Mortality in First Five Months of 2024 Was Slightly Higher than Prediction

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

Excess deaths to 31 May 2024

Figure 1 shows the results of our analysis, comparing actual deaths each week to our predicted values and the 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.

As our baseline measurement for 2024 differs from that for earlier years, the measurement of the excess for earlier years is not comparable to that for 2024. Therefore, we have only shown 2024 in Figure 1.

Figure 1 – Weekly actual and predicted deaths – all causes

With one exception, actual weekly deaths from all causes have been within the 95% prediction interval. The final week of May was higher than the prediction interval (with the rest of the month being close to expected). One exceptional week out of 21 is not statistically significant, so the June data will confirm whether this was anything more than a single outlier.

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

Since March, deaths from COVID-19 have been higher than predicted. Mortality continued at a higher level than we anticipated following the wave that commenced in late 2023.

In the most recent wave that started in late April 2024, COVID-19 mortality has increased more sharply than we predicted. The peak is at least as high as the previous wave, contrary to our prediction that peaks will be lower from wave to wave – noting that the late 2023 wave was relatively low and long. Surveillance in New South Wales and Victoria shows COVID-19 prevalence has been falling since June, so the peak of the current mortality wave may have occurred earlier than predicted.

Excess deaths in 2024 by cause of death

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

Table 1 – Excess deaths in Australia (versus 2023-based expectation) – by cause of death for January to May 2024

In the first five months of 2024:

• Total deaths were 800 (1%) more than predicted – i.e., the overall experience for the first five months of 2024 is slightly higher than in 2023 after allowing for pre-pandemic levels of mortality improvement.
• Deaths from COVID-19 were significantly^[2] 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.
• COVID-19 was a much more significant cause of mortality in the first five months of 2024 than influenza (1,610 doctor-certified deaths for COVID-19 versus 144 for influenza).
• Deaths from pneumonia were also significantly higher than predicted.
• Total deaths from non-COVID-19 respiratory causes were 5% higher than predicted, but this is not statistically significant.
• Deaths from all other causes were slightly lower than the prediction, with dementia and cancer being the primary drivers of this, although none of these outcomes is statistically significant.

Data and terminology

The Mortality Working Group has examined the latest Provisional Mortality Statistics, covering deaths occurring up to 31 May 2024 and registered by 31 July 2024, released by the Australian Bureau of Statistics (ABS) on 30 August 2024.

We have used additional data supplied by the ABS in a periodical customised report^[3] 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]

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 (the reasoning for the change to the baseline can be found here), 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:

• Ronald Lai                              
• Jennifer Lang (Chair)
• Richard Lyon                          
• Matt Ralph
• Michael Seymour                   
• Amitoze Singh

The Mortality Working Group would like to thank Han Li, Zhan Wang and Mengyi Xu for their past contributions and we extend a special thanks to Karen Cutter, our former Chair and founding member, for her hard work and dedication. Karen is now taking a well-deserved break from volunteering.

The Working Group is now seeking three volunteers to help provide insight into mortality data and its implications. Volunteering four-to-five hours per month, activities include analysing, reporting, writing and reviewing articles on population mortality statistics and developing thought leadership content. Express your interest here.  

References

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