The disability-adjusted life year (DALY) is calculated as the sum of years of life lost (YLL) and years lived with disability (YLD). In which scenario would the DALY for a condition be dominated almost entirely by YLD rather than YLL?

• A Acute myocardial infarction in a 55-year-old man with high early case fatality
• B Cholera outbreak with high CFR among children under 5
• C Non-fatal road traffic injury causing permanent limb disability in a 25-year-old ✓
• D Childhood pneumonia causing death at age 3

Explanation

YLL = (years of expected life remaining at age of death) × (number of deaths); YLD = (disability weight) × (years lived with disability). In a non-fatal road traffic injury causing permanent disability in a young person, there are zero YLL (no death) but substantial YLD accumulating over decades of living with the disability. Conditions with high early mortality (options A, C, D) accumulate large YLL. Non-fatal disabling conditions — depression, back pain, osteoarthritis, vision loss, non-fatal RTIs — contribute predominantly through YLD, which is why DALY analysis often reveals that non-fatal conditions account for more of the global burden than previously recognised from mortality statistics alone.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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