Volume 192 - Issue 8
Appearances may deceive: what’s going on with Australian suicide statistics?
Authors: Clare E Bradley, James E Harrison and Amr Abou Elnour
Med J Aust 2010; 192 (8): 428-429. || doi: 10.5694/j.1326-5377.2010.tb03578.x
Published online: 19 April 2010
Published online: 19 April 2010
Publication deadlines for reporting causes of deaths not yet finalised by coroners and different methods employed by different jurisdictions may have disguised Australia’s true suicide rate
Suicide is a topic of public health, public policy and general community interest. Accurate and timely suicide statistics are needed to measure and monitor this cause of death, to guide the development of prevention programs, and to enable evaluation and research.1 The main source of suicide data in Australia is the national mortality database of the Australian Bureau of Statistics (ABS).2 Recently, the ABS data have been used to report reductions in the annual rates and overall numbers of completed suicides since 1997;3,4 another such report, by Large and Nielssen, appears in this issue of the Journal.5
Surely a decline in suicide rates is good news? It is good news if the reported declines have really occurred. However, there are reasons to think that part of the apparent recent decline in suicide, as estimated using ABS data, is the result of changes in the data collection system.1,6-8 The ABS has published cautionary notes concerning suicide statistics in recent years,9,10 and has changed its process for coding deaths registered after 2006, prompted by awareness of the problem of slow finalisation of some cases.1,11
The system underlying cause-of-death statistics is quite complex, and suicide is a particularly challenging cause to record and classify. If a death is suspected to be the result of suicide, an obligation arises to refer it to a coroner. Police, forensic pathologists and staff at the coroner’s office are involved in obtaining and preparing information for the coroner. Sometimes the coroner decides that a formal inquest is warranted, but most cases are dealt with by a simpler administrative process. Details differ between jurisdictions, but the process always results in a conclusion on the cause of death. Coroners are alert to the sensitivity of a finding of “suicide”. Accordingly, they require positive evidence before making a finding of suicide. Findings normally state the means of death (eg, “ligature asphyxiation”), but often remain silent on intent.
Coroners’ records are used by ABS officers to guide their selection of a cause of death code. Historically, this information was mainly obtained by ABS officers visiting coroners’ offices and inspecting records. In 2000, an electronic register of coroner cases, the National Coroners Information System (NCIS), commenced operation. ABS officers began to use information in the NCIS, from about 2003, to supplement visits to coroners’ offices; then, from 2006, to replace these visits.11 NCIS records are entered by coroners’ staff. Some information can be entered soon after a death is referred to a coroner, but the record cannot be finished and the finding cannot be entered until the case has been closed by the coroner, sometimes years after the death has occurred.
The ABS has operated a system in which all of the deaths registered in a particular year were processed by a deadline, and then reported as final data. For this system to work well, the information that is necessary for coding the causes of all of the deaths registered in that year must be available to the ABS before its deadline. It turned out that the NCIS did not provide complete information on some deaths, including many suicides, in time to meet the ABS deadline.1,9 Often, the mechanism of injury was known by the deadline (eg, gunshot) but the final conclusion on intent was not. Following advice about the use of the International Classification of Diseases codes in this situation, ABS officers assigned to such cases the same codes that are used for unintentional injury deaths.7 Hence, suicide was under-enumerated.
The ABS has changed its system for coroner-certified deaths registered after 2006.11 A death registered in 2007 and incomplete in the NCIS at the former ABS deadline (early in 2009) will have been reported in the first release of ABS data on deaths registered in 2007, probably with a code in a range being used as a “holding bay” for incomplete cases (eg, “Hanging, strangulation and suffocation, undetermined intent”), or as unknown cause of death. If the NCIS record for that death closed during 2009, then the ABS reviewed and, if necessary, recoded it for the second release of 2007 deaths data, issued in March 2010.2 Many of the deaths that were initially assigned “holding bay” codes have characteristics suggesting that they will be recoded as suicides when final information is available. As expected, a rise in the number of suicide deaths was observed between the first and second releases of 2007 deaths data, and further rises are likely in subsequent releases. The first estimate of suicides for 2008, based on a further modification of the ABS system, is 2191, which is higher than the first (1881) and second (2054) estimates for 2007.
We don’t yet know final ABS suicide numbers for 2007 or 2008. We do know that ABS suicide counts for the several years before that are low. It is likely that this problem reflects the increasing reliance placed on the NCIS by the ABS in the period 2003–2006.
Accordingly, a great deal of caution must be employed when interpreting trends in suicide in Australia during the past decade, particularly when making comparisons between jurisdictions (as these have been found to be differentially affected, as a result of differences in coronial processing times1). Unfortunately, it is likely that at least part of the apparent decline since about 2002 shown by ABS statistics and reported by various authors, including Large and Nielssen,5 is an artefact of increased misclassification of suicide deaths. Changes that have been put in place, chiefly by the ABS, are likely to result in materially more reliable suicide statistics in future, providing a better (though still imperfect) basis for efforts to analyse and interpret changes in this important cause of death.
Competing interests
James Harrison is chairperson of the Australasian Mortality Data Interest Group, a member of the World Health Organization Revision Steering Group is leading the revision of the part of the International Classification of Diseases that is used to classify suicide, a member of the National Committee for Standardised Reporting of Suicide, and an external member of the management advisory committee of the NCIS.
References
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- Australian Bureau of Statistics. Information paper: external causes of death, data quality, 2005. Canberra: ABS, 2007. (ABS Cat. No. 3317.0.55.001.) http://www.abs.gov.au/ausstats/abs@.nsf/mf/3317.0.55.001 (accessed Feb 2010).
- Australian Bureau of Statistics. Causes of death, Australia, 2007. Explanatory notes. Technical note 1 ABS coding of suicide deaths. Canberra: ABS, 2009. ABS cat. no. 3303.0.) http://www.abs.gov.au/ausstats/abs@.nsf/Products/3303.0~2007~Technical+Note~ABS+Coding+of+Suicide+Deaths+(Technical+Note)?OpenDocument (accessed Feb 2010, link updated Apr 2010).
- Australian Bureau of Statistics. Causes of death, Australia, 2007. Explanatory notes. Technical note 2 coroner certified deaths. Canberra: ABS, 2009. (ABS Cat. No. 3303.0) http://www.abs.gov.au/ausstats/abs@.nsf/Products/3303.0~2007~Technical+Note~Coroner+Certified+ Deaths+%28Technical+Note%29?OpenDocument#2812172427 18994948 (accessed Feb 2010).