Healthcare settings that substitute lower-level staff for registered nurses do so at their own peril, according to an extensive review of nurse skill mix at more than 240 hospitals in Belgium, England, Finland, Ireland, Spain and Switzerland.

Researchers examined discharge data to develop key outcome measurements in patient mortality, patient ratings of care, care quality, patient safety, adverse events and nurse burnout and job dissatisfaction. Results appeared in the November 15 issue of BMJ Quality and Safety.

Overall, richer nurse skill mixes (determined by every 10-point increase in the percentage of professional nurses among all nursing staff) were associated with lower odds of mortality, lower odds of low hospital ratings from patients and reports of poor quality, poor safety grades and other less satisfactory outcomes. Conversely, each 10-point reduction in the percentage of professional nurses was associated with an 11% increase in the odds of death. 

Substituting one nurse assistant for a professional nurse for every 25 patients was associated with a 21% increase in the odds of dying.

Researchers concluded that diminishing the richer skill mix by replacing professional nurses with less qualified staff could “contribute to preventable deaths, erode quality and safety of hospital care and contribute to hospital nurse shortages.”