California's minimum nurse staffing legislation: results from a natural experiment.

In 1999, California became the first state in the United States to pass legislation requiring minimum nurse-to-patient staffing ratios in acute care hospitals. The legislation, for which nursing unions were outspoken advocates, was, in part, a response to a reported decline in hospitals' nurse staffing and skill mix induced by pressures from increasing managed care penetration. California Assembly Bill (AB 394) required the California State Department of Health Services to establish unit-specific minimum staffing levels for licensed nurses (registered nurses [RNs] and licensed vocational nurses [LVNs]) in acute care hospitals. The draft regulations were released in January 2002 and, after a period of highly contentious public comment, implemented in January 2004. The ratios were phased beginning January 1, 2004, the staffing ratio for medical-surgical areas was set at 1 : 6; in March 2005, the ratio was enriched to 1 : 5. In 2008, additional specialty units were subject to the regulations. Up to 50 percent of licensed nursing hours could be provided by LVNs (Spetz 2004). Studies have concluded that the legislation led to increases in nurse staffing (Donaldson et al. 2005; Spetz et al. 2009; Aiken et al. 2010; Donaldson and Shapiro 2010; Serratt et al. 2011; Cook et al. 2012). McHugh et al. (2011) found that California hospitals increased their nurse staffing significantly more after the legislation than did hospitals in other states and did not simultaneously reduce their skill mix—the ratio of RNs to total nursing staff. However, their study included hospitals in states that had adopted other approaches, for example, hospital-specific staffing requirements, public reporting of nurse staffing, potentially minimizing the extent to which the effects of the legislation could be seen (American Nurses Association [ANA] 2011). Although these studies demonstrated improvements in aggregate RN staffing, due to wide variability in hospitals' prelegislation staffing levels, it is likely that there were heterogeneous hospital responses to the regulations based on their prelegislation staffing levels, and that some hospitals met “minimum” requirements by differentially increasing their use of LVN/LPNs. The conclusions of research investigating whether quality improved following the legislation are mixed (Donaldson and Shapiro 2010). Neither Donaldson et al. (2005) nor Bolton et al. (2007) found significant decreases in falls, decubitus ulcers, or restraint use following implementation of the regulations. Using the Agency for Healthcare Research and Quality's (AHRQ) Patient Safety Indicators (PSIs), Spetz et al. (2009) found no significant improvement in postoperative sepsis, deep vein thrombosis, decubitus ulcers, mortality following pneumonia, or failure to rescue (FTR, death following a complication). Cook et al. (2012), using a panel of California hospitals from 2000 to 2006, found no statistically significant decrease in FTR or decubitus ulcers following implementation of the ratios, and Aiken et al. (2010), using cross-sectional data from California, New Jersey, and Pennsylvania, concluded that hospitals with staffing levels consistent with those mandated in California had significantly better nurse-reported quality and lower levels of mortality and FTR. More recently, Spetz et al. (2011), also using data from California hospitals from 2000 to 2006, found statistically significant decreases in postoperative respiratory failure and pressure ulcers, but no reductions in FTR or selected infections due to medical care, postoperative pulmonary embolism, or deep vein thrombosis. Finally, a trend analysis of state snapshots in AHRQ's most recent National Health Care Quality Report (http://www.ahrq.gov/qual/measureix.htm#quality) reveals that, from 2000 to 2007, overlapping the period of our study, rates of postoperative sepsis and infections due to medical care increased significantly more in California than in 25 other states (authors' unpublished analysis, 2012; see Appendix Table 1). However, the conclusions of these studies are limited by convenience sampling, cross-sectional designs, and failure to use a measure of nurse staffing that takes account of patients' needs for nursing care. Table 1 Variable Means (Standard Deviations) for California and Comparison States, by Preregulation Staffing Quartile* We address these concerns by relying on the natural experiment provided by the passage of California's minimum nurse staffing legislation and using a large panel of hospitals within a before-after comparison group design. We develop measures of acuity-adjusted nurse staffing, using Nursing Intensity Weights (NIWs) (ANA1997; ANA 2000; Needleman et al. 2002; Mark and Harless 2011) that provide a more accurate measure of staffing relative to patient need. We examined the following research questions: Following implementation of the nurse staffing legislation, did acuity-adjusted nurse staffing increase significantly more in California hospitals than in hospitals in comparison states? Did some California hospitals, especially those most affected by the staffing regulations, rely more on LVNs to meet the minimum staffing requirements than other hospitals? If California hospitals increased their acuity-adjusted nurse staffing significantly more than hospitals in comparison states, did quality of care improve significantly more in California hospitals than in hospitals in comparison states?