892Quantification of mortality incorporating multiple causes of death: Application of weighting strategies to Australian data

Background Mortality statistics are typically based on a single underlying cause of death (UCoD). Although UCoD provides a useful construct, the relevance of assuming that a single disease caused the death is diminishing, especially with increased life expectancy and high proportions of deaths in older ages from chronic/degenerative diseases. Focussing on common underlying causes of death in Australia, we quantified mortality incorporating weighting strategies for multiple causes of death (MCoD). Methods All deaths registered in Australia from 2015-2017 (478,396 deaths) and coded using International Classification of Diseases Version 10 were classified using an extended cause list (n = 136 causes) based on a World Health Organization short list. Age-standardised rates (ASR) were estimated using three weighting methods: (1) traditional approach using UCoD alone; (2) UCoD and associated causes of death (ACoDs) equally weighted and (3) UCoD weighted 0.5 arbitrarily and remaining 0.5 apportioned to the remaining ACoDs. Results Common UCoD were ischaemic heart diseases, cerebrovascular diseases, dementia; 57671, 31515 and 27377 deaths respectively. There were substantial changes in ASR depending on the weighting method used. Variation in mortality patterns estimated using the three weighting methods and challenges to further refinement of the weighting strategy will be discussed. Conclusions Mortality indicators incorporating MCoD enhance traditional measures of mortality and provide a means to reassess the role of diseases in causing death. Further disease specific methods are required to refine current weighting strategies. Key messages Weighting strategies for are useful for quantifying mortality incorporating MCoD, but methodological challenges exist.