What is DALY and Why Use it?

It’s interesting when someone talks to public health researchers working on different diseases or health problems! Every research group always says that the problem they are working on, is the most pressing and timely problem in that community! But as policy makers or working in donor agencies, which diseases we should be giving priority? There are some diseases which are more fatal when others are more disabling, but non-fatal.

It’s sometimes very necessary to know both morbidity and mortality of a particular health condition. To do that we use Summary Measure of Population Health (SMPH) which transforms information on mortality and disability into a single composite number.

What is DALYs?

Disability Adjusted Life Years (DALYs) is also a summary measure of population health which takes Years of Life Lost (YLLs) due to premature dealth and Years of life lost to disability (YLDs) due to loss of function.

DALYs= YLLs + YLDs

1200px-DALY_disability_affected_life_year_infographic.svg

Image attribution: Wikipedia [http://en.wikipedia.org/wiki/Disability-adjusted_life_year]

In calculating DALYs we assume that 86 years is the optimal healthy life years because it the highest life expectancy at this moment (for Japanese women!). If a child dies of malaria at the age of 10 years, then YLL would be 76 years. On the other hand, if a person get paralyzed due to stroke at the age of 50 years, he/she would lose (36 x 0.8) years or 28.8 years as YLDs. Here, 0.8 is the disability weight which ranks the disabilities.

By using DALYs we calculate burden of disease, the health loss due to disease, injury or risk factor by age, sex and region.

Why use DALYs?

There are many potential uses  of DALYs in public health. These include:

  • We can compare and contrast between health status of two population. Also, we can assess the overall health inequalities within a population.
  • Public health policy makers can give an appropriate and balanced attention to non-fatal but disabling diseases.
  • Policy makers can prioritize the health resources for public health intervention programmes.
  • When we calculate cost-effectiveness of an intervention, DALYs can give us more insights on accurate calculation of cost-effectiveness.

For more information on DALYs please visit WHO webpage: http://www.who.int/healthinfo/global_burden_disease/metrics_daly/en/

References

1. McKee M, Sim F, editors. Issues in Public Health. Second edition. England: McGraw-Hill Companies; 2011.

2. World Health Organization. Metrics: Disability Adjusted Life Year (DALY). Accessed on 23 September 2014.  http://www.who.int/healthinfo/global_burden_disease/metrics_daly/en/

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