Inpatient Addiction Medicine Consultation Service Impact on Post-discharge Patient Mortality: a Propensity-Matched Analysis.

BACKGROUND: Inpatient addiction medicine consultation services (AMCS) have grown rapidly, but there is limited research of their impact on patient outcomes. OBJECTIVE: To examine whether AMCS is associated with all-cause mortality and hospital utilization post-discharge. DESIGN: This was a propensity-score-matchedcase-control study from 2018 to 2020. PARTICIPANTS: The intervention group included patients referred to the AMCS from October 2018 to March 2020. Matched control participants included patients hospitalized from October 2017 to September 2018 at an urban academic hospital with a large suburban and rural catchment area. MAIN MEASURES: The effect of treatment was estimated as the difference between the proportion of subjects experiencing the event (7-day and 30-day readmission, emergency department visits, and mortality within 90 days) for each group in the matched sample. KEY RESULTS: There were 711 patients in the intervention group and 2172 patients in the control group. The most common substance use disorders among the intervention group were primary alcohol use disorder (n=181; 25.5%) and primary opioid use disorder (n=175, 24.6%) with over a third with polysubstance use (n=257, 36.1%). Intervention patients showed a reduction in 90-day mortality post-hospital discharge (average treatment effect [ATE]: -2.35%, 95% CI: -3.57, -1.13; p-value <0.001) compared to propensity-matched controls. We found a statistically significant reduction in 7-day hospital readmission by 2.15% (95% CI: -3.65, -0.65; p=0.005) and a nonsignificant reduction in 30-day readmission (ATE: -2.38%, 95% CI: -5.20, 0.45; p=0.099). There was a statistically significant increase in 30-day emergency department visits (ATE: 5.32%, 95% CI: 2.19, 8.46; 0.001) compared to matched controls. CONCLUSIONS: There was a reduction in 90-day all-cause mortality for the AMCS intervention group compared to matched controls, although the impact on hospital utilization was mixed. AMCS are systems interventions that are effective tools to improve patient health and reduce all-cause mortality.