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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

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
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
A large and increasing number of studies have reported a relationship between low nurse staffing levels and adverse outcomes, including higher mortality rates. Despite the evidence being extensive in size, and having been sometimes described as “compelling” and “overwhelming”, there are limitations that existing studies have not yet been able to address. One result of these weaknesses can be observed in the guidelines on safe staffing in acute hospital wards issued by the influential body that sets standards for the National Health Service in England, the National Institute for Health and Care Excellence (NICE), which concluded there is insufficient good quality evidence available to fully inform practice.

In this paper we explore this apparent contradiction. After summarising the evidence review that informed the NICE guideline on safe staffing and related evidence, we move on to discussing the complex challenges that arise when attempting to apply this evidence to practice. Among these, we introduce the concept of endogeneity, a form of bias in the estimation of causal effects. Although current evidence is broadly consistent with a cause and effect relationship, endogeneity means that estimates of the size of effect, essential for building an economic case, may be biased and in some cases qualitatively wrong. We expand on three limitations that are likely to lead to endogeneity in many previous studies: omitted variables, which refers to the absence of control for variables such as medical staffing and patient case mix; simultaneity, which occurs when the outcome can influence the level of staffing just as staffing influences outcome; and common-method variance, which may be present when both outcomes and staffing levels variables are derived from the same survey.

Thus while current evidence is important and has influenced policy because it illustrates the potential risks and benefits associated with changes in nurse staffing, it may not provide operational solutions. We conclude by posing a series of questions about design and methods for future researchers who intend to further explore this complex relationship between nurse staffing levels and outcomes. These questions are intended to reflect on the potential added value of new research given what is already known, and to encourage those conducting research to take opportunities to produce research that fills gaps in the existing knowledge for practice. By doing this we hope that future studies can better quantify both the benefits and costs of changes in nurse staffing levels and, therefore, serve as a more useful tool for those delivering services.
0020-7489
213-225
Griffiths, P.
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Ball, J.
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Drennan, J.
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Dall'ora, Chiara
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Jones, J.
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Maruotti, A.
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Pope, C.
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Recio Saucedo, A.
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Simon, M.
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Griffiths, P.
ac7afec1-7d72-4b83-b016-3a43e245265b
Ball, J.
85ac7d7a-b21e-42fd-858b-78d263c559c1
Drennan, J.
dad7b3ad-8b7d-428b-8dea-ccb1d50819eb
Dall'ora, Chiara
4501b172-005c-4fad-86da-2d63978ffdfd
Jones, J.
270b303b-6bad-4be7-8ea0-63d0e8015c91
Maruotti, A.
7096256c-fa1b-4cc1-9ca4-1a60cc3ee12e
Pope, C.
21ae1290-0838-4245-adcf-6f901a0d4607
Recio Saucedo, A.
d05c4e43-3399-466d-99e0-01403a04b467
Simon, M.
e4faadf3-74bb-4f7d-b406-ab05cb919600

Griffiths, P., Ball, J., Drennan, J., Dall'ora, Chiara, Jones, J., Maruotti, A., Pope, C., Recio Saucedo, A. 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, 213-225. (doi:10.1016/j.ijnurstu.2016.03.012).

Record type: Article

Abstract

A large and increasing number of studies have reported a relationship between low nurse staffing levels and adverse outcomes, including higher mortality rates. Despite the evidence being extensive in size, and having been sometimes described as “compelling” and “overwhelming”, there are limitations that existing studies have not yet been able to address. One result of these weaknesses can be observed in the guidelines on safe staffing in acute hospital wards issued by the influential body that sets standards for the National Health Service in England, the National Institute for Health and Care Excellence (NICE), which concluded there is insufficient good quality evidence available to fully inform practice.

In this paper we explore this apparent contradiction. After summarising the evidence review that informed the NICE guideline on safe staffing and related evidence, we move on to discussing the complex challenges that arise when attempting to apply this evidence to practice. Among these, we introduce the concept of endogeneity, a form of bias in the estimation of causal effects. Although current evidence is broadly consistent with a cause and effect relationship, endogeneity means that estimates of the size of effect, essential for building an economic case, may be biased and in some cases qualitatively wrong. We expand on three limitations that are likely to lead to endogeneity in many previous studies: omitted variables, which refers to the absence of control for variables such as medical staffing and patient case mix; simultaneity, which occurs when the outcome can influence the level of staffing just as staffing influences outcome; and common-method variance, which may be present when both outcomes and staffing levels variables are derived from the same survey.

Thus while current evidence is important and has influenced policy because it illustrates the potential risks and benefits associated with changes in nurse staffing, it may not provide operational solutions. We conclude by posing a series of questions about design and methods for future researchers who intend to further explore this complex relationship between nurse staffing levels and outcomes. These questions are intended to reflect on the potential added value of new research given what is already known, and to encourage those conducting research to take opportunities to produce research that fills gaps in the existing knowledge for practice. By doing this we hope that future studies can better quantify both the benefits and costs of changes in nurse staffing levels and, therefore, serve as a more useful tool for those delivering services.

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Accepted/In Press date: 17 March 2016
e-pub ahead of print date: 30 March 2016
Published date: November 2016
Organisations: Faculty of Health Sciences

Identifiers

Local EPrints ID: 390209
URI: http://eprints.soton.ac.uk/id/eprint/390209
ISSN: 0020-7489
PURE UUID: 3178750f-b104-491e-8ecc-27f785ae59ae
ORCID for P. Griffiths: ORCID iD orcid.org/0000-0003-2439-2857
ORCID for J. Ball: ORCID iD orcid.org/0000-0002-8655-2994
ORCID for J. Drennan: ORCID iD orcid.org/0000-0001-7365-4345
ORCID for Chiara Dall'ora: ORCID iD orcid.org/0000-0002-6858-3535
ORCID for C. Pope: ORCID iD orcid.org/0000-0002-8935-6702
ORCID for A. Recio Saucedo: ORCID iD orcid.org/0000-0003-2823-4573

Catalogue record

Date deposited: 22 Mar 2016 11:42
Last modified: 08 Oct 2020 04:36

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Contributors

Author: P. Griffiths ORCID iD
Author: J. Ball ORCID iD
Author: J. Drennan ORCID iD
Author: Chiara Dall'ora ORCID iD
Author: J. Jones
Author: A. Maruotti
Author: C. Pope ORCID iD
Author: M. Simon

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