Quality Adjusted Life Years. A QALY is often used to compare different health interventions and treatments. A QALY is based on the how long a person having an intervention would live, but it also takes into account the quality of that life. Each year in perfect health is assigned a value of one (with death assigned a value of zero). If the person does not have perfect quality of life a value between zero and one is assigned for each year. The cost effectiveness of treatments can be compared using the cost of the intervention and the QALY of that intervention. Interventions with a lower cost to QALY ratio are better than those with a high cost to QALY ratio. Quality as well as duration of life are also used in relation to disability adjusted life years (DALY) and health life expectancy.
Also see: Disability Adjusted Life Years, Years of Life Lost, Years of Life Lost Due to a Disability, and Life Expectancy (as healthy life expectancy and disability-adjusted life expectancy adjust life expectancy estimates for quality of life).