Patient safety including mortality

The fundamental importance of having enough registered nurses present to deliver care is well supported by evidence. Lower registered nurse staffing levels are associated with higher risks to patients and poorer quality care. This has been known for decades and there have been many, many studies that demonstrate the relationship, including systematic reviews._{^{i, ii, iii, iv}}

A key paper published in the Lancet (using European data) reported that an increase in a registered nurses’ workload by one patient increased the likelihood of an inpatient dying by 7%.^v  Hospitals with a larger proportion of degree-educated nurses also had lower case mix adjusted mortality rates.

In the wake of the Francis Inquiry, which found that patient safety risks associated with low registered nurse staffing levels had not been considered in the decision to reduce the number of nursing posts at Mid-Staffordshire Trust, NICE produced guidelines for safe nurse staffing in adult inpatient settings. It said:

“There is no single nursing staff-to-patient ratio that can be applied across all acute adult inpatient wards. However … there is evidence of increased risk of harm associated with a registered nurse caring for more than 8 patients.”

NHS Improvement subsequently commissioned University of Southampton to summarise the evidence that had supported the guidelines. One of the concerns identified about the evidence base at that time^vi was the reliance on cross-sectional studies. While these ‘observational’ studies show that lower nurse staffing levels were correlated with worse outcomes, correlation does not equate to causation. There was the possibility that another factor explained both things observed (the staffing levels and the outcomes).

Needleman’s groundbreaking study^vii addressed criticisms of previous research. Their study adjusted for many of these other factors and included direct measurement of individual patients' exposure to staffing levels. They demonstrated that adverse outcomes followed exposure to lower staffing – supporting the theory that low registered nurse staffing is responsible for higher rates of avoidable mortality.

Why? Studies examining missed care show that when registered nurse staffing levels are low, more care is missed. And crucially, when more care is missed, a larger number of patients die (even when adjusting for case mix).  Each 10% increase in missed care is associated with a 16% increase in risk of death.^viii  So we have a clear theoretical pathway that explains how it is that low registered nursing staffing levels lead to compromised care and higher risk of avoidable patient deaths.

Since then, more longitudinal studies have been undertaken, strengthening the evidence base further, and showing that worse outcomes arise after patients are exposed to lower RN staffing levels. A recent review of these studies^ix concluded: “Having more registered nurses on hospital wards is causally linked to reduced mortality – new review shows there is little room for doubt.”

Cost effectiveness and workforce planning

Ensuring there are adequate levels of registered nurse staffing does not just reduce adverse outcomes, but there is evidence that it is cost effective.  A recent review^x of the evidence reported:

“In an era of registered nurse scarcity, these results favour investment in registered nurse supply as opposed to using lesser qualified staff as substitutes, especially where baseline nurse staffing and skill mix are low.”

Similarly, Needleman^xi concluded: “efforts to substitute registered nurses with other lesser-skilled staff, such as nursing assistants, ultimately cost more in longer lengths of stay than is saved in staffing costs.”

So, what has happened to nurse staffing since the Francis Inquiry, more than10 years ago? Following the NICE guidance and safe staffing initiatives, chief nurses reported that Trust boards not only had a better understanding of the importance of nurses staffing but were committed to improving staffing levels. And use of the NICE-endorsed tools to plan staffing, made evidence the numbers needed. However, growth in registered nurse staff employed in acute trusts was constrained by trusts’ inability to fill posts due to an ongoing national shortage of registered nurses.

The nursing workforce deficits created by underinvestment in domestic supply have been long-lasting – vacancy levels have been around 10% for over a decade. Responding to the crisis in 2019, the government took unprecedented action, launching an initiative to recruit 50,00 more registered nurses into the NHS in England by 2024. This target was achieved, but with a heavy reliance on international recruitment. The long-awaited NHS Long Term Workforce Plan indicated that this was just the beginning – the NHS was going to need to continue to radically grow its nursing workforce to keep up with demand.

And yet, in 2025 we are hearing reports of nursing posts being frozen – how can this be? At a time when we know we have a shortage of nurses, too few in post and too few in the system, we are curtailing workforce growth? Are we once again at risk, this time national, of financial pressures shaping the nursing workforce, without consideration of the risks to patient care?

Our next steps

The RCN sees all too clearly the immense pressure nursing workforce challenges place on every part of the system. Insufficient registered nurses on shift places front line nurses under daily pressure, experiencing moral injury and burnout, as they compromise care or compromise themselves. Equally, chief nurses are faced with impossible scenarios of running nursing services with insufficient registered nurses and being pressured to find savings.

The RCN has a duty to uphold standards in nursing, support all members of the nursing team and lead the way towards safe and effective care. In relation to safe staffing, the RCN Nursing Workforce Academy (launched as part of the RCN Institute of Nursing Excellence) is leading the way by:

• Launching refreshed nursing workforce standards, making explicit what we see as the fundamentals needed to underpin safe and effective care delivery.
• Sharing the evidence on safe staffing (this article has highlighted some key references, but a more formal summary of the evidence is being produced).
• Bringing together the nurse staffing guidance that exists for each specialty and making explicit where there are recommended registered nurse to patient ratios.
• Taking forward the RCN’s commitment to ‘safety critical redlines’ – minimum nurse to patient ratios to protect patients and staff from harm caused by low registered nurse staffing levels.
• Our forthcoming ‘nest’ community platform will offer all relevant resources, latest publications and networking opportunities.

Other resources

A consensus development project set out what is known about nurse staffing, and what further action is needed to make safe and effective staffing a reality.^xii  For a reflective overview on the evidence and its significance to enabling quality, see the book chapter, published by THIS Institute.^xiii  

References

1. Shin, S., Park, J.H. and Bae, S.H., 2018. Nurse staffing and nurse outcomes: A systematic review and meta-analysis. Nursing outlook, 66(3), pp.273-282.
2. Kane, R.L., Shamliyan, T.A., Mueller, C., Duval, S. and Wilt, T.J., 2007. The association of registered nurse staffing levels and patient outcomes: systematic review and meta-analysis. Medical care, 45(12), pp.1195-1204
3. Griffiths, P., Recio‐Saucedo, A., Dall'Ora, C., Briggs, J., Maruotti, A., Meredith, P., Smith, G.B., Ball, J. and Missed Care Study Group, 2018. The association between nurse staffing and omissions in nursing care: A systematic review. Journal of advanced nursing, 74(7), pp.1474-1487.
4. Lankshear, A.J., Sheldon, T.A. and Maynard, A., 2005. Nurse staffing and healthcare outcomes: a systematic review of the international research evidence. Advances in nursing science, 28(2), pp.163-174.
5. Aiken, L.H., Sloane, D.M., Bruyneel, L., Van den Heede, K., Griffiths, P., Busse, R., Diomidous, M., Kinnunen, J., Kózka, M., Lesaffre, E. and McHugh, M.D., 2014. Nurse staffing and education and hospital mortality in nine European countries: a retrospective observational study. The lancet, 383(9931), pp.1824-1830.
6. Griffiths, P., Ball, J., Drennan, J., Dall’Ora, C., Jones, J., Maruotti, A., Pope, C., Saucedo, A.R. and Simon, M., 2016. Nurse staffing and patient outcomes: Strengths and limitations of the evidence to inform policy and practice. A review and discussion paper based on evidence reviewed for the National Institute for Health and Care Excellence Safe Staffing guideline development. International journal of nursing studies, 63, pp.213-225. 
7. Needleman, J., Buerhaus, P., Pankratz, V.S., Leibson, C.L., Stevens, S.R. and Harris, M., 2011. Nurse staffing and inpatient hospital mortality. New England Journal of Medicine, 364(11), pp.1037-1045.
8. Ball, J.E., Bruyneel, L., Aiken, L.H., Sermeus, W., Sloane, D.M., Rafferty, A.M., Lindqvist, R., Tishelman, C., Griffiths, P. and RN4Cast Consortium, 2018. Post-operative mortality, missed care and nurse staffing in nine countries: A cross-sectional study. International journal of nursing studies, 78, pp.10-15. 
9. Dall'Ora, C., Saville, C., Rubbo, B., Turner, L., Jones, J. and Griffiths, P., 2022. Nurse staffing levels and patient outcomes: a systematic review of longitudinal studies. International Journal of Nursing Studies, 134, p.104311. 
10. Griffiths, P., Saville, C., Ball, J., Dall'Ora, C., Meredith, P., Turner, L. and Jones, J., 2023. Costs and cost-effectiveness of improved nurse staffing levels and skill mix in acute hospitals: A systematic review. International Journal of Nursing Studies, p.104601. 
11. Needleman, J. (2024). Achieving safe staffing in hospitals. Nursing Economic$, 42(4), 203-205. https:// doi.org/10.62116/NEC.2024.42.4.203
12. Ball, J.E. and Griffiths, P., 2022. Consensus Development Project (CDP): An overview of staffing for safe and effective nursing care. Nursing Open, 9(2), pp.872-879.
13. Maben, J., Ball, J. and Edmondson, A.C., 2023. Workplace conditions and health care improvement. In Workplace Conditions. Cambridge University Press.