Distribution of years of life lost by broader causes (percentage of total)
Rationale for use
Years of life lost (YLLs) take into account the age at which deaths occur by giving greater weight to deaths occurring at younger ages and lower weight to deaths occurring at older ages. The YLLs (percentage of total) indicator measures the YLLs due to a particular cause of death as a proportion of the total YLLs lost due to premature mortality in the population.
Definition
YLLs are calculated from the number of deaths multiplied by a standard life expectancy at the age at which death occurs. The standard life expectancy used for YLLs at each age is the same for deaths in all regions of the world and is the same as that used for the calculation of disability-adjusted life years (DALYs). Additionally, 3% time discounting and non-uniform age weights that give less weight to years lived at young and older ages were used, as for the DALY. With non-uniform age weights and 3% discounting, a death in infancy corresponds to 33 YLLs, and deaths at age 5 to 20 years to around 36 YLLs.
Associated terms
The DALYs are a health-gap measure that extends the concept of potential years of life lost due to premature death (PYLLs) to include equivalent years of ‘healthy’ life lost by virtue of being in states of poor health or disability (Lopez et al., 2006). DALYs for a disease or health condition are calculated as the sum of the YLLs because of premature mortality in the population and the years lived with a disability (YLDs) for incident cases of the health condition.
Data sources
Death registration data for 112 WHO Member States, sample registration systems (India, China), available data on child and adult mortality from censuses and surveys, together with population-based epidemiological studies, disease registers and notifications systems for the estimation of mortality due to 21 specific causes of death.
Methods of estimation
Life tables specifying all-cause mortality rates by age and sex for 192 WHO Member States were developed from available death registration data for 2002, sample registration systems (India, China) and data on child and adult mortality from censuses and surveys.
Cause-of-death distributions were estimated from death registration data for 107 countries, together with data from population-based epidemiological studies, disease registers and notifications systems for selected specific causes of death. Causes of death for populations without useable death-registration data were estimated using cause-of-death models together with data from population-based epidemiological studies, disease registers and notifications systems for 21 specific causes of death.
Disaggregation
By age and sex.
References
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Global burden of disease and risk factors
Lopez AD, Mathers CD, Ezzati M, Murray CJL, Jamison DT. Global burden of disease and risk factors. New York, Oxford University Press, 2006. -
Uncertainty and data availability for the global burden of disease estimates 2000–2002
pdf, 151kb
Mathers CD. Uncertainty and data availability for the global burden of disease estimates 2000–2002. Geneva, World Health Organization, 2005 (Evidence and Information for Policy Working Paper) -
Counting the dead and what they died from: an assessment of the global status of cause of death data
Mathers CD, Ma Fat D, Inoue M, Rao C, Lopez AD. Counting the dead and what they died from: an assessment of the global status of cause of death data. Bulletin of the World Health Organization, 2005, 83:171–177.
Database
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WHO Mortality Database: Tables
The data available on this web site comprise deaths registered in national vital registration systems, with underlying cause of death as coded by the relevant national authority. -
Death and disability-adjusted life years (DALYs) estimates for 2002 by cause for WHO Member States
xls, 3.03Mb
Death and disability-adjusted life years (DALYs) estimates for 2002 by cause for WHO Member States. This Excel spreadsheet contains estimates of numbers, crude rates and age-standardized rates, as well as information on data sources and levels of evidence
Comments
Uncertainty in the percentage of estimated all-cause YLL ranges from around ±1% for high-income countries to ±15–20% for sub-Saharan Africa, reflecting large differences in the availability of data on mortality, particularly for adult mortality. Uncertainty ranges are generally larger for estimates of deaths from specific diseases. For example, the relative uncertainty for deaths from ischaemic heart disease ranges from around ±12% for high-income countries to ±25–35% for sub-Saharan Africa. The relatively large uncertainty for high-income countries reflects a combination of uncertainty in overall mortality levels, in cause-of-death assignment, and in the attribution of deaths coded to ill-defined causes.