Methods
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Estimating fatal burden
Expressed as years of life lost (YLL), fatal burden is a measure of years lost due to premature death, measured against an ideal life expectancy. Analysis of fatal burden takes into account all deaths that occur in a population during a reference period. In this study, YLL estimates for the fatal burden of suicide and self-inflicted injuries were based on deaths that occurred in the reference year 2019.
Deriving YLL requires both:
- mortality data – the actual number of deaths and the ages at which those deaths occurred
- a reference life table – a measure of life expectancy at each age to derive years of life lost at each age. The reference life table used in calculating YLL for this report was the Global Burden of Disease (GBD) 2010 standard reference life table (Murray et al. 2012), which has a life expectancy at birth of 86.0 years for both males and females. This is consistent with the life table used in the 2018 Australian Burden of Disease Study (ABDS).
For this report, deaths are counted by year of occurrence and aligned to the ABDS causes; therefore they may differ from the number of suicide deaths reported elsewhere.
The analyses included all deaths with an underlying cause of death with an external cause of injury as ‘suicide and self-inflicted injuries’ (ICD-10 codes X60–X84, Y87.0) occurring during the reference periods (calendar years 2003, 2011, 2015 and 2018). For 2019, due to late registration of some deaths that occurred in November and December 2019 that are not captured in the latest 2019 deaths data, deaths that occurred between November 2018 to October 2019 were used to adjust for this undercount of 2019 deaths.
The analysis data set for this study comprised mostly cause of death information based on a final version of data. Specifically, deaths for the 2003, 2011 and 2015 reference years used a final version of cause of death data, while those for 2018 and 2019 used a preliminary version of cause of death. Since 2006, deaths certified by a coroner are revised and causes are updated, pending the status of coroner investigation. As such, some cause of death information is subject to change. The Australian Bureau of Statistics (ABS) revisions process is described in detail elsewhere (ABS 2020).
For more information on estimating fatal burden of disease for suicide and self-inflicted injuries, see AIHW forthcoming 2021b.
Estimating non-fatal burden
Expressed as years lived with disability (YLD), non-fatal burden is a measure of healthy years lost due to ill health. Calculating YLD can be quite complex, but in simple terms it incorporates:
- the number of people with the disease, and the consequences of the disease (referred to as ‘sequelae’) during the reference year
- the duration of the disease sequelae (duration is expressed as a fraction of a year)
- the severity of the ill health associated with the disease sequelae (referred to as the ‘disability weight’).
Disability weights attempt to capture the severity of the effects of a disease or injury on a scale from 0 (perfect health) to 1 (equivalent to death). In this report, disability weights from the Global Burden of Disease Study 2010 (also used in the 2018 ABDS) were used for YLD estimates for suicide and self-inflicted injuries.
The analysis of YLD for suicide and self-inflicted injuries includes 2 components:
- the short-term consequences of cases from the reference year admitted to hospital plus those that present at an emergency department but do not get admitted
- a proportion of suicides and self-inflicted injuries from previous years that have ongoing health loss – these are the long-term consequences of cases from previous years.
In general, the short-term consequences of admitted injuries is derived directly from hospitalisations data (incidence multiplied by duration). Short-term non-admitted estimates are derived using emergency department data and by applying an inflation factor (derived by the ratio of non-admitted to admitted cases for injuries by age and sex) to the short-term admitted cases to more fully capture the cases presenting to the emergency department but not admitted.
For more information on calculating inflation factors for non-admitted injuries, see AIHW forthcoming 2021b.
The long-term prevalence for injuries for the reference years 2003, 2011, 2015 and 2018 was sourced from the 2018 ABDS. The long-term prevalence of injuries in 2019 was derived from the 2018 ABDS by adding the injury incidence from 2018 (adjusted for all‑cause mortality) to the long-term prevalence in 2018; that is, the long-term cases in 2018 (who are still alive in 2019) were added to the new cases from 2018.
The major data sources used to estimate YLD injuries in 2019 were the NHMD and the NNAPEDCD. For further information on these databases, including data quality statements, see National Hospitals Data Collection.
Consequences of suicide and self-inflicted injuries
This analysis of injury YLD sourced from hospitalisations data is carried out on the nature of injury; that is, what is being treated in the hospital (traumatic brain injury, broken bone and so on). A separate analysis of the nature of injury and its corresponding external cause allows for different types of injury to be mapped to the cause of the injury (car accident, fall and so on) – in this case, suicide and self-inflicted injuries. This mapping (nature of injury to external cause mapping) is used to estimate injuries that are attributed to the suicide and self-inflicted injuries category.
The short-term injury prevalence is the sum of the short-term admitted prevalence and the short-term non-admitted prevalence. The short-term injury prevalence is added to the long-term injury prevalence, giving an estimate of total injury prevalence. The mapping is then used to estimate the proportion of injury health loss (prevalence and YLD) caused by suicide and self-harm.
For more information on estimating non-fatal burden of disease for suicide and self‑inflicted injuries, see AIHW forthcoming 2021b.
Estimating risk factor attributable burden
Attributable burden reflects the direct link between a risk factor (for example, alcohol use) and a disease or injury outcome (for example, suicide and self-inflicted injury). Population attributable fractions (PAFs), a measure from 0 to 1, are used to determine the proportion of a particular disease that could have potentially been avoided if the population had never been exposed to a risk factor.
- PAFs equal to zero means there is no burden attributable to the risk factor.
- PAFs equal to 1 means that all the burden of the linked disease(s) is attributable to the risk factor.
To estimate the risk factor attributable burden for suicide and self-inflicted injuries in 2019, the PAFs estimated for suicide and self-inflicted injuries in the 2018 ABDS (AIHW forthcoming 2021b) were multiplied by the 2019 YLL, YLD and DALY estimates for suicide and self-inflicted injuries.
Four individual risk factors (6 risk factor exposures) were included in the analysis of attributable burden for suicide and self-inflicted injuries as having convincing or probable evidence in the literature of a causal association:
- child abuse and neglect during childhood among people aged 5 and over
- alcohol use among people aged 15 and over
- illicit drug use (specifically amphetamine use, cocaine use, and opioid use) among people aged 15 and over
- intimate partner violence among women aged 15 and over.
For more information on estimating attributable burden, including how PAFs were calculated in the 2018 ABDS, see AIHW forthcoming 2021b.
Geography
Remoteness area
The remoteness areas divide Australia for statistical purposes into broad geographic regions that share characteristics of remoteness. The Remoteness Structure, which divides each state and territory into several regions based on their relative access to services, has 5 classes of remoteness: Major cities, Inner regional, Outer regional, Remote and Very remote. The category Major cities includes Australia’s capital cities, except for Hobart and Darwin, which are classified as Inner regional.
Remoteness areas are based on the Accessibility and Remoteness Index of Australia. For 2015, 2018 and 2019, the remoteness structure was based on the Australian Statistical Geography Standard 2016.
Socioeconomic area
Socioeconomic areas are based on the Index of Relative Socio-economic Disadvantage (IRSD) in this report. The IRSD is one of 4 Socio-Economic Indexes for Areas (SEIFA) developed by the ABS. This index is based on factors such as average household income, education levels and unemployment rates. The IRSD is not a person-based measure; rather, it is an area-based measure of socioeconomic disadvantage in which small areas of Australia are classified on a continuum from disadvantaged to affluent. This information is used as a proxy for the socioeconomic disadvantage of people living in those areas and may not be correct for each person in that area.
Socioeconomic areas are presented as approximate quintiles in this report. The lowest quintile (Quintile 1, or Q1) represents the approximate 20% of the population living in areas with the lowest socioeconomic characteristics; that is, it is the most disadvantaged. The level of socioeconomic position increases with each quintile, through to the approximate 20% of the population living in areas with the highest socioeconomic characteristics (Quintile 5, or Q5); that is, the least disadvantaged. For 2015, 2018 and 2019, socioeconomic areas were based SEIFA 2016 IRSD (ABS 2018).