Association between patient-to-nurse ratios in emergency departments and patient, staff, and organizational outcomes: a systematic review

In many settings, studies have shown that establishing patient-to-nurse ratios has benefits for both patients and staff. Whether this is transposable to emergency department (ED) is unclear. The primary objective was to assess the association between patient-to-nurse ratios in EDs and mortality. In this systematic review, a search strategy identified studies published in 2004-2025 in MEDLINE, Cochrane, and CINAHL. Two independent reviewers performed selection and data extraction, followed by a narrative synthesis. The primary outcome was in-hospital mortality. Secondary outcomes were other patient outcomes, staff, and organizational outcomes. Of 2214 identified references, 17 studies were included and all of which were observational. The primary outcome was assessed in only one cohort study (n = 73 EDs), where an increase in the number of nurses per patient was associated with a reduction in ED mortality (adjusted odds ratio = 0.68; 95% confidence interval: 0.49; 0.94). An increase in the number of nurses per patient was also associated with a reduction in cardiac arrests (one study: relative risk = 1.33, 95% confidence interval: 1.05, 1.67 for ≥8.5 patients/nurse vs. <8.5) and medication errors (one of two studies), and an improvement in patient experience (two studies) and nurse satisfaction (one study). Mixed results were observed with regard to reducing length of stay (one of two studies), administration time (three of four studies) and the number of patients who left without being seen (three of four studies), while waiting time before diagnosis or treatment improved (three studies). Although evidence is limited, several observational studies suggest that a higher nurse-to-patient ratio is associated with better patient, nurse, and ED organizational outcomes.