California's Minimum Nurse Staffing Legislation: Results from a Natural Experiment

Objective To determine whether, following implementation of C alifornia's minimum nurse staffing legislation, changes in acuity‐adjusted nurse staffing and quality of care in C alifornia hospitals outpaced similar changes in hospitals in comparison states without such regulations. Data Sources/Study Setting Data from the A merican H ospital A ssociation A nnual S urvey of H ospitals, the C alifornia O ffice of S tatewide H ealth P lanning and D evelopment, the H ospital C ost R eport I nformation S ystem, and the A gency for H ealthcare R esearch and Q uality's H ealth C are C ost and U tilization P roject's S tate I npatient D atabases from 2000 to 2006. Study Design We grouped hospitals into quartiles based on their preregulation staffing levels and used a difference‐in‐difference approach to compare changes in staffing and in quality of care in C alifornia hospitals to changes over the same time period in hospitals in 12 comparison states without minimum staffing legislation. Data Collection/Extraction Methods We merged data from the above data sources to obtain measures of nurse staffing and quality of care. We used A gency for H ealthcare R esearch and Q uality's P atient S afety I ndicators to measure quality. Principal Findings With few exceptions, C alifornia hospitals increased nurse staffing levels over time significantly more than did comparison state hospitals. Failure to rescue decreased significantly more in some C alifornia hospitals, and infections due to medical care increased significantly more in some C alifornia hospitals than in comparison state hospitals. There were no statistically significant changes in either respiratory failure or postoperative sepsis. Conclusions Following implementation of C alifornia's minimum nurse staffing legislation, nurse staffing in C alifornia increased significantly more than it did in comparison states' hospitals, but the extent of the increases depended upon preregulation staffing levels; there were mixed effects on quality.