Disability-adjusted life years (cont.)
The disability-adjusted life year or DALY is a composite measure of loss of healthy life that combines the Years of Life Lost (YLL) to deaths from some disease or injury, i, and the Years Lived with Disability (YLD) caused by the same disorder:
The Years Lived with Disability are weighted by the severity of that disability. A YLD with a weight of 1 represents a year of life that is no better than death and, like a single YLL, equals 1 DALY. A YLD with a weight of 0 represents the complete absence of disability from the disorder being considered and would contribute nothing to the count of DALYs.
DALYs are an absolute measure. Other things being equal, population growth will lead to the loss of more DALYs and changes in the age and sex structure of a population will affect both how many DALYs it loses in total and the disorders to which they are lost.