COVID-19 Mortality Working Group – While Still High, Excess Mortality Falls a Little in June
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 30 June 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
Three of the four weeks of June were above the upper end of the 95% prediction interval, and two of those weeks were substantially higher.
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. (Note that we did not request our customised report from the ABS for this analysis, so the weekly COVID-19 deaths for the four weeks of June are an approximation. The approximation uses the pattern of weekly doctor-certified deaths from COVID-19 in June to spread the monthly numbers of deaths that are from COVID-19 and COVID-19 related.)
Figure 2 – Weekly deaths from COVID-19 and COVID-19 related*
* COVID-19 data until end May from ABS customised report 2023, approximation for June. 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 peaked in the latest wave in the first week of June 2023 before falling across the remaining three weeks.
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 95th percentile levels for two of the four weeks of June 2023. Two weeks were below the predicted level, which has been very rare in the last 18 months.
Excess deaths to 30 June 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 six months of 2023 plus the full year 2022[1].
Table 1 – Excess deaths in Australia – by cause of death for 2023 year-to-date and for 2022
In the first six months of 2023:
- total deaths were 7% (95% confidence interval: 5% to 8%) or +5,500 higher than predicted. 1,000 of these excess deaths occurred in January (7% excess), 500 in February (4% excess), 800 in March (6% excess), 900 in April (6% excess),1,500 in May (10% excess) and 1,000 in June (6% excess);
- there were 2,919 deaths from COVID-19, representing 53% of the excess deaths;
- there were 1,005 COVID-19 related deaths included among the other causes of death, representing a further 18% of the excess deaths. The remaining 29% of excess deaths (c. 1,600) have no mention of COVID-19 on the death certificate; and
- doctor-certified deaths from other cardiac conditions, cerebrovascular disease, diabetes, other unspecified diseases and coroner referred deaths were all significantly higher than predicted (by between 3% and 15%). Deaths from pneumonia and lower respiratory disease were significantly lower than predicted (by 16% and 6% respectively).
Figure 5 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 5 – 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.[2]
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.
Data and terminology
The COVID-19 Mortality Working Group has examined the latest Provisional Mortality Statistics, covering deaths occurring prior to 30 June 2023 and registered by 31 August 2023, released by the Australian Bureau of Statistics (ABS) on 22 September. This release is the first of the ABS’ shortened format reporting (a short format report will be released every second month).
We have previously used additional data supplied by the ABS in a customised report in relation to COVID-19 deaths, 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.[3]
With the new short format Provisional Mortality Statistics report, we were not sure how much information was going to be included, and therefore how much of our usual analysis we would be able to carry out. As such, we did not request the customised report this month.
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] 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).
[3] 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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