COVID-19 Mortality Working Group – Excess Mortality Falls in July as Another COVID-19 Wave Subsides in Australia
Catch up on the Actuaries Institute’s COVID-19 Mortality Working Group’s latest analysis of excess deaths.
In summary:
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Excess deaths to 31 July 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
Deaths in all weeks of July were above predicted, with the first two weeks above the upper end of the 95% prediction interval.
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 deaths from COVID-19 and COVID-19 related*
* COVID-19 data from ABS customised report 2023. Predicted COVID-19 deaths are zero as our baseline is intended to represent predicted deaths in the absence of the pandemic.
Deaths from COVID-19 have continued to fall since the peak in early May 2023.
Since early 2022, COVID-19 related deaths have broadly followed the same pattern of peaks and troughs as from COVID-19 deaths. However, the relationship has not been as strong over this most recent wave.
Surveillance reporting indicates that COVID-19 deaths continued to decline across August and were at low levels in September. However, there are early indications that COVID-19 deaths have started to trend upwards again towards the end of October.
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 close to predicted levels in July 2023.
Excess deaths to 31 July 2023 by cause of death
Table 1 shows our estimate of excess deaths broken down by cause. We have shown the figures for the first seven 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 (“COVID”), and those without COVID-19 on the death certificate (“non-COVID”)[1].
Table 1 – Excess deaths in Australia – by cause of death for 2023 year-to-date and for 2022
In the first seven months of 2023:
- total deaths were 6% (95% confidence interval: 5% to 8%) or +6,500 higher than predicted. For the month of July 2023, deaths were 600 higher than predicted (4% excess)
- there were 3,246 deaths from COVID-19, representing 50% of the excess deaths;
- there were 1,137 COVID-19 related deaths included among the other causes of death (4,383 less 3,246), representing a further 17% of the excess deaths. The remaining 33% of excess deaths (c. 2,100) have no mention of COVID-19 on the death certificate; and
- doctor-certified deaths from ischaemic heart disease, other cardiac conditions, cerebrovascular disease, diabetes, other unspecified diseases and coroner referred deaths were all significantly higher than predicted (by between 4% and 14%). Deaths from pneumonia and chronic lower respiratory disease were significantly lower than predicted (by 16% and 8%, respectively).
Figure 4 shows excess deaths (as a percentage of predicted) for each month of 2022 and 2023. 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 broadly 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 account for most of the excess mortality.
Deaths from respiratory disease have mostly been a negative contributor to excess mortality. Influenza surveillance reporting for 2023 indicates that the 2023 flu season was, like 2022, earlier than pre-pandemic normal. To 15 October 2023, 269 surveillance influenza deaths were reported, which is only 107 more than the 162 surveillance deaths reported to 23 July 2023. Therefore, we expect that respiratory disease will have a similar negative contribution to excess mortality in August and September as for those months in 2022.
Excess mortality 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 lower 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.
Excess deaths to 31 July 2023 by age band and gender
Table 2 shows our estimate of excess deaths broken down by age band and gender. We have shown the figures for the first 30 weeks[2] of 2023 plus the full year 2022, with the contribution of COVID-19 deaths[3] shown separately.
As discussed in our Research Paper, we have to use a more approximate method to estimate excess deaths by age band/gender due to the data available. There are, therefore, small differences in the totals shown in Table 1 and Table 2. Our cause of death models represent our best estimate of the total excess mortality.
Table 2 – Excess deaths in Australia – By age band/gender for 2023 year-to-date and for 2022
In the first seven months of 2023:
- for ages 0-44, excluding the small number of COVID-19 deaths, there is a significant negative excess for males but a significant positive excess for females;
- for ages 45-64, deaths are close to predicted for both males and females (no excess);
- for both the 65-74 and 75-84 age bands, there is a significant excess for both males and females, of which around 40-50% is explained by COVID-19 deaths; and
- in the 85+ age band, there is a significant excess that is wholly attributable to COVID-19.
Data and terminology
The COVID-19 Mortality Working Group has examined the latest Provisional Mortality Statistics, covering deaths occurring prior to 31 July 2023 and registered by 30 September 2023, released by the Australian Bureau of Statistics (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 2023.
We have used additional data supplied by the ABS in a customised report in relation to COVID-19 deaths registered by 30 September 2023, namely the total number of deaths each week (doctor-certified and coroner-referred) both from COVID-19 and COVID-19 related, defined as:
- deaths from COVID-19 are deaths where COVID-19 is listed as the primary/underlying cause of death; and
- deaths that are COVID-19 related are 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.[4]
Baseline predictions
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). As always, our intent is for the baseline to reflect the expected number of deaths “in the absence of the pandemic”.
The derivation of our baselines and a fuller description of our methodology is documented in our Research Paper. 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.
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] 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.
[2] Note that the dates covered in Table 2 differ slightly from Table 1. Table 1 includes the full seven months from 1 January to 31 July, whereas Table 2 includes the first 30 ISO weeks that run from 2 January to 30 July
[3] Due to confidentiality provisions applied by the ABS to data included in the customised report, the sum of male and female figures does not necessarily add to the person total
[4] 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.
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