Decomposition of years of life lost due to premature death (YLL): a method for spatial and temporal comparative assessment

BACKGROUND: Acceptance of Disability-Adjusted Life Year (DALY) as a measure of health summary and progression has increased over the years, which in turn has instigated comparative analysis studies of DALY across time and geography. Thus, it is important to explore methodological underpinnings of comparative analysis. RESULTS: A crude comparison of disease burden across time or space may mislead the interpretation of the health system’s performance because the quantum and pattern of DALY can be influenced by the age structure of the society. A significant proportion of this burden is due to the Years of Life Lost (YLL) component. The paper proposes a mathematical exposition to decompose the change in YLL over time or region into burden attributed to a) population age structure, b) death rate, and c) age at death gradient. CONCLUSION: We reasoned that the death rate and age at death burden gradient signify the real contribution of the health systems. Hence, the method of decomposition can be utilized to measure the health service progression of a region in real terms.