A Quality-Adjusted Life Year (QALY) is a unit of measurement for wellbeing used in Life Cycle Assessment and cost-benefit analysis, expressed in person-years weighted by the degree of wellbeing on a scale from 0 to 1, where 1 is full wellbeing and 0 is equivalent to death.
The QALY provides a comprehensive measure that combines both the quantity and quality of life. Each year of life is adjusted according to its quality. For example, one year lived in perfect health equals 1.0 QALY, whilst one year lived with a health condition that reduces quality of life to 70% of full wellbeing equals 0.7 QALY.
This metric is useful in sustainability assessment for quantifying human wellbeing impacts across a product's life cycle. QALYs can capture health-related quality of life and other dimensions of wellbeing beyond physical health, such as psychological wellbeing, social functioning, and general life satisfaction.
The QALY differs from Disability-Adjusted Life Years (DALY) in two important ways. First, QALYs use a positive sign, meaning that wellbeing loss is measured as a reduction in QALYs rather than as an increase in negative burden. This makes QALYs suited to measuring gains in wellbeing rather than losses. Second, whilst DALYs focus specifically on health-related quality of life, QALYs consider a broader range of wellbeing aspects beyond health alone.
In LCA applications, QALYs help quantify the social dimension of sustainability by translating diverse impacts on human wellbeing into a single, comparable unit that can be integrated into decision-making frameworks alongside environmental and economic indicators.
As Chief Operating Officer, Iris leads our organisational development and oversees day-to-day operations. Before joining 2-0, she worked in the biotechnology sector. As an LCA consultant, Iris has devoted her expertise primarily to the domains of sustainable agriculture and food production. She is dedicated to teaching LCA and is responsible for our educational efforts. Iris holds an M.Sc. in Biology – Biotechnology from the University of Copenhagen.
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Glossary terms are clearer once you have seen them applied. Our guide to what LCA is and how it works walks through the complete methodology: goal and scope, inventory modelling, impact assessment, and interpretation.
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