Purpose

• Structure of the report

The injury experience of Aboriginal and Torres Strait Islander peoples is not well documented. The National Injury Surveillance Unit published an overview of Aboriginal injury-related deaths in the triennium 1990-1992 (Harrison & Moller, 1994). Occasionally, some State health authorities have released monographs that have included an analysis of broad patterns of injury hospitalisation (e.g. Sleet et al., 1991; Kirke et al., 1993). All of these report higher rates of injury among Aboriginal and Torres Strait Islander peoples compared with non-Aboriginals. However, relatively small numbers of cases have prevented these authors from undertaking more in-depth analyses of Aboriginal and Torres Strait Islander injury patterns.

The purpose of this report is to:

• provide a description of injury hospitalisation patterns among Aboriginal and Torres Strait Islander peoples across all States and Territories (with the exception of the Northern Territory) that is as sound as possible given the nature of available data;
• identify key injury issues in the Aboriginal and Torres Strait Islander peoples;
• draw comparisons between the injury experience of Aboriginal and Torres Strait Islander peoples and the non-Aboriginal population; and
• point out the limitations of existing data sources and how they might affect the interpretation of the injury problem among Aboriginal and Torres Strait Islander peoples.

The period covered in this report is the 1991/92 financial year. We have combined hospitalisations data from all Australian States and the Australian Capital Territory to obtain sufficient numbers for a more detailed level of analysis. This is not without its problems as little is known about how identification of Aboriginality varies from state to state. This and other data-related issues are further discussed later in the report.

While recognising the limitations of the available data, we thought it important to describe what can be reasonably known from the best available data. The results should be treated with caution. Many of the comparative findings are so striking that it seems reasonable to assume that while correction of errors in the data set might alter numerical values somewhat, the conclusions to be drawn from these results would not change significantly. On the other hand, where differences in rates and patterns of injury are less pronounced, the impact of measurement errors in the data set might account for the observed discrepancies. It was not possible to estimate the magnitude of measurement errors in the present data set. Accordingly, we have not calculated or presented confidence intervals around our findings of differences in rates (and rate ratios).

Aside from measurement errors in the data set, the observed number of hospitalisations in any arbitrarily chosen period of time will be subject to random variation. It is possible to estimate the magnitude of the "error" associated with random variation by assuming an appropriate probability distribution and deriving confidence intervals. If the observed numbers of hospitalisations are assumed to be generated by a simple Poisson process, approximate 95% Poisson confidence intervals can be calculated using the Poisson variability factors shown in Table 1.

For example, the transportation injury rate for Aboriginal and Torres Strait Islander males is 614 per 100,000 based on 661 cases. The Poisson variability factor is 0.08 (approximate interpolation from figures in Table 1). The lower bound is calculated as 614 - (614 * 0.08) = 565. Similarly, the upper bound is calculated as 614 + (614 * 0.08) = 663. Thus the approximate 95% Poisson confidence interval for this rate is 565 - 663 per 100,000.

Note: To use this table, select the number of cases (N) on which a rate (R) is based and look up the Poisson variability factor (P). The lower (L) and upper (U) bounds of an approximate 95% confidence interval are calculated as L = R - (R * P) and U = R + (R * P).

In commenting on our results and assessing whether our findings could be justified, we considered the numbers of injuries, the consistency of injury patterns across age groups and causes, as well as existing knowledge of injury occurrence. This qualitative approach was considered to be appropriate given the nature of the data.

Structure of the report

Firstly, we describe the purpose of this report and the important issues relating to the quality of the available data. This is followed by a comparative overview of injury in Aboriginal and Torres Strait Islander peoples and non-Aboriginal populations. From this, a number of specific injury causes are selected for more in-depth analysis. Criteria for selection included: contribution to injury rates across the age range; the existence of particular age-specific patterns that could be the target of preventive strategies; and causes where differentials between Aboriginal and Torres Strait Islander peoples and non-Aboriginals were particularly high.

For each specific caused that was analysed in detail, the following items are presented:

• a definition of cases;
• the number of cases, crude and age-adjusted rates of hospitalisation for Aboriginal and Torres Strait Islander peoples;
• the key injury risks for Aboriginal and Torres Strait Islander peoples;
• the number of cases, crude and age-adjusted rates of hospitalisation for non-Aboriginals;
• a comparison between the two populations.