An analysis of the variation in event rates, case fatality and mortality of Acute Coronary Syndrome across English districts 2006-2010

Abstract

Ischaemic heart disease (IHD) is a leading cause of hospitalisation, mortality and healthcare spending in the industrialised world. Wide temporal, spatial and social class variations show that high IHD mortality is not inevitable. The temporal decline in IHD in the UK and other industrialised countries since the 1960’s and 1970’s has been decomposed into that caused by reductions in population risk which affect event rate versus that caused by changes in case fatality which can potentially be ameliorated by the health system. The persistent Northern excess in IHD mortality in England has not been studied in the same way. This is because there is no national database of IHD events and thus no systematic way to assess sub-national variation. I focused on the acute, life-threatening component of IHD – acute coronary syndrome (ACS). I constructed a national data set of ACS events using routine hospitalisation and mortality data and estimated ACS event rates, mortality and case fatality for each of the 354 English Local Authority Districts using a Bayesian spatial model to smooth away unwarranted variability. I decomposed spatial variation in ACS mortality into its constituent components of event rates and case fatality. 60-80% of the between district variation in mortality is due to variation in event rates depending on age and sex, and an additional 15-30% is due to variation in case fatality. Further, the proportion of events resulting in an out-of-hospital ACS death has more impact on differences in case fatality than do deaths following hospitalisation. These findings have important implications for directing health policies aimed at reducing ACS burden and addressing regional inequalities in health in England.