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QALY (Quality Adjusted Life Years) Vs DALY (Disability Adjusted Life Years)

 Below is a clear, exam-oriented, MBBS-level explanation of QALY vs DALY, expanding every line of the table you provided.

🔵 QALY (Quality Adjusted Life Years) Vs

🔴 DALY (Disability Adjusted Life Years)

These two are the most important summary measures in Health Economics and Burden of Disease studies, especially in Community Medicine.

✅ 1. What they fundamentally measure

🔵 QALY → “Health gained”

  • QALY measures quality of life × years lived after an intervention.

  • It tells you how much healthy life is added because of a treatment.

  • Used in cost-effectiveness analysis of medical interventions.

Example:

If a treatment gives a patient:

  • 1 extra year of life

  • but at 70% quality (0.7 utility score)
    → QALY gained = 1 × 0.7 = 0.7

🔴 DALY → “Health lost”

  • DALY quantifies loss of a healthy life because of a disease.

  • Used by WHO to measure burden of disease in populations.

  • Higher DALY = worse disease burden.

DALY = YLL (Years of Life Lost) + YLD (Years Lived with Disability)

✅ 2. Purpose

🔵 QALY = Indicator of cost-effectiveness

Used by health economists and government agencies to decide:

  • Which drug to fund

  • Which intervention gives the best value for money

  • Which treatment yields the maximum healthy years

🔴 DALY = Indicator of burden of disease

Used in:

  • Global Burden of Disease (GBD) studies

  • Public health planning

  • Identifying priority diseases in a country

✅ 3. Meaning of “expressed as 0 or 1”

🔵 QALY scale

  • 1 = Perfect health

  • 0 = Death
    Values between 0 and 1 represent severity:

  • 0.9 = minor discomfort

  • 0.5 = moderate disability

  • 0.2 = severe disability

(Some diseases may have negative values like –0.1 if life is perceived worse than death.)

🔴 DALY scale

Here the interpretation flips.

  • 0 = Perfect health (no loss)

  • 1 = Death (complete loss of 1 year of healthy life)

So, a disease like:

  • Mild anemia → disability weight 0.052

  • Blindness → 0.6

  • Quadriplegia → 0.9

This shows how much of a healthy year is lost.

✅ 4. Core difference in a single line

QALY = Healthy life gained by treatment (higher is better)

DALY = Healthy life lost due to disease (lower is better)

🔥 5. Simple analogy for memory

Think of life as money:

  • QALY → How much you earn (health gained)

  • DALY → How much you lose (health lost)

📚 6. Quick Comparative Table (expanded)

Feature QALY DALY
What it measures Health gained Health lost
Used for Cost-effectiveness analysis Burden of disease
Value meaning Higher = good Higher = bad
Scale 0 (death) → 1 (perfect health) 0 (perfect health) → 1 (death)
Application Evaluating vaccines, drugs, surgery, rehab Planning national health programs
Perspective Clinical & economic Public health & epidemiology

✨ 7. Exam-oriented summary (write this in paper)

  • QALY = Quality × Quantity of life. Measures health gained. Used in cost-utility & cost-effectiveness analysis. Scale: 0 = death, 1 = perfect health.

  • DALY = YLL + YLD. Measures health lost due to disease. Used to quantify burden of disease. Scale: 0 = perfect health, 1 = death.

  • QALY → higher is better. DALY → lower is better.

If you want, I can also make:
✅ A mnemonic to remember QALY vs DALY
✅ A flowchart
✅ Exam-specific 3–5-marker notes (AIIMS pattern)

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