Nurse staffing and adverse patient outcomes.

Abstract

In the past several years, there has been public concern that inadequate nurse staffing may jeopardize the quality of patient care and increase medical errors. In response to this growing concern, this study examined the effects of nurse staffing on adverse events, morbidity, mortality, and medical costs. Using a cross-sectional study design, 232 acute care hospitals in California and the patients they discharged in 1997 were included. Nurse staffing was quantified using four measures: All Hours (hours worked by all nursing personnel per patient day); RN Hours (hours worked by registered nurses per patient day); RN Proportion, (proportion of hours worked by registered nurses); and Contracted Hours (proportion of hours worked by temporary contract nursing personnel). Adverse events included patient falls/injuries, pressure ulcers, adverse drug events, pneumonia, urinary tract infections, wound infections, and sepsis. Multivariate analyses found statistically significant relationships between hospital characteristics and nurse staffing. A greater average nursing intensity that reflects the level of nurse workload was associated with greater All Hours. Medium-sized hospitals (100--299 beds) had the lowest mean All Hours and RN Hours. Investor-owned hospitals used more Contracted Hours than did non-profit hospitals. Patient characteristics (e.g., number of diagnoses, type of admission) significantly affected the occurrence of adverse events. Among the seven adverse events studied, nurse staffing had a significant inverse relationship only with pneumonia. An increase of one RN Hour was associated with an 8.9% decrease in the predicted odds of pneumonia. Similarly, a 10% increase in RN Proportion corresponded to a 9.5% decrease in the odds of pneumonia. Having each adverse event was associated with a significantly prolonged length of stay and increased medical costs. Patients who had pneumonia, wound infection or sepsis had a greater probability of death during hospitalization. Having pneumonia was associated with a 1.74-fold increase in length of stay, a 3.39-fold increase in the odds of mortality, and a 1.84-fold increase in costs. These findings suggest that patients are experiencing avoidable, preventable adverse events during hospitalization. Hospitals and nurses, as patient advocates, need to develop safe care systems to reduce adverse events and their consequences.