Licensed nurse staffing and adverse events in hospitals.

Objective: To examine the changes in licensed nursing staff in Pennsylvania hospitals from 1991 to 1997, and to assess the relationship of licensed nursing staff with patient adverse events in hospitals.

Data source: A convenience sample of all Pennsylvania, acute-care, hospitals, 1991 to 1997.

Study design: The study first describes the percentage change of licensed nursing staff categories in Pennsylvania hospitals from 1991 to 1997. Second, random effects Poisson regressions are used to assess the association of the numbers and proportions of licensed nurses with yearly iatrogenic lung collapse, pressure sores, falls, pneumonia, posttreatment infections, and urinary tract infections. Controls are the yearly number of patients, hospital acuity, and other hospital characteristics.

Data collection: Secondary data containing patient- and hospital-level measures from three sources were recoded to establish the incidence of adverse events, aggregated to the hospital level, and merged to form one data set.

Principal funding: Licensed nurses' acuity-adjusted patient load increased from 1991 to 1997. Licensed nurse/total nursing staff declined from 1994 to 1997. Greater incidence of nearly all adverse events occurred in hospitals with fewer licensed nurses. Greater incidence of decubitus ulcers and pneumonia occurred in hospitals with a lower proportion of licensed nurses.

Conclusions: This study suggests that licensed nurses' patient load began increasing in the 1990s. Adequate licensed nurse staffing is important in minimizing the incidence of adverse events in hospitals. Ensuring adequate licensed nurse staffing should be an area of major concern to hospital management. Improved measures of nurse staffing and patient outcomes, and further studies are suggested.