Background: Hospital crowding is a major challenge facing US health care systems, but few studies have evaluated the association between inpatient occupancy and patient mortality. Our objective was to determine how increasing hospital occupancy is associated with the likelihood of inpatient and 30-day out-of-hospital mortality using a novel measure of inpatient occupancy.
Methods: We conducted a retrospective, observational study using secondary data from the California Office of Statewide Health Planning and Development including non-federal, acute care facilities from 1998-2012. Using measures of relative hospital occupancy, we ran logistic regressions to assess the relationship between increasing hospital occupancy and inpatient mortality and 30-day out-of-hospital mortality among Medicare patients 65 years and older with myocardial infarction, heart failure or pneumonia.
Results: Higher admission day occupancy (odds ratio [OR] = 0.96, 95% confidence interval [CI]: 0.94–0.99) and higher discharge day occupancy (OR = 0.62, 95% CI: 0.60–0.64) were associated with decreased inpatient mortality. Thirty-day out-of-hospital mortality increased with higher discharge day occupancy (OR=1.28, 95% CI: 1.24-1.32), but was unrelated to admission day occupancy.
Conclusions: We found a counterintuitive relationship between admission and discharge day occupancy and inpatient mortality. Higher discharge day occupancy appears to displace deaths into the outpatient setting. Understanding why higher inpatient occupancy is associated with lower overall mortality merits investigation to inform best practices for inpatient care in busy hospitals.