Using and understanding the data – FAQs
Burden of disease analysis measures the impact of fatal (or years of life lost, YLL) and non-fatal burden (years lived with disability, YLD), with the sum of non-fatal and fatal burden equating the total burden (disability-adjusted life year, DALY). YLD are weighted to account for the severity of health impact.
1 DALY is equivalent to 1 year of healthy life lost.
High quality information on the health impacts and distribution of different diseases and injuries provides an important contribution to the evidence base to inform health policy and program and service delivery. Burden of disease studies allow dying from disease and living with illness to be compared and reported in a consistent manner.
For a more detailed explanation, refer to this 'What is burden of disease?' video.
Disability-adjusted life years (DALY) are estimated by combining the years of life lost (YLL) with the years lived with disability (YLD) in a single reference year for each sex, age group and disease or injury.
DALY = YLL + YLD
YLL equals the sum of: the number of deaths due to the disease at each age multiplied by the number of remaining years that a person would on average expected to have lived according to an aspirational life expectancy.
YLD is estimated by multiplying the point prevalence of all sequelae (i.e. consequences of a disease) by a disability weight which reflects the severity of the health state. Point prevalence is defined as the number of people with a condition at a particular point in time, for a reference year. The disability weights used in Australian Burden of Disease Study 2018 were sourced from the Global Burden of Disease Study 2013 (GBD 2013 Collaborators 2015).
Burden disease analysis provides estimates for an extensive list of diseases and injuries, and has been devised to be mutually exclusive (non-overlapping).
The Australian Burden of Disease Study 2018 disease list comprises over 200 specific diseases or conditions (such as coronary heart disease, stroke, lung cancer or bowel cancer), grouped into 17 disease groups of related diseases or conditions—such as cardiovascular diseases or cancer. Estimates for injuries are calculated from two perspectives— external cause of injury (for example, road traffic accident) and nature of injury (such as traumatic brain injury).
Conditions that could not be individually specified are included in a residual category for each disease group— such as ‘other cardiovascular conditions’.
Mortality data to calculate YLL estimates was sourced from the AIHW’s National Mortality Database (NMD). Given the high quality of these data, no modelling had to be undertaken to adjust for coverage or completeness for national estimates. Some transformation of the data was undertaken to reassign some causes of death to fit the purposes of burden of disease analysis. For Aboriginal and Torres Strait Islander YLL estimates, adjustments were made to account for under-identification of Indigenous Australians in mortality records. More information is provided in Australian Burden of Disease Study 2018: methods and supplementary material and in Appendix A of the Australian Burden of Disease Study 2018: impact and causes of illness and death in Aboriginal and Torres Strait Islander people report.
For YLD estimates, as there is no single comprehensive and reliable source of data on the incidence, prevalence, severity and duration of all non-fatal health conditions, morbidity estimates were drawn from a wide variety of sources, and generally based on the best single source. This included administrative data, national surveys, disease registers and epidemiological studies. Potential sources for disease-specific morbidity data were required to: have case definitions appropriate to the disease being analysed; be relevant to the Indigenous Australian population; and be timely, accurate, reliable and credible.
Further information on the data and methods used in Australian Burden of Disease Study 2018 can be found in the Australian Burden of Disease Study 2018: methods and supplementary material report.
The Australian Burden of Disease Study 2018 was undertaken to build on the AIHW’s previous burden of disease studies and current disease monitoring work. The Australian Burden of Disease Study 2018 provides an update of burden of disease estimates using the infrastructure developed as part of Australian Burden of Disease Study 2011 and 2015, and includes several methodological improvements.
This Australian Burden of Disease Study 2018 Aboriginal and Torres Strait Islander component provides burden of disease estimates best matched to the Australian public health context for the Indigenous Australian population (including subnational estimates) for 2018. It also provides estimates for 2011 and 2003, revised using the same methods as for 2018, to enable direct comparisons. The latest year, 2018, reflects the data availability from key data sources (such as the National Aboriginal and Torres Strait Islander Health Survey, deaths data, hospital admissions data and various disease registers) at the time analyses began.
Improvements made in the Australian Burden of Disease Study 2018 include:
- a more comprehensive list of diseases
- new data sources or evidence from latest epidemiological studies
- new or revised conceptual models to estimate YLD for some diseases in line with changes to the disease list or new evidence
- recalculation of estimates for 2003 and 2011, where methods were updated, to enable comparison with 2018 estimates.
Therefore, published estimates from previous Australian studies are not directly comparable with those for the Australian Burden of Disease Study 2018 due to methodology changes.
Some diseases do not have YLL or YLD estimates as either mortality does not occur from that disease (such as hearing loss) or the disease is only fatal and as such there is no morbidity (Sudden Infant Death Syndrome). For some rare infections, there were no deaths or morbidity associated with the disease in certain reference years.
All Indigenous population-based rates were calculated using Aboriginal and Torres Strait Islander backcast and projected population estimates as at 30 June 2018 (based on the 2016 Census) (ABS 2019). For the calculation of Indigenous rates of burden by remoteness, experimental Indigenous population estimates derived by the AIHW from the published ABS estimates were used (for 5 remoteness categories, by 5-year age group and sex, as at 30 June).
Non-Indigenous population estimates were calculated by subtracting the Aboriginal and Torres Strait Islander population estimates from the total Australian population estimates for the same years.
The Australian 2001 standard population (published 15 December 2016) was used for all age-standardisation, as per AIHW and ABS standards (ABS 2016).
More information on the Australian Burden of Disease Study 2018 Aboriginal and Torres Strait Islander estimates can be found in the following reports:
- Australian Burden of Disease Study 2018 – key findings for Aboriginal and Torres Strait Islander people (BOD 28)
- Australian Burden of Disease Study: impact and causes of illness and death in Aboriginal and Torres Strait Islander people 2018 —Summary (BOD 33)
- Australian Burden of Disease Study: impact and causes of illness and death in Aboriginal and Torres Strait Islander people 2018 (BOD 32)
- Australian Burden of Disease Study: methods and supplementary material 2018 (BOD 26)
- Australian Burden of Disease Study 2018: Interactive data on risk factor burden (BOD 36)
For further information or for customised data requests please contact the AIHW Indigenous Burden of Disease team via [email protected].
ABS (Australian Bureau of Statistics) 2016. Australian Demographic Statistics, June 2016. ABS cat. No. 3101.0. Canberra: ABS. Viewed 21 November 2017.
ABS 2019. Estimates and Projections, Aboriginal and Torres Strait Islander Australians 2006–2031. Viewed 22 July 2020.
GBD (Global Burden of Disease Study) 2013 Collaborators 2015. Supplement to: Global, regional, and national incidence, prevalence, and years lived with disability for 301 acute and chronic diseases and injuries in 188 countries, 1990–2013: a systematic analysis for the Global Burden of Disease Study 2013: The Lancet 2015. 386(10010): S1–1868. doi:org/10.1016/S0140-6736(15)60692-4.