The Association of Inpatient Occupancy with Hospital-Acquired Clostridium difficile Infection

Few studies have evaluated the relationship between high hospital occupancy and hospital-acquired complications. We evaluated the association between inpatient occupancy and hospital-acquired Clostridium difficile infection (CDI) using a novel measure of hospital occupancy. We analyzed administrative data from California hospitals from 2008-2012 for Medicare recipients aged 65 years with a discharge diagnosis of acute myocardial infarction, heart failure, or pneumonia. Using daily census data, we constructed patient-level measures of occupancy on admission day and average occupancy during hospitalization (range: 0-1), which were split into 4 groups. We used logistic regression with cluster standard errors to estimate the adjusted and unadjusted relationship of occupancy with hospital-acquired CDI. Across 327 hospitals, 558,344 discharges met our inclusion criteria. Higher admission day occupancy was associated with significantly lower adjusted likelihood of CDI. Compared to the 0-0.25 occupancy group, patients admitted on a day of 0.51-0.75 occupancy had 0.86 odds of CDI (95% CI 0.75-0.98). The 0.76-1.00 admission occupancy group had 0.87 odds of CDI (95% CI 0.75-1.01). With regard to average occupancy, intermediate levels of occupancy 0.26-0.50 (odds ratio [OR] = 3.04, 95% CI 2.33-3.96) and 0.51-0.75 (OR = 3.28, 95% CI 2.51-4.28) had over 3-fold increased adjusted odds of CDI relative to the low occupancy group; the high occupancy group did not have signifcantly different odds of CDI compared to the low occupancy group (OR = 0.96, 95% CI 0.70-1.31). These findings should prompt exploration of how hospitals react to occupancy changes and how those care processes translate into hospital-acquired complications in order to inform best practices.