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What’s New in the Patient Safety World

January 2022

Another Striking Nurse Staffing Study



We’ve often cited the work of Linda Aiken and colleagues, who have demonstrated that patient outcomes are better with stronger nurse:patient ratios and higher educational levels of nursing staffing. They found that each additional patient per nurse was associated with a 7% increase in the likelihood of dying within 30 days of admission and a 7% increase in the odds of failure-to-rescue (Aiken 2002), and a 10% increase in the proportion of nurses holding a bachelor's degree was associated with a 5% decrease in the likelihood of patients dying within 30 days of admission and the odds of failure to rescue for surgical patients (Aiken 2003).


A study in the UK (Griffiths 2018) looked at in-hospital mortality in relation to nursing staffing, comparing those with staffing levels above to those below the mean staffing level. They found the hazard of death was increased by 3% for every day a patient experienced RN staffing below the ward mean. Each additional hour of RN care available over the first 5 days of a patient’s stay was associated with 3% reduction in the hazard of death. And days where admissions per RN exceeded 125% of the ward mean were associated with an increased hazard of death (aHR 1.05). Although low nursing assistant staffing was associated with increases in mortality, high nursing assistant staffing was also associated with increased mortality.


Once again, Aiken and her colleagues from the University of Pennsylvania recently analyzed nursing staffing patterns in 87 acute care hospitals in the state of Illinois (Lasater 2021). They assessed patient:nurse ratios via nurse responses to a survey and correlated those with mortality and length-of-stay (LOS) data on Medicare patients.


They found that patient-to-nurse staffing ratios on medical-surgical units varied substantially (from 4.2 to 7.6). After adjusting for hospital and patient characteristics, the odds of 30-day mortality for each patient increased by 16% for each additional patient in the nurse’s average workload. In addition, the odds of staying in the hospital a day longer at all intervals increased by 5% for each additional patient in the nurse’s workload.


Illinois is one of the several states in which legislation to mandate patient-to-nurse staffing ratios is actively being debated. Apparently, a 4:1 patient per nurse ratio is being proposed in the legislation. The authors calculate that, if study hospitals staffed at a 4:1 ratio during the 1-year study period, more than 1595 deaths would have been avoided and hospitals would have collectively saved over $117 million.


Nurses responding to the survey in the current study also reported safety concerns related to the number of patients they cared for during their last shift. Over half (51.2%) of nurses reported that their patient assignment during their last shift exceeded the number they assessed they could safely care for. Two-thirds of nurses (67.0%) who were assigned 6 or more patients assessed that workload was unsafe. On the other hand, 82.7% of nurses who were assigned four or fewer patients assessed that patient assignment constituted a safe workload.


We’ve long been supporters of legislation that improves nursing staffing. But the issue is more complex than simple patient:nurse ratios. Those ratios do not take into account actual nurse workload nor do they take into account the fatigue factor that may accompany long work shifts or forced overtime. Even a 4:1 patient:nurse ratio may be too high if the intensity of patient care needed is excessive or the nurses are too fatigued to deliver all necessary care. One factor that comes into play in those conditions is the concept of “missed nursing care” or “care left undone” (see our Patient Safety Tips of the Week for November 26, 2013 “Missed Care: New Opportunities?” and May 9, 2017 “Missed Nursing Care and Mortality Risk”). We discussed the issue of nursing workload in detail in our Patient Safety Tips of the Week for March 6, 2018 “Nurse Workload and Mortality” and May 29, 2018 “More on Nursing Workload and Patient Safety”. In those columns we discussed the issue of how to best measure workload and match nursing staffing levels to that workload.


But, for the time being, the patient:nurse ratio is probably a reasonable focus. There are now multiple studies linking high patient:nurse ratios to increased mortality and other adverse patient outcomes. The studies suggest that not only are better nurse staffing ratios better for our patients, but they would likely improve hospital bottom lines as well.


Unfortunately, the near future does not bode well for improving patient:nurse ratios. The COVID-19 pandemic has taken its toll on the nursing profession in addition to virtually all other healthcare worker categories. Burnout, retirements, and shifts to other venues has already impacted hospital nursing staffing and the shortage is likely to worsen soon.


In our September 1, 2020 Patient Safety Tip of the Week “NY State and Nurse Staffing Issues” we noted another article by Lasatar et al. (Lasater 2020). They were actually collecting survey data in New York and Illinois just prior to the first COVID-19 wave. They found that over half the nurses in both states experienced high burnout. Half gave their hospitals unfavorable safety grades and two-thirds would not definitely recommend their hospitals. One-third of patients rated their hospitals less than excellent and would not definitely recommend it to others. After adjusting for confounding factors, each additional patient per nurse increased odds of nurses and per cent of patients giving unfavorable reports; odds ratio’s ranged from 1.15 to 1.52 for nurses on medical-surgical units and from 1.32 to 3.63 for nurses on intensive care units. Their conclusion was that hospital nurses were already burned out and already working in understaffed conditions in the weeks prior to the first wave of COVID-19.


Co-author of the current study Linda Aiken seems to be more optimistic, stating “This independent scientific study shows that setting a quality standard for nurse staffing in hospitals is in the public’s interest. And there are plenty of nurses to take good jobs in hospitals with the nation’s nursing schools producing an all-time high of over 180,000 new nurses every year.” (UPenn 2021). Indeed, the American Association of Colleges of Nursing reported that student enrollment in baccalaureate, master’s, and doctoral nursing programs increased in 2020 despite concerns that the pandemic might diminish interest in nursing careers (AACN 2021). In programs designed to prepare new registered nurses (RNs) at the baccalaureate level, enrollment increased by 5.6% with 251,145 students now studying in these programs nationwide.


Once again, the new study demonstrates that improving the patient:nurse ratio can have a beneficial effect on both patient safety and outcomes and economically feasible.



Some of our other columns on nursing workload and missed nursing care/care left undone:


November 26, 2013    Missed Care: New Opportunities?

May 9, 2017                Missed Nursing Care and Mortality Risk

March 6, 2018             Nurse Workload and Mortality

May 29, 2018              More on Nursing Workload and Patient Safety

October 2018               Nurse Staffing Legislative Efforts

February 2019             Nurse Staffing, Workload, Missed Care, Mortality

July 2019                    HAI’s and Nurse Staffing

September 1, 2020      NY State and Nurse Staffing Issues

February 9, 2021         Nursing Burnout

August 2021               The New NY State Law on Nursing Staffing






Aiken LH, Clarke SP, Sloane DM, et al. Hospital Nurse Staffing and Patient Mortality, Nurse Burnout, and Job Dissatisfaction. JAMA 2002; 288(16): 1987-1993



Aiken LH, Clarke SP, Cheung RB, et al. Educational levels of hospital nurses and surgical patient mortality. JAMA 2003; 290(12): 1617-1623



Griffiths P, Maruotti A, Recio Saucedo A, et al. on behalf of the Missed Care Study Group. Nurse staffing, nursing assistants and hospital mortality: retrospective longitudinal cohort study. BMJ Qual Saf 2018; Published Online First: 04 December 2018



Lasater KB, Aiken LH, Sloane D, et al. Patient outcomes and cost savings associated with hospital safe nurse staffing legislation: an observational study. BMJ Open 2021; 11: e052899



Lasater KB, Aiken LH, Sloane DM, et al. Chronic hospital nurse understaffing meets COVID-19: an observational study. BMJ Quality & Safety 2020; Published Online First: 18 August 2020



University of Pennsylvania School of Nursing. News Release “Illinois nurse staffing legislation predicted to reduce hospital deaths and improve care“; EurekAlert 2021’ News Release 8-Dec-2021



AACN (American Association of Colleges of Nursing). Student Enrollment Surged in U.S. Schools of Nursing in 2020 Despite Challenges Presented by the Pandemic. AACN News Release 2021; Published April 01, 2021





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