Objectives To determine the association of hospital nursing skill mix with patient mortality, patient ratings of their care and indicators of quality of care.
Design Cross-sectional patient discharge data, hospital characteristics and nurse and patient survey data were merged and analysed using generalised estimating equations (GEE) and logistic regression models.
Setting Adult acute care hospitals in Belgium, England, Finland, Ireland, Spain and Switzerland.
Participants Survey data were collected from 13 077 nurses in 243 hospitals, and 18 828 patients in 182 of the same hospitals in the six countries. Discharge data were obtained for 275 519 surgical patients in 188 of these hospitals.
Main outcome measures Patient mortality, patient ratings of care, care quality, patient safety, adverse events and nurse burnout and job dissatisfaction.
Results Richer nurse skill mix (eg, every 10-point increase in the percentage of professional nurses among all nursing personnel) was associated with lower odds of mortality (OR=0.89), lower odds of low hospital ratings from patients (OR=0.90) and lower odds of reports of poor quality (OR=0.89), poor safety grades (OR=0.85) and other poor outcomes (0.80<OR<0.93), after adjusting for patient and hospital factors. Each 10 percentage point reduction in the proportion of professional nurses is associated with an 11% increase in the odds of death. In our hospital sample, there were an average of six caregivers for every 25 patients, four of whom were professional nurses. Substituting one nurse assistant for a professional nurse for every 25 patients is associated with a 21% increase in the odds of dying.
Conclusions A bedside care workforce with a greater proportion of professional nurses is associated with better outcomes for patients and nurses. Reducing nursing skill mix by adding nursing associates and other categories of assistive nursing personnel without professional nurse qualifications may contribute to preventable deaths, erode quality and safety of hospital care and contribute to hospital nurse shortages.
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Contributors All of the named authors participated in data collection, the writing of the manuscript and revisions.
Funding European Union's Seventh Framework Program (223468), National Institute of Nursing Research, National Institutes of Health (NR014855), Spanish Ministry of Science and Technology.
Competing interests None declared.
Ethics approval The study was approved by the University of Pennsylvania human subjects committee.
Provenance and peer review Not commissioned; externally peer reviewed.
RN4CAST consortium Walter Sermeus (Director), Koen Van den Heede, Luk Bruyneel, Emmanuel Lesaffre, Luwis Diya (Belgium, Catholic University Leuven); Linda Aiken (Codirector), Herbert Smith, Douglas Sloane (USA, University of Pennsylvania); Anne Marie Rafferty, Jane Ball, Simon Jones (UK, King's College London); Peter Griffiths (UK, University of Southampton); Juha Kinnunen, Anneli Ensio, Virpi Jylhä (Finland, University of Eastern Finland); Reinhard Busse, Britta Zander, Miriam Blümel (Germany, Berlin University of Technology); John Mantas, Dimitrios Zikos, Marianna Diomidous (Greece, University of Athens); Anne Scott, Anne Matthews, Anthony Staines (Ireland, Dublin City University); Ingeborg Strømseng Sjetne (Norwegian Knowledge Centre for the Health Services) Inger Margrethe Holter (Norwegian Nurses Organization); Tomasz Brzostek, Maria Kózka, Piotr Brzyski (Poland, Jagiellonian University Collegium Medicum); Teresa Moreno-Casbas, Carmen Fuentelsaz-Gallego, Esther Gonzalez-María, Teresa Gomez-Garcia (Spain, Institute of Health Carlos III); Carol Tishelman, Rikard Lindqvist, Lisa Smeds (Sweden, Karolinska Institute); Sabina De Geest, Maria Schubert, René Schwendimann (Switzerland, Basel University); Maud Heinen, Lisette Schoonhoven, Theo van Achterberg (Netherlands, Radboud University Nijmegen Medical Centre).
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