Association between time spent in the emergency department and 30-day mortality: a population-level observational study in England
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Objective
To investigate the association between patient time spent in Type 1 emergency departments (EDs) and all-cause mortality 30 days after leaving the department alive.
Design
Cross-sectional, retrospective, observational study using national linked data.
Setting
All NHS Type 1 emergency departments in England.
Participants
6,721,179 individuals (mean age 41.3 years, 52.6% female, 81.4% White ethnicity) attended an ED at least once between 21st March 2021 and 31st March 2022; had a record populated with a “non-immediate” acuity level and a chief complaint at arrival; and survived to either discharge from the ED or admission to hospital for inpatient care.
Main outcome measures
All-cause mortality within 30 days of the ED attendance.
Results
Within the study population, 88,657 patients (1.3%) died within 30 days of ED attendance. A positive non-linear relationship was observed between time spent in the ED and post-discharge mortality, with the probability of death increasing after two hours. The marginal probabilities of death (controlling for socio-economic characteristics, clinical factors such as chief complaint, and comorbidities) at two hours in the ED were 0.02% for patients aged 20 years, rising to 0.1% at 40 years, 0.3% at 60 years, and 0.8% at 80 years. Compared with patients who spent two hours in the ED, the adjusted odds of post-discharge death were: 1.1 times higher (1.07 to 1.14) for three hours; 1.6 times (1.48 to 1.68) for six hours; 1.9 times (1.80 to 2.03) for nine hours; and 2.1 times (2.02 to 2.28) for 12 hours.
Conclusions
Longer time spent in the ED for non-immediate care is associated with increased risk of all-cause mortality within 30 days of discharge or admission, in a non-linear manner. Our findings suggest that time in the ED may be a risk factor for death after discharge, not just during the visit. These findings could inform policy makers and health professionals when setting ED time targets. Further research is needed to understand causal drivers of post-discharge mortality and confirm whether our findings generalise to more recent periods.
Summary box
Section 1: What is already known on this topic
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Small, single-centre studies have suggested that there is an increased mortality rate among patients who experience delays between arrival at the emergency department and admission to an inpatient bed.
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A larger study of over five million individual admitted patients in England, using data from between 2016 and 2018, found an increase in all-cause 30-day mortality that was associated with delays to hospital admission. The quantifiable increase in mortality started as early as five hours after arrival at the emergency department (ED) and increased in a linear “dose-related” fashion.
Section 2: What this study adds
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Our study suggests that longer ED stays for non-immediate care are associated with an increased risk of all-cause mortality within 30 days of both discharge or admission.
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Our study builds on previous research by incorporating more recent data, treating time spent in the ED as a continuous rather than a discrete variable; controlling for a broad range of socio-economic variables recorded in England and Wales National Census; and including all patients who attended emergency departments, for both those that were admitted and those that were discharged (rather than just those who were subsequently admitted to hospital for inpatient care).
