Nurse -patient ratios – what is the evidence?

Peter Griffiths of Southampton University wrote on the researchgate site:

“…..this is an area with a massive literature. The positive association (between more nurses and better patient outcomes) has been demonstrated against a range of quality and safety measures – primarily safety. Linda Aiken is not the only researcher in the area but possibly the best known. 

Try : Kane, R.L., Shamliyan, T.A., Mueller, C., Duval, S., Wilt, T.J., 2007. The Association of Registered Nurse Staffing Levels and Patient Outcomes: Systematic Review and Meta-Analysis. Medical Care 45 (12), 1195-1204 1110.1097/MLR.1190b1013e3181468ca3181463.

…for a comprehensive if slightly dated overview of the safety literature.

Recent reports from the RN4CAST study show associations with other outcomes e.g.:

Ball, J.E., Murrells, T., Rafferty, A.M., Morrow, E., Griffiths, P., 2013. ‘Care left undone’ during nursing shifts: associations with workload and perceived quality of care. BMJ Quality & Safety.

Aiken, L.H., Sermeus, W., Van den Heede, K., Sloane, D.M., Busse, R., McKee, M., Bruyneel, L., Rafferty, A.M., Griffiths, P., Moreno-Casbas, M.T., Tishelman, C., Scott, A., Brzostek, T., Kinnunen, J., Schwendimann, R., Heinen, M., Zikos, D., Sjetne, I.S., Smith, H.L., Kutney-Lee, A., 2012. Patient safety, satisfaction, and quality of hospital care: cross sectional surveys of nurses and patients in 12 countries in Europe and the United States. British Medical Journal 344.

Aiken, L.H., Sloane, D.M., Bruyneel, L., Van den Heede, K., Sermeus, W., 2013. Nurses’ reports of working conditions and hospital quality of care in 12 countries in Europe. International Journal of Nursing Studies 50 (2), 143-153.

…although limited as they are all self report.

The translation of this to specific ratios is difficult – largely for the reasons highlighted above and the evidence on that policy is less clear cut. Try

McHugh, M.D., Brooks Carthon, M., Sloane, D.M., Wu, E., Kelly, L., Aiken, L.H., 2012. Impact of Nurse Staffing Mandates on Safety-Net Hospitals: Lessons from California. Milbank Quarterly 90 (1), 160-186.

For a favourable gloss.

Some of the limitations are covered in:

Griffiths, P., 2009. RN+RN=better care? What do we know about the association between the number of nurses and patient outcomes? International Journal of Nursing Studies 46 (10), 1289-1290.

…one issue that is very germane for many health sectors is the absence of medical staffing from this literature. See

Griffiths, P., Jones, S., Bottle, A., 2013. Is “failure to rescue” derived from administrative data in England a nurse sensitive patient safety indicator for surgical care? Observational study. International Journal of Nursing Studies 50 (2), 292.


I would add:

This question is rooted within a wider context – that of managerialist control of care environments (Traynor 1999, Lees 2013) in which efficiency, effectiveness and economy are to the fore. This approach can militate against the consideration of qualitative, non measurable, outcomes which make a real difference to patients’ experience (Tadd et al 2011, Dixon-Woods et al 2013, Hillman et al 2013). The reality is that many health and social care sectors, in the UK, are under such financial pressure and managerialist control,  that the quality of the care experience is squeezed. Given current narratives of austerity, female undervalued labour and ‘private = good public = bad’, UK society has accepted that for example long term care of older people, and mental health, have to fight their corner for government and personal funding. I suspect that funders (e.g. DoH and FTs) ignore evidence, in any case, of staff-patient ratios, viewing it as idealistic and costly. However, they will not frame it in this way – the response will be that ratios are a blunt tool and should not be set down in terms of basic minimums. While I think it is imperative that evidence comes forth on this topic, we might need to consider that the translational model of evidence to policy is flawed. In the context of climate science,  Pielke (2010) describes the actual relationship between public policy and scientific research as problematic; it is not a linear ‘evidence to policy’ model.  The translational model, or ‘knowledge translation’ (Kerr and Wood 2008), in which scientists come up with answers which are then put into practice by policy makers (Wynne 2010) is contextualised within political and ideological frameworks such as that of neoliberalism and its adjutant, managerialism.  Naively we may think that the job of scientists, and their allies, is to improve the process of knowledge translation so that policy makers, guided by clear evidence, can make the right decisions. Drugs policy research is another example of the failure of this model. In nursing, even if we had irrefutable evidence, there is no necessary link to this and health policy on nurse staffing. The UK’s NHS is a ‘highly politicized setting’ (Traynor 2013), staffing of wards is as much a political as an empirical question.

Dixon-Woods, M., Baker, R., Charles, K., et al (2013) Culture and behaviour in the English National Health Service: overview of lessons from a large multimethod study. BMJ Quality and Safety (published online) September 2013 accessed February 25th 2014
Hillman, A., Tadd, W., Calnan, S., Calnan, M., Bayer, A., and Read, S. (2013) Risk, Governance and the experience of Care. Sociology of Health and Illness. 35 (6) pp 939-955
Kerr, T., and Wood, E. (2008) Closing the gap between evidence and action: the need for knowledge translation in the field of drug policy. International Journal of Drug Policy 19 (3) pp 223-234
Lees, A., Meyer, E., and Rafferty, J. (2013) From Menzies Lyth to Munro: The problem of Manageralism. British Journal of Social Work. 43 (3) 542-558
Pielke, R. (2010) The Climate Fix. Basic Books. New York.
Tadd, W., Hillman, A., Calnan, S., Calnan, M., Bayer, T., and Read, S. (2011) Dignity in Practice: An exploration of the care of older adults in acute NHS Trusts. NIHR Service Delivery and Organisation Programme. Project 08/1819/218. NETSCC – SDO: Southampton
Traynor, M. (1999) Managerialism and Nursing: beyond profession and oppression. Routledge. London
Traynor, M. (2013) Nursing in Context. Policy, Politics, Profession. Palgrave Macmillan.
Wynne, B. (2010) Strange Weather, Again. Climate Science as political art. Theory Culture and Society 27 (2-3): 289-305