Which metric weights life years by quality to reflect both quantity and quality of life?

• A. Health-adjusted life expectancy
• B. Disability-adjusted life year
• C. Cost-effectiveness ratio
• D. Quality-adjusted life year

Answer: (D)

Quality-adjusted life year weights life years by the quality of health, capturing both how long people live and how well they live. Each year is given a value between 0 and 1, where 1 means perfect health and 0 means death. By multiplying years lived by this utility, you get QALYs, which lets you compare interventions that trade off longer life with better or worse health. For instance, two extra years in a health state valued at 0.8 equal 1.6 QALYs. This directly reflects both quantity and quality of life in a single measure, which is why it’s the best fit for the described concept. Other metrics weigh or count years differently—for example, life expectancy focuses on length without quality weighting, while DALYs and cost-effectiveness ratios serve other purposes—so they don’t specifically weight life years by quality in the same way.