Unpacking the link between substance use disorders and 30-day unplanned readmission.

Background and aims: Given the more than twofold increase in the prevalence of substance use disorders in the United States in the past decade, more hospital inpatients can be expected to carry substance use disorder diagnoses, necessitating evaluation of potential links to 30-day unplanned readmissions, a marker of quality of care. This study aimed to measure the association between substance use disorder diagnoses, discharge disposition and 30-day unplanned hospital readmissions.

Design: This retrospective cohort study extracted data from electronic health records of all inpatients. The index admission was defined as a patient's first admission in 2022.

Setting: Two urban, academic medical centers in Los Angeles, California, USA.

Participants: Among 22 108 inpatients aged 18 and over and who did not expire during the hospital stay, 7.4% had at least one substance use disorder. The median age was 58, and 56.1% identified as female. Most patients identified as white (43.3%), followed by 22.5% Hispanic/Latinx, 10.8% Asian and 9.1% Black; 14.3% identified as another race.

Measurements: The exposure was diagnosis of any substance use disorder at index admission. The outcome was 30-day unplanned readmission.

Findings: Patients with any substance use disorder [adjusted risk ratio (aRR) = 1.24, 95% confidence interval (CI) = 1.05-1.45) and patients specifically with opioid use disorder (aRR = 1.40, 95% CI = 1.09-1.80) were more likely to have a 30-day unplanned readmission compared with patients without substance use disorders. When assessing an interaction with discharge disposition, the association only held for patients discharged to home/self-care (aRR = 1.33, 95% CI = 1.05-1.69). Among patients who had zero, one, two and three or more unplanned readmissions, 7.1%, 8.8%, 14.0% and 15.5% had a substance use disorder at their index admission, respectively (P < 0.001).

Conclusions: In the United States, hospital patients with substance use disorder diagnoses appear to have a higher risk of 30-day unplanned readmission to hospital and account for a disproportionate share of patients who have multiple unplanned readmissions than hospital patients without substance use disorder diagnoses.