Disability-adjusted life year


Disability-adjusted life year
Disability-adjusted life year for all causes per 100,000 inhabitants in 2004.[1]
  no data
  less than 9250
  9250-16000
  16000-22750
  22750-29500
  29500-36250
  36250-43000
  43000-49750
  49750-56500
  56500-63250
  63250-70000
  70000-80000
  more than 80000

The disability-adjusted life year (DALY) is a measure of overall disease burden, expressed as the number of years lost due to ill-health, disability or early death. Originally developed by Harvard University for the World Bank in 1990, the World Health Organization subsequently adopted the method in 2000. The DALY is becoming increasingly common in the field of public health and health impact assessment (HIA). It "extends the concept of potential years of life lost due to premature death...to include equivalent years of ‘healthy’ life lost by virtue of being in states of poor health or disability."[2] In so doing, mortality and morbidity are combined into a single, common metric.

Traditionally, health liabilities were expressed using one measure: (expected or average number of) Years of Life Lost (YLL). This measure does not take the impact of disability into account, which can be expressed by: Years Lived with Disability (YLD). DALYs are calculated by taking the sum of these two components. In a formula:

DALY = YLL + YLD.[3]

The DALY relies on an acceptance that the most appropriate measure of the effects of chronic illness is time, both time lost due to premature death and time spent disabled by disease. One DALY, therefore, is equal to one year of healthy life lost. Japanese life expectancy statistics are used as the standard for measuring premature death, as the Japanese have the longest life expectancies.[4]

Looking at the burden of disease via DALYs can reveal surprising things about a population's health. For example, the 1990 WHO report indicated that 5 of the 10 leading causes of disability were psychiatric conditions. Psychiatric and neurologic conditions account for 28% of all years lived with disability, but only 1.4% of all deaths and 1.1% of years of life lost. Thus, psychiatric disorders, while traditionally not regarded as a major epidemiological problem, are shown by consideration of disability years to have a huge impact on populations.

Contents

Social weighting

Some studies use DALYs calculated to place greater value on a year lived as a young adult. This formula produces average values around age 10 and age 55, a peak around age 25, and lowest values among very young children and very old people.

A crucial distinction among DALY studies is the use of "social weighting", in which the value of each year of life depends on age. Commonly, years lived as a young adult are valued more highly than years spent as a young child or older adult. This weighting system reflects society's interest in productivity and receiving a return on its investment in educating children. Society has invested relatively little in very young children, and it has already received a substantial return on its investment in older people. Young adults, however, have received the maximum amount of investment and, at the beginning of their working life, have had the least opportunity for society to benefit from its investment.

The global burden of disease (GBD) 2001-2002 study counted life years equally, but the GBD 1990 and GBD 2004 studies used the following formula:[5]

W = 0.1658 Y e-0.04 Y[6]

Where Y is the age at which the year is lived and W is the value assigned to it relative to an average value of 1.

In these studies future years were also discounted at a 3% rate, so that a weighted year of life saved next year is worth 97% of a year of life saved this year.

The effects of the interplay between life expectancy and years lost, discounting, and social weighting are complex, depending on the severity and duration of illness. For example, the parameters used in the GBD 1990 study generally give greater weight to deaths at any year prior to age 39 than afterward, with the death of a newborn weighted at 33 DALYs and the death of someone aged 5–20 weighted at approximately 36 DALYs.[7]

Examples by country

Australia

Cancer (25.1/1,000), cardiovascular (23.8/1,000), mental problems (17.6/1,000), neurological (15.7/1,000), chronic respiratory (9.4/1,000) and diabetes (7.2/1,000) are the main causes of good years of expected life lost to disease or premature death.[8]

PTSD rates for the 25 most populous countries

A table comparing the PTSD DALY rates for the world's 25 most populous countries may be found in the Epidemiology section of the Wikipedia Posttraumatic stress disorder (PTSD) article. Comparison of this rate across these countries makes clear that the region of the world most impacted by PTSD is Asia.

History and usage

The DALY was first conceptualized by Murray and Lopez in work carried out with the World Health Organization and the World Bank known as the global burden of disease study, which was published in 1990. It is now a key metric employed by the United Nations World Health Organization in such publications as its Global Burden of Disease

See also

References

  1. ^ "WHO Disease and injury country estimates". World Health Organization. 2009. http://www.who.int/healthinfo/global_burden_disease/estimates_country/en/index.html. Retrieved Nov. 11, 2009. 
  2. ^ "Death and DALY estimates for 2004 by cause for WHO Member States: Persons, all ages" (xls). World Health Organization. 2002. http://www.who.int/entity/healthinfo/global_burden_disease/gbddeathdalycountryestimates2004.xls. Retrieved 2009-11-12. 
  3. ^ Havelaar, Arie (August 2007) (pdf). Methodological choices for calculating the disease burden and cost-of-illness of foodborne zoonoses in European countries. Med-Vet-Net. http://www.medvetnet.org/pdf/Reports/Report_07-002.pdf. Retrieved 2008-04-05. 
  4. ^ Menken M, Munsat TL, Toole JF. The Global Burden of Disease Study - Implications for Neurology. Arch Neurol. 2000;57:418-420
  5. ^ "Disability weights, discounting and age weighting of DALYs". WHO. http://www.who.int/healthinfo/global_burden_disease/daly_disability_weight/en/index.html. 
  6. ^ "The Global Burden of Disease concept". WHO. http://www.who.int/quantifying_ehimpacts/publications/en/9241546204chap3.pdf. 
  7. ^ Mathers, Colin D. et al. (2007-11). "Measuring the Burden of Neglected Tropical Diseases: The Global Burden of Disease Framework". PLoS Neglected Tropical Diseases. doi:10.1371/journal.pntd.0000114#pntd.0000114-Barendregt1. 
  8. ^ Chant, Kerry (November 2008) (pdf). The Health of the People of New South Wales (summary report). Chief Health Officer, Government of New South Wales. http://mhcs.health.nsw.gov.au/pubs/2008/pdf/chorep_summary_08.pdf. Retrieved 2009-01-17. 

External links


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Disability-adjusted life years — (DALY) is a measure for the overall disease burden. Originally developed by the World Health Organization, it is becoming increasingly common in the field of public health and health impact assessment (HIA). It is designed to quantify the impact… …   Wikipedia

  • Quality-adjusted life years — Quality adjusted life years, or QALYs, is a way of measuring disease burden, including both the quality and the quantity of life lived, as a means of quantifying in benefit of a medical intervention. The QALY model requires utility independent,… …   Wikipedia

  • year — disability adjusted life years (DALYs) a measure of the burden of disease on a defined population, based on adjustment of life expectancy to allow for long term disability as estimated from official statistics. SEE ALSO …   Medical dictionary

  • Life table — 2003 US mortality table, Table 1, Page 1 In actuarial science, a life table (also called a mortality table or actuarial table) is a table which shows, for each age, what the probability is that a person of that age will die before his or her next …   Wikipedia

  • Life Sciences — ▪ 2009 Introduction Zoology       In 2008 several zoological studies provided new insights into how species life history traits (such as the timing of reproduction or the length of life of adult individuals) are derived in part as responses to… …   Universalium

  • quality of life — a measure of a person s wellbeing that is often used to determine who will benefit most from a treatment and, on this basis, who should receive priority where resources are scarce. In such cases a calculation of quality adjusted life years… …   The new mediacal dictionary

  • Early life and military career of John McCain — The early life and military career of John Sidney McCain III spans forty five years (1936 ndash;1981). McCain s father and grandfather were admirals in the United States Navy. McCain was born in the Panama Canal Zone, and attended many schools… …   Wikipedia

  • DALY(s) — disability adjusted life year(s) …   Medical dictionary

  • DALY — • disability adjusted life year …   Maritime acronyms and abbreviations

  • DALY(s) — • disability adjusted life year(s) …   Dictionary of medical acronyms & abbreviations


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.