Excess Mortality 5% Higher Than Pre-Pandemic Expectations for 2023
Catch up on the Actuaries Institute Mortality Working Group’s latest analysis of excess deaths.
In summary:
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Excess deaths to 31 December 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 were much higher than expected for each of the four weeks in December (as they were in November).
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 and COVID-19 related deaths continued to be high in December. COVID-19 waves are very clear in Figure 2, showing an encouraging trend of reducing impact.
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 higher than predicted for almost every week between October 2021 and mid-2023. The weeks in 2023 with lower-than-predicted non-COVID-19 deaths tend to coincide with weeks with low COVID-19 prevalence. All weeks of November and December 2023, when there was another COVID-19 wave, have higher-than-expected non-COVID-19 deaths.
Excess deaths in 2023 by cause of death
Table 1 shows our estimate of excess deaths broken down by cause. We have shown the figures for 2023 and 2022[1].
Table 1 – Excess deaths in Australia – By cause of death for 2023 and 2022
In 2023:
- total deaths were 5% (95% confidence interval: 3% to 7%) or +8,400 higher than predicted;
- there were 4,630 deaths from COVID-19, representing 55% of the excess deaths;
- there were 1,478 COVID-19 related deaths included among the other causes of death, representing a further 18% of the excess deaths;
- the remaining 27% of excess deaths (c. 2,300) have no mention of COVID-19 on the death certificate;
- deaths from pneumonia, lower respiratory disease and dementia were significantly lower than predicted (by between 9% and 18% respectively); and
- doctor-certified deaths from non-respiratory diseases other than dementia, and coroner referred deaths, were significantly higher than predicted (by between 1% and 14%).
Deaths from influenza were also lower than predicted, but the very wide range of the confidence interval means that the difference is not statistically significant. Interestingly, there have been small numbers of deaths with influenza listed as the underlying cause in the months of October to December 2023. This is despite influenza surveillance showing that prevalence was low. This suggests there could be small numbers of COVID-19 deaths being miscoded as influenza deaths. We understand that this situation could arise when a person dies without having the type of their respiratory infection diagnosed, which is most likely to occur when the death happens at home. While we have noticed possible miscoding of COVID-19 deaths as influenza deaths, this may not be limited to influenza (due to generally lower levels of COVID-19 testing now compared with earlier in the pandemic).
Lower than expected deaths from respiratory disease and dementia suggest that defensive measures are still providing some protection to aged care residents. If so, it is likely that deaths from COVID-19 are lower than would otherwise have been the case.
Key contributors to excess mortality over time
Figure 4 shows excess deaths (as a percentage of the predicted total) for each month of 2022 and 2023. We have shown the total excess (blue) and the contributions to that total 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);
- deaths from dementia (green); and
- deaths from all other causes (grey).
Figure 4 – Excess deaths (% of predicted total) by month in 2022 and 2023
COVID-19 deaths account for most of the excess mortality.
Deaths from respiratory disease have mostly been a negative contributor to excess mortality. The 2023 flu season was, like 2022, earlier than pre-pandemic normal [2].
Deaths from dementia are correlated with COVID-19 and respiratory deaths. Our Research Paper shows that a high proportion of deaths from dementia have either influenza or COVID-19 listed as a contributory cause, so it is no surprise to see the excess dementia deaths move broadly in line with COVID-19 and influenza waves.
Excess mortality from other causes (i.e., non-COVID-19, non-respiratory), somewhat follows the pattern of COVID-19 mortality. The correlation has been stronger in 2023 than in 2022.
Excess deaths in 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 2023[3] and 2022, with the contribution of deaths from COVID-19 and COVID-19 related deaths 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 and 2022
In 2023:
- for the 0-44 and 45-64 age bands, male mortality is close to expected but for females there is a significant excess, as in 2022;
- for the 65-74 and 75-84 age bands, there is a significant excess for both males and females, of which around one-third is explained by COVID-19 deaths (2022: around one-half); and
- in the 85+ age band, there is a significant excess that is almost wholly attributable to COVID-19 (2022: around two-thirds).
2023 mortality in context
Figure 5 shows the standardised death rates (SDRs) for 2015 to 2023, putting the 2023 year into context. The actual SDRs include allowance for late-registered deaths. We have also shown our predicted SDRs.
Figure 5 – Standardised Death Rates 2015 to 2023
The actual SDR for 2023 is just 0.6% lower than the SDR for 2019, compared with the non-pandemic expectation that it would have been 5.2% lower than 2019.
The 2023 SDR is 7% lower than the very high 2022 year.
Data and terminology
The COVID-19 Mortality Working Group has examined the latest Provisional Mortality Statistics, covering deaths occurring prior to 31 December 2023 and registered by 29 February 2024, released by the Australian Bureau of Statistics (ABS) on 26 March 2024.
We have 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.[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 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.
Mortality Working Group
The members of the Working Group are:
- Karen Cutter
- Ronald Lai
- Jennifer Lang
- Han Li
- Richard Lyon
- Matt Ralph
- Amitoze Singh
- Michael Seymour
- Zhan Wang
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 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] Note that the dates covered in Table 2 differ from those in Table 1 by one day. Table 1 includes the calendar year of 2023, whereas Table 2 includes 52 ISO weeks that run from 2 January to 31 December.
[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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