Comparisons at an individual level - Including Australian-born and all other overseas-bom birth

4. Including Australian-born and all other overseas-bom birthplace groups.

4.5 Comparisons at an individual level

In this section a comparison is made between the observed and expected number of joint occurrences of various disease conditions which were mentioned as causes of

death. This analysis is restricted to all the death records of Aborigines aged 15 years and over in the total data set — a subset of 375 male and 211 female deaths.

In total, information was gathered from the death records on the incidence of 17 specific disease classes: ischaemic (coronary) heart disease; other circulatory system diseases; liver disease; other digestive system diseases; kidney disease; diabetes; other pancreatic diseases; alcohol-related conditions; chronic obstructive airways disease; other

respiratory system diseases; malignant neoplasms (cancer); external causes (accidents, poisonings or violence); infectious diseases; epilepsy; broken bones or osteoporosis; malnutrition or cachexia; and old age or senility.

A measure of association between two disease conditions was obtained by dividing the observed number of joint occurrences by the expected number. The expected number was obtained by multiplying the number of individual records which mention the first disease condition by those which mention the second for each age group, and then dividing this sum by the total number of deaths which occurred at that same age group. A total was obtained by summing over the various age groups. If this measure of association is more than one, the observed number of joint occurrences is higher than expected, and if it is less than one, the observed number of joint occurrences is lower than expected. For example, for males the measure of the association between

ischaemic heart disease and liver disease was calculated to be 1.00 (19 observed divided by 19 expected occurrences). In this and some other cases, the expected number is equal to the observed number of joint occurrences of two disease conditions. Measures of association were only calculated for observed frequencies numbering five or more in an effort to limit the effects of small numbers.

Page 129 A chi square test at one degree of freedom was used to test the statistical significance of the measures of association obtained. Statistical significance was evaluated by

determining whether the calculated chi square values exceeded a critical value at a 5 per cent, 1 per cent, or 0.1 per cent level of significance. However, because of the

repetitive nature of this test, there is a high probability that some significant associations will occur purely by chance.

Tables 4.17 and 4.18 highlight various associations between 11 prevalent types of disease conditions mentioned in the death records as causes of Aboriginal death. In particular, these matrices summarize the association and joint occurrences between: ischaemic heart disease; other circulatory system diseases; liver disease; other digestive system diseases; kidney disease; diabetes; alcohol-related conditions; chronic

obstructive airways disease; other respiratory system diseases; infectious diseases; and malnutrition or cachexia. The most notable associations seem to occur between

ischaemic heart disease, other circulatory system diseases, liver disease, alcohol-related conditions, chronic obstructive airways disease, other respiratory system diseases, and infectious diseases. No notable associations were observed between the six disease conditions that were dropped from these tables.

Generally, the measures of association between heart disease (both ischaemic heart disease and other circulatory system diseases) and other disease conditions are either less than one or not much greater than one and not statistically significant. However, some associations were statistically significant — heart disease was associated with kidney disease and diabetes for males, and diabetes and alcohol-related conditions for females. For males, the most important association was between kidney disease and other circulatory system diseases, where the observed number of joint occurrences is twice the expected number (p<0.001). For females, there were negative associations between both ischaemic heart disease and other circulatory system diseases and alcohol- related conditions (p<0.05).

One of the more striking associations, for either sex, was found between alcohol-related conditions and liver disease. In this case the observed number of joint occurrences is for males (35 cases) nearly three times and for females (9 cases) nearly four times the expected number (pcO.OOl). This strong association is not surprising considering that most deaths due to liver disease in the data set were from alcoholic cirrhosis of the liver. Also, alcohol-related conditions were shown to be associated with infectious diseases, other digestive system diseases, and malnutrition or cachexia for males, and infectious diseases for females; and liver disease was shown to be associated with kidney disease and infectious diseases for males.

The associations between other respiratory system diseases and a range of other

conditions simply seem to be due to the fact that people of both sexes, often the elderly, eventually die of pneumonia after fighting diseases of all types.

What is interesting about this analysis is that ischaemic heart disease, or for that matter other circulatory system diseases, was not positively associated with alcohol-related conditions. As shown in Tables 4.17 and 4.18, joint occurrences of heart disease and alcohol-related conditions were mentioned in many death records. However, what is being established here is that the observed number of joint occurrences of these two disease conditions is not significantly higher than what would be expected if the two conditions were independent of one another. What this analysis indicates is that circulatory system diseases would most probably retain their importance as causes of death among Aborigines even without the existence of alcohol-related conditions.

Page 131 Table 4.17 Measure of association1 between 11 disease conditions mentioned as causes of death for male Aborigines2 who died in western New South Wales, 1979-1989.

Disease condition3 1L 2 3 4 5 6 7 8 9 10 11 1 1.0 1.0 1.4 1.0 1.1 0.9 0.7 0.6 (44) (19) (2) (3) (17) (36) (17) (37) (13) (6) 2 - 1.1 - 1.9** 1.5* 1.2 0.8 0.8 1.1 _ (12) (3) (7) (10) (25) (6) (17) (5) (4) 3 _ - 2.4** _ _2.7*** _ _1.1 _1.6* _ (1) (5) (2) (35) ₍₁₎ (8) (6) (2) 4 _ 2.1** _ 3.1** - _ (1) (1) (5) (0) (5) (2) (2) 5 (1) (4) (0) (2) (3) (1) 6 _ 1.0 _ 1.4 _ - (5) (1) (8) (3) (0) 7 1.0 1.0 1.7* 2.1** (5) (15) (12) (9) 8 _ 1.4 _ _ (11) (4) (2) 9 _ 2.6*** 1.5* (24) (7) 10 _ (3) 11 -

1. The measure of association is the observed number of joint occurrences of the two conditions divided by the expected

number based on independent distributions. The measure was only calculated for observed frequencies numbering five or more. The figures in brackets show the observed number of joint occurrences.

2. Comprising a sample of 375 deaths of males aged 15 years and over.

3. This matrix compares the joint occurrences between types of disease conditions mentioned as causes of death including: ischaemic heart disease (1); other circulatory system diseases (2); liver disease (3); other digestive system diseases (4); kidney disease (5); diabetes (6); alcohol-related conditions (7); chronic obstructive airways disease (8); other respiratory system diseases (9); infectious diseases (10); and malnutrition or cachexia (11). An asterisk represents a significant difference between the observed and expected number of deaths at a 0.05 probability level; two asterisks represent a significant difference at a 0.01 probability level; and three asterisks represent a significant difference at a 0.001 probability level.

of death for female Aborigines2 who died in western New South Wales, 1979-1989. Disease condition3 1 2 3 4 5 6 7 8 9 10 11 1 1.0 1.2 1.3 0.2* 0.8 0.9 0.6 (34) (4) (1) (15) (26) (5) (7) (18) (7) (1) 2 - - - 0.9 1.6* 0.3* - 0.8 1.1 _ (1) (1) (8) (24) (5) (2) (12) (9) (1) 3 _ - _ 3.9*** - _ - (1) (3) (1) (9) (1) (2) (9) (1) 4 (2) (1) (1) (2) (2) (1) (0) 5 _ 1.2 _ - 0.9 - - (6) (2) (2) (5) (4) (0) 6 _ _ 1.0 _ - (3) (2) (9) (3) (0) 7 _ _ 1.5 2.7*** - (1) (6) (7) (0) 8 _ _2.0** _{2.8*** -} (9) (6) (0) 9 - 3.4*** - (19) (0) 10 _ _ (0) 11 -

1. The measure of association is the observed number of joint occurrences of the two conditions divided by the expected

number based on independent distributions. The measure was only calculated for observed frequencies numbering five or more. The figures in brackets show the observed number of joint occurrences.

2. Comprising a sample of 211 deaths of females aged 15 years and over.

4.6 Summary

Page 133

This chapter has attempted to evaluate current Aboriginal mortality trends in western New South Wales by making comparisons at regional, community, and individual levels. At a regional level, Aboriginal mortality rates have been shown to differ significantly from those exhibited by the total New South Wales population. In particular, the analysis has demonstrated that in comparison to the total New South Wales population: the relative risk of death for Aborigines of both sexes was at least two times higher; Aboriginal life expectancy at birth was 15 to 20 years lower; and Aboriginal cause-specific death rates were much higher for most underlying causes of death. Deaths from circulatory system diseases accounted for the greatest proportion of the excess risk between the Aboriginal and total New South Wales cause-specific rates. Additionally, regional comparisons noted few differences in the level of Aboriginal mortality between 1980-1983 and 1984-1987, but very substantial disparities between Aboriginal mortality patterns and those exhibited by other Australian- and overseas- bom birthplace groups. During the 1980s, Aboriginal life expectancy and age- and cause-specific mortality rates did not change significantly. However, among males there has been a small increase in age-specific mortality during adulthood and cause- specific mortality from circulatory system diseases. When Aboriginal sex- and cause- specific standardized mortality ratios were compared with those of other birthplace groups, Aboriginal ratios were found to be considerably higher.

At a community level, significant differences were found between the mortality rates of a select sample of communities. As a rule, mortality rates in these communities tend to fall into three broad categories — very high, moderately high, and low — and to be somewhat correlated with household size, employment, the proportion of Aboriginal descent, and the dependency ratio.

At an individual level, there are two notable findings from the analysis of the joint occurrences of various disease conditions. The first and most important finding is the

lack of association between circulatory system diseases and alcohol-related conditions. This suggests that alcohol-related conditions are not a major cause of heart disease. The second finding is the significant association between alcohol-related conditions and liver disease, which is not at all surprising.

These comparisons have demonstrated that the Aboriginal mortality rates in western New South Wales are remarkably higher than those exhibited by other Australians. Furthermore, as among other Aboriginal groups in Australia, circulatory system

diseases account for the greatest proportion of this difference (see section 2.4 in chapter 2). Without substantial reductions in the incidence of heart disease, Aboriginal

CHAPTER FIVE

RISK FACTOR PREVALENCE SURVEY

5.1 Introduction and overview

In addition to gathering information on Aboriginal deaths in western New South Wales, I conducted a risk factor prevalence survey in Bourke during April and May of 1989. This survey was designed to assess the prevalence of and level of association between various behavioural and biological risk factors of coronary heart disease among Aborigines aged 18 years and over. The purpose of the survey, apart from gathering information for my own research needs, was to provide the community, especially the Aboriginal Health Service, with an assessment of the risk factors among Bourke Aborigines so that appropriate health promotion programs could be designed and implemented.

This was not the first such survey conducted in Bourke. Over the past 20 years Bourke Aborigines have been the subject of various health and social research projects. Many of the local research endeavours have been conducted by the town's health care

practitioners. There is the well-known work conducted by Kamien and associates on Aboriginal health and nutrition in Bourke during the late 1960s and early 1970s as part of a project on the Human Ecology of the Arid Zone (Kamien et al., 1974, 1975a; Kamien, 1975a, 1975b, 1975c, 1976); the morbidity survey by Coolican (1971, 1974) on his medical practice in 1968-69; the work by Cameron and colleagues (1986) on Aboriginal diabetes; and the work by Harris and colleagues on Aboriginal respiratory health and living conditions (Harris and Davies, 1984; Harris et al., 1984).

Additionally, the community has been studied by external researchers. Among others, there is the work of Castle and Hagan on Aboriginal employment (Castle and Hagan,

1983; Castle, 1987); Parkinson (1982) on the Aboriginal history of Bourke; Rowley

(1982) on Aboriginal health and living conditions; Gray and Hogg (1989) on Aboriginal mortality; and the New South Wales Ministry of Aboriginal Affairs (1987) on the Bourke disturbances in August of 1986.

5.2 The setting

Bourke is situated on the Darling River, about 800 kilometres northwest of Sydney in the far northwest of New South Wales (see Figure 3.1). In 1986, the town and

surrounding area had approximately 4,260 residents of whom 900 or 23 per cent were of Aboriginal descent (Australian Bureau of Statistics 1986 census of population and housing). The Aboriginal population resides in two main areas — the town settlers live in the east and northeast parts of town, and the fringe and former reserve settlers live west of town in an area of mostly old and run-down housing stock. Few Aborigines in Bourke are descendants of the Ngjamba tribe whose territory at contact included the present site of Bourke. Rather, most are descendants of a wide variety of Aboriginal groups from the surrounding region who arrived in Bourke 50 to 60 years ago (Kamien,

1975a). The descendants of the Ba:gundji tribe came from Wilcannia, the Marawari tribe from around the Paroo River, and from Peak Hill came descendants of the Wiradjuri and Wongaibon tribes. Other local inhabitants are descendants of the Wangkumara people who in 1935 were herded into cattle trucks and taken to Brewarrina from the Tibooburra region and who ended up residing in Bourke (see Beckett, 1958a; Long, 1970).

While the Aborigines in Bourke form a large proportion of the total population, they have little economic or political control (New South Wales, Ministry of Aboriginal Affairs, 1987). Although local Aboriginal services, such as the Aboriginal Health Service, the Widjeri Housing Co-operative, and the Land Council and legal office, have been established in recent years, real political control remains entirely in the hands of the non-Aboriginal population. The local shire council and chambers of commerce are made up entirely of non-Aborigines. In addition, the local court administration, the

Page 137 banks, the police, the Community Employment Service, Australia Post, Telecom, and the schools and various other government agencies and services are generally staffed by non-Aborigines. Despite the fact that most businesses in town depend to a large extent on the Aboriginal population, especially on their social security payments, no local businesses are owned or operated by Aborigines and few, if any, have Aboriginal staff (see section 3.3.3 in chapter 3).

Economically, like other country towns in the region, Bourke is basically a service, retail, and distribution centre for the northwest part of the state (Castle, 1987: 26). Until relatively recently, sheep and wool production formed the primary industry; however, cotton, citrus fruit, grain, and some beef cattle production have recently broadened this economic base. In the 1986-87 growing season, the gross value of agricultural

commodities produced in the shire was $38 million. Over 23,000 beef cattle were produced and 1,000,000 sheep and lambs were shorn. In addition, the shire produced over 1,000 tonnes of cereal grains, 15,000 tonnes of cotton, and 200 tonnes of citrus fruit (Australian Bureau of Statistics, 1988a). Until 1987, the major secondary industry in Bourke was an abattoir. Now, however, there are only a few engineering and motor repair shops. The tertiary sector, or service industry, which expanded considerably in the early 1980s, is made up of an array of local, state, and commonwealth government agencies and services and local retail and tourist enterprises.

Since the closing of the abattoir in 1987, employment prospects for both Aborigines and non-Aborigines have deteriorated considerably (Castle, 1987: 27-28). There is no other large industry in town and no realistic chance of any being established. The main source of employment (as for Aborigines in other rural areas of New South Wales) remains the public sector, especially the shire council and hospital. However, with the past and probable future consolidation of government services, it is unlikely that this sector will provide future growth in employment. As discussed in chapter 3 (see section 3.3.3), Aborigines' access to employment on agricultural properties has declined during

the 1980s because of a reluctance on the part of farmers and pastoralists to hire during a period of increasing costs and debt levels.

In document Australian Aboriginal mortality and coronary heart disease : a demographic inquiry (Page 147-157)