Mortality in First Eight Months of 2024 2% Higher Than Predicted

In their latest article, the Mortality Working Group shares excess mortality analysis for the first eight months of 2024.

We projected mortality for 2024 to include two waves of Covid-19, both lower than 2023, and all other mortality to be an improvement on 2023.

In the year to August 2024, rather than lower levels of mortality than in 2023, Covid-19 has led to about the same level of deaths as 2023 in aggregate, with the winter wave being significantly worse than projected, lasting longer and peaking at higher levels of deaths than predicted.

Other deaths from respiratory illnesses have also been worse than expected, with all other mortality in line with predictions to date.

Covid-19 continues to be a significant new source of mortality in the Australian population, with no signs that it is replacing deaths from other causes, leading to overall deaths being 2%, or more than 2,000 deaths higher than expected in the eight months to August 2024.

Excess deaths to 31 August 2024

We measure excess deaths by comparing actual deaths each week to a baseline.  For 2024, this baseline is our predicted values, based on 2023 mortality and expected improvement rates, and including COVID-19.  This is different from our baselines for previous years, which were based on the absence of a pandemic.  Note that our allowance for COVID-19 is necessarily a much more approximate estimate than other potential causes of death, because of the limited data from which to estimate both the timing and severity of waves of COVID-19.

Figure 1 – Weekly actual and predicted deaths – all causes

Figure 1 shows the results of our analysis of the experience up to August 2024.  We only show 2024 on this chart, because the measurement of excess mortality for earlier years is not comparable to that for 2024.

We also show our 95% prediction interval.  As noted in our Actuaries Digital article in June, for 2024 we have based our prediction intervals on our analysis for the 2023 baseline (i.e. it represents pre-pandemic variance, excluding COVID-19). As a result, the prediction interval shown in Figure 1 is narrower than the true 95% prediction interval including COVID-19 deaths.

Actual weekly deaths have nearly always been within the 95% confidence interval. However, most weeks in June, July and August were above the prediction and this is significant in aggregate for the eight-month period.

Figure 2 shows actual deaths from COVID-19 and COVID-19 related deaths from the start of 2022. We have also shown our predicted values for deaths from COVID-19 for 2024, which were based on the assumption of two waves of COVID-19 per annum, gradually decreasing in size each time.

Figure 2 – Weekly deaths from COVID-19 and COVID-19 related

_{Actual deaths include allowance for late reporting. Predicted deaths come from the fitted trend in each week’s standardised death rate. COVID-19 data from ABS customised report 2024.}

COVID-19 mortality in 2024 has followed the basic pattern that we predicted, albeit with slightly different timing.  The wave that hit in late 2023 abated early in the year, and a new wave arrived in the middle of the year before it too abated.  However, deaths from COVID-19 have been much higher than predicted.

Between the late-2023 and mid-2024 waves, COVID-19 mortality continued at a higher level than we anticipated. The mid-2024 wave, which commenced in May, rose more sharply and reached a higher level than we predicted. The peak of that wave was higher than the previous one, contrary to our prediction that peaks will be lower from wave to wave. In fact, the mid-2024 wave was similar in height to the mid-2023 wave.

Surveillance of COVID-19 PCR tests in New South Wales and Victoria shows an increase in positive results commencing in late October, consistent with the timing of the predicted late-2024 wave.

COVID-19 is a new disease, and its mortality impact is difficult to predict.  The first eight months of 2024 have proven to be materially worse than we anticipated, in terms of both the peak mortality of each wave and the underlying mortality between waves.

Excess deaths in 2024 by cause of death

Table 1 shows our estimate of excess deaths broken down by cause^[1].

Table 1 – Excess deaths in Australia (v 2023-based expectation) – by cause of death for Jan-Aug 2024

In the first eight months of 2024:

• • • Total deaths were 2,200 (2%) more than predicted – i.e., the overall experience for the first eight months of 2024 is higher than 2023 after allowing for pre-pandemic levels of mortality improvement.
    • Deaths from COVID-19 were 70% higher than predicted. It should be noted that there are high levels of uncertainty surrounding both the number of deaths from COVID-19 and the timing of COVID-19 waves.
    • There were 3,190 deaths from COVID-19. This is already well above our prediction of 2,400 for the whole of 2024, and similar to the equivalent period in 2023.
    • Influenza deaths remained high through August, indicating a later peak than in 2022 and 2023. Surveillance suggests considerably lower Influenza mortality after August.
    • COVID-19 was a much more significant cause of death than influenza, with five deaths from COVID-19 for every death from influenza.
    • Deaths from pneumonia and other lower respiratory disease were also significantly higher than predicted.
    • Total deaths from non-COVID-19 respiratory causes were significantly (8%) higher than predicted.
    • Deaths from all other causes were in line with the prediction, which contrasts with 2021-2023 where deaths for many of these causes were significantly higher than anticipated.
    • Deaths for cancer, heart disease, diabetes and dementia were all lower than predicted although we do not consider any of these outcomes to be statistically significant.
    • Deaths from other unspecified diseases (where the ABS does not specify a cause) are significantly higher than predicted. This is a catch-all category and a variety of factors are likely to be influencing the outcome.

Data and terminology

The Mortality Working Group has examined the latest Provisional Mortality Statistics, covering deaths occurring up to 31 August 2024 and registered by 31 October 2024, released by the Australian Bureau of Statistics (ABS) on 29 November 2024.

We have used additional data supplied by the ABS in a periodical customised report^[2] 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]

A new approach to setting the baseline predicted number of deaths

Annual baseline

Our April 2024 Actuaries Digital article discussed in some detail the reasoning behind our change in approach to setting the baseline for 2024. We have moved away from answering the question “How has the pandemic affected mortality?” to instead ask, “How is current mortality tracking relative to last year?”

More completely, our estimate of excess deaths measures how 2024 mortality compares to the expected level based on 2023, after allowing for one year’s mortality improvement. Specifically:

• • • for deaths due to COVID-19, we have adopted age-standardised death rates (SDRs) for 2024 that allow for two waves per annum, with each successive wave resulting in 20% fewer deaths than the previous wave, reflecting the trend that we have seen since borders were re-opened;
    • for respiratory causes, we have adopted the 2023 SDRs for 2024, since it seems reasonable not to allow for any year-to-year mortality trend; and
    • for all other causes of death, we have adopted the 2023 SDRs plus an allowance for the pre-pandemic rate of mortality improvement to continue into 2024.

Historical context

Excess mortality was 11% in 2022 and 5% in 2023, both measured relative to pre-pandemic expectations of mortality. In adopting a 2024 baseline based on 2023 mortality (adjusted as discussed above), we note that:

• • • this baseline will include any temporary pandemic impacts affecting 2023 mortality;
    • any such temporary pandemic impacts are impossible to quantify;
    • we are assuming that underlying non-COVID-19 mortality will continue to improve, which it had done for decades prior to the pandemic.
    • it is increasingly unclear whether – and to what extent – the underlying mortality improvement rate would, by now, be higher or lower than the pre-pandemic trend; and
    • therefore, there is more than usual uncertainty around the appropriate baseline for expected mortality and this uncertainty will continue as we move towards “new normal” post-pandemic mortality.

We stress the high uncertainty (and correspondingly wide confidence interval) relating to the resultant calculation of excess mortality. 

The new approach to estimating the baseline results in a predicted 186,300 deaths for 2024, including 2,400 deaths from COVID-19. This compares to 183,700 actual deaths in 2023 (including estimated late reports), of which 4,600 were from COVID-19. Predicted numbers of deaths are increasing faster from demographic changes (ageing and population size) than they are reducing due to mortality improvement, even though age-adjusted death rates are reducing. Therefore, our model predicts higher baseline numbers of deaths for 2024 compared with 2023.

Disclaimer

This excess 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 Jenny Gibson, Cecilia Huang, Jenny Ingram, Ronald Lai, Jennifer Lang, Richard Lyon, Matt Ralph, Michael Seymour, Amitoze Singh, Colin Yellowlees and Richard Zheng.

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] The latest such report covered deaths from and related to COVID-19 that were registered by 31 August 2024.
[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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