COVID-19 Mortality Working Group: High excess mortality continues into June 2022

Background

The COVID-19 Mortality Working Group has examined the latest Provisional Mortality Statistics, covering deaths occurring prior to 30 June 2022 and registered by 31 August 2022, released by the Australian Bureau of Statistics (ABS) on 30 September. This release also includes the article COVID-19 Mortality in Australia, with details on all COVID-19 deaths occurring and registered by 31 August 2022.

We compared observed deaths to our ’baseline’ predicted number of deaths for doctor-certified deaths (by cause) and coroner-referred deaths (for all causes combined).

We also provide an indicative estimate of excess mortality due to COVID-19 only, for the three months subsequent to the ABS data (July to September 2022).

Baseline prediction

Our previous Actuaries Digital article discussed in some detail how we arrived at our baseline predicted deaths. In short, our baselines are set by extrapolating linear regression models fitted to standardised death rates (SDRs), which are then re-expressed as numbers of deaths. For the pandemic years, we have included different years to train the regression models:

• For 2020 and 2021, we have used the 2015-19 experience.

• For 2022, we have:
  • used 2015-19 experience to set our baseline for deaths from respiratory disease and dementia, on the basis that 2020 and 2021 experience for these causes was materially affected by the pandemic. We have also shown the average experience in 2020-21, for reference, when analysing mortality from these causes; and

  • used 2015-21 experience to set our baseline for deaths from all other causes and for coroner-referred deaths, on the basis that it is likely that 2020 and 2021 experience more closely reflects a slow-down in underlying mortality improvement than the impacts of the pandemic.

The baseline for our estimates of excess deaths remains ‘in the absence of the pandemic’ for each of the three years 2020 to 2022. We have not included any COVID-19 deaths in the baseline, as these would not exist in the absence of the pandemic.

As always, it is important to note that predicted death numbers are increasing faster from demographic changes (ageing and population size) than they are reducing due to mortality improvement. Therefore, our model predicts higher baseline numbers of deaths in each successive year. 

Comparison with ABS reporting

The results we present here differ from those quoted by the ABS in its commentary surrounding the release of the Provisional Mortality Statistics. For 2022, the most significant difference is in the determination of the baseline, where the ABS uses a simple average of the number of deaths from 2017, 2018, 2019 and 2021, with no allowance for mortality trends or demographic changes. In our view, this understates the baseline and therefore overstates the measure of excess deaths.

For example, the ABS has reported about 13,500 (17%) excess deaths in the first six months of 2022, in comparison with our estimate of 11,200 (13%).

Excess deaths to 30 June 2022

Figure 1 and Table 1 summarise the results of our analysis. This article concentrates on the experience in 2022, but we have also shown the 2020 and 2021 results for context.

As in previous work, we have assumed that coroner-referred COVID-19 deaths will be 5% of all COVID-19 deaths in 2022, based on the experience of late 2021. If our estimate of coroner-referred COVID-19 deaths is too high (or low), this will not affect the total level of excess deaths measured; it will just mean that our estimate of non-COVID-19 coroner-referred deaths will be too low (or high) by the same amount.

Figure 1 – Weekly actual and predicted deaths in Australia – All causes

Deaths in the most recent four weeks of data (June 2022) were again well above the upper end of the prediction interval (i.e. above the 97.5^th percentile). So far, all but one week of 2022 has been above the 97.5^th percentile. 

Table 1 – Excess deaths in Australia

For the month of June 2022:

• total deaths were 16% (or +2,400) higher than predicted;

• around one third of the excess deaths were due to COVID-19, a lower proportion than the average of 54% in the other months of 2022;

• while numbers remain relatively low, there were more influenza deaths in June than predicted, reflecting an early flu season. Surveillance reporting suggests that hospitalisations peaked in May, and deaths in July, and that we will finish the year with fewer flu deaths than predicted. We also note that having flu circulating in the community can lead to more deaths from other causes, notably from other respiratory causes and dementia, which may be influencing the results for these causes;

• deaths from dementia were much higher than predicted. As noted above, this may be due to the reappearance of flu in the community but may also be impacted by high numbers of COVID-19 cases in aged care homes in June;

• ischaemic heart disease and other unspecified causes also made a significant contribution to excess deaths; and

• cancer deaths were up a little, the result of one high outlier week rather than an overall higher trend for the month.

For the first six months of 2022:

• total deaths were 13% (or +11,200) higher than predicted. This compares with excess deaths of -4,500 for 2020 and +3,200 for 2021;

• there were 5,620 deaths from COVID-19, representing just over 50% of the excess deaths. 98 of these deaths were reported as due to Long COVID;

• doctor-certified deaths from respiratory disease continue to be lower than expected (4% lower), despite May and June having a sizeable number of influenza deaths;

• while doctor-certified deaths from cancer are close to expected in percentage terms (2% higher), now that we are six months into the year, this difference has become statistically significant;

• doctor-certified deaths from heart disease, cerebrovascular disease, diabetes and dementia were all significantly higher than predicted (by between 7% and 14%);

• doctor-certified deaths from other unspecified diseases were significantly higher than predicted (by 12%), continuing a trend observed since April 2021. Note that this is a large ’catch-all‘ category and it is difficult to infer the reason for this large increase, although history suggests that non-ischaemic heart diseases probably make up around 25% of deaths from other unspecified causes; and

• non-COVID-19 coroner-referred deaths were 6% higher than expected.

The ABS’s COVID-19 Mortality in Australia article shows that, in the first six months of 2022, there were 1,291 deaths with (rather than from) COVID-19. The ABS has provided us with the underlying cause of death for these deaths, shown in the same main groupings as included in the Provisional Mortality Statistics. 

Table 2 shows for the first six months of 2022:

• our estimate of excess deaths as shown in Table 1 (excluding deaths where the underlying cause is COVID-19);

• the number of people who have died with COVID-19;

• excess deaths excluding people who have died with COVID-19;

• the percentage excess both before and after excluding deaths in people who died with COVID-19.

Table 2 – Underlying cause of death for ‘with COVID-19’ deaths (January to June 2022)

It is unclear how many people who have died with COVID-19 would have died during this six-month period anyway, and how many may have had their death hastened by COVID-19. Thus, the table may overstate the contribution of COVID-19 to excess mortality from other causes. However, it does indicate that, even after removing all deaths with COVID-19 from our excess death estimates:

• there remain significant numbers of excess deaths from ischaemic heart disease, dementia and other diseases; but

• excess mortality for diabetes is reduced to very low levels.

Figure 2 shows the breakdown of excess deaths in the first six months of 2022 into those due to COVID-19, those from COVID-19, and those where COVID-19 does not appear on the death certificate. We have shown both numbers of excess deaths and the percentage excess.

Figure 2 – Excess deaths by involvement of COVID-19

The month of June 2022 has the highest number of excess deaths not involving COVID-19.

What could be causing the non-COVID-19 excess deaths?

The measurement of higher numbers of deaths than predicted does not tell us why this is occurring. There are a number of reasons hypothesised around the world (where this effect is occurring to a greater or lesser extent). It isn’t possible to identify from death counts alone what is causing the non-COVID-19 excess deaths, but we have listed below the most likely explanations.

We note that multiple factors are likely in play, and different factors may be more or less pronounced at various times. The following indicates which factors, in our view, are likely to be having a greater or lesser impact on Australian excess mortality in 2022.

1. Post-COVID-19 sequelae or interactions with other causes of death:

An earlier COVID-19 illness could be causing later illness and death, and/or COVID-19 could have worsened other diseases which ultimately caused death. Studies have shown that COVID-19 is associated with higher subsequent mortality risk from heart disease and other causes. To some extent, this shows on death certificates in the 1,291 deaths in the first six months of 2022 where COVID-19 is listed as a contributory cause, and a further 98 deaths that were identified as from Long COVID. However, we understand that medical science has not yet established a causative link that would allow, say, a heart attack several months after a COVID-19 infection to be attributed back to COVID-19. As such, it seems likely that there would be more of these deaths than identified.

Possible impact in Australia: High

2. Delayed deaths from other causes:

Some of the reduction in deaths in 2020 and 2021 that resulted from the absence of many respiratory diseases may be reversing. People who otherwise may have died of flu or other respiratory diseases in those years had their systems been stressed may now be succumbing to their underlying illnesses.

Possible impact in Australia:Moderate, likely to reduce over time

3. Delay in emergency care:

Pressure on the health, hospital and aged care systems, including ambulance ramping and bed block, could lead to people not getting the care they require, either as they avoid seeking help, or their care is not as timely as it might have been in pre-pandemic times.

Possible impact in Australia: Low to moderate

4. Delay in routine care:

Lack of earlier diagnostic testing for non-COVID-19 causes and delays in elective surgery could lead to later mortality. The delays in diagnostic testing may have arisen from a variety of factors – people avoiding healthcare settings due to fear of catching COVID-19; a reduction in social interactions meaning friends/family may not have noticed ill health in others as early as usual; less availability of routine care with medical resources being diverted to the pandemic effort. While delays in diagnostic testing do not yet appear to be occurring for cancer deaths, it may be a factor in higher deaths from other causes, such as ischaemic heart disease, diabetes, and the large ‘other’ category.

Possible impact in Australia: Low to moderate, likely to increase over time

5. Pandemic-influenced lifestyle changes:

There is evidence from the UK that a higher proportion of people made less healthy lifestyle choices during lockdowns (e.g. drinking more alcohol, exercising less, higher rates of childhood obesity), and that these less healthy practices have continued. It is unclear to what extent similar factors may be affecting mortality in Australia in 2022. Deaths directly caused by drug and/or alcohol abuse are relatively low, compared with those from other causes, but there would be an indirect impact.

Possible impact in Australia: Low

6. Vaccine-related deaths:

While there have been deaths in Australia caused by the administration of COVID-19 vaccines, the number of such deaths has been small. Australia has a sound vaccine approval and safety monitoring process, administered by the Therapeutic Goods Administration. The latest vaccine safety report (to 23 September) shows 136,000 adverse events have been reported from 63.3 million vaccines administered (a rate of 0.2% per vaccine administered). Of those adverse events, 939 were reports of death following vaccination. Of those deaths, 14 were found to have been caused by the administration of the vaccine. 13 deaths were following a first dose of AstraZeneca which is now in limited use in Australia, and 1 death occurred after a booster dose of Moderna and was related to myocarditis.

Possible impact in Australia: Negligible

7. Undiagnosed COVID-19:

Some of the excess deaths could actually be from non-identified COVID-19. This effect happened early in the pandemic, but seems less likely in 2022, as testing is much more available, particularly for those who are seriously ill. Also, for any deaths where COVID-19 may be suspected, post-mortem testing is occurring in Australia.

Possible impact in Australia: Negligible

COVID-19 deaths in July to September 2022

While the ABS provisional mortality statistics data is only available up to the end of June 2022, surveillance COVID-19 deaths are available up to the end of September 2022. Figure 3 shows the number of such deaths in each month since January 2020. 

Note that, with the change to weekly reporting of COVID-19 surveillance statistics, the last day of September (the last three days in the case of Queensland) has not yet been reported by the state/territory health departments. We have estimated the number of missing deaths based on reports to-date in September.

Figure 3 – COVID-19 deaths in Australia, reported from surveillance systems

In the nine months to 30 September 2022, there have been approximately 12,900 COVID-19 deaths. Of these, 5,300 occurred in the three months to 30 September 2022 (where we have no provisional mortality statistics). Reported deaths in the month of September were considerably lower than in July and August.

The COVID-19 Mortality in Australia article shows the proportion of those death certificates mentioning COVID-19 where COVID-19 was the underlying cause. Figure 4 shows a comparison of deaths ‘from’ COVID-19 versus those ‘with’ COVID-19. For the most recent months, a large proportion of deaths have not yet been registered, so we have also shown our estimate of the numbers of as-yet unregistered deaths. Figure 6 also contains a line showing the proportion of registered COVID-19-related deaths that were ‘from’ rather than ‘with’ COVID-19.

Figure 4 – A comparison of deaths ‘from’ COVID-19 to those ‘with’ COVID-19 (source: ABS)

The proportion of registered COVID-19 deaths from COVID-19 has reduced in 2022, from 88% in January, to 75% in May to July, and then a substantial drop to 70% in August. Many deaths are still to be registered in August, so this percentage could change – hence, this point is shown as a preliminary estimate.

We consider it reasonable to assume that, of the 5,300 ‘COVID-19’ deaths reported in July to September 2022, 74% may have been from COVID-19 rather than with COVID-19. This assumption effectively assumes that 75% of July surveillance reports and 70% of August and September reports are from COVID-19. Therefore, we estimate that around 3,900 deaths in this period may have been due to COVID-19.

Our prediction model suggests that, without a pandemic, there would have been a total of around 47,200 deaths in the three months July to September 2022.

Thus, COVID-19 deaths represent around 8% extra mortality over July to September 2022 (9% in July and August, and 6% in September). There have probably been fewer deaths from respiratory diseases in this period than our pre-pandemic predictions. However, we consider it likely that mortality from non-COVID-19, non-respiratory causes will be higher than our pre-pandemic predictions, given the higher-than expected mortality in 2021 and the first half of 2022, and that this will outweigh the benefit from respiratory disease. Therefore, we expect that total excess mortality in July to September 2022 will have been higher than the 8% explained by COVID-19.

Excess mortality across the pandemic

Figure 5 combines our preliminary estimate of excess deaths due to COVID-19 only for July to September 2022 with our detailed excess death estimates shown earlier, to reveal cumulative excess mortality since the start of 2020.

Figure 5 – Estimated cumulative excess deaths in Australia since 1 January 2020

Deaths from the Delta wave in the latter part of 2021 and the Omicron wave in early 2022 had fully eroded the negative excess deaths experienced earlier in the pandemic by early January 2022. Cumulatively across the pandemic, our conservative estimate is that Australia had experienced around 13,800 excess deaths by the end of September 2022. This represents an average excess mortality rate of about 3% across the pandemic.

These impacts by year can be seen separated into excess deaths from COVID-19 and other causes in the table below.

Table 3 – Excess deaths separated into COVID-19 and other causes

We estimate that there have been 11,800 deaths from COVID-19 in Australia to the end of September 2022. 

For non-COVID-19 causes, the lower than predicted deaths in 2020 have now been more than offset by higher than predicted deaths in 2021 and the first six months of 2022.

Excess mortality across the pandemic

Figure 6 shows the cumulative standardised mortality rates (SDRs) for 2015 to 2022, expressed relative to the rate for 2019. The SDRs are from the Provisional Mortality Statistics, plus allowance for late-reported deaths.

Figure 6 – Cumulative standardised mortality rate relative to 2019

The graph shows that:

• mortality rates improved over the 2015 to 2019 pre-pandemic years, noting that both 2017 and 2019 were bad influenza years, resulting in higher than usual deaths both from and related to influenza.

• the 2020 year is considerably lower than 2019, a result of the lower number of respiratory and respiratory-related deaths in this year due to measures introduced to curb COVID-19.

• 2021 is higher than 2020, a combination of both deaths from COVID-19 during the Delta wave and excess mortality from other causes of death.

• experience for the first half of 2022 is higher than for any other year shown.

Leading cause of death

In this section, we assess where COVID-19 sits in terms of leading causes of death in Australia.

The ABS reports on the top 20 leading causes of death by grouping deaths based on their International Classification of Diseases, version 10 (ICD-10) code. Cancers are grouped based on the region of the body rather than included as a whole. In this analysis, we have followed the ABS classification system.

We have estimated deaths for the leading causes for the first nine months of 2022. To do this, we have:

• taken doctor-certified deaths by cause to 30 June as shown in Table 1;

• added our predicted doctor-certified deaths for the three months of July to September 2022;

• included an allowance for coroner-referred deaths (using the historical ratio of doctor-certified to coroner-referred deaths); and

• for the leading cancer causes, we have estimated deaths from all cancers and then assumed lung cancers and colon cancers make up 18% and 12% respectively of all cancer deaths. These proportions have been stable over the recent period examined.

We have also estimated leading causes for the whole of 2022, noting that we have not made any estimate of COVID-19 deaths in the three months from October to December 2022.

Table 4 – Excess deaths separated into COVID-19 and other causes

Ischaemic heart disease has been the leading cause of death in Australia for many years. However, the mortality rate for this cause has been declining. At the same time, the population has been aging, resulting in an increasing number of dementia deaths. We estimate that dementia will overtake ischaemic heart disease to be the leading cause of death in 2022 by a small margin (17,600 versus 17,100). 

We expect there will be just over 9,000 deaths from each of cerebrovascular diseases (largely stroke) and cancers of the lung in 2022.

Turning to COVID-19 deaths, we estimate deaths from COVID-19 in the first nine months of 2022 at about 9,500:

• 5,340 doctor-certified deaths in six months to June; plus

• 280 coroner-referred deaths in the six months to June; plus

• 3,900 deaths in the three months from July to September.

This puts COVID-19 as the third leading cause of death for the first nine months of 2022, and we expect that COVID-19 will also be the third leading cause of death over the whole of 2022.

COVID-19 deaths

Figure 7 – Weekly actual and predicted doctor-certified deaths in Australia – COVID-19

There were 824 doctor-certified deaths from COVID-19 in June 2022, compared with 1,374 surveillance deaths (550 fewer). We would not expect the numbers to be identical, because:

• there are delays between time of death and lodgement of the doctor’s certificate;

• the reporting criteria are different, with the main difference being that the surveillance reporting includes all deaths in people who have died while COVID-19 positive and without another clearly obvious unrelated cause (e.g. trauma), whereas the ABS deaths included in this chart only include deaths where COVID-19 was certified as the primary cause of death; and

• some COVID-19 deaths will be referred to the coroner (e.g. deaths occurring at home).

COVID-19 deaths in 2022 have far exceeded deaths from this cause earlier in the pandemic. COVID-19 deaths in June 2022 averaged around 200 per week, similar to the level in May 2022.

Deaths from respiratory disease

Figure 8 – Weekly actual and predicted doctor-certified deaths in Australia – all respiratory diseases

In three of the four weeks of June 2022, deaths from respiratory disease were higher than predicted, different from the trend throughout most of the pandemic. However, they remained below the 97.5^th percentile.

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

Figure 9 – Weekly actual and predicted doctor-certified deaths in Australia – Influenza

There were 150 influenza deaths in the month of June, with two weeks sitting above the 97.5^th percentile. We note that influenza surveillance reporting indicates that the flu season in Australia was earlier in the year than usual and that deaths peaked in July, so we expect that these higher deaths are a shift in timing rather than an indication of excess mortality over the whole of 2022.

Figure 10 – Weekly actual and predicted doctor-certified deaths in Australia – Pneumonia

There were fewer deaths from pneumonia in June 2022 than predicted, and one of the four weeks was below the bottom end of the 95% prediction interval. Deaths so far in 2022 are similar to the levels seen in 2020 and 2021.

Figure 11 – Weekly actual and predicted doctor-certified deaths in Australia – Lower respiratory diseases

Deaths from lower respiratory disease were a little higher than the predicted for three of the four weeks in June 2022 and may be related to flu circulating in the community.

Figure 12 – Weekly actual and predicted doctor-certified deaths in Australia – Other respiratory diseases

Deaths from other respiratory diseases were also a little higher than predicted for three of the four weeks in June 2022.

Non-COVID-19 and Non-Respiratory Deaths

Figure 13 – Weekly actual and predicted doctor-certified deaths in Australia – All causes other than respiratory diseases and COVID-19

Excluding deaths from COVID-19 and respiratory diseases, deaths were well above the prediction interval in all four weeks of June 2022. This is mainly driven by deaths from ischaemic heart disease, cerebrovascular disease, dementia and ‘other’ causes.

The following figures show a breakdown of non-respiratory/non-COVID-19 deaths into cancer, heart disease, cerebrovascular disease, diabetes, dementia, and all other causes.

Figure 14 – Weekly actual and predicted doctor-certified deaths in Australia – Cancer

Cancer deaths continue to be close to predicted numbers for most weeks, except two high outlier weeks – one in May and one in June. With diagnostic testing down in 2020, there were concerns that there would be a spike in cancer deaths in 2021 and beyond. We are not yet seeing any clear evidence of this effect. 

Figure 15 – Weekly actual and predicted doctor-certified deaths in Australia – Ischaemic heart disease

Deaths from ischaemic heart disease were again significantly higher than predicted in most weeks of June, and at or outside the prediction interval for three of these weeks. Very few weeks have been below the predicted line since March 2021. Although it is possible that our methodology results in over-aggressive expectations of mortality improvement from this cause, this could only explain up to around 4% of the 14% measured excess mortality.

Figure 16 – Weekly actual and predicted doctor-certified deaths in Australia – Cerebrovascular disease\

For cerebrovascular disease, deaths were higher than predicted for three out of the four weeks of June 2022, and above the prediction interval for one of those weeks.

Figure 17 – Weekly actual and predicted doctor-certified deaths in Australia – Diabetes

Deaths from diabetes were also higher than predicted in June 2022, although within the prediction interval.

Figure 18 – Weekly actual and predicted doctor-certified deaths in Australia – Dementia

Deaths from dementia were significantly higher than predicted in June 2022 and were above the upper limit of the prediction interval. This may be related to high levels of COVID-19 in aged care homes during June and/or to flu circulating in the community; pre-pandemic, around 20% of dementia deaths had influenza/pneumonia coded as a secondary cause of death.

Figure 19 – Weekly actual and predicted doctor-certified deaths in Australia – Other unspecified diseases

Deaths from other causes, i.e. those not explicitly reported on by the ABS, were again much higher than predicted in June 2022. All weeks were well above the upper limit of the prediction interval.

Coroner-referred deaths

Figure 20 – Weekly actual and predicted coroner-referred deaths in Australia – All causes 

Coroner-referred deaths continued to be higher than predicted every week in June 2022 and were above the prediction interval for three of the four weeks of that month. Note that actual deaths data included in the graph includes coroner-referred deaths from COVID-19.

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