Disability-Adjusted Life Years (DALYs) are defined as the sum of which components?

• A. DALYs measure years of life lost due to premature mortality.
• B. DALYs reflect only years lived with disability.
• C. DALYs represent the total number of deaths in a population.
• D. The sum of years of life lost due to premature mortality and years lived with disability.

Answer: (D)

Disability-Adjusted Life Years combine fatal and non-fatal health losses into one measure. It adds two pieces: years of life lost due to premature mortality (YLL) and years lived with disability (YLD). YLL accounts for deaths, using the number of deaths times the standard life expectancy at the age of death. YLD accounts for non-fatal outcomes, calculated from how many people live with a condition, the severity of the condition (disability weight), and the duration. By summing these two components, you get the total burden of disease in healthy years, which is exactly what DALYs represent. So the correct description is the sum of years of life lost due to premature mortality and years lived with disability.