COVID-19 Mortality Working Group: Another month of high excess mortality in July 2022

Catch up on the Actuaries Institute’s COVID-19 Mortality Working Group’s latest analysis of excess deaths.

Background

The COVID-19 Mortality Working Group has examined the latest Provisional Mortality Statistics, covering deaths occurring prior to 31 July 2022 and registered by 30 September 2022, released by the ABS on 27 October.  This release also includes the article COVID-19 Mortality in Australia, with details on all COVID-19 deaths occurring and registered by 30 September 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 (August to October 2022).

We will shortly be publishing two accompanying pieces to this article; the first covering analysis of excess mortality by gender and age band, and the second focusing on the 2022 influenza season.

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 that 16,375 (17.3%) excess deaths occurred by 31 July 2022, in comparison with our estimate of 13,700 (14%).

Excess deaths to 31 July 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.

Deaths in the five new weeks of data (July 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. 

For the month of July 2022:

• total deaths were 16% (or +2,600) higher than predicted;
• just over half of the excess deaths were due to COVID-19, similar to the average of other months of 2022;
• there were fewer influenza deaths in July than predicted, reflecting the early flu season that is evident in surveillance reporting, from which we expect to finish the year with fewer flu deaths than predicted;
• deaths from cancer and dementia were close to predicted;
• ischaemic heart disease, cerebrovascular disease, diabetes and other unspecified causes made a significant contribution to excess deaths; and
• coroner-referred deaths were also considerably higher than expected.

For the first seven months of 2022:

• total deaths were 14% (or +13,700) higher than predicted. This compares with excess deaths of -4,300 for 2020 and +3,000 for 2021;
• there were 7,070 deaths from COVID-19, representing just over 50% of the excess deaths. 123 of these deaths were reported as due to long covid;
• doctor-certified deaths from respiratory disease continue to be lower than expected (5% lower);
• while doctor-certified deaths from cancer are close to expected in percentage terms (2% higher), this difference is statistically significant;
• doctor-certified deaths from heart disease, cerebrovascular disease, diabetes and dementia were all significantly higher than predicted (by between 8% and 16%);
• doctor-certified deaths from other unspecified diseases were also 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 7% higher than expected.

The ABS’s COVID-19 Mortality in Australia article shows that, in the first seven months of 2022, there were 1,696 deaths in people who were COVID-19 positive at death but where COVID-19 was not the primary cause of death.  It is unclear how many people who died with COVID-19 would have died during this seven-month period anyway, and how many may have had their death hastened by COVID-19.  However, COVID-19 may have been a contributory factor in around one quarter of the excess mortality from non-COVID-19 causes.

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

The excess death percentage in July 2022 is the same as for June (16%).  However, the mix of COVID-19 versus non-COVID-19 deaths has changed; following a very high proportion of excess deaths not involving COVID-19 in June 2022 (8%), the excess has come down in July (5%).

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.

• 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 1,696 deaths in the first seven months of 2022 where COVID-19 is listed as a contributory cause, and a further 123 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.
  • Likely impact in Australia: High
• Delayed deaths from other causes: 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.
  • Likely impact in Australia: Moderate, likely to reduce over time
• 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.
  • Likely impact in Australia: Low to Moderate
• 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.
  • Likely impact in Australia: Low to Moderate, likely to increase over time
• 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.
  • Likely impact in Australia: Low
• 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 very good vaccine approval and safety monitoring processes, administered by the Therapeutic Goods Administration.  The latest vaccine safety report (to 20 October) shows 136,500 adverse events have been reported from 63.8 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.
  • Likely impact in Australia: Negligible
• Undiagnosed COVID-19: Some of the excess deaths could actually be from unidentified COVID-19. This effect happened early in the pandemic, but it 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.
  • Likely impact in Australia: Negligible.

COVID-19 deaths in August to October 2022

While the ABS Provisional Mortality Statistics data is only available up to the end of July 2022, surveillance COVID-19 deaths are available up to the end of October 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, it is no longer possible to report full calendar months.  The month of September 2022 shown runs from 1 September to 29 September (27 September for Queensland), while the month of October 2022 is from 30 September to 27 October (28 September to 25 October for Queensland).

In the ten months to end October 2022, there have been approximately 13,350 COVID-19 deaths.  Of these, around 3,800 occurred in the three months to end October 2022 (where we have no provisional mortality statistics).  Reported deaths in the month of October were the lowest so far of 2022.

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 4 also contains a line showing the proportion of registered COVID-19-related deaths that were “from” rather than “with” COVID-19.  Many deaths are still to be registered in the last month shown, so this percentage could change – hence, this point is shown as a preliminary estimate.

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 71% in August and September. 

We consider it reasonable to assume that, of the 3,800 “COVID-19” deaths reported in August to October 2022, 71% may have been from COVID-19 rather than with COVID-19.  Therefore, we estimate that around 2,700 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 46,300 deaths in the three months August to October 2022.

Thus, COVID-19 deaths represent around 6% extra mortality over August to October 2022 (9% in August, 6% in September and 2% in October).  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 seven months of 2022, and that this will outweigh the benefit from respiratory disease.  Therefore, we expect that total excess mortality in August to October 2022 will have been higher than the 6% explained by COVID-19.

Excess mortality across the pandemic

Figure 5 combines our preliminary estimate of excess deaths due to COVID-19 only for August to October 2022 with our detailed excess death estimates shown earlier, to reveal cumulative excess mortality since the start of 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.  After very sharp increases in excess deaths over the first seven months of 2022, we estimate the excess will slow down with the lower level of COVID-19 deaths in September and October. 

Cumulatively across the pandemic, our conservative estimate is that Australia had experienced just over 15,000 excess deaths by the end of October 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.

We estimate that there have been 12,100 deaths from COVID-19 in Australia to the end of October 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 seven months of 2022.

Standardised Mortality Rates

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.

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; and
• experience for the first seven months of 2022 is higher than for any other year shown.

Leading causes 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 ten months of 2022.  To do this, we have:

• taken doctor-certified deaths by cause to 31 July as shown in Table 1;
• added our predicted doctor-certified deaths for the three months of August to October 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 remaining two months of 2022.

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 17,500). 

We expect there will be around 9,500 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 ten months of 2022 at about 9,800:

• 6,720 doctor-certified deaths in seven months to July; plus
• 350 coroner-referred deaths in the seven months to July; plus
• 2,700 deaths in the three months from August to October.

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

The remainder of this article shows actual versus predicted deaths to 31 July 2022.  Analysis and discussion of individual causes of death refer to doctor-certified deaths, while coroner-referred deaths are shown for all causes combined (including COVID-19).

COVID-19 deaths

There were 1,338 doctor-certified deaths from COVID-19 in July 2022, compared with 1,934 surveillance deaths (596 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 July 2022 averaged around 300 per week, higher than the level in June 2022.

Deaths from Respiratory Disease

Deaths from respiratory disease at the end of June and early July were higher than predicted, different from the trend throughout most of the pandemic.  However, they remained below the 97.5^th percentile, and then fell below the expected level again in the last three weeks of July.  This experience is largely driven by influenza deaths.

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

There were 55 influenza deaths in the month of July.  We note that influenza surveillance reporting indicates that the flu season in Australia was earlier in the year than usual, and this is borne out by these death statistics.

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

Deaths from lower respiratory disease were close to predicted for most weeks in July 2022 and all within the 95% prediction interval.

Deaths from other respiratory diseases were also similar to predicted in July 2022.

Non-COVID-19 and Non-Respiratory Deaths

Excluding deaths from COVID-19 and respiratory diseases, deaths were well above the prediction interval in four weeks out of the five weeks of July 2022.  This is mainly driven by deaths from ischaemic heart disease, cerebrovascular disease 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.

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. 

Deaths from ischaemic heart disease were again significantly higher than predicted in July, and outside the prediction interval for three of the five 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 16% measured excess mortality.

For cerebrovascular disease, deaths were higher than predicted for all five weeks of July 2022, and above the prediction interval for two of those weeks.

Deaths from diabetes were also higher than predicted in July 2022, although within the prediction interval.  Few weeks have been below predicted since early 2021.

Deaths from dementia were close to predicted in July 2022. 

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

Coroner-referred deaths

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

COVID-19 Mortality Working Group

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