The disability-adjusted life year is a type of health-adjusted life year (HALY) that attempts to quantify the burden of disease or disability in populations. They are similar to quality-adjusted life year (QALY) measures, but rather than attach health-related quality of life (HRQL) estimates to health states that can be linked to health risks and self-reported/diagnosed sources of ill-health, DALYs assign HRQLs to specific diseases and disabilities.
Traditionally, health liabilities were expressed using one measure, the Years of Life Lost (YLL) due to dying early. A medical condition that did not result in dying younger than expected was not counted. The Years Lived with Disability (YLD) component measures the burden of living with a disability.
DALYs are calculated by taking the sum of these two components:[3]