Nurses play an important role in triage and delivering emergency care. According to previous studies, advanced practice nurses may be associated with better patient outcomes in emergency departments. However, existing evidence is limited, largely derived from high-income Western countries. Thus, the results may not be applicable to other regions. Broader and contextually diverse evidence is needed to inform international workforce planning and policy.

To determine whether the presence of advanced nursing roles (certified nurses and certified nurse specialists) in emergency departments is associated with patient outcomes among adults undergoing triage.

Retrospective cohort study using a nationwide inpatient database.

Acute care hospitals across Japan.

A total of 440,420 patients admitted after emergency department triage at 1012 hospitals between 2013 and 2022.

In-hospital mortality and length of stay were evaluated using multivariable regression with generalized estimating equations, adjusting for detailed patient and hospital characteristics and accounting for within-hospital clustering. To address potential heterogeneity across clinical contexts, the analyses were stratified by the International Classification of Diseases, 10th Revision major diagnostic categories, and random effects meta-analysis was used to synthesize pooled estimates.

In-hospital mortality was significantly lower in hospitals with certified nurses and/or certified nurse specialists in the emergency department for specific diagnostic categories, including certain infectious and parasitic diseases (adjusted odds ratio, 0.57; 95% confidence interval, 0.38–0.84) and endocrine, nutritional, and metabolic diseases (adjusted odds ratio, 0.65; 95% confidence interval, 0.45–0.94). By contrast, the overall pooled association between certified nurses/certified nurse specialists and in-hospital mortality was not statistically significant (adjusted odds ratio, 0.88; 95% confidence interval, 0.77–1.01). However, the pooled estimate suggested a potential protective effect. Regarding length of stay, no consistent association was observed.

Despite the absence of a significant pooled effect across all patients, the presence of certified nurses and/or certified nurse specialists in emergency departments was associated with lower in-hospital mortality in selected diagnostic groups. These findings suggest the potential value of advanced nursing roles, even in systems where prescriptive and diagnostic authority is limited, and may help to inform future discussion regarding workforce deployment and policy in Japan and other healthcare systems with similar structures.

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