Education And Debate

The value of DALY life: problems with ethics and validity of disability adjusted life years

BMJ 1999; 319 doi: http://dx.doi.org/10.1136/bmj.319.7222.1423 (Published 27 November 1999) Cite this as: BMJ 1999;319:1423
  1. Trude Arnesen, research fellow (trude.arnesen@folkehelsa.no),
  2. Erik Nord, senior researcher
  1. National Institute of Public Health, PB 4404 Torshov, N-0403 Oslo, Norway
  1. Correspondence to: T Arnesen
  • Accepted 30 July 1999

Disability adjusted life years (DALYs) have been launched by the World Bank and backed by the World Health Organisation as a measure of the global burden of disease. 1 2 The aim is ambitious: “The burden of disease has yet to entirely replace traditional approaches to the assessment of health needs as an influence on political decision making.”3

Just like quality adjusted life years (QALYs), DALYs combine information about morbidity and mortality in numbers of healthy years lost. In the DALY approach, each state of health is assigned a disability weighting on a scale from zero (perfect health) to one (death) by an expert panel.2 To calculate the burden of a certain disease, the disability weighting is multiplied by the number of years lived in that health state and is added to the number of years lost due to that disease (figure) Future burdens are discounted at a rate of 3% per year, and the value of the lifetime is weighted so that years of life in childhood and old age are counted less.

DALYs and QALYs are complementary concepts. QALYs are years of healthy life lived; DALYs are years of healthy life lost. Both approaches multiply the number of years (x axis) by the quality of those years (y axis). QALYs use “utility” weights of health states; DALYs use “disability weights” to reflect the burden of the same states. For example, if the utility of deafness is 0.67, the disability weight of deafness is 1−0.67=0.33 Disregarding age weighting and discounting, and assuming life expectancy of 80 years, a deaf man living 50 years represents 0.67×50=33.4 QALYs gained and 0.33×50+30×1=46.6 DALYs lost

Summary points

DALYs (disability adjusted life years) have been launched by the World Bank and the World Health Organisation as a combined measure of morbidity and mortality

The …

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