Authors' objectives: The National Health Service faces significant challenges in recruiting and retaining registered nurses. Recruiting unregistered staff is often adopted as a solution to the registered nurse shortage, but recent research found lower registered nurse staffing levels increase hospital mortality with no evidence that higher levels of assistant staff reduced risk. To estimate the consequences, costs and cost-effectiveness of variation in the size and composition of the staff on acute hospital wards in England. To determine if results are likely to be sensitive to staff groups such as doctors and therapists, who are not on ward rosters, associations between staffing and outcomes for multiple staff groups, including medical, are explored at hospital level. The consequences of staff shortages in the NHS are potentially serious. Several inquiries, NHS guidance and an extensive body of research indicate that lower registered nurse (RN) staffing levels are associated with adverse patient and staff outcomes. Patient outcomes associated with lower nurse staffing include increased risk of death, hospital-acquired infections, falls, poor patient experience and nursing care omissions. Adverse nurse outcomes include burnout, job dissatisfaction and intention to leave. Maintaining adequate staffing for hospital wards is challenging. As of March 2022, approximately 10% of nursing posts in acute settings were vacant, totalling 38,972 vacancies. In the aftermath of the Francis inquiry and the publication of guidance for safe staffing in adult wards in acute hospitals by the National Institute for Health and Care Excellence in 2014, the number of RNs employed in acute hospitals increased. However, this followed a period where absolute numbers fell, and the increases have not matched activity growth. Although there appeared to be an immediate uplift in the number of applicants for nursing courses following the start of the COVID-19 pandemic in 2020, this has not been sustained. Steps taken to increase supply will not resolve shortages for some time, assuming they are successful. In the face of such scarcity and the need to manage expenditure on staff, care providers and policy-makers face difficult decisions as they plan how to provide adequate nurse staffing levels. Despite extensive evidence demonstrating associations between low nurse staffing levels and adverse outcomes, important uncertainties remain. Most evidence is from cross-sectional studies which have not considered staffing by other staff groups. This means that estimates of nurse staffing effects could be biased, and the importance of the multidisciplinary team may not be recognised. Although there is a growing body of longitudinal studies which avoid many of the limitations of cross-sectional studies, these are still limited. Most economic studies rely on studies with a high risk of bias to estimate the effects of changes in staffing configurations.

Authors' results and conclusions: In the cross-sectional study, lower staffing levels from doctors and allied health professionals were associated with increased risk of death. Higher nurse staffing levels were associated with better patient experience and staff well-being. In the longitudinal study, for adult inpatients, exposure to days with lower-than-expected registered nurses or nursing assistant staff was associated with increased hazard of death (adjusted hazard ratio 1.08/1.07, 95% confidence interval 1.07 to 1.09/1.06 to 1.08) and longer hospital stays. Low registered nurse staffing was also associated with increased hazard of re-admission (adjusted hazard ratio 1.01, 95% confidence interval 1.01 to 1.02). Eliminating low staffing cost £2778 per quality-adjusted life-years gained. Avoidance of registered nurse understaffing gave more benefits and was more cost-effective for highly acute patients. Although high bank or agency staffing was associated with increased hazard of death, avoiding low staffing using temporary staff still reduced mortality but was more costly and less effective than using permanent staff. If costs of avoided hospital stays are included, avoiding low staffing generates a net cost saving. Exploration of thresholds for low staffing indicated a greater beneficial effect from registered nurse staffing higher than current norms. Our results show the adverse effects of low nurse staffing but also show that medical and allied health professional staffing are important considerations for patient safety. Eliminating low registered nurse staffing gave more benefits than eliminating assistant staffing. Cross-sectional study We included 138 hospital Trusts. The number of beds per full-time equivalent (FTE) staff member varied considerably between Trusts. The largest variation was in allied healthcare professional (AHP) staff (mean 2.4 beds per FTE) and support to AHP staff (mean 11.1 beds per FTE), where the standard deviation was 38% and 44% of the mean, respectively. RN staffing levels were strongly correlated with staffing levels by doctors (ρ > 0.71). Although the number of beds per RN had the largest effect on mortality in models including single staff groups [rate ratio (RR) 1.33, 95% confidence interval (CI) 1.15 to 1.54], this was greatly reduced and no longer statistically significant when all staff groups were included in the model, although it remained the largest effect size (RR 1.07, 95% CI 0.88 to 1.31). In multiprofessional models, more occupied beds per AHP (RR 1.04, 95% CI 1.02 to 1.06) and per medical doctor (RR 1.04, 95% CI 1.02 to 1.06) were associated with increased risk of death. More beds per nurse support (RR 0.85, 95% CI 0.79 to 0.91) and AHP support (1.00, 95% CI 0.99 to 1.00) were associated with lower death rates. In multiprofessional models, having more beds per RN was associated with lower scores for patient experience, staff health and well-being, and staff reports of quality of care. More beds per nurse support were associated with lower morale scores but more beds per surgical doctor were associated with higher morale scores. Using ward-level reports of nurse staffing we found that wards with more RN hours per patient day reported fewer harms on the national ‘safety thermometer’ but calculating a staffing shortfall, relative to the Trusts’ reported staffing plans, did not strengthen the observed relationship and, for nursing assistant staff, shortfalls were associated with reduced harms. The NHS faces multiple competing demands for scarce resources. The evidence presented here suggests that investment in nurse staffing in acute hospitals could be cost-effective, on a par with many public health interventions. If the benefits of reduced length of stay are considered and realised, for example through freeing capacity to improve flow through emergency departments or for elective surgery, then there could be net gains. The relative increase in costs is modest, although the supply of staff to meet demand remains challenging. It is important that this scarcity does not obscure the need and demonstrated value for money. While decision-makers may, of necessity, need to experiment with novel approaches to addressing staffing shortages, this needs to be done in the context of a full understanding of what is already known. The safety and cost-effectiveness of alternatives should not be assumed. Several priorities for future research emerge from this work. More research is needed into methods to determine nurse staffing requirements in hospital wards, for planning, real-time monitoring and for use in research. The requirements of service should inform decisions about the required timeliness of data, acceptable data gathering load and the necessary precision. Our findings, combined with the results of previous research, leave uncertainty about the trade-offs between staff shortages and temporary staffing levels, including the relative (adverse) effects of temporary staff at different levels and from different sources. Both qualitative and quantitative research would be of value. There remains uncertainty about the interaction between RN and assistant staffing levels which should be addressed through both qualitative and quantitative research. Research is required to better understand whether the observed variation in AHP staffing is based on variation in service and patient need. The observed association with mortality rates in this study suggests it may not be, and if that is the case, evidence-based methods for determining appropriate staffing need to be developed. Our results not only show the adverse effects of low nurse staffing but also show that medical and AHP staffing are important considerations for patient safety. Eliminating low RN staffing gives more benefits than eliminating assistant staffing but both interventions are cost-effective in terms of QALYs gained relative to many public health interventions. Using agency staff to reduce staffing shortages is also less cost-effective than using substantive staff, because of higher costs but also reduced benefits. However, these findings suggest that while relatively less cost-effective, the use of agency staff to avoid staff shortages is still cost-effective relative to many public health interventions. These findings lend support to policy initiatives aimed at increasing the supply of RNs.

Authors' methods: A national cross-sectional panel study and a patient-level longitudinal observational study using routine data. All English acute hospital Trusts and a subsample of four Trusts for the patient-level study. Naturally occurring variation in the size and composition of the workforce. Patients experiencing a hospital admission with an overnight stay and nursing staff providing care on inpatient wards. Publicly available records of hospital activity, staffing and outcomes (cross-sectional study) and hospital administrative systems (longitudinal study). This is an observational study. Causal inferences cannot be made from these results in isolation. Quality-adjusted life-years gains were estimated, although conclusions are not sensitive to assumptions or discount rates. We used current ward norms as reference for low staffing. We undertook a national cross-sectional panel study using routine data from all English acute hospital Trusts and a patient-level longitudinal observational study in four Trusts. We used natural variation in workload (beds per staff member) and, for the longitudinal study, staffing shortfalls relative to the expected staffing for the ward to determine the association between staffing levels and outcomes and to estimate the effects of change. For nursing, we considered RNs (band 5+) and nursing assistant staff (bands 2–4), which would include nursing associates (although current numbers are small). In the longitudinal study, we also considered the composition of the nursing team in terms of the staff grade mix (proportion of band 4 assistant staff, proportion of band 6+ RNs) and the proportion of bank and agency staff. Across the two studies, we considered a range of outcomes including death, length of stay, re-admission, patient experience, staff experience and staff sickness. For the economic analysis, we considered costs, consequences and quality-adjusted life-years (QALYs), estimating incremental cost-effectiveness ratios (cost per life saved and cost per QALY gained) for eliminating low staffing. Our data were derived from publicly available records of hospital activity, staffing and outcomes for the cross-sectional study and hospital administrative systems for the longitudinal study. We tested associations with multivariable mixed statistical models including random terms to account for the clustering of observations in Trust or ward, as appropriate. We used the national standardised hospital mortality indicator model to adjust for risk of death and for national patient and the staff experience models included the Trust’s mortality rate to adjust for the acuity of the case mix.

Project Status: Completed

URL for project: https://www.journalslibrary.nihr.ac.uk/programmes/hsdr/NIHR128056

Year Published: 2025

URL for published report: https://www.journalslibrary.nihr.ac.uk/hsdr/ZBAR9152

URL for additional information: English

English language abstract: An English language summary is available

Publication Type: Full HTA

Country: England, United Kingdom

DOI: 10.3310/ZBAR9152

Organisation Name: NIHR Health Services and Delivery Research programme

Contact Address: NIHR Journals Library, National Institute for Health and Care Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK

Contact Name: journals.library@nihr.ac.uk

Contact Email: journals.library@nihr.ac.uk