Quality Adjusted Life Years, which takes into account both quantity and quality of life generated by health care interventions. It is the product of life expectancy and a measure of the quality of remaining life years.

a measure of the utility associated with health outcomes that combines morbidity and mortality into a single measure of annual well-being

"The essence of a QALY is that it takes a year of healthy life expectancy to be worth 1, but regards a year of unhealthy life expectancy as worth less than 1. Its precise value is lower the worse the quality of life of the unhealthy person (which is what the 'quality adjusted' bit is all about). A. Williams, 'The Value of QALYs', Health and Social Service Journal July (1985), 3