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Australian Indigenous HealthBulletin
 

spacing1Mortality

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Mortality

In 2011, 454 of the 12,724 deaths registered in WA were identified as being of an Indigenous person [1], but, because of the under-identification of Indigenous people in death registrations, the actual number of Indigenous deaths is likely to be higher than the number registered.

The following summary measures of mortality are based on the numbers of registered deaths, so some caution should be exercised in their interpretation.

Box 2: Adjusting for differences in the age-structures of populations

Comparison of Indigenous and non-Indigenous mortality needs to take account of differences in the age structures of the Indigenous and non-Indigenous populations using a process known as standardisation. (The process is also referred to as age-adjustment.)

Direct standardisation, the preferred method, applies detailed information about Indigenous deaths, including sex and age, to a ‘standard’ population [2]. (In Australia in recent years, the 2001 Australian population has generally been used as the standard population.) Direct standardisation enables accurate comparisons of Indigenous and non-Indigenous rates, and time-series analyses.

If detailed information is not available, it is still possible to use indirect standardisation to estimate standardised mortality ratios (SMRs). SMRs allow for the comparison of numbers of registered Indigenous deaths with the numbers expected from the corresponding age-sex-specific death rates for the total population or, preferably, the non-Indigenous population. The SMR is the ratio of the numbers of deaths (or of other health measures) registered/observed and expected.

Age-standardised death rates

After age-adjustment, the death rate for Indigenous people in WA of 1,431 per 100,000 was 2.5 times the rate for non-Indigenous people in 2006-2010 [3].

Between 1991 and 2010, there was a 35% reduction in the death rates for Indigenous people in WA (there was a 31% reduction for other Western Australians) [3]. Between 2001 and 2010, there was no significant change in the death rates for Indigenous people, but a reduction of 9% for non-Indigenous people in WA.

Expectation of life

In 2009, the ABS revised its estimates for expectation of life at birth for Indigenous people [4]. After adjustment for the underestimate of the number of deaths identified as Indigenous, the ABS estimates that Indigenous males born in WA in 2005-2007 could be expected to live to 65.0 years, 14 years less than the 79.0 years expected for non-Indigenous males. (Life expectancy at birth is the number of years a person born in the reference year can expect to live if they experience the current age-specific death rates.) The expectation of life at birth of 70.4 years for Indigenous females born in WA was 12.5 years less than the expectation of 82.9 years for non-Indigenous females born in WA. For the same time period, the estimates for Indigenous people nation-wide were 67.2 years for males and 72.9 years for females.

Age at death

In 2011, the median age at death for Indigenous males in WA was 52.2 years, 25.2 years less than that for non-Indigenous males (77.4 years) [1]. 7 The median age at death for WA Indigenous females was 54.2 years, 30.2 years less than that for WA non-Indigenous females (84.4 years).

In 2007-2011, death rates in WA were higher for Indigenous people than for non-Indigenous people across all age-groups, with rate ratios highest in the middle adult years (Table 3) [1]. 8 (These ratios, being based on the numbers of deaths registered, are likely to underestimate the true differences between death rates for Indigenous people and the total population.) The greatest difference occurred among males and females aged 35-44 years with Indigenous:non-Indigenous rate ratios of around seven to eight.
Table 3: Age-specific death rates, by sex and Indigenous status, and Indigenous:non-Indigenous rate ratios, WA, 2007-2011
Age-group (years) Males Females
Indigenous Non-Indigenous Rate ratio Indigenous Non-Indigenous Rate ratio
Source: ABS, 2012 [1]
Notes:
  1. Rates are per 100,000 population, except for age 0
  2. Rate ratio is the Indigenous rate divided by the non-Indigenous rate
  3. Deaths for which Indigenous status was not stated were excluded from the calculation of rates
0 10 3 3.4 5 3 1.8
1- 4 63 22 2.8 48 12 4.0
5-14 38 9 4.3 29 9 3.1
15-24 241 56 4.3 106 26 4.1
25-34 406 89 4.6 219 36 6.1
35-44 834 121 6.9 510 66 7.7
45-54 1,388 260 5.3 1,021 153 6.7
55-64 2,381 579 4.1 1,671 343 4.9
65+ 6,380 3,819 1.7 5,296 3,423 1.5

Infant mortality

The infant mortality rate (IMR) is the number of deaths of children under one year of age in a calendar year per 1,000 live births in the same calendar year. In 2009-2011, the IMR of 7.0 infant deaths per 1,000 live births for Indigenous people in WA was 2.4 times the rate for non-Indigenous infants [1]. The IMR of 10.2 per 1,000 for Indigenous male infants was 2.8 times higher than the rate of 3.7 per 1,000 for Indigenous female infants.

Causes of death

In 2006-2010, the most common cause of death among Indigenous people in WA was circulatory disease (also known as cardiovascular disease, which includes heart disease and stroke), accounting for 26% of Indigenous deaths in WA [3]. The next leading causes of death were injury and neoplasms (almost entirely cancer), responsible for 18% and 16% respectively of Indigenous deaths in WA (Table 4).
Table 4: Age-standardised death rates, by Indigenous status and cause, and Indigenous:non-Indigenous rate ratios, WA, 2006-2010
Cause of death Indigenous Non-Indigenous Rate ratio
Source: AIHW, 2013[3]
Notes:
  1. Due to the under-identification of Indigenous deaths, these rates are likely to under-estimate the true difference between the Indigenous and non-Indigenous populations
  2. Rates per 100,000 population
  3. Ratio is the Indigenous rate divided by the non-Indigenous rate
Circulatory disease 415 181 2.3
Injury 137 41 3.4
Neoplasms (cancer) 265 177 1.5
Endocrine, metabolic and nutritional disorders (including diabetes) 165 24 6.9
Respiratory disease 123 43 2.9
Digestive disease 72 20 3.6
Kidney disease 55 10 5.4
Nervous system disease 42 28 1.5
Infectious and parasitic disease 29 7 4.0
Conditions originating in the perinatal period 5 2 2.8
Other causes 123 41 3.0
All causes 1431 574 2.5

Avoidable mortality

Avoidable mortality refers to deaths that could have been prevented with timely and effective health care, including early detection and effective treatment, as well as appropriate modifications to lifestyle behaviours (such as quitting smoking) [5]. In the five year period 2006-2010, there were 1,417 avoidable deaths among Indigenous people aged 0-74 years in WA [3]. After age-adjustment, the rate of avoidable deaths for Indigenous people was 4.8 times higher than the rate for non-Indigenous people in WA. In 2006-2010, the leading causes of avoidable Indigenous deaths in WA were coronary heart disease (responsible for 19% of avoidable deaths), cancer (13%), and diabetes (11%) [3]. Other causes included intentional self-harm (10%), road traffic injury (9.0%) and alcohol-related disease (5.8%).

Between 1997 and 2010, there were significant reductions in death rates from avoidable causes for Indigenous and non-Indigenous Western Australians, but no closing of the gap in death rates [3]. Between 2001 and 2010, there was no change in death rates from avoidable causes for Indigenous people in WA, but there was a reduction in the rates for non-Indigenous people in WA.

Endnotes

  1. The median age at death is the age below which 50% of people die. The measure partly reflects the age structures of the respective populations, so it is a less precise measure than age-specific death rates.
  2. Rate ratios are the Indigenous rate divided by the non-Indigenous rate for each age-group.

References

  1. Australian Bureau of Statistics (2012) Deaths, Australia, 2011. Canberra: Australian Bureau of Statistics
  2. Australian Institute of Health and Welfare (2011) Principles on the use of direct age-standardisation in administrative data collections: for measuring the gap between Indigenous and non-Indigenous Australians. Canberra: Australian Institute of Health and Welfare
  3. Australian Institute of Health and Welfare (2013) Aboriginal and Torres Strait Islander health performance framework 2012 report: Western Australia. Canberra: Australian Institute of Health and Welfare
  4. Australian Bureau of Statistics (2009) Experimental life tables for Aboriginal and Torres Strait Islander Australians: 2005-2007. Canberra: Australian Bureau of Statistics
  5. Page A, Tobias M, Glover J, Wright C, Hetzel D, Fisher E (2006) Australian and New Zealand atlas of avoidable mortality. Adelaide: Public Health Information Development Unit, University of Adelaide
 

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    Last updated: 25 October 2013
     
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