Global Burden of Disease study and the DALY

In 1992 the World Bank commissioned an estimate of how much ill health each disease and injury caused around the world, for its next World Development Report. Chris Murray of Harvard University and Alan Lopez of the World Health Organization carried out the work with a network of more than 100 scientists. Earlier global estimates had mostly counted deaths in broad cause groups. This study covered more than 100 diseases and injuries in eight regions of the world in 1990.

The study needed a unit that made time lived with disability comparable with time lost to early death. The disability-adjusted life year, or DALY, added years of life lost to premature death to years of healthy life lost to illness or disability. Murray set out the assumptions in the Bulletin of the World Health Organization in 1994. Life lost at each age was measured against a standard life table, time lived with disability fell into six severity classes weighted between 0 and 1, years lived at different ages carried different weights to reflect the dependence of the young and the old on adults, and future years were discounted at 3 percent.

Investing in Health, the sixteenth World Development Report, appeared in 1993. It argued that good health raises the productivity of individuals and the growth of economies, and it based its findings largely on the burden estimates and on analyses of the cost-effectiveness of interventions. It said that packages of public health measures and essential clinical care could reduce the burden of disease in developing countries by 25 percent.

The results surprised many policy makers who were used to mortality statistics: childhood diseases, mental disorders and road traffic accidents ranked among the leading causes of disease burden in 1990. C. D. Mathers, in a 2020 history written from long involvement in WHO's work, lists the controversies: heavy imputation and modeling where data were missing, disability weights, and discounting and age weighting. Murray and Lopez published the full study in 1996, with projections to 2020. In 2007 the Institute for Health Metrics and Evaluation was set up, funded by the Bill and Melinda Gates Foundation, to carry out new burden of disease studies.