DALY and QALY

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DALY and QALY

Epidemiology

DALY and QALY

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USMLE® Step 2 style questions USMLE

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An anesthesiologist is studying the effects of chronic low back pain on patients’ quality of life. Which of the following values would the physician require to calculate the quality-adjusted life-year (QALY) associated with the condition?

Transcript

Contributors

Disability-adjusted life years or DALYs are a measurement of disease burden, which is the impact of a health problem on an individual or in a population.

Typically, disability-adjusted life years are used to compare the burden of two diseases, like type II diabetes - which is a chronic condition where the body doesn’t produce enough insulin - and malaria - which is an infectious disease spread by mosquitoes that causes a person to have flu-like symptoms.

These two diseases are usually hard to compare because they affect different populations, have different short-term and long-term complications, and are managed completely differently.

So, to compare the two diseases, you could calculate the disability-adjusted life years for both diabetes and malaria, and the disease with the highest disability-adjusted life years has the highest disease burden.

Disability-adjusted life years are particularly useful for helping determine how resources should be allocated to a specific health issue.

For example, if you have 100 thousand dollars to donate, do you want to spend it towards helping people with type II diabetes in Canada or helping people with malaria in India?

So let’s try to calculate the disability-adjusted life years for diabetes in Canada, and that requires knowing two things.

First, you need to know the years of life lost to premature death, or YLL.

The years of life lost is calculated by multiplying the number of deaths that were the result of the disease (N), and the standard life expectancy at the age of death (L).

The standard life expectancy is just the average life expectancy in a population minus the age of the person who died.

For example, the average life expectancy in Canada is 82 years old, so the standard life expectancy of a person at age 60 is 22 years, because 82 minus 60 is 22. And if we’re only talking about 1 person who died, the number of deaths is 1.

So the years of life lost for a 60-year-old person that died from diabetes would be 1 times 22, or 22 years.

Summary

The Disability-Adjusted Life Year (DALY) and Quality-Adjusted Life Year (QALY) are measures of population health used to quantify the burden of disease and injury. A DALY is a measure of lost healthy life years, while a QALY is a measure of how many years of life are lived in good health. Both measures incorporate the severity and duration of illness or injury and the age at which it occurs. They can be used to compare different diseases or injuries, or to compare the burden of disease between different populations.

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