What do QALYs measure?

• A. QALYs measure length of life without considering quality.
• B. QALYs assess cost effectiveness by price per year.
• C. QALYs weight life years by quality of life.
• D. QALYs are equivalent to years of life lost.

Answer: (C)

QALYs measure life years weighted by quality of life. This means each year of life is not treated equally; a year in perfect health counts as 1 QALY, while a year with illness or disability counts as some fraction between 0 and 1, reflecting the health-related quality of life during that year. By multiplying the years lived by the quality weight and summing over time, you get the total QALYs. This creates a single metric to compare how different health interventions balance extending life with maintaining or improving quality of life. For example, extending life by two years at a quality of 0.8 yields 1.6 QALYs, whereas one additional year in full health is 1 QALY.

The other ideas miss parts of the concept: focusing only on length of life ignores quality; tying it to price per year describes cost-effectiveness in economic terms but not the measurement itself; and equating QALYs with years of life lost conflates quality-weighted survival with a mortality burden.