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1.23 Leading causes of mortality

Why is it important?

Mortality rates are a useful measure of the overall health status of a population, particularly to compare one population with another or to measure improvements over time. The gap between the Aboriginal and Torres Strait Islander population and the rest of the Australian population for particular causes of death provides an indication of the prevention, prevalence and management of particular diseases for Aboriginal and Torres Strait Islander peoples, relative to the rest of the population. This provides a useful indication of the diseases that have a greater impact on Aboriginal and Torres Strait Islander peoples. However, some significant health problems will not be reflected in mortality statistics; many conditions that cause serious health problems may not be fatal (such as depression, arthritis and intellectual disability) and so do not appear as common causes of death. As health status and health services improve for Aboriginal and Torres Strait Islander peoples, it is anticipated that premature mortality will reduce over time.

Findings

During the period 2008–12, in the five jurisdictions with adequate quality data (NSW, Qld, WA, SA and the NT), the most common cause of death among Aboriginal and Torres Strait Islander peoples was circulatory diseases (25% of all deaths), followed by neoplasms (including cancer) (20%) and external causes (15%). Circulatory diseases were also the most common cause of death for non-Indigenous Australians followed by cancer. After adjusting for age, circulatory disease accounted for the largest gap in death rates (24% of the gap) followed by endocrine, metabolic and nutritional disorders (including diabetes) (21%); neoplasms (including cancer) (12%); and respiratory diseases (12%). Deaths due to diabetes were 6 times higher for Indigenous Australians than non-Indigenous Australians and the leading cause of the gap for females. While the pattern of the leading causes of Indigenous deaths were the same across jurisdictions, the leading causes contributing to the gap varied: in NSW and WA the largest gap was in circulatory diseases, in Qld and the NT it was endocrine, metabolic and nutritional disorders (including diabetes) and in SA it was external causes.

For Indigenous Australians, the leading causes of death due to external causes were suicide (32%), transport accidents (26%), accidental poisoning (11%), assault (11%) and accidental drowning (4%). Around 60% of these deaths were for people between 15 and 39 years of age. For non-Indigenous Australians external causes made up 6% of all deaths. For the total Australian population, the leading external causes of death were suicide (27%), accidental falls (22%) and transport accidents (16%) (ABS 2014f). Mortality rates for circulatory diseases showed the largest decline in deaths for both Indigenous Australians and non-Indigenous Australians. Between 1998 and 2012 there was a significant decline of 40% in death rates due to circulatory diseases for Indigenous Australians and a significant narrowing of the gap. A study in the NT found that while there was an increase in incidence of acute myocardial infarction between 1992 and 2004 for Aboriginal and Torres Strait Islander peoples, at the same time there was an improvement in survival due to reductions in death both pre-hospital and after hospital admission (You et al. 2009).

Between 1998 and 2012 there was a significant decline in mortality rates due to respiratory disease for Indigenous Australians (by 27%) and a significant narrowing of the gap. For kidney disease mortality there was a significant decrease in both the Aboriginal and Torres Strait Islander mortality rate and the gap (over the period 2006 to 2012). Since 2006 there has been a significant increase in the age-standardised mortality gap due to cancer, reflecting an increase in mortality rates for Indigenous Australians and a decrease in rates for non-Indigenous Australians. For injury deaths, there was no significant reduction in short-term trends, or in the longer term. No significant changes were detected for diabetes mortality rates or the gap in diabetes mortality between Indigenous and non-Indigenous Australians.

Implications

Chronic conditions account for approximately 70% of Indigenous deaths and 81% of the gap in mortality between Indigenous and non-Indigenous Australians (including circulatory diseases, diabetes, cancer, kidney and respiratory diseases). In the period 1998–2012 there was a significant decline in mortality due to chronic diseases and a significant narrowing of the gap between Indigenous and non-Indigenous Australians. External causes such as suicide and transport accidents are also important contributors to the gap in mortality; however, there have been no significant changes in these deaths over time.

The health system can contribute to sustained improvements, in partnership with Aboriginal and Torres Strait Islander peoples, through identification of Indigenous clients, health promotion, early detection, chronic disease management and specialist and acute care to treat the more severe outcomes. A recent study of the gap in life expectancy between Indigenous and non-Indigenous Australians in the NT found socio-economic disadvantage was the leading factor accounting for one-third to one-half of the gap (Zhao et al. 2013a). Another recent study found chronic disease mortality increased with remoteness, reflecting differentials in health care and socio-economic status across areas. This finding was consistent across Australia and within most states and territories (Chondur et al. 2014). Improved management of chronic diseases can prevent the development of life-threatening complications but cannot cure these diseases. For example, a study of incidence and survival of acute myocardial infarction found improvements in survival for the NT Indigenous population associated with pre-hospital management of conditions. Also within-hospital specialised coronary care services and greater emphasis on post-hospital management was a factor in improved survival rates (You et al. 2009). Another study in the NT found the largest gains for the Indigenous population in avoidable mortality were for conditions amenable to medical care, but only marginal change for potentially preventable conditions such as lung cancer, chronic liver disease and cirrhosis and motor vehicle accidents (Li et al. 2009).

The 20–24 year age group had the highest number of deaths from suicide while deaths due to transport accidents were highest in the 15–19 year age group. Acute care services can save the lives of seriously injured people, and there is scope for improvements in timely access to life-saving emergency care for Indigenous Australians. High levels of intentional self-harm highlight the need for cross-sectoral approaches to healing, self-esteem and social and emotional wellbeing (see measure 1.18).

Closing the gap in life expectancy between Aboriginal and Torres Strait Islander peoples and other Australians within a generation has been adopted as a target by COAG. In the five years since the target was set there has been limited time for investment to impact on population level death rates. For example, reductions in population level smoking rates take five years to impact on heart disease and up to twenty years for cancer. Improvements in educational attainment will take 20 to 30 years to impact on early deaths from chronic disease in the middle years. The results signal the need for significant and concerted efforts to continue improving Indigenous health outcomes, both directly through health interventions and by addressing the social determinants of health.

Table 1.23-1 Causes of death, by Indigenous status, NSW, Qld, WA, SA and the NT, 2008–12
Underlying cause of death Per cent of deaths
Indig.
Per cent of deaths
Non-Indig.
Age standardised deaths
per 100,000 persons
Indig.
Age standardised deaths
per 100,000 persons
Non-Indig.
Ratio Gap % of total gap
Circulatory diseases 25.5 32.3 285.7 191.8 1.5 93.8 24.1
Neoplasms 20.2 30.1 224.1 177.9 1.3 46.2 11.9
Digestive organs 5.8 8.1 62.9 47.7 1.3 15.2 3.9
Lung cancer 4.9 5.7 56.4 33.5 1.7 22.9 5.9
Cervical cancer 0.5 0.2 3.5 1.0 3.5 2.5 0.6
External causes 15.2 6.1 75.2 38.2 2.0 37.0 9.5
Endocrine, metabolic & nutritional disorders 9.1 3.8 103.3 22.7 4.6 80.6 20.7
Diabetes 7.9 2.6 89.9 15.6 5.8 74.3 19.1
Respiratory diseases 7.6 8.4 96.3 49.8 1.9 46.5 12.0
Digestive diseases 5.6 3.4 47.4 20.5 2.3 26.9 6.9
Nervous system diseases 2.5 4.3 24.0 25.8 0.9 -1.8 -0.5
Kidney diseases 2.5 1.9 29.6 11.2 2.6 18.4 4.7
Infectious & parasitic diseases 2.4 1.5 19.4 9.2 2.1 10.2 2.6
Conditions originating in perinatal period 2.1 0.4 4.3 2.6 1.6 1.7 0.4
Other causes 7.4 7.8 76.4 47.0 1.6 29.4 7.6
All causes 100.0 100.0 985.6 596.7 1.7 388.9 100.0

Source: ABS and AIHW analysis of National Mortality Database

Figure 1.23-1 Deaths of Indigenous Australians from external causes of injury and poisoning, by age, NSW, Qld, WA, SA and the NT, 2008–2012
chart showing the number of deaths from external causes

Figure 1.23-1 shows the number of deaths of Aboriginal and Torres Strait Islander peoples from external causes of injury and poisoning in NSW, Qld, WA, SA and NT, for the period 2008 to 2012. The data is presented in 5-year age groups from 0-5 years to 75 years and over. For Indigenous Australians, the leading causes of death due to external causes were suicide (32%), transport accidents (26%), accidental poisoning (11%), assault (11%) and accidental drowning (4%). Around 60% of these deaths occurred between 15 and 39 years of age. The 20–24 year age group had the highest number of deaths from suicide while deaths due to transport accidents were highest in the 15–19 year age group.

Source: ABS and AIHW analysis of National Mortality Database

Table 1.23-2 Detailed causes of death for circulatory disease, cancer and respiratory disease, by sex, Aboriginal and Torres Strait Islander peoples, NSW, Qld, WA, SA and the NT, 2008–12
Underlying cause of death Males
Deaths
Males
%
Females
Deaths
Females
%
Total
Deaths
Total
%
Circulatory diseases
Ischaemic heart disease 1,041 63.3 587 44.7 1,628 55.0
Acute myocardial infarction 389 23.6 249 19.0 638 21.6
Other heart disease 245 14.9 264 20.1 509 17.2
Cerebrovascular disease 220 13.4 281 21.4 501 16.9
Stroke 180 10.9 231 17.6 411 13.9
Hypertension disease 55 3.3 65 5.0 120 4.1
Rheumatic heart disease 33 2.0 63 4.8 96 3.2
Other 51 3.1 53 4.0 104 3.5
Total circulatory diseases 1,645 100.0 1,313 100.0 2,958 100.0
Neoplasms (includes cancer, by site of neoplasm)
Digestive organs 380 31.5 297 26.2 677 28.9
Bowel 66 5.5 67 5.9 133 5.7
Respiratory and intrathoracic organs 353 29.3 251 22.1 604 25.8
Breast - - 150 13.2 150 6.4
Lip, oral cavity and pharynx 110 9.1 24 2.1 134 5.7
Female genital organs - - 133 11.7 133 5.7
Cervix - - 53 4.7 53 2.3
Lymphoid, haematopoietic and related tissue 63 5.2 68 6.0 133 5.6
Male genital organs 76 6.3 - - 76 3.2
Non-malignant neoplasms 16 1.3 24 2.1 40 1.7
Other 207 17.2 188 16.6 395 16.9
Total neoplasms 1,205 100.0 1,135 100.0 2,340 100.0
Respiratory diseases
Chronic lower respiratory diseases 280 61.3 284 65.9 564 63.5
COPD 231 50.5 240 55.7 471 53.0
Asthma 14 3.1 21 4.9 35 3.9
Pneumonia and influenza 91 19.9 76 17.6 167 18.8
Other 86 18.8 71 16.5 157 17.7
Total respiratory diseases 457 100.0 431 100.0 888 100.0

Source: ABS and AIHW analysis of National Mortality Database

Figure 1.23-2 Age-standardised mortality rates for selected causes of death, by Indigenous status, NSW, Qld, WA, SA and NT, 1998 to 2012
charts showing age-standardised mortality rates

Figure 1.23-2 shows age-standardised mortality rates for circulatory disease, cancer, respiratory disease, external causes, diabetes and kidney disease by Indigenous status over the period 1998 to 2012. Mortality rates for circulatory disease showed the largest decline in deaths for both Indigenous Australians and non-Indigenous Australians. Between 1998 and 2012 there was a significant decline of 40% in death rates due to circulatory disease for Indigenous Australians and a significant closing of the gap. Between 1998 and 2012 there was a significant decline in mortality rates due to respiratory disease for Indigenous Australians and non-Indigenous Australians and a significant closing of the gap. For kidney disease mortality there was a significant decrease in both the Aboriginal and Torres Strait Islander mortality rate and the gap (between 2006 and 2012). Since 2006 there has been a significant increase in the age-standardised mortality gap due to cancer, reflecting an increase in mortality rates for Indigenous Australians and a decrease in rates for non-Indigenous Australians. For injury deaths, there was no significant reduction in short term trends, or in the longer term. No significant changes were detected for diabetes mortality rates or the gap in diabetes mortality between Indigenous and non-Indigenous Australians.

Source: ABS and AIHW analysis of National Mortality Database