Response to Re: 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 Key findings• Previous research indicated that ED overcrowding and access block are strongly associated with increased mortality but our longitudinal data in 16 hospitals across several states showed significant longterm reductions in mortality rates in WA but not in the other jurisdictions.• The association between access block and 30 day mortality remains controversial.• Longer time series analyses are required to confirm or reject the hypothesis that mortality can be reduced by improving chronic ED overcrowding.