Higher mortality from other causes is offset by lower mortality from respiratory diseases

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).

Key points from this latest analysis:

• In the month of August, deaths from respiratory disease continued to be low, at 28% below trend. However, across winter (June to August) 2021, respiratory deaths were not as low as for the same period in 2020.

• There were 79 COVID-19 deaths in August, while deaths from all other causes were close to expected.

• In the eight months to end-August, respiratory deaths are down 15% but deaths from other causes have been higher; resulting in overall deaths being close to expected.

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 August 2021:

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

• around 1,300 deaths in August were from respiratory disease, 28% (500) lower than the expected number of around 1,800;

• deaths from heart disease were again higher than expected in August (up 4%), noting that the predicted values allow for continued strong mortality improvement in this cause;

• deaths from dementia were 8% (120) lower than expected in August, possibly related to lower than usual levels of respiratory disease in the community; and

• deaths from other causes, i.e. those not explicitly reported on by the ABS, were again higher than expected (up 3%).

In the year to date, deaths from all causes were close to predicted (only 100 higher) and:

• there have been 8,700 respiratory deaths, 15% lower than the 10,200 predicted deaths;

• deaths from cancer were close to expected (down 1% at 32,400 from an expected 32,700);

• there were higher-than-expected deaths from both heart disease (up 4%) and cerebrovascular disease (up 2%), noting that the predicted values allow for continued strong mortality improvement in these causes and that 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 slightly lower than expected (down 2%); and

• deaths from other causes are substantially higher than expected (up 5%, or 1,400 more deaths than predicted). We understand that the ABS has a program of work underway to investigate the reasons for this increase.

There were 79 doctor-certified deaths in August from COVID-19. This compares to 82 officially recorded COVID-19 deaths in the month.

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 (5%) above the 2015-19 average.

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

COVID-19 deaths

There were 79 doctor-certified deaths in August from COVID-19. This is close to the 82 officially recorded COVID-19 deaths in the month.  We would not expect the numbers to be identical, because the reporting criteria are slightly different, and it is possible that some COVID-19 deaths were referred to the coroner.  However, we find it reassuring that the discrepancy generally seems to be very small.

In the year to 31 August, there have been 95 doctor-certified deaths, compared with 97 officially recorded COVID-19 deaths.

Respiratory Deaths

Following the trend observed since the beginning of the COVID-19 pandemic, Australia continued to see significantly lower deaths from all respiratory illnesses in the month of August 2021.  Note that deaths from respiratory illness in 2021, while much lower than trend, have been higher than in 2020 since around mid-June.

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

There were no deaths from influenza in August 2021.

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. From June to August, 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-COVID-19 and Non-Respiratory Deaths

Excluding deaths from COVID-19 and respiratory disease, deaths in August were close to expected. This followed a period from mid-April until end-July where deaths were higher than predicted and above the 95^th percentile in quite a number of weeks. This is mainly driven by the experience of ‘other’ deaths, and, to a lesser extent, heart disease.

The following figures show a breakdown of non-respiratory/non-COVID-91 deaths into cancer, heart disease, cerebrovascular disease, diabetes, dementia and all other causes.

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. 

In the year to end-August, 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, actual deaths are only 2% 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 were lower than expected in August by quite a significant amount (down 8%), possibly related to lower than usual levels of respiratory disease in the community.

Deaths from other causes, i.e. those not explicitly reported on by the ABS, continue to be substantially higher than expected (up 5%, or 1,400 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. Whether there is any particular cause that is driving this increase.

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