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. 2019 Aug;28(8):609-617.
doi: 10.1136/bmjqs-2018-008043. Epub 2018 Dec 4.

Nurse staffing, nursing assistants and hospital mortality: retrospective longitudinal cohort study

Peter Griffiths  1   2   3 , Antonello Maruotti  4   5 , Alejandra Recio Saucedo  4   3 , Oliver C Redfern  6   7 , Jane E Ball  4   2   3 , Jim Briggs  6 , Chiara Dall'Ora  4   3 , Paul E Schmidt  3   8 , Gary B Smith  9 ; Missed Care Study Group
Collaborators, Affiliations

Nurse staffing, nursing assistants and hospital mortality: retrospective longitudinal cohort study

Peter Griffiths et al. BMJ Qual Saf. 2019 Aug.

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.

Keywords: health policy; health services research; mortality (standardized mortality ratios); nurses; patient safety.

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Conflict of interest statement

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.

Figures

Figure 1
Figure 1
Non-linear effects of nurse staffing. Change in the hazard of death associated with variation in staffing levels, relative to the mean. RN, registered nurse.
See this image and copyright information in PMC

Comment in

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