A population-based measure of the burden of disease and injury expressed in terms of hypothetical healthy life years that are lost as a result of specified diseases and injuries. DALYs display the difference between a country's life expectancy and either the maximum life expectancy empirically found, which currently is in Japan, or an arbitrary standard of 80 years for males and 82.5 years for females. DALYs comprise lifetimes lost completely because of death and healthy life years “lost” from onsets of nonfatal diseases and injuries, weighted to equivalent years completely lost (e.g., 2 years in a state half as bad as death has a “disability weight” of 0.5). Lost years of healthy life are calculated from a reference life table, usually with life expectancy of 80 years for males and 82.5 years for females. Estimates of DALYs attributable to various causes are derived from many sources, including consolidated mortality and morbidity statistics, health survey data, epidemiological studies, other health indicators, such as health-related census records, expert judgment, and modeling studies aimed at ensuring consistency. DALYs use a “disability weight” multiplied by chronological age to reflect the burden of disability, and yield estimates that accord greater value to fit than to disabled persons and to those in middle years of life than to youthful or elderly people. A methodological weakness of calculating DALYs is inadequate evidence to estimate the impacts of each major specific cause of chronic disability. Another weakness is that the concept of DALYs assumes a continuum from good health to disease, disability, and death that is not universally accepted, especially by representatives of the community of long-term disabled persons. Nevertheless, DALYs are useful in health policy making and in setting priorities. A discussion of the significance and a description of methods used in calculating DALYs can be found at http://www.worldbank.org/html/extdr/hnp/hddflash/workp/wp_00068.html.
Subjects: Public Health and Epidemiology.