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Estimating the fatal burden
Estimating the fatal burden
Expressed as years of life lost (YLL), fatal burden is a measure of years lost due to premature death. Analysis of fatal burden takes into account all deaths that occur in a population during a reference period. In the ABDS 2018, YLL estimates were based on deaths that occurred in the reference years: 2003, 2011, 2015 and 2018.
Deriving YLL requires both:
- mortality data – the actual number of deaths and the ages at which those deaths occurred; and
- a reference life table – a measure of life expectancy at each age to derive the years of life lost at each age.
Box 3.1: Key terms used in this chapter
redistribution: A method in a burden of disease study for reassigning deaths with an underlying cause of death that is not in the study’s disease list. Typically, the deaths reassigned include those with a cause that is implausible as an underlying cause of death, those with an intermediate cause in the chain of events leading to death, or those for which there is insufficient detail to ascertain a specific cause of death.
reference life table: A table that shows, for each age, the number of remaining years a person could potentially live—used to measure the years of life lost from dying at that age.
YLL (years of life lost): measures years of life lost due to premature death.
Overview of methods
YLL measures the impact of dying prematurely; that is, the fatal component of burden of disease. YLD (discussed in Estimating the non-fatal burden) represents the non-fatal component.
The first step for estimating YLL is to compile all deaths by age and disease. Deaths are aligned to the study’s disease list using the cause of death.
YLL is then calculated for each disease using single year of age at death. Each death is weighted according to the remaining potential life expectancy at that age of death using the reference life table.
The weighted deaths are summed, and the result is the total number of years of life lost. For YLL from all causes, this is described mathematically as:

Mortality data
Australian deaths data are collected through a vital registrations system. This is a system collecting and maintaining records of life events—such as births, deaths and marriages—by a government authority. In Australia, this is done by the Registrars of Births, Deaths and Marriages in each state and territory.
Information on causes of deaths nationally is sourced from the Registrars of Births, Deaths and Marriage in each state and territory and from the National Coronial Information System managed by the Victorian Department of Justice and coded to the International Classification of Disease (ICD) by the Australian Bureau of Statistics (ABS). The AIHW website About our data - Deaths Data provides detailed information on the registration of deaths and coding of causes of death in Australia (AIHW 2018a). The completeness, accuracy and coding of these data are described elsewhere (ABS 2018a). The deaths data are collated by the ABS into an administrative data set for statistical analysis. The AIHW houses a set of these data in the AIHW’s National Mortality Database (NMD). The data quality statements underpinning the AIHW NMD can be found in the ABS’s quality declaration summary for Deaths, Australia and Causes of death, Australia.
All deaths data used in the ABDS 2018 were extracted from the AIHW’s NMD. This is a register of all deaths in Australia since 1964, sourced from the cause of death unit record files as described above. The database comprises information about the causes of death and other characteristics about the person, such as sex, age at death, Indigenous status and area of usual residence.
Australian mortality data are believed to be virtually complete, so no adjustment needs to be done to account for missing death records. Despite completeness, causes of death that do not directly align to the study’s disease list need to be reassigned to a disease in the list (see ‘Redistribution of deaths’).
Mortality data in ABDS 2018
Cause of death data for deaths occurring in 2003, 2011, 2015 and 2018 were used for this analysis. Deaths for the four reference years were extracted from the NMD for deaths registered in 2003 up to and including deaths registered in 2019. As a result, the analysis set includes deaths that occurred in 2018 but were not registered until 2019; on average, between 4% and 7% of deaths that occur in a given year are not registered until a later year—most of these in the following 2 years (ABS 2019).
Deaths for the 2003, 2011 and 2015 reference years are almost all (at least 99%) based on a final version of cause of death data and most (95%) for 2018 are from a revised version of data. Since 2006, deaths certified by a coroner undergo revision and causes of death may be updated, pending the status of coroner investigation. As such, some cause of death information is subject to change. The ABS revisions process is described in detail elsewhere (ABS 2019).
Missing age and sex
Age at death is missing from some records in the mortality database. As age at death is required to estimate YLL, death records missing this data item were coded according to the median age at death for all deaths in the same sex-cause group.
There were no deaths with missing sex information for the reference years used in YLL calculations.
Indigenous identification
Due to small numbers, analysis of indigenous mortality was an average of the three years around the reference year. A separate calculation of non-indigenous burden was calculated with the three years of data.
Aligning causes of death to the ABDS disease list
Having first assembled the deaths that are to be counted when calculating YLL, the causes of those deaths are then ascribed to diseases in the ABDS disease list (as described in Overarching methods and choices for ABDS 2018).
Deaths data used in the ABDS 2018 are coded to the ICD-10 (ABS 2019; WHO 2016). The procedure for assigning ICD-10 coded death records to items in the ABDS disease list is set out in the next section.
Some ICD-10 codes could not be classified directly to a specific disease in the ABDS disease list. To include these deaths in the calculation of YLL, they were redistributed using methods described in the section ‘Redistribution of deaths’.
It is important to note that the alignment of ICD-10 codes to diseases in the ABDS disease list might not be the same as alignment to the disease lists used in other burden of disease studies. In particular, a disease in the ABDS disease list might have the same label but comprise different ICD-10 codes compared with other studies’ disease lists. Table 2.1 provides a list of ICD-10 codes for each disease used for the estimates of fatal burden in the ABDS 2018.
Redistribution of deaths
Identifying deaths for redistribution
Some ICD-10 codes are not appropriate or valid causes of death for burden of disease analysis. Some examples are:
- causes considered implausible as the underlying cause of death (such as hypertension and paraplegia)
- intermediate causes that have a precipitating cause (such as septicaemia and pneumonitis)
- immediate causes that occur in the final stages of dying (such as cardiac arrest and respiratory failure)
- causes that are ill-defined or unspecified, such as ill-defined digestive diseases and unspecified diabetes
Despite their overall high quality, Australian deaths data are affected by these issues. To quantify their contribution to the fatal burden, deaths coded to these underlying causes must be reassigned to one or more of the diseases (target diseases) according to what could be a more probable underlying cause. This process, referred to as ‘redistribution’ ensures that all the deaths in the reference year, hence all years of life lost, are counted in calculating YLL and is undertaken using the methods described.
Redistribution groups
The ICD-10 codes identified for redistribution were firstly assigned to redistribution groups. Each group was redistributed as a whole to the same range of target diseases. For example, non-specific digestive cancers formed one redistribution group and were reassigned to digestive cancers only. All deaths assigned to a group were redistributed using the same algorithm.
The redistribution groups used in the ABDS 2018 largely align with those used in the ABDS 2015. The table below shows the ABDS redistribution groups, target diseases and method for redistribution. The method by which each group was redistributed depended upon the level of available evidence.