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The value of health: Why do DALYs better reflect society's overall disease burden than QALYs?
In the field of public health, one of the indicators used to evaluate the health status and life expectancy of different countries is the disability-adjusted life year (DALY). This indicator not only considers years of life lost due to premature death, but also years of healthy life lost due to disease or disability, effectively merging the two dimensions of death and disease to provide a more comprehensive measure of the burden of disease in society.
Disability-adjusted life years (DALYs) express the number of years lost due to poor health, disability or premature death and have become an increasingly important indicator in public health and health impact assessment (HIA).
Comparison of DALY and QALY
Although quality-adjusted life years (QALY) are also commonly used to assess health status, it mainly focuses on the effects of individual medical intervention and does not fully reflect the health burden of the entire society. Therefore, QALYs are only used to measure the effect of treatment, but cannot quantify the overall disease burden in society. In contrast, DALY combines data on death (YLL) and disability (YLD), making it a more socially relevant health indicator.
The calculation of DALY not only shows the number of years lost due to death, but more importantly, it takes into account the years of healthy life lost due to illness or disability, providing a more comprehensive evaluation.
Calculation methods and composition
The calculation formula for DALY is to add the values of YLL and YLD to form: DALY = YLL + YLD. This calculation allows researchers to use years as the primary measure of health, forcing us to reflect on the relationship between life and health. YLL is calculated based on life expectancy at the time of death, while YLD is based on the number of years lost due to poor health with appropriate disability weights.
The impact of disability weighting
Disability weight (DW) refers to the degree of impact of a certain disease or disability on an individual. This value does not change with age. Several studies have compiled a detailed weighting table of diseases and disabilities, covering thousands of conditions, from Alzheimer's to fingertip loss, to assess the health impact of different conditions.
In Global Burden of Disease (GBD) studies, the definition of disability is widely used to describe any deviation in health.
Economic Application and Resource Allocation
Although DALY does not directly specify the economic value of a person or situation, it is of great significance in guiding the allocation of health resources. Through DALY data, the government can allocate resources to health problems that have the greatest impact or prioritize treatment. For example, the cost per DALY saved in Gambia is US$670, which helps policymakers evaluate the cost-effectiveness of various medical interventions.
Criticism and controversy
Although DALY has become an important tool for studying disease burden, it still has its share of criticism. Some commentators believe that DALY may reflect people's emphasis on productivity and neglect of other important factors in human health. However, proponents point out that disability weightings are based on health-related quality of life assessments, rather than relying solely on productivity data, and thus provide a more comprehensive picture of the complexity of health.
The context of DALY allows us to better understand the global burden of disease, especially in the fields of mental health and reproductive health.
Conclusion
As global health challenges become increasingly severe, DALY provides a powerful framework to help us understand the impact of different diseases on society. The thinking about the allocation of health resources it triggers is not only about individual health problems, but also an indicator of the overall health status of a country or region. Based on this background, can we think more deeply and find a measurement method that better reflects the overall value of human health?
