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Nurse staffing, nursing assistants and hospital mortality: retrospective longitudinal cohort study
  1. Peter Griffiths1,2,3,
  2. Antonello Maruotti1,4,
  3. Alejandra Recio Saucedo1,3,
  4. Oliver C Redfern5,6,
  5. Jane E Ball1,2,3,
  6. Jim Briggs5,
  7. Chiara Dall'Ora1,3,
  8. Paul E Schmidt3,7,
  9. Gary B Smith8
  10. On behalf of Missed Care Study Group
    1. 1 Faculty of Environmental and Life Sciences, University of Southampton, Southampton, UK
    2. 2 Department of Learning, Informatics, Management and Ethics, Karolinska Institutet, Stockholm, Sweden
    3. 3 National Institute for Health Research Collaboration for Leadership in Applied Health Research and Care (NIHR CLAHRC) Wessex, Southampton, UK
    4. 4 Dipartimento di Scienze Economiche, Politiche e delle Lingue Moderne, Libera Universita Maria Santissima Assunta, Roma, Italy
    5. 5 Centre for Healthcare Modelling and Informatics Portsmouth, University of Portsmouth, Portsmouth, UK
    6. 6 Medical Sciences Division, University of Oxford Nuffield Department of Clinical Neurosciences, Oxford, UK
    7. 7 Acute Medicine Unit, Portsmouth Hospitals NHS Trust, Portsmouth, UK
    8. 8 Faculty of Health and Social Sciences, University of Bournemouth, Bournemouth, UK
    1. Correspondence to Professor Peter Griffiths, Faculty of Health Sciences, University of Southampton, Southampton SO17 1BJ, UK; peter.griffiths{at}soton.ac.uk

    Abstract

    Objective To determine the association between daily levels of registered nurse (RN) and nursing assistant staffing and hospital mortality.

    Design This is a retrospective longitudinal observational study using routinely collected data. We used multilevel/hierarchical mixed-effects regression models to explore the association between patient outcomes and daily variation in RN and nursing assistant staffing, measured as hours per patient per day relative to ward mean. Analyses were controlled for ward and patient risk.

    Participants 138 133 adult patients spending >1 days on general wards between 1 April 2012 and 31 March 2015.

    Outcomes In-hospital deaths.

    Results Hospital mortality was 4.1%. The hazard of death was increased by 3% for every day a patient experienced RN staffing below ward mean (adjusted HR (aHR) 1.03, 95% CI 1.01 to 1.05). Relative to 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 (aHR 0.97, 95% CI 0.94 to 1.0). Days where admissions per RN exceeded 125% of the ward mean were associated with an increased hazard of death (aHR 1.05, 95% CI 1.01 1.09). Although low nursing assistant staffing was associated with increases in mortality, high nursing assistant staffing was also associated with increased mortality.

    Conclusion Lower RN staffing and higher levels of admissions per RN are associated with increased risk of death during an admission to hospital. These findings highlight the possible consequences of reduced nurse staffing and do not give support to policies that encourage the use of nursing assistants to compensate for shortages of RNs.

    • health services research
    • mortality (standardized mortality ratios)
    • nurses
    • health policy
    • patient safety

    This is an open access article distributed in accordance with the Creative Commons Attribution 4.0 Unported (CC BY 4.0) license, which permits others to copy, redistribute, remix, transform and build upon this work for any purpose, provided the original work is properly cited, a link to the licence is given, and indication of whether changes were made. See: http://creativecommons.org/licenses/by/4.0

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    Footnotes

    • Collaborators The Missed Care Study Group Comprises Jane Ball, Karen Bloor, Dankmar Böhning, Jim Briggs, Chiara Dall’Ora, Anya De Iongh, Peter Griffiths, Jeremy Jones, Caroline Kovacs, Antonello Maruotti, Paul Meredith, Alejandra Recio-Saucedo, David Prytherch, Oliver Redfern, Paul Schmidt, Nicky Sinden, Gary Smith.

    • Contributors PG: conceived and designed the study; secured funding, interpreted the data, and drafted and revised the paper. JEB: contributed to the design of the study, acquisition of funding and interpretation of data; commented on drafts and made significant revisions to the paper. JB: contributed to the design of the study, acquisition of funding and interpretation of data; supervised the building of the project database; commented on drafts and made significant revisions to the paper. CD’O: contributed to the acquisition of workforce data and ward profiles; contributed to the analysis and interpretation of data; commented on drafts and made significant revisions to the paper. AM: contributed to the design of the study, statistical analysis plan, acquisition of funding and interpretation of data; undertook survival and mediation analysis; contributed to drafting the report. AR-S: day-to-day project management; contributed to the acquisition of all data and drafting the paper, including review of background literature; contributed to the interpretation of data. OR: built project database and undertook coding to extract analysis data sets; undertook statistical analysis for staffing/missed care relationships and contributed to drafting the report and interpreting all aspects of analysis. PES: contributed to the design of the study, acquisition of funding and interpretation of data; commented on drafts and made significant revisions to the paper. GBS: contributed to the design of the study, acquisition of funding and interpretation of data; commented on drafts and made significant revisions to the paper.

    • Funding This project was funded by the NIHR Health Services and Delivery Research Programme (HS&DR 13/114/17) and will be published in full in the Health Services and Delivery Research journal. Further information is available at https://www.journalslibrary.nihr.ac.uk/programmes/hsdr/1311417/%23/.

    • Disclaimer The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care.

    • Competing interests PM, NS and PES are employees of Portsmouth Hospitals NHS Trust (PHT), which had a royalty agreement with The Learning Clinic (TLC) to pay for the use of PHT intellectual property within the Vitalpac product, which expired during the course of this study. DP and GBS are former employees of PHT. PES, and the wives of DP and GBS, held shares in TLC until 2015. JB’s research has previously received funding from TLC through a Knowledge Transfer Partnership. PG was an unpaid member of the advisory group for NHS Improvement's work developing improvement resources for safe staffing in adult inpatient wards.

    • Patient consent Not required.

    • Ethics approval The study was approved by the National Research Ethics Service, East Midlands – Northampton Committee Ref: 15/EM/0099.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Data sharing statement The data sharing agreement we have with the host Trust means that we are unable to share data with third parties.

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