In England the demand for emergency care is increasing, while there is also a staffing shortage. This has implications for quality of care and patient safety. One solution may be to concentrate resources on fewer sites by closing or downgrading emergency departments (EDs). Our aim was to quantify the impact of such reorganisation on population mortality.We undertook a controlled interrupted time series analysis to detect the impact of closing or downgrading five EDs, which occurred due to concerns regarding sustainability. We obtained mortality data from 2007 to 2014 using national databases. To establish ED resident catchment populations, estimated journey times by road were supplied by the Department for Transport. Other major changes in the emergency and urgent care system were determined by analysis of annual NHS Trust reports in each geographical area studied. Our main outcome measures were mortality and case fatality for a set of 16 serious emergency conditions.For residents in the areas affected by closure, journey time to the nearest ED increased (median change 9 min, range 0-25 min). We found no statistically reliable evidence of a change in overall mortality following reorganisation of ED care in any of the five areas or overall (+2.5% more deaths per month on average; 95% CI -5.2% to +10.2%; p=0.52). There was some evidence to suggest that, on average across the five areas, there was a small increase in case fatality, an indicator of the 'risk of death' (+2.3%, 95% CI +0.9% to+3.6%; p<0.001), but this may have arisen due to changes in hospital admissions.We found no evidence that reorganisation of emergency care was associated with a change in population mortality in the five areas studied. Further research should establish the economic consequences and impact on patient experience and neighbouring hospitals.