Measuring health and disability.

Disability-adjusted life years (DALYs)—a frequent indicator for assessment of the relative eff ects of public-health interventions—explicitly incorporate disability. This Viewpoint will argue, however, that the notion of disability embodied in DALYs does not accord with that in WHO’s International Classifi cation of Functioning, Disability, and Health (ICF). Underlying this inconsistency is the basic issue of what is meant by health and disability. The result is that DALYs are a poor indicator of the eff ect of public-health interventions that improve the lives of people with disabilities. An argument can be made that DALYs are better suited for assessment of the eff ect of programmes and policies aimed at prevention of disabilities, but even in this case their approach to measurement of disability needs to be enhanced. Disability and health are diffi cult concepts to defi ne and measure. In fact, the appropriate defi nition of disability depends on the reason behind its measurement. Thus, when monitoring or assessing public-health interventions, having a clear defi nition of disability is very important. Before the advent of DALYs (and the earlier but related idea of quality-adjusted life years [QALYs]), health-outcome measures typically relied on mortality (an exception was the method of disability-free life expectancy and its complement, the number of years lived with a disability). In view of the wide range of eff ects that various health conditions can engender, the approach of using only mortality was judged inadequate. Injury and disease can cause many disabling conditions that have substantial eff ects on the quality of life. DALYs were developed to combine both mortality and these other eff ects into one measure. Basically, DALYs are calculated by adding together years lost from premature mortality and the loss experienced by living a certain number of years with a disability (see panel for a full explanation). According to the World Bank’s 1993 global burden of disease study, DALYs have three major objectives: “to facilitate the inclusion of nonfatal health outcomes in debates on international health policy, to decouple epidemiological assessment from advocacy so that estimates of the mortality or disability from a condition are developed as objectively as possible, and to quantify the burden of disease using a measure that could be used for cost-eff ectiveness analysis”. The overriding goal was to create a measure that could help enhance the allocation of resources battling poor health. This goal is very important. Developing countries generally have many competing needs and scarce resources, forcing governments to make hard decisions about how best to improve the lives of their citizens. Having a transparent, well-understood, and practical way of assessing their options is essential for understanding the trade-off s they face. However, an indicator that does not properly embody the intended goals can build in systematic bias against achieving them. Critics claim that DALYs devalue the lives of disabled people. A year lived with a disability is counted as something less than a year lived without one. Conversely, saving the life of an individual with a disability does not improve the summary measure of health as much as saving the life of a person without a disability. The fear is that this fact will drive resources away from disabled people, making them even more vulnerable and disadvantaged than they already are in many societies. Lancet 2007; 369: 1658–63