Spatial analysis of suicide mortality in Australia: Investigation of metropolitan-rural-remote differentials of suicide risk across states/territories
Highlights
► Greater suicide risk was found in the states/territories with less economic development and lower urbanization level. ► Male suicide risk was elevated in rural areas, and even higher in remote areas. ► The metropolitan-rural-remote differential of male suicide was significant across states/territories, except New South Wales and Northern Territory.
Introduction
Suicide is a major public health issue in Australia. According to official mortality data from the Australian Bureau of Statistics (ABS), the age-standardized completed suicide rate in 2008 was 10.2 per 100,000 standard population, 16.0 for males and 4.5 for females. This made it the 17th leading cause of death overall, and the 10th leading cause of death for males (Australian Bureau of Statistics, 2010b).
Internationally, suicide rates have been shown to vary across different geographical units. Several overseas studies have used spatial analysis to demonstrate the spatial patterns of suicide risk across a whole country, often breaking these patterns down by sex, age groups and methods (Chang, Gunnell, Wheeler, Yip, & Sterne, 2010; Congdon, 1997, 2000; Middleton, Sterne, & Gunnell, 2008b; Pirkola, Sund, Sailas, & Wahlbeck, 2009). These studies have applied a smoothing technique to estimate local standardized mortality ratios (SMRs) with Poisson hierarchical regression models and the Markov chain Monte Carlo method. These techniques have aided the inspection of suicide risks and generated maps that can enhance understanding of the geographical pattern of suicide, and identification of the areas that need more attention. Relatively little work of this kind has been conducted in Australia. Qi et al., used geographical information system (GIS) tools in Queensland to investigate the suicide rate across different local government areas (Qi, Tong, & Hu, 2009, 2010), and several investigators have explored the differences in suicide rates between rural and urban areas at an aggregate level (Caldwell, Jorm, & Dear, 2004; Taylor, Page, Morrell, Harrison, & Carter, 2005; Yip, Callanan, & Yuen, 2000). A country-level analysis of suicide risk with visual inspection of the spatial pattern is needed to identify the regions which warrant particular attention in terms of suicide prevention activities.
The majority of studies in other countries have observed higher suicide rates or smaller reductions over time in suicide rates in rural areas than in urban areas (Chang et al., 2011; Pearce, Barnett, & Jones, 2007; Pirkola et al., 2009; Pridemore & Spivak, 2003; Razvodovsky & Stickley, 2009), although a small number of studies have identified suicide risk elevation in urban areas (Middleton, Sterne, & Gunnell, 2008a; Qin, 2005). Recent studies of suicide mortality in Australia suggested that Australian remote or rural areas also have a higher suicide risk than urban areas (Large & Nielssen, 2010; Qi et al., 2010; Taylor et al., 2005). It has been suggested that this phenomenon may be rooted in the fact that rural areas have not experienced the same social and economic development as some urban areas, and suicide prevention activities may not have been as well targeted in these areas (Pearce et al., 2007).
The current study builds on previous aggregated comparisons of metropolitan, rural and remote zones, and extends this comparison to a deeper exploration of the spatial difference of suicide risk within the geographical context of Australia. Area variation of health can be classified into three area levels: (1) differences between states/territories; (2) differences across levels of remoteness; and (3) differences among areas according toremoteness level. The first and the second differential can be studied through inspection of suicide prevalence and spatial pattern across state/territory or remoteness level. There are differences in terms of socio-economic circumstances, healthcare service provisions, and general health status across these levels (Australian Bureau of Statistics, 2007, 2010c), so it might be expected that there would be variations in locality-based suicide risk across states/territories. The third differential can be studied through exploring areas with unusual elevation of suicide risk which are not found in other areas in the same remoteness level. Such classification of area variation would facilitate a structured inspection and hence direct a targeted interpretation of area risk factors. Australia is an excellent country for conducting this analysis because it is split into eight major states/territories, and the remoteness of postal area in community level can be defined with a remoteness index.
Section snippets
Methods
The study was approved by the Human Research Ethics Committee of the Victorian Department of Justice.
Overall findings from mapping of relative risks
Appendix shows the unsmoothed SMRs for PAs in Australia which are calculated by dividing the observed number of suicide by the expected number. The intervals of unsmoothed SMRs for males and females were 0–171.31 and 0–74.63 respectively. The standard deviations of unsmoothed SMRs were 5.02 and 3.88 respectively. As some PAs had very low population sizes, they had very low expected suicide counts and hence a few cases of suicide could result in extremely high SMR values. Also, PAs which had no
Interpreting the findings
This study explored the spatial pattern of suicide risks for the whole of Australia with a reliable set of suicide data from the NCIS. Higher risk of suicide was found in the Northern Territory, Tasmania, northern Queensland and northern Western Australia. In contrast, the Australian Capital Territory, the majority of New South Wales and Victoria had lower risk of suicide. Male suicide risk had an apparent metropolitan-rural-remote gradient, whereas females had a more homogenous pattern. In
Conclusions
Our findings suggest that it is important to take geographical variations in suicide risk into account in national policy making. Particular suicide prevention interventions might be targeted at males living in remote areas, and some localized areas in metropolitan zones.
Acknowledgement
We thank the National Coroners Information System for providing us access to the database of coronial cases.
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