Disability-Adjusted Life Year
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Introduction & definition[edit | edit source]
DALY = Disability Adjusted Life Year = the sum of years of potential life lost due to premature death, and the years of productive life lost due to disability[1].
DALYs are used to measure the combined quantity and quality of life of a population.
The WHO website summarises the DALY thus:
"One DALY can be thought of as one lost year of 'healthy' life. The sum of these DALYs across the population, or the burden of disease, can be thought of as a measurement of the gap between the current health status and an ideal health situation where the entire population lives to an advanced age, free of disease and disability."
ie. One DALY is equivalent to the loss of a healthy life year.
Calculation of DALY[edit | edit source]
This measurement is a combination of 2 measurements (shown below):
DALY = YLL + YLD
ie. Disability Adjusted Life Year [DALY] is equal to the sum of the Years of Life Lost [YLL] due to premature mortality in the population and the Years Lost due to Disability [YLD} for people living with the health condition.
YLL[edit | edit source]
YLL = Years of Life Lost
This consists of the number of deaths multiplied by the standard life expectancy at the age at which death occurs.
The formula for this is: YLL = N x L
N = number of deaths and L = standard life expectancy at age of death (in years)
YLD[edit | edit source]
YLD = Years Living with a Disability
There are two methods of calculating the YLD.
1. The number of cases, in a particular time period, multiplied by the average duration of the disease combined with a weight factor which represents the severity of the disease on a scale from 0 (perfect health) to 1 (dead).
The formula is: YLD = I x DW x L
I = number of incident cases
DW = disability weight
L - average duration of he case until remission or death (in years)
2. Known as the Prevalence YLD:
The formula is: YLD = P = DW
P = number of prevalent cases
DW = disability weight
Function/Uses of DALYs[edit | edit source]
DALYs are used to indicate the impact of disease on a population.
They measure the difference between the current situation and an ideal situation where everyone lives to the standard life expectancy, and is in perfect health. For this calculation, the standard life expectancy is set at 80 years for men and 82.5 years for women.
DALYs for a number of diseases can be added together to indicate the total burde of disease in a country.
DALYs are a summary metric of population health. DALYs represent a health gap; they measure the state of a population's health compared to a normative goal. The goal is for individuals to live the standard life expectancy in full health[2].
Limitations of DALYs[edit | edit source]
DALYs are based on baseline measurements from the wealthy countries, so it is likely that the differential found between developing and developed populations means that DALYs may not reflect the differenes in resources[3][4].
Recent Related Research (from Pubmed)[edit | edit source]
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References[edit | edit source]
- ↑ Murray, C. (1994). “Quantifying the burden of disease: the technical basis for disability-adjusted life years.” Bulletin of the World Health Organization 72(3): 429-445
- ↑ CJL Murray et al. Disability-adjusted life years (DALYs) for 291 diseases and injuries in 21 regions, 1990–2010: a systematic analysis for the Global Burden of Disease Study 2010. The Lancet, 15 Dec 2012, Vol 380, No 9859, 02197-2223
- ↑ Anand, S., & Hanson, K. (1997). “Disability Adjusted Life Years: A Critical Perspective.” Journal of Health Economics 16:685-702
- ↑ Parks, R, The Rise, Critique and Persistence of the DALY in GLobal Health. Journal of Global Health, 10 Aug 2014
