Injurious Assault Rates on Inpatient Psychiatric Units: Associations With Staffing by Registered Nurses and Other Nursing Personnel.
The study examined associations between staffing levels by registered nurses (RNs) and non-RNs on psychiatric units and the rate of injurious assaults against hospital personnel, the rate of injurious assaults against other patients, and the total rate of injurious assaults. Generalized mixed models were used to analyze 2011-2013 data from 461 adult inpatient psychiatric units in 327 U.S. hospitals. Monthly data were aggregated to the unit level. The analyses considered RN and non-RN hours per patient day (HPPD) as linear and nonlinear predictors of the three assault rates, controlling for hospital ownership, size, and teaching status. Both staffing variables had statistically significant linear associations with assault rates. Higher values of HPPD for non-RNs were associated with a higher rate of assaults against hospital personnel (exp[B]=1.23), a higher rate of assaults against patients (exp[B]=1.31), and a higher total rate of injurious assaults (exp[B]=1.21). Higher values of HPPD for RNs were associated with a higher rate of assaults against hospital personnel (exp[B]=1.11) and a lower rate of assaults against patients (exp[B]=.81). This is the largest published study to date of the association between psychiatric unit staffing and violence and the first to examine separately assaults against hospital personnel and assaults against patients in relation to staffing. Results confirm and qualify previous findings of a positive staffing-violence association. Injurious assaults against hospital personnel and against patients have different associations with nurse staffing and should be studied as separate phenomena with different causes.