohol screening was use more likely in the unhoused (RR=2.83, 95% CI 2.65, 3.01), and negative testing for all substances was 30% less likely in the unhoused (RR=0.70, 95% CI 0.70, 0.71). When accounting for all polysubstance combinations, the unhoused had a significantly higher risk of preinjury polysubstance use. (RR=2.59, 95% CI 2.51, 2.66).

Conclusion Unhoused trauma patients have higher rates of positive tests for alcohol, drug, and polysubstance use than housed patients; however, there is a discrepancy in substance screening based on housing status.