Quality Adjusted Life Years (QALYs) are defined as what?

• A. A population size metric.
• B. A quality of life index adjusted annually.
• C. A rate of incidence per year.
• D. A measure of health status that assigns to each period of time a weight, ranging from 0-1, corresponding to the health related quality of life during that period. These are then summed across time period to calculate.

Answer: (D)

Quality Adjusted Life Years measure health outcomes by combining how long a person lives with how good or bad their quality of life is during that time. For each period, a weight between 0 and 1 is assigned that reflects health-related quality of life—1 means perfect health, 0 means death, and values in between reflect lesser health states. You multiply the duration of that period by its weight and then add (sum) these products over all periods to get the total QALYs. This captures both length of life and quality of life in one metric, which is why it’s useful for comparing health interventions in terms of overall benefit.

For example, living one year in perfect health equals 1 QALY. Living one year with a quality weight of 0.7 equals 0.7 QALYs. If you have multiple years with different weights, you sum those products to get the total.

This isn’t a population size metric, nor simply a yearly quality-of-life index, nor a rate of disease incidence. It’s a health-status measure that translates time lived in various health states into a single, comparable number.