Serving and ex-serving Australian Defence Force members who have served since 1985: suicide monitoring 2001 to 2019

Analysis in this study is based on year of occurrence of death. The NDI is the source of information on fact of death in this study. Fact of death information from the NDI is supplemented with cause of death information from the National Mortality Database (NMD). Results published in the report National suicide monitoring of serving and ex-serving Australian Defence Force personnel: 2020 update for deaths that occurred in 2018 were based on preliminary cause of death information from the NMD. This was the most recent version of cause of death information at the time of reporting.

Analysis of the NMD for all Australian deaths shows that between 4% and 7% of deaths are not registered until the next year (ABS 2018). These deaths are not captured in cause of death information, until data for the next year become available. This means that while fact of death information was complete for 2018 at the time of publishing the National suicide monitoring of serving and ex-serving Australian Defence Force personnel: 2020 update, cause of death information was missing for a number of deaths included in the analysis at that time. Additional suicides that occurred in 2018 but that were not registered until 2019 have now been identified with the inclusion of preliminary 2019 cause of death information in the current results.

Cause of death information for the Serving and ex-serving Australian Defence Force members who have served since 1985: suicide monitoring 2001 to 2019 release is based on final cause of death information for the years 2001 to 2016. Revised data are used for 2017 and preliminary data for 2018 and 2019. Cause of death for a small number of records linked to the 2017 (revised), 2018 (preliminary) and 2019 (preliminary) cause of death data may change where a death is being investigated by a coroner and more up-to-date information becomes available as a result of the ABS revisions process. This may have a small effect on the number of deaths attributed to suicide in these years, as some deaths currently coded as ‘undetermined intent’ could later be identified as ‘intentional self-harm’ (or vice-versa).

Although this method likely captures the vast majority of suicides, there is potential for some to be missed if coronial findings take longer than four years and the finding results in an update to the initial coded intent of death.

Care needs to be taken when interpreting data derived from deaths registered in Victoria. Following investigations between the ABS and the Victorian Registry of Births, Deaths and Marriages, 2,812 additional registrations from 2017, 2018 and 2019 were identified that had not previously been provided to the ABS. A time series adjustment has been applied to these deaths to enable a more accurate comparison of mortality over time. Affected deaths are presented in the year in which they were registered (i.e. removed from 2019 and added to 2017 or 2018). For detailed information on this issue please refer to Technical note: Victorian additional registrations and time series adjustments in Causes of death, Australia (ABS cat. no. 3303.0) available from the ABS website.

Changes to previously published results may also occur as additional information becomes available to the study.

For example, changes affecting recording of deaths in jurisdictional systems (including administrative and system changes, certification practices, classification updates or coding rule changes) can affect the data sets underlying this study. Data users should note the potential impact of these changes when making comparisons between reference periods. While such changes will not explain all differences between years, they are a factor that may influence the magnitude of any changes in suicide numbers as revisions are applied (ABS 2018)

Improvements in available information and linkage processes over time have also resulted in additional suicides being identified for periods previously reported on.

The following information on mortality coding is sourced from the ABS. For further information, see the ABS Causes of death, Australia report.

Substantial changes to ABS cause of death coding were undertaken in 2006, improving data quality by enabling the revision of cause of death for open coroner’s cases over time. Deaths that are referred to a coroner (including deaths due to suicide) can take time to be fully investigated. To account for this, all coroner-certified deaths registered after 1 January 2006 are subject to a revisions process. This allows cause of death for open coroner’s cases to be included at a later stage where the case is closed during the revision period. Cause of death data are deemed preliminary when first published, with revised and final versions of the data being historically published 12 and 24 months after initial processing. Prior to 2006, revisions did not take place and as such it is recognised by the ABS that deaths by suicide may have been understated during this period (ABS 2018).

As well as the above changes, new coding guidelines were applied to deaths registered from 1 January 2007. The new guidelines improve data quality by enabling deaths to be coded as suicide by ABS mortality coders if evidence from police reports, toxicology reports, autopsy reports and coroners’ findings indicates the death was due to suicide. Previously, coding rules required a coroner to determine a death as due to suicide for it to be coded as suicide.

The combined result of both changes has been the more complete capture of deaths by suicide, and a reduced number of deaths coded as ‘undetermined intent’, within Australian mortality data.

Detailed information on coding guidelines for intentional self-harm, and administrative and system changes that can have an impact on the mortality data set, can be found in Explanatory Notes 91-100 of Causes of death, Australia report (ABS 2018).

Rates based on small numbers of events can fluctuate from year to year for reasons other than a true change in the underlying frequency of the event.

In this report, rates are not reported when there are fewer than 5 events, as rates produced using small numbers can be sensitive to small changes in counts of deaths over time.

This report uses incidence rates to measure how often suicide occurs amongst the three ADF service groups, as well as in the Australian population. The incidence rate is the total number of deaths by suicide in a population over a specific period of time, divided by population time at risk during this time. In this study, the sum of the population at 30 June in each year of the relevant period is used as a proxy for population time at risk. Suicide incidence rates are expressed as the number of deaths per 100,000 population per year.

In previous years, a complex procedure was used to identify rehires between Defence personnel (PMKeyS) data extracts, and include these individuals in the ex-serving population in the time between re-hires. This was not possible this year, so it is possible that the total ex-serving population is slightly underestimated. However, investigations showed that identifying rehires made less than 1% difference to the total ex-serving population in every year.

The study population used in this report comprises all members with ADF service since 1 January 1985, whereas suicide rates are calculated from 2002 to 2019. This gap between the beginning of the study period (1985) and the start of the reporting period (2002) could cause some bias in the calculation of rates by time since separation. Although this is unlikely to be large, it should be taken into account when interpreting these results. Time since separation suicide rate are incidence rates for the indicated periods post separation. The numerator consists of the number of suicide deaths that occurred whilst the person was within the post separation time frame (for example between one and five years since the person’s separation). The denominator is the total time at risk spent by all ex-serving people in the post separation time frame.

Age-adjusted comparisons between the suicide rate in each of the three ADF service status groups and the Australian population were calculated using Standardised Mortality Ratios (SMRs). The SMR is a widely recognised measure used to account for differences in age structures when comparing death rates between populations. This method of standardisation can be used when analysing relatively rare events, that is, where number of deaths is less than 25 for the analysed time period. The SMR is used to control for the fact that the three ADF service status groups have a younger age profile than the Australian population, and rates of suicide vary by age in both the study populations and the Australian population. The SMRs control for these differences, enabling comparisons of suicide counts between the three service status groups and Australia without the confounding effect of differences in age.

The SMR is calculated as the observed number of events (deaths by suicide) in the study population divided by the number of events that would be expected if the study population had the same age and sex specific rates as the comparison population. SMRs greater than 1.0 indicate a greater number of suicides in the ADF population than expected; and SMRs less than 1.0 indicate a lower number of suicides than expected in the ADF population.

Unlike suicide rates, SMR cannot be used to compare suicide rate between service groups or across time. This is due to the fact that each SMR measure provides a comparison that is specific to the two populations involved. SMRs only compare the study population with the comparison population.

Comparisons with the Australian population are not calculated for other breakdowns such as by rank and reason for separation as only adjusting for age and sex does not account for all the differences in the populations. In addition, it is considered more useful to compare between the different levels of these groups rather than with the Australian population.

Age-standardised rates are rates standardised to a specific standard age structure to facilitate comparison between populations and over time. In this report, they are directly age-standardised rates adjusted using the Australian standard population, that is, the Australian estimated resident population (ERP) as at 30 June 2001.