32.L. Workshop: Deconstructing the DALY: step by step guide to calculating YLL and YLD

Abstract

Abstract A Burden of Disease (BoD) approach can be used to summarise the debilitating effects of morbidity and premature mortality in a population in a consistent and comparable manner. Summary measures of population health such as the Disability-Adjusted Life Year (DALY) have become key metrics for quantifying burden of disease. DALYs quantify the health gap between a life lived in perfect health and current health status, as the number of healthy life years lost due to illness (Years Lived with Disability, YLDs) and premature death (Years of Life Lost, YLLs). DALYs combine the effects of morbidity and mortality in an equitable way, and can therefore be used to identify the leading causes of disease or injury that cause BoD and to quantify the relative importance of specific risk factors. BoD studies are becoming an increasingly popular way to assess national and local population health as a means to influence national and local policy decisions. The increasing prominence of the burden of disease approach, however, comes at a cost. Calculations of DALYs involve multiple components and as such can be difficult for people to interpret. Burden of disease methodology is complex and highly data intensive, which has led to major disparities across researchers and nations in their capacity to perform studies, to interpret the soundness of available estimates, or to evidence and advocate for the use of particular methodological choices. In this skills-building seminar, we will give an overview of the methodology of calculating the DALY. It will outline the single steps to be undertaken, and the necessary assumptions that have to be taken, on the way to the calculation of the DALYs. This workshop will be supported by technical presentations from burden of disease experts about different choices of estimation methods to calculate both the fatal burden (YLL) and the non-fatal burden (YLD). Throughout the presentations, cerebrovascular disease will be used as a case study, giving a complete, real-life example of how DALYs are calculated. Overall, the aim is to demonstrate the importance of the choices researchers make when designing and interpreting BoD studies as a means of supporting evidence-based decision making. The workshop will foresee ample time for interaction with the audience and discussion of the implications of the different methodological choices. Key messages Although burden of disease methodology is complex, with calculations of DALYs involving multiple components, simple roadmaps can be created to enhance methodological knowledge. The choices and assumptions researchers make are important when designing and interpreting burden of disease studies.