Impact of integrated health system changes, accelerated due to an earthquake, on emergency department attendances and acute admissions: a Bayesian change-point analysis

Objective To chart emergency department (ED) attendance and acute admission following a devastating earthquake in 2011 which lead to Canterbury's rapidly accelerated integrated health system transformations. Design Interrupted time series analysis, modelling using Bayesian change-point methods, of ED attendance and acute admission rates over the 2008-2014 period. Setting ED department within the Canterbury District Health Board; with comparison to two other district health boards unaffected by the earthquake within New Zealand. Participants Canterbury's health system services approximate to 500000 people, with around 85000 ED attendances and 37000 acute admissions per annum. Main outcome measures De-seasoned standardised population ED attendance and acute admission rates overall, and stratified by age and sex, compared before and after the earthquake. Results Analyses revealed five global patterns: (1) postearthquake, there was a sudden and persisting decrease in the proportion of the population attending the ED; (2) the growth rate of ED attendances per head of population did not change between the pre-earthquake and postearthquake periods; (3) postearthquake, there was a sudden and persisting decrease in the proportion of the population admitted to hospital; (4) the growth rate of hospital admissions per head of the population declined between pre-earthquake and postearthquake periods and (5) the most dramatic reduction in hospital admissions growth after the earthquake occurred among those aged 65+ years. Extrapolating from the projected and fitted deseasoned rates for December 2014, approximate to 676 (16.8%) of 4035 projected hospital admissions were avoided. Conclusions While both necessarily and opportunistically accelerated, Canterbury's integrated health systems transformations have resulted in a dramatic and sustained reduction in ED attendances and acute hospital admissions. This natural intervention experiment, triggered by an earthquake, demonstrated that integrated health systems with high quality out-of-hospital care models are likely to successfully curb growth in acute hospital demand, nationally and internationally.