Deviations in Monthly Staffing and Injurious Assaults Against Staff and Patients on Psychiatric Units

It is widely thought that low staffing levels are associated with higher risk of psychiatric inpatient violence. The purpose of this study was to determine whether odds of an injurious assault are higher in months in which unit staffing levels are higher or lower relative to unit average, using a design allowing each unit to serve as its own control. Using 2011-2013 National Database of Nursing Quality Indicators data from 480 adult and 90 geriatric units in 361 US hospitals, monthly assault odds were modeled as functions of unit staffing. Monthly RN and non-RN staffing (hours per patient day) were categorized as very low, low, average, high, or very high, based on deviation from the unit's average staffing across study months. Endpoints were binary indicators for one or more injurious assaults against staff during the month and for one or more injurious assaults against patients during the month. Despite large sample sizes, neither RN nor non-RN staffing was a statistically significant predictor of odds of assault, nor was there a consistent trend of odds of assault being higher at below- or above-average staffing levels. There was little evidence that monthly deviation in unit staffing is associated with the odds of an injurious assault on a unit. This suggests that staffing-assault rate associations in previous studies of monthly data are largely attributable to between-unit rather than within-unit staffing differences. Hospitals may need to look beyond below- or above-average nurse staffing as a cause of assaults. © 2016 Wiley Periodicals, Inc.