Technical notes

Expanded study population demographics

The population used in this report includes all ADF members who have served at least one day since 1 January 1985. As of 31 December 2019, almost 373,500 Australians had served at least one day in the ADF since 1 January 1985. Of these, just over 358,000 were still alive of which 59,000 were permanent, 38,700 reserve and nearly  261,000 ex-serving.

Since 1985, the ex-serving population with at least one day of service since 1 January 1985 has increased each year as permanent and reserve ADF members separate. At the end of 1985, almost 6,100 members had separated and by the end of 2019 this had grown to nearly 274,000. Due to the method used to assemble the study population, as members leave the permanent and reserve service, they are counted as members of the ex-serving study population until they die.

In comparison, the previous version of the report included all ADF members who had served at least one day since 1 January 2001. At 31 December 2019, there were the same numbers of permanent and reserve, however only 125,000 ex-serving. Therefore, the ex-serving population included in this report is more than double that of the previous report.

For more information on the demographics of this population, see the report Serving and ex-serving Australian Defence Force members who have served since 1985: population characteristics.

Figure 19: Ex-serving population totals between 1985 and 2000 and 2000 and 2019, as at 31 December 2019

Source: AIHW analysis of linked Defence Historical Personnel data–PMKeyS–NDI data 1985–2019; NMD 2002–2019.

How does the expanded study population affect the results?

The increased size of the ex-serving population with the addition of those with service between 1985 and 2000 has resulted in a similar increase in the number of ex-serving deaths by suicide reported. For example, the 2020 update reported a total of 267 ex-serving suicides between 2001 and 2018, whereas 1,062 are reported here (between 2001 and 2019). However, it is important to understand that this increased suicide count doesn’t reflect a higher risk of suicide to the ADF population. Rather, the number of deaths by suicide identified has increased because we’re reporting on deaths from within a much larger group of people.

Care should be taken in comparing data in this report with previous AIHW publications. When comparing the results published here to those released in earlier updates, it’s more useful to focus on suicide rates, as these give a better indication of the risk of suicide to different groups within the ADF population. As shown in Figure 20, the suicide rates have not significantly changed due to the expanded study population. Notice that the width of the confidence intervals for ex-serving males and females have approximately halved with the addition of members with post-1985 service, indicating that the results are more statistically reliable.

Figure 20: Suicide rates by service status group and sex, post-2001 and post-1985 service, 2002–2019

Source: AIHW analysis of linked Defence Historical Personnel data–PMKeyS–NDI data 1985–2019; NMD 2002–2019; Defence population snapshots, 2002–2019.

Limitations in the study population

The study population does not include ADF members with service prior to 1 January 1985. The analysis is constrained by technical limitations in Department of Defence systems and information infrastructure for records before 1985.

Changes to previously published suicide information

An additional 808 suicide deaths are reported here compared to the 2020 update. The breakdown of changes in the number of suicide deaths reported is as follows:

  • 717 suicide deaths between 2001 and 2018 in members who separated between 1 January 1985 and 31 December 2001 (and were therefore previously out of scope)
  • 84 suicide deaths that occurred in 2019
  • 6 additional suicides in 2018 due to lag in reporting cause of death
  • 1 additional suicide in 2017 due to a change in the reported cause of death from unspecified to suicide
  • 1 additional suicide death was identified in 2015 due to an update in the Defence Suicide Database
  • less 1 death in 2016 that was reported as a suicide in the 2020 report but has since been recoded to a different cause of death
  • 1 suicide death for which the year of death was updated from 2014 to 2015 in the National Death Index (NDI).

As well as the expansion of the study population and addition of a new year of cause of death data, there are three main reasons for changes to previously published suicide results, as described below.