Despite COVID-19, Australian mortality improvement is on trend

The analysis is based on monthly ABS data for doctor-certified deaths (which excludes the approximately 10% of total deaths that are certified by the coroner) and this article uses the latest available data to 31 July 2021.

In brief, the Working Group’s analysis:

• scales actual weekly deaths from 2015 to 2020 so that they are representative of the number of deaths in those years if they had the 2021 population size and age mix;

• fits a linear regression model to the scaled deaths from 2015 to 2019, giving overall mortality improvements of around 1.8% per annum over the five-year period;

• extrapolates the linear regression model to arrive at a predicted number of deaths for each week in 2020 and 2021 (assuming that the same 1.8% per annum mortality improvement continues); and

• compares predicted deaths to the actual deaths in 2021 (after a small allowance for late reported deaths).

This approach is the same as adopted by the Working Group last year, however we have made some refinements to the linear regression modelling, mainly to reduce the variability of predicted values from one week to the next.

The graph and table below summarise the results of the analysis. This article concentrates on the experience in 2021, but we have also shown the 2020 results for context.

For the month of July 2021:

• total deaths were close to predicted, continuing the trend of 2021 to date;

• around 1,300 deaths in July were from respiratory disease, 19% (300) lower than the expected number of 1,600, albeit there were two influenza deaths, the first deaths from this cause in almost 12 months; and

• there were just over 200 more deaths from other unspecified causes (i.e. those not explicitly reported on by the ABS) compared with predicted.

In the year to date, deaths from all causes were close to predicted (1% higher) and:

• there have been 7,300 respiratory deaths, 11% lower than the 8,200 predicted deaths;

• deaths from cancer were close to expected (down 1% at 27,600 from an expected 27,900);

• there were higher than expected deaths from both heart disease (up 4%) and cerebrovascular disease (up 3%), noting that the predicted values allow for continued strong mortality improvement in these causes and deaths in 2021 from both causes are close to 2020 levels;

• deaths from diabetes are higher than expected (up 5%), noting that deaths from this cause make up only a small proportion of all deaths and are therefore somewhat volatile;

• deaths from dementia are close to expected; and

• deaths from other causes are substantially higher than expected (up 5%, or 1,100 more deaths than predicted). We understand that the ABS has a program of work underway to investigate the reasons for this increase.

There were 10 doctor-certified deaths in July from COVID-19, at the start of the Delta wave.  When compared with the 14 officially recorded COVID-19 deaths in the month, this suggests that four deaths have been referred to the coroner.

It is important to note that expected deaths are increasing faster from population changes than they are reducing due to mortality improvement, which explains why the ABS has reported year-to-date deaths at 4,800 (6%) above the 2015-19 average.

The following graphs show the detailed comparisons for each cause of death.

Respiratory Deaths

Australia has continued to see significantly lower deaths from respiratory disease in 2021, a trend first set when Australians began to lock down at the beginning of the COVID-19 pandemic. We note that, while deaths from respiratory disease in June and July of 2021 remain lower than predicted, deaths over this period were not as low as for the same period in 2020.

The following figures present a breakdown of respiratory disease into influenza, pneumonia, lower respiratory disease and other respiratory disease.

There were two deaths from influenza in July 2021, the first deaths from this cause in almost 12 months.

Pneumonia deaths remain low; deaths from this cause are lower than predicted for every week of 2021, and lower than the lower bound for most weeks.

Deaths from lower respiratory disease were close to predicted for most weeks until end May 2021.  In both June and July, when we normally would see the start of the ‘winter hump’, deaths from this cause are lower than predicted, however they are not as low as in 2020.

Deaths from other respiratory diseases are close to predicted for most weeks.

Non-Respiratory Deaths

Cancer deaths continue to be close to the predicted values for most weeks. With diagnostic testing down in 2020, there were concerns that there would be a spike in cancer deaths in 2021 and beyond. While it is still early days, we are not yet seeing any evidence of this effect on the number of deaths from cancer. 

In the year to end-July, there have been higher than expected deaths from heart disease (up 4%). This has been fairly consistent across most weeks. We note that the predicted values allow for continued strong mortality improvement in 2021 in this cause. Deaths in 2021 are close to 2020.

For cerebrovascular disease, the picture is similar to that for heart disease – actual deaths are 3% higher than predicted, noting that the predicted values incorporate a continuation of strong mortality improvement.

Deaths from diabetes are higher than expected (up 5%), however deaths from this cause make up only a small proportion of all deaths and are therefore somewhat volatile. 

Deaths from dementia are close to expected.

Deaths from other causes, i.e. those not explicitly reported on by the ABS, are substantially higher than expected (up 5%, or 1,100 more deaths than predicted). Deaths from this cause have been substantially above the upper limit of the confidence interval from around mid-April until end-June. We understand that the ABS are looking into these ‘other’ deaths in more detail to identify whether there is any particular cause that is driving this increase.

COVID-19 deaths

There were 10 doctor-certified deaths in July from COVID-19, at the start of the Delta wave. When compared with the 14 officially recorded COVID-19 deaths in the month, this suggests that four deaths have been referred to the coroner.

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