Reevaluating health metrics: Unraveling the limitations of disability-adjusted life years as an indicator in disease burden assessment

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Abstract
In 1993, the World Bank released a global report on the efficacy of health promotion, introducing the disability-adjusted life years (DALY) as a novel indicator. The DALY, a composite metric incorporating temporal and qualitative data, is grounded in preferences regarding disability status. This review delineates the algorithm used to calculate the value of the proposed DALY synthetic indicator and elucidates key methodological challenges associated with its application. In contrast to the quality-adjusted life years approach, derived from multi-attribute utility theory, the DALY stands as an independent synthetic indicator that adopts the assumptions of the Time Trade Off utility technique to define Disability Weights. Claiming to rely on no mathematical or economic theory, DALY users appear to have exempted themselves from verifying whether this indicator meets the classical properties required of all indicators, notably content validity, reliability, specificity, and sensitivity. The DALY concept emerged primarily to facilitate comparisons of the health impacts of various diseases globally within the framework of the Global Burden of Disease initiative, leading to numerous publications in international literature. Despite widespread adoption, the DALY synthetic indicator has prompted significant methodological concerns since its inception, manifesting in inconsistent and non-reproducible results. Given the substantial diffusion of the DALY indicator and its critical role in health impact assessments, a reassessment is warranted. This reconsideration is imperative for enhancing the robustness and reliability of public health decision-making processes.

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