Impact of the four-hour National Emergency Access Target on 30 day mortality, access block and chronic emergency department overcrowding in Australian emergency departments.

Objective: Previous research reported strong associations between ED overcrowding and mortality. We assessed the effect of the Four-Hour Rule (4HR) intervention (Western Australia (WA) 2009), then nationally rolled out as the National Emergency Access Target (Australia 2012) policy on mortality and patient flow.

Methods: A longitudinal cohort study of a population-wide 4HR, for 16 hospitals across WA, New South Wales (NSW), Australian Capital Territory (ACT) and Queensland (QLD). Mortality trends were analysed for 2-4 years before and after 4HR using interrupted time series technique. Main outcomes included the effect of 4HR on patient flow markers; admitted 30 day mortality trends; and patient flow marker performance during the study period.

Results: There were 40 281 deaths from 952 726 emergency admissions. All jurisdictions, except ACT, had improved flow and access block after 4HR. Age-standardised mortality was decreasing before the intervention. Post-intervention, WA had a significant reduction in mortality rate of -0.28 per 1000 patients per quarter (P = 0.040) while QLD had mixed results and NSW/ACT trends did not change significantly. Meta-regression of aggregated data for hospitals grouped on flow performances did not show significant mortality changes associated with the policy.

Conclusions: The 4HR was introduced as a means of driving hospital performance by applying a time target. Patient flow improved, but the evidence for mortality benefit is controversial with improvement only in WA. Further research with more representative data from a larger number of hospitals over a longer time across Australia is needed to increase statistical power to detect long-term effects of the policy.