Measuring Australia's excess mortality during the COVID-19 pandemic (doctor-certified deaths)

Provisional deaths data for measuring changes in patterns of mortality during the COVID-19 pandemic and recovery period.

Cite
Print
Released
25/05/2022
Source
Provisional Mortality Statistics, Jan - Feb 2022

This article provides excess mortality estimates for doctor-certified deaths in Australia until the end of February 2022, covering the period when infections and deaths from the Omicron variant were most prevalent. It updates the article on excess mortality in Australia that was published in March and provided estimates until the end of December 2021. Excess mortality estimates in this article are provided for doctor-certified deaths in Australia only. Excess mortality estimates by selected cause of death are available in the data download tab of this article.    

Excess mortality is typically defined as the difference between the observed number of deaths in a specified time period and the expected numbers of deaths in that same time period. Excess mortality measures can account for deaths due to COVID-19, potentially misclassified or undiagnosed COVID-19 deaths, and other mortality that may be indirectly related to the pandemic (e.g. relating to social isolation or changed access to health care). 

Measuring excess mortality

Across the world, health and statistical authorities have sought to measure excess mortality during the COVID-19 pandemic. Different methodologies can be applied, with the goal to predict an expected number of deaths for a given year. Estimating the expected future seasonality for deaths can be a challenge in many models. The suitability of a model can depend on factors such as country context, data quality and collection methods, or outcomes sought from analysis.

The ABS has adopted aspects of a methodology used by New South Wales (NSW) Health, applying a cyclical linear regression with a robust estimation procedure to produce both an expected number of deaths and a range of expected deaths for 2022. The model has been applied to all-cause and cause-specific mortality to identify significant changes in patterns of mortality over time. See the methodology section at the end of the excess mortality article for additional detail on the method. 

Interpreting results

Outputs from excess mortality estimates will differ depending on the calculation applied and the scope of the input data. When interpreting the results in this report the following factors must be taken into consideration. 

Only deaths certified by a doctor are included in the analysis. Approximately 87-89% of deaths annually are certified by a doctor, with some variability across jurisdictions. 

The expected number of deaths in 2022 has been projected using 2016 as the beginning of the baseline period. 

This report places emphasis on observed numbers of excess deaths that are statistically significant. In any given time period, even if no temporary health hazards influence the number of deaths (such as community transmission of influenza or COVID-19) there is some natural variation in patterns of mortality. While the actual number of deaths may be different from the expected number of deaths, it should fall within an expected range (i.e. there is a 95% chance that the expected number of deaths would lie between the upper and lower bounds of the confidence intervals). When actual observations (counts of death) exceed the upper threshold or drop below the lower threshold this indicates a statistically significant change in the pattern of mortality. 

A single week above threshold does not necessarily suggest statistically significant excess mortality. Prolonged periods (2 or more weeks) where counts exceed thresholds suggest more strongly that the numbers of deaths are above or below normal. 

The section below presents two graphs –

The first graph is a time series of doctor certified deaths from January 2016 to February 2022 that has the number of actual observations plotted against the expected number of deaths estimated from the regression. The upper and lower thresholds (1.96 standard errors) of the regression are also plotted.

The second graph focuses on 2020, 2021 and 2022, allowing closer inspection of patterns of death during the COVID-19 pandemic. 

Weekly all-cause mortality: Australia

  • There were 4,732 more deaths than expected in the first two months of 2022.
  • For all weeks in 2022 the number of deaths was higher than expected. 
  • For all weeks in 2022 the number of deaths exceeded the upper limit of usual variation reaching statistical significance (3,105 deaths). 
  • Deaths due to dementia, diabetes, ischaemic heart diseases and cerebrovascular diseases also recorded some statistically significant excess mortality in the first two months of 2022. There were 164 people who died from these diseases who were COVID-19 positive at death. See the datacube in the data downloads section of this article for more information on specific causes of death. 
  • In past years excess mortality has typically occurred during the winter months associated with virulent influenza seasons. Sustained excess mortality during the summer months of 2021-2022 aligns with the Delta and Omicron waves. 
  1. Dates for key events are indicative only and may differ to other sources. 
  2. Data is provisional and will change as additional death registrations are received.
  3. 2016 is the starting point for the regression when modelling the projected number of deaths. 
  4. Data includes all doctor certified deaths occurring by the end of February 2022 and registered and received by the ABS until 30 April 2022. 
  5. People who died with COVID-19 as an associated cause of death (as opposed to the underlying cause of death) are included in the without COVID-19 series.
  6. Data is for January and February is expected to be approximately 98% complete. See section on Timeliness and completeness of data for more information.
  1. Dates for key events are indicative only and may differ to other sources. 
  2. Data is provisional and will change as additional death registrations are received.
  3. 2016 is the starting point for the regression when modelling the projected number of deaths. 
  4. Data includes all doctor certified deaths occurring by the end of February 2022 and registered and received by the ABS until 30 April 2022. 

  5. People who died with COVID-19 as an associated cause of death (as opposed to the underlying cause of death) are included in the without COVID-19 series.

  6. Data is for January and February is expected to be approximately 98% complete. See section on Timeliness and completeness of data for more information.

Excess mortality in Australia, Jan 2016 - Feb 2022

Data files
Download xlsx [342.13 KB]