By the Numbers: New Aiken Study Highlights Benefits of California’s Nurse-to-Patient Ratios

By Marcia Faller, RN, PhD, senior vice president and chief clinical officer, AMN Healthcare

May 5, 2010 - What if there were a way to lower your hospital’s mortality rate by as much as 14 percent while improving job satisfaction and retention rates among your largest group of employees? There is, according to new research, and it doesn’t involve investing in new technology, revamping facilities or hiring outside consultants.

It is a relatively straightforward formula related to how many nurses you have caring for how many patients.

Some of the livelier discussions about healthcare quality in recent years have centered on the subject of nurse staffing: specifically, whether government should be mandating the minimum nurse-to-patient ratios for various units in acute care hospitals. Managing workloads based on patient acuity and common sense are all that is needed, some have said, while others have argued for state legislatures to get involved to ensure patients get the care and attention they need and nurses are not overworked.

In 2004, California became the first state to implement minimum nurse-to-patient staffing requirements in hospitals. Now, the latest study from Linda Aiken, RN, Ph.D., FAAN, and her team at the Center for Health Outcomes and Policy Research at the University of Pennsylvania, School of Nursing has shown that these lower ratios could save a significant number of lives if observed in other states. (See "Saving Lives" sidebar below for a comparison on ratios.) The researchers also found that the reduced workload in California created positive outcomes for nurses who are then more likely to stay on the job.

The research study involved 2006 survey data collected from practicing hospital nurses and patient outcome information, including 30-day inpatient mortality and failure-to-rescue rates, drawn from state hospital databases in California, New Jersey and Pennsylvania.

Here are some statistics worth noting:  

  • 22,336 nurses – the final number of nurses surveyed for the research study, working in 604 adult nonfederal acute care hospitals in the three states; 94 percent were staff nurses, 6 percent were frontline nurse managers or assistant managers/supervisors, and 1 percent were nursing administrators or higher level supervisors
  • 1:2 – the minimum nurse-to-patient ratio in California ICUs in 2006; other mandated ratios included 1:3 in labor and delivery; 1:4 in pediatrics; 1:5 in med/surg, telemetry (lowered to 1:4 in 2008) and oncology; and 1:6 in psychiatric units
  • 1 less patient per nurse - two years after the staffing law went into effect, California hospital nurses cared for one less patient on average than nurses in New Jersey and Pennsylvania
  • 2 less patients in med/surg - in medical and surgical units, California nurses averaged over two fewer patients each than their counterparts in New Jersey, and 1.7 fewer patients than nurses in Pennsylvania
  • 11 percent and 14 percent drops in mortality – based on a sophisticated analysis of real data, the researchers estimated that Pennsylvania hospitals would have had 11 percent fewer deaths and New Jersey would have had 14 percent fewer deaths among surgical patients during the 2004-2006 period if they had observed the same nurse-to-patient ratios as those mandated in California.
  • 486 deaths that may have been prevented - the estimated drop in mortality rates equaled 486 lives that might have been saved in New Jersey and Pennsylvania in just two years, from 2004-2006, if their med/surg units had observed the lower ratios.

The 486 deaths that might have been avoided represent a significant number of surgical patients, especially if you consider that was in just two states over two years’ time. By using simple multiplication we can quickly figure out that, if the averages held true in the other 47 states, these lower nurse-to-patient ratios would amount to several thousand lives saved in the United States every year.

Not surprisingly, Aiken and her team also found that the nurses with lower workloads reported better evaluations of their work environment. Higher percentages of the nurses working in California reported that they had reasonable workloads with consistent breaks, they received substantial support, and there were enough nurses during their shifts to get their work done and provide high-quality care. A smaller percentage of nurses in California than in the other two states indicated that their workloads caused them to miss changes in patient conditions.

Most California staff nurses, supervisors and managers agreed that the legislation had produced its intended effects regarding quality of care, nurse workloads, nurse retention, and the relative attractiveness of employment in California hospitals.

This latest study adds to growing evidence of the link between increased nurse staffing and better patient outcomes. For instance, a 2002 Aiken team study found that each patient added to a nurses’ workload was associated with a 7 percent increase in mortality following common surgeries. That study also found that nurse burnout and job dissatisfaction, which add to nurse turnover, increased significantly as nurses’ workloads increased. These findings were soon replicated in other studies. In 2007, a meta-analysis of 90 studies commissioned by the Agency for Healthcare Research and Quality (AHRQ) concluded that there is a clear association between nurse staffing and patient outcomes.

What now?  

How seriously should healthcare providers take these kinds of study results? Should hospitals wait to increase nursing staff when and if their state insists that they do? Or will some hospitals decide it is a matter of corporate responsibility and become accountable for pushing through lower ratios on their own?

Some hospitals already maintain nurse-to-patient ratios at recommended levels. When California enacted their staffing law in 2004, for example, just over half of the hospitals in the state were already found to be in compliance with the mandated ratios. Two years later, according to the data from this study, the vast majority were found to be in compliance.

With the country’s growing emphasis on quality and safety ratings, plus reimbursement cuts due to avoidable errors, there are already substantial reasons for hospitals outside of California to consider increasing their nursing staff to meet these benchmark ratios.

Now, with the added evidence of the lives that could be saved, it is time to act.


Saving Lives: An Apples and Oranges Comparison  

Consider all of the media attention and lawsuits in recent months involved with the lives lost to specific automobile safety issues. As of early March 2010, the U.S. National Highway Traffic Safety Administration had received 52 reports of deaths across the country possibly connected to problems with unintended acceleration in Toyota vehicles since 2000. These reports have contributed to a nationwide recall of 8.5 million vehicles and billions of dollars in losses to the country’s top automaker.

By comparison, more than nine times that many lives – an estimated 486 surgical patients – might have been saved in just two years in just two states (New Jersey and Pennsylvania) with lower nurse-to-patient ratios like those mandated in California, based on the latest study from the Center for Health Outcomes and Policy Research (see main article).


See related story: National Study Shows Temporary Nurses Deliver Quality Care