Excess mortality running at 6% for the first three months of 2023
Catch up on the Actuaries Institute’s COVID-19 Mortality Working Group’s latest analysis of excess deaths.
In summary:
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Background
The COVID-19 Mortality Working Group has examined the latest Provisional Mortality Statistics, covering deaths occurring prior to 31 March 2023 and registered by 31 May 2023, released by the Australian Bureau of Statistics (ABS) on 28 June 2023.
This release also included the article COVID-19 Mortality in Australia, with details on all COVID-19 deaths occurring and registered by 31 May 2023.
We calculate excess deaths by comparing observed deaths to our “baseline” predicted number of deaths for doctor-certified deaths (by cause) and coroner-referred deaths (for all causes combined).
Throughout this article, we separate COVID-19 deaths[1] into:
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- deaths “from COVID-19”, namely deaths where COVID-19 is listed as the primary/underlying cause of death; and
- deaths that were “COVID-19 related”, namely deaths where the underlying cause of death has been determined as something other than COVID-19, but COVID-19 was a contributing factor mentioned on the death certificate.
We have used additional data supplied by the ABS in a customised report in relation to COVID-19 deaths registered by 31 May 2023, namely the total number of deaths each week (doctor-certified and coroner-referred) both from COVID-19 and COVID-19 related.
Baseline predictions
Our previous Actuaries Digital articles have discussed in some detail how we arrived at our baseline predicted deaths. Our baselines will be fully documented in a forthcoming Research Note.
In short, our baselines by cause of death are set by extrapolating linear regression models fitted to Standardised Death Rates (SDRs), which are then re-expressed as numbers of deaths. That means that our baselines allow for changes in the size and age composition of the population, plus the continuation of pre-pandemic mortality trends.
As always, our intent is for the baseline to reflect the expected number of deaths “in the absence of the pandemic”.
Excess deaths to 31 March 2023
Figure 1 shows the results of our analysis, comparing actual deaths each week to our predicted values and the 95% prediction interval.
Figure 1 – Weekly actual and predicted deaths – All Causes
Each of the four weeks of March 2023 were well above the upper end of the 95% prediction interval, as has been the case for most weeks since late 2021.
Figure 2 shows deaths from COVID-19 and COVID-19 related deaths, noting that, given small numbers, weekly data for COVID-19 related deaths is not available for 2020 or 2021.
Figure 2 – Weekly actual and predicted deaths – from COVID-19 and COVID-19 related*
Deaths from COVID-19 reached a low point in the first half of March 2023 before increasing again. COVID-19 related deaths follow broadly the same pattern as from COVID-19 deaths.
Figure 3 compares actual and predicted deaths, after removing deaths from COVID-19 and COVID-19 related deaths.
Figure 3 – Weekly actual and predicted deaths – All Causes excluding deaths from COVID-19 and COVID-19 related deaths
Non-COVID-19 deaths were above the predicted level for all four weeks of March 2023, and above the 95% prediction interval for two of those weeks.
Excess deaths to 31 March 2023 by Cause of Death
Table 2 shows our estimate of excess deaths broken down by cause. We have shown the figures for the first three months of 2023 plus the full year 2022. We have shown actual deaths broken down into those that are either from COVID-19 or COVID-19 related, and those without COVID-19 on the death certificate (“non-Covid”)[2].
Table 2 – Excess deaths in Australia – By Cause of Death for the first three months of 2023 and for 2022
In the first three months of 2023:
- total deaths were 6% (or +2,300) higher than predicted. 1,000 of these excess deaths occurred in January (7% excess), 500 in February (4% excess) and 800 in March (6% excess);
- there were 1,246 deaths from COVID-19, representing 54% of the excess deaths;
- there were 456 COVID-19 related deaths included among the other causes of death (1,702 less 1,246), representing a further 20% of the excess deaths. The remaining 26% of excess deaths (c. 600) have no mention of COVID-19 on the death certificate; and
- doctor-certified deaths from other cardiac conditions, diabetes and other unspecified diseases were all significantly higher than predicted (by between 7% and 16%).
Figure 4 shows excess deaths (as a % of predicted) for each month of 2022 and 2023, with dotted lines for preliminary estimates of COVID-19 deaths and total excess deaths for April and May 2023 (based on the information contained in the ABS COVID-19 Mortality in Australia article). We have shown the total excess (blue) and the contributions of:
- deaths from COVID-19 and COVID-19 related deaths (orange), noting that Figure 2 showed that deaths from these two sources move in the same pattern;
- deaths from respiratory disease (yellow); and
- deaths from all other causes (grey).
Figure 4 – Excess deaths (% of predicted) by month in 2022 and 2023
Deaths from COVID-19 and COVID-19 related deaths are the clear drivers of the majority of the excess mortality. Based on the preliminary COVID-19 figures for April and May 2023 and the persistence of non-COVID-19 excess mortality, we expect that total excess mortality for these months is likely to be around 7-8% (April) and 8-10% (May).
Deaths from respiratory disease have mostly been a negative contributor to excess mortality. We can see the impact of the early, lighter than average, influenza season in 2022 with a small contribution to excess mortality in June 2022, more than offset by high negative contributions in August and September 2022 (the months where influenza deaths usually peaked before the pandemic).
Excess deaths from other causes (i.e., non-COVID-19, non-respiratory), somewhat follows the pattern of COVID-19 mortality; it tends to be higher when COVID-19 (and respiratory) deaths are high and tends to be low when COVID-19 deaths are low. However, the relationship is not 100% correlated – e.g., there was substantial non-COVID-19, non-respiratory excess mortality in September and October 2022 when both COVID-19 and respiratory deaths were relatively low.
Further analysis
We have not estimated excess deaths by age group/gender or state/territory in this article. We will report on this breakdown next month. For a more detailed examination of these breakdowns to 31 December 2022, see our previous article.
Disclaimer
This monthly COVID-19 mortality analysis is intended for discussion purposes only and does not constitute consulting advice on which to base decisions. We are not medical professionals, public health specialists or epidemiologists.
To the extent permitted by law, all users of the monthly analysis hereby release and indemnify The Institute of Actuaries of Australia and associated parties from all present and future liabilities that may arise in connection with this monthly analysis, its publication or any communication, discussion or work relating to or derived from the contents of this monthly analysis.
COVID-19 Mortality Working Group
The members of the Working Group are:
- Karen Cutter
- Jennifer Lang
- Han Li
- Richard Lyon
- Zhan Wang
- Mengyi Xu
References
[1] The COVID-19 deaths covered in this article are distinct from “incidental COVID-19” deaths, namely deaths where the person was COVID-19 positive at the time of death, but COVID-19 was not recorded on the death certificate. These deaths are generally included in surveillance reporting where identified (other than where there is a clear alternative cause of death, such as trauma) but are not separately identified in the ABS statistics.
[2] As in our previous work, we have estimated the number of coroner-referred COVID-19 deaths based on the experience of late 2021 and the emerging experience in 2022. 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.
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