Bed Occupancy Rates and Hospital-Acquired Clostridium difficile Infection: A Cohort Study

BACKGROUND. An emergent strain (ribotype 027) of Clostridium difficile infection (CDI) has been implicated in epidemics worldwide. Organizational factors such as bed occupancy have been associated with an increased incidence of CDI; however, the data are sparse, and the association has not been widely demonstrated. We investigated the association of bed occupancy and CDI within a large hospital organization in the United Kingdom. OBJECTIVE. To establish whether bed occupancy rates are a significant risk factor for CDI in the general ward setting. METHODS. A retrospective cohort study was carried out on data from 2006 to 2008. Univariate and multivariate Cox regression modeling was used to examine the strength and significance of the associations. Variables included patient characteristics, antibiotic policy exposure, case mix, and bed occupancy rates. RESULTS. A total of 1,589 cases of hospital-acquired CDI were diagnosed (1.7% of admissions), with an overall infection rate of 2.16 per 1,000 patient-days. Median bed occupancy was 93.3% (interquartile range, 83.3%-100%) Univariate and multivariate analyses showed positive and statistically significant associations. In the adjusted model, patients on wards with occupancy rates of 80%-89.9% had rates of CDI that were 56% higher (hazard ratio, 1.56 [95% confidence interval, 1.18-2.04]; P<.001) compared with baseline (0%-69.9% occupancy). CDI rates were 55% higher for patients on wards with maximal bed occupancy (100%). CONCLUSIONS. There is strong evidence of an association between high bed occupancy and CDI. Without effective interventions at high levels of bed occupancy, the economic benefits sought from reducing bed numbers may be negated by the increased risk of CDI.