Nurse staffing levels, missed vital signs and mortality in hospitals: retrospective longitudinal observational study

• Published in: Health services and delivery research 2018-11, Vol.6 (38), p.1-120
• Main Authors: Griffiths, Peter, Ball, Jane, Bloor, Karen, Böhning, Dankmar, Briggs, Jim, Dall’Ora, Chiara, Iongh, Anya De, Jones, Jeremy, Kovacs, Caroline, Maruotti, Antonello, Meredith, Paul, Prytherch, David, Saucedo, Alejandra Recio, Redfern, Oliver, Schmidt, Paul, Sinden, Nicola, Smith, Gary
• Format: Article
• Language: English
• Subjects: hospital mortality; hospitals; nurses; nursing administration research; nursing staff; patient safety; personnel staffing and scheduling; quality of health care; vital signs; workload
• ISSN: 2050-4349; 2050-4357
• DOI: 10.3310/hsdr06380

Background: Low nurse staffing levels are associated with adverse patient outcomes from hospital care, but the causal relationship is unclear. Limited capacity to observe patients has been hypothesised as a causal mechanism. Objectives: This study determines whether or not adverse outcomes are more likely to occur after patients experience low nurse staffing levels, and whether or not missed vital signs observations mediate any relationship. Design: Retrospective longitudinal observational study. Multilevel/hierarchical mixed-effects regression models were used to explore the association between registered nurse (RN) and health-care assistant (HCA) staffing levels and outcomes, controlling for ward and patient factors. Setting and participants: A total of 138,133 admissions to 32 general adult wards of an acute hospital from 2012 to 2015. Main outcomes: Death in hospital, adverse event (death, cardiac arrest or unplanned intensive care unit admission), length of stay and missed vital signs observations. Data sources: Patient administration system, cardiac arrest database, eRoster, temporary staff bookings and the Vitalpac system (System C Healthcare Ltd, Maidstone, Kent; formerly The Learning Clinic Limited) for observations. Results: Over the first 5 days of stay, each additional hour of RN care was associated with a 3% reduction in the hazard of death [hazard ratio (HR) 0.97, 95% confidence interval (CI) 0.94 to 1.0]. Days on which the HCA staffing level fell below the mean were associated with an increased hazard of death (HR 1.04, 95% CI 1.02 to 1.07), but the hazard of death increased as cumulative staffing exposures varied from the mean in either direction. Higher levels of temporary staffing were associated with increased mortality. Adverse events and length of stay were reduced with higher RN staffing. Overall, 16% of observations were missed. Higher RN staffing was associated with fewer missed observations in high-acuity patients (incidence rate ratio 0.98, 95% CI 0.97 to 0.99), whereas the overall rate of missed observations was related to overall care hours (RN + HCA) but not to skill mix. The relationship between low RN staffing and mortality was mediated by missed observations, but other relationships between staffing and mortality were not. Changing average skill mix and staffing levels to the levels planned by the Trust, involving an increase of 0.32 RN hours per patient day (HPPD) and a similar decrease in HCA HPPD, would be associated with