Disability-Adjusted Life Year

The disability-adjusted life year (DALY) is a summary measure of overall disease burden, expressing a year of healthy life lost to a disease, disability or early death as a single number: one DALY equals one lost year of healthy life, and the DALYs a disease imposes on a population are the sum of the years of life lost to premature death (YLL) and the years lived with the disability the disease causes (YLD), so DALY = YLL + YLD. Harvard researchers developed the measure for the World Bank's 1990 Global Burden of Disease Study, conducted jointly with the World Health Organization, and the WHO adopted the method formally in 1996. The measure has drawn criticism for resting on disability weights that critics read as an implicit economic measure of a person's lost productive capacity; its defenders respond that the weights are built from the disability's effect on a person's life in general rather than on ability to work.