Will Mandatory Nurse Staffing Ratios Lead to Better Patient Outcomes in Hospitals?
- Presenter:
Chair: Sally Stearns; Discussant: David Grabowski Tue June 6, 2006 13:45-15:15 Room 325
U.S. Congress require mandatory minimum nurse staffing ratios in hospitals, and are motivated by several prominent cross-sectional studies reporting significant associations between higher nurse staffing levels and better patient outcomes. Yet legislating arbitrary mandatory nurse staffing ratios for all hospitals on the basis of evidence from cross-sectional studies without knowing if and when changing the staffing levels to meet such ratios improves outcomes could result in an inefficient allocation of resources that may or may not improve quality. Using 1991-2003 panel data from California hospitals, which are broadly representative of hospitals nationally, this study pursues the following aims: (1) determining whether increasing nurse staffing improves patient outcomes, (2) characterizing the marginal benefit of increasing staffing, and (3) identifying subgroups of hospitals that benefit the most from increasing staffing levels. Staffing measures include patients-per-nurse ratios for RNs, LVNs, and nurse aides, as well as RN skill mix (i.e., the percent of nursing personnel that are RNs). Four inpatient quality indicators—30-day mortality among patients with a principal diagnosis of acute myocardial infarction, stroke, hip fracture, or gastro-intestinal hemorrhage—and two patient safety indicators—failure-to-rescue rate and rates of post-operative pulmonary embolism or deep vein thrombosis among general and orthopedic surgical patients—that are from AHRQ’s inventory of quality indicators will serve as outcome measures. We use multivariate regression analyses to determine whether changes in nurse staffing over this twelve year period contributed to changes in patient outcomes. We control for differences in the mix of patients across hospitals using validated and well-established severity-adjustment methods, and for secular changes over time that could influence overall staffing levels. We characterize the marginal benefit of staffing increases by examining whether the returns to quality diminish as staffing levels increase and whether there are thresholds in the relationship between staffing and outcomes. Stratified analyses of subgroups of hospitals are undertaken to identify hospitals demonstrating the greatest improvement in outcomes with changes in nurse staffing. We employ standard panel data techniques of fixed or random effects as appropriate and correct standard errors to account for clustering of patients within hospitals. This study extends prior work through its longitudinal design, its use of refined measures of nurse staffing uniquely available in California and nurse sensitive outcome measures from AHRQ’s quality indicators, and its thorough examination of the marginal benefit of increasing nurse staffing across all and subgroups of hospitals. The findings will help to explicate the quality and cost implications of increasing nurse staffing in hospitals and guide payers and policy makers on the development of strategies to achieve their quality goals.
