Using and understanding the data – FAQs
What is burden of disease?
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).
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.
How are burden of disease estimates calculated?
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 2015 were sourced from the Global Burden of Disease Study 2015.
Australian Burden of Disease Study disease list
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 2015 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’.
Where can I find the data used in the Australian Burden of Disease Study 2015?
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 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 Australian population; and be timely, accurate, reliable and credible.
Further information on the data and methods used in Australian Burden of Disease Study 2015 can be found in the Australian Burden of Disease Study 2015: methods and supplementary material report.
Why use estimates from the Australian Burden of Disease Study 2015 instead of the Australian Burden of Disease Study 2011 study?
The Australian Burden of Disease Study 2015 was undertaken to build on the AIHW’s previous burden of disease studies and current disease monitoring work. The Australian Burden of Disease Study 2015 provides an update of burden of disease estimates using the infrastructure developed as part of Australian Burden of Disease Study 2011, and includes several methodological improvements.
This Australian Burden of Disease Study 2015 provides burden of disease estimates best matched to the Australian public health context for the Australian population (including subnational estimates) for 2015. It also provides estimates for 2011 and 2003, revised using the same methods as for 2015, to enable direct comparisons. The latest year, 2015 reflects the data availability from key data sources (such as the National Health Survey, deaths data, hospital admission data and various disease registers) at the time analyses began.
Improvements made in Australian Burden of Disease Study 2015 include:
- a more comprehensive list of diseases
- new data sources or evidence from latest epidemiological studies
- notably greater use of linked hospital/deaths data
- new or revised conceptual models to estimate YLD for some diseases in line with changes to the disease list or new evidence
- Estimates for 2003 and 2011 were recalculated, where methods were updated to enable comparison with 2015 estimates.
Therefore, published estimates from previous Australian studies are not directly comparable with those for the Australian Burden of Disease Study 2015 due to the methodology changes
Why do some diseases have no fatal or non-fatal estimates?
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.
What population data was used?
All Australian population-based rates for 2015 were calculated using populations rebased to the 2016 Census (released 27 June 2017) (ABS 2017). Population-based rates for 2011 were calculated using final population estimates from the 2011 Census (released 15 December 2016).
The Australian 2001 standard population (published 15 December 2016) was used for all age-standardisation, as per AIHW and ABS standards (ABS 2016).
ABS 2017. ABS Australian Demographic Statistics, Dec 2016. ABS cat. No. 3101.0. Canberra: ABS. Viewed 21 November 2017. <http://www.abs.gov.au/AUSSTATS/[email protected]/allprimarymainfeatures/432B4729A87614B1CA2581A70015892B?opendocument>.
ABS 2016. ABS Australian Demographic Statistics, June 2016. ABS cat. No. 3101.0. Canberra: ABS. Viewed 21 November 2017. <http://www.abs.gov.au/AUSSTATS/[email protected]/allprimarymainfeatures/9D56A542A17EF188CA2580EB001335A8?opendocument>.
Where to get more information on data and methods used in ABDS 2015?
More information on the Australian Burden of Disease 2015 study can be found in the following reports:
- Australian Burden of Disease Study 2015 detailed report
- Australian Burden of Disease Study 2015 summary report
- Australian Burden of Disease Study 2015 methodological report
For further information or for customised data requests please contact the AIHW Burden of Disease team: [email protected]