Summary
The strength of the evidence underpinning the association between nurse staffing and patient outcomes has been challenged because studies are typically cross-sectional in design, use hospital-level administrative data that imprecisely allocate staffing to individual patients, and do not account for differences in patients' requirements for nursing care. Other observers have asked whether differences in mortality are linked not to nursing but to unmeasured variables correlated with nurse staffing.
In this study, the authors address these concerns by examining the association between mortality and day-to-day, shift-to-shift variations in staffing at the unit level in a single institution that has lower-than-expected mortality and high average nurse staffing levels and has been recognized for high quality by the Dartmouth Atlas, rankings in U.S. News and World Report, and Magnet hospital designation. In addition, the analysis includes extensive controls for potential sources of an increased risk of death other than nurse staffing.