Multimorbidity and Inpatient Utilization Among Older Adults with Opioid Use Disorder in New York City

Background: Nationally, there is a sharp increase in older adults with opioid use disorder (OUD). However, we know little of the acute healthcare utilization patterns and medical comorbidities among this population.

Objective: This study describes the prevalence of chronic conditions, patterns of inpatient utilization, and correlates of high inpatient utilization among older adults with OUD in New York City (NYC).

Design: Retrospective longitudinal cohort study.

Participants: Patients aged ≥55 with OUD hospitalized in NYC in 2012 identified using data from New York State's Statewide Planning and Research Cooperative System (SPARCS).

Main measures: The prevalence of comorbid substance use diagnoses, chronic medical disease, and mental illness was measured using admission diagnoses from the index hospitalization. We calculated the ICD-Coded Multimorbidity-Weighted Index (MWI-ICD) for each patient to measure multimorbidity. We followed the cohort through September 30, 2015 and the outcome was the number of rehospitalizations for inpatient services in NYC. We compared patient-level factors between patients with the highest use of inpatient services (≥7 rehospitalizations) during the study period to low utilizers. We used multiple logistic regression to examine possible correlates of high inpatient utilization.

Key results: Of 3669 adults aged ≥55 with OUD with a hospitalization in 2012, 76.4% (n=2803) had a subsequent hospitalization and accounted for a total of 22,801 rehospitalizations during the study period. A total of 24.7% of the cohort (n=906) were considered high utilizers and had a higher prevalence of alcohol and cocaine-related diagnoses, congestive heart failure, diabetes, schizophrenia, and chronic obstructive pulmonary disease. Multivariable predictors of high utilization included being a Medicaid beneficiary (adjusted odds ratio [aOR]=1.70, 95% confidence interval [CI]=1.37-2.11), alcohol-related diagnoses (aOR=1.43, 95% CI: 1.21-1.69), and increasing comorbidity measured by MWI-ICD (highest MWI-ICD quartile: aOR=1.98, 95% CI=1.59-2.48).

Conclusions: Among older adults with OUD admitted to the hospital, multimorbidity is strongly associated with high inpatient utilization.