Hospital Utilization by Substance Use Disorder Subtype and Diagnosis Position Among US Adult Hospitalizations: A National Inpatient Sample Analysis

Objectives: Documented substance use disorders (SUDs) are common among hospitalized adults and contribute to healthcare utilization. We examined factors associated with documented SUDs and evaluated whether hospital length of stay (LOS) and facility costs varied according to SUD diagnosis position and major SUD subtype. Methods: We conducted a cross-sectional study using the 2021 Healthcare Cost and Utilization Project National Inpatient Sample. Documented SUDs were identified using ICD-10-CM codes F10-F16 and F18-F19 in any diagnosis position; tobacco-related disorders (F17) were evaluated in a sensitivity analysis. Survey-weighted regression models examined factors associated with documented SUDs and compared adjusted LOS and inflation-adjusted facility costs by diagnosis position and major SUD subtype. Results: Among 6,666,752 sampled discharges representing 33.3 million US hospitalizations, documented SUDs were identified in 10.8% of hospitalizations. Greater comorbidity burden was the strongest independent predictor of documented SUDs (adjusted OR: 1.49; 95% CI: 1.48–1.49). Secondary-diagnosis SUD hospitalizations had longer adjusted LOS than hospitalizations without documented SUDs, whereas principal-diagnosis SUD hospitalizations had shorter LOS. Opioid-related disorders demonstrated the greatest excess LOS and were the only major subtype associated with higher adjusted facility costs. Conclusions: Hospital utilization varied substantially according to SUD diagnosis position and subtype. Aggregating documented SUDs obscured clinically important differences, particularly among secondary opioid-related disorders. These findings support subtype-specific inpatient addiction medicine strategies.