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Key Words burden of disease, cost-effectiveness analysis, health-related quality of life
* Abstract Health-adjusted life years (HALYs) are population health measures permitting morbidity and mortality to be simultaneously described within a single number. They are useful for overall estimates of burden of disease, comparisons of the relative impact of specific illnesses and conditions on communities, and in economic analyses. Quality-adjusted life years (QALYs) and disability-adjusted life years (DALYs) are types of HALYs whose original purposes were at variance. Their growing importance and the varied uptake of the methodology by different U.S. and international entities makes it useful to understand their differences as well as their similarities. A brief history of both measures is presented and methods for calculating them are reviewed. Methodological and ethical issues that have been raised in association with HALYs more generally are presented. Finally, we raise concerns about the practice of using different types of HALYs within different decision-making contexts and urge action that builds and clarifies this useful measurement field.
INTRODUCTION
Health has long been evaluated by mortality-based indicators, both in the United States and internationally. Life expectancy, all-cause and disease-specific mortality, and infant mortality are compared by region, by nation, and across nations. Death rates and life expectancies are disaggregated and presented by sociodemographic and ethnic descriptors in efforts to evaluate population health and, at times, to monitor the impact of health interventions. Although mortality-based rates are useful in a cursory way, they provide insufficient information with which to make any but the most basic judgments about the health of a population or the comparative impact of an intervention. The contribution of chronic disease, injury, and disability to population health goes unrecorded.
As commitment to monitoring health and rational allocation of health resources has grown in the United States and internationally, so too have the methods that researchers and policymakers use to evaluate health and medical outcomes in individuals and in populations. Health-adjusted life years (HALYs) are summary measures of population health that allow the combined impact of death and morbidity to be considered simultaneously. This feature makes HALYS useful for comparisons across a range of illnesses, interventions, and populations. A 1998 Institute of Medicine report (15) found these measures to be "increasingly relevant to both...