DALY Computation

The disability-adjusted life year, or DALY, is the central metric of the global burden of disease, expressing the total health loss from a disease, injury, or risk factor as a single time-based number. One DALY is one healthy year of life lost. The metric, developed by Christopher Murray and elaborated with Alan Lopez in the 1990s, combines two distinct kinds of loss on a common scale: the years of life lost when people die earlier than a reference life expectancy, and the years of healthy life lost when people live with illness or disability rather than in full health. By weighting time lived in poor health by its severity and adding it to time lost to premature death, the DALY makes it possible to compare conditions as different as a fatal cancer and a chronic non-fatal disease, and to rank causes of ill health across populations in a way mortality statistics alone cannot.