How many deaths and how many causes?

Four in 5 deaths involved more than one cause 

In 2022, 190,939 deaths were registered in Australia. Four in 5 of these deaths (80%) involved more than one cause. The proportion of deaths involving a single cause was similar in all years assessed: 19% in 2014 and 2018, and 20% in 2022. (Figure 3.1). The proportion of deaths with 5 or more causes was higher in 2022 (23%) compared with 2014 (20%).

Figure 3.1: Multiple cause of death metrics, 2014, 2018 and 2022

There are two types of multiple cause of death metrics for 2014, 2018 and 2022. One describes the average number of causes per death. This is typically highest for deaths at younger ages (15 to 44 years) and lowest under 14. From age 45, the average number of causes increases with increasing age until the oldest age (95 or more) where the average number declines to about the same as the deaths at ages 75 to 84. The other metric shows the distribution of the number of causes per death. This ranges from one sequentially up to five or more causes. It shows that, consistently across the years assessed, about 1 in 5 deaths have one cause. In 2022 almost one-quarter of deaths had five or more causes.

The number of causes recorded on death certificates can be influenced by a range of factors including certification practices (which can also vary over time), access to medical records including medical history, the resources (personnel and technology) for completing the death certificate and the nature of the underlying health condition. Variation over time might also be related to better diagnostics and increasing multimorbid chronic disease (that is, the presence of 2 or more long-term health conditions) (Harrison and Siriwardena 2018).

Other reasons could be the arrival of new widespread infectious diseases such as COVID-19, where presumably people continue to experience the same level of chronic comorbidity involvement in death as in pre-COVID years, but with the addition of COVID-19-related complications and causes. In 2017, an initiative was undertaken by the Australian Bureau of Statistics to improve the coding of information in coroner-certified deaths. As a result, the psychosocial contexts that contributed to a death were able to be included in the Australian cause of death data (ABS 2019). This practice is likely to increase the number of causes recorded in specific circumstances.

External causes have the highest average number of causes

When the deaths are grouped according to the underlying cause, the highest average number of causes per death (5.1) was for external causes (events causing injury, for example) (Figure 3.2). This is not surprising as external causes of death are usually reported to a coroner for a detailed assessment of the causes and circumstances involved in the death. As a result, the causes of death include the range of injuries sustained in an accident or all toxic substances involved in deaths due to accidental poisoning. More recently, the coding of non-medical (psychosocial) circumstances could also contribute to this high average number of causes (see Psychosocial factors contribute to death).

Figure 3.2: Average number of causes per death by cause group as the underlying cause, 2022

The average number of causes per death differs by the underlying cause of death. All causes of death only have one underlying cause. Deaths due to external, oral, musculoskeletal, reproductive & maternal, and endocrine disorders have the highest average number of causes involved in death. Oral, musculoskeletal, reproductive & maternal, and endocrine disorders have the highest average number of direct causes of death, while external causes have the highest average number of contributory causes. Ill-defined or unspecified/undetermined causes have the lowest average number across all cause types.

Notes: 

  1. Deaths registered in 2022 are based on the preliminary version and are subject to further revision by the Australian Bureau of Statistics.
  2. Average number of multiple causes may not equal the sum of the averages for the underlying, direct, and contributory causes, due to rounding.

Source: AIHW National Mortality Database, Table S3.3.

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